Clubjazz - Honda Jazz & HR-V Forums

Honda Jazz Forums => Honda Jazz Mk4 2020 - => Topic started by: Fredbassett on April 01, 2026, 07:05:07 PM

Title: Battery failure
Post by: Fredbassett on April 01, 2026, 07:05:07 PM: I bought a 2022 Jazz SR a week ago and used it for the first time today. I got 500 yards from home and it died on me going around a roundabout! The screen went blank and pushing the accelerator did nothing. After a minute of pressing the power button a few times it started to move again. I immediately returned home and checked the 12v battery with a voltmeter. It read 8v. I assume the battery is dead. However, it had managed to start the traction battery at the beginning of my journey. My question is why did allow me to drive it if there wasn’t enough power in the 12v battery? It was incredibly dangerous cutting out like that on the road. A battery state of charge meter on the screen for the 12v system would be more useful then the one for the traction battery.
Title: Re: Battery failure
Post by: Pine on April 02, 2026, 09:37:58 AM: Let us know how you get on when you have a new 12v battery.
Title: Re: Battery failure
Post by: Kremmen on April 02, 2026, 10:23:17 AM: It surely has to be the 12v battery ?

Once you got the engine started it would have set the HV battery to start charging the 12v at about 14v so dying whilst driving must be failure
Title: Re: Battery failure
Post by: Jazzik on April 02, 2026, 11:33:17 AM: Go to a dealer and have the error codes scanned. It is virtually impossible stalling like this to be caused by the 12-volt battery once the car was in "ready" mode and driving.
Mind you: I am not saying that the 12-volt battery cannot be a bit less "healthy" after 4 years.
Title: Re: Battery failure
Post by: jaytee on April 02, 2026, 03:05:27 PM: When I bought mine , 3 years old also, the battery was replaced by the dealer,but i think it had been unused for a few weeks/months, the 12v battery is small and it can be run down quite quickly if not in use .
Title: Re: Battery failure
Post by: coldstart on April 04, 2026, 05:47:15 PM: Quote from: Fredbassett on April 01, 2026, 07:05:07 PM
I bought a 2022 Jazz SR a week ago...

As it is a pre-facelift model: Have you checked, if the car has had the brake simulator issue fixed already?
Title: Re: Battery failure
Post by: Jazzfan49 on April 11, 2026, 02:41:05 PM: Quote from: coldstart on April 04, 2026, 05:47:15 PM
Quote from: Fredbassett on April 01, 2026, 07:05:07 PM
I bought a 2022 Jazz SR a week ago...

As it is a pre-facelift model: Have you checked, if the car has had the brake simulator issue fixed already?

Mine is a 2023 pre facelift SR version, my dealer confirmed that it does not require the brake simulator replacement, I hit a pothole recently and burst a rear tyre the 12v battery lasted less than an hour with hazard warning lights on so had to be jump started by the RAC recovery engineer, tyre too badly damaged to use the emergency repair kit so they fitted an emergency space saver wheel to get me home.
;D ;D
Title: Re: Battery failure
Post by: Kremmen on April 11, 2026, 03:26:58 PM: Sounds like the trick may have been to start EV mode every now and again to recharge the 12v battery
Title: Re: Battery failure
Post by: coldstart on April 13, 2026, 02:55:44 PM: Quote from: Fredbassett on April 01, 2026, 07:05:07 PM
... and checked the 12v battery with a voltmeter. It read 8v. I assume the battery is dead. However, it had managed to start the traction battery at the beginning of my journey. My question is why did allow me to drive it if there wasn’t enough power in the 12v battery? ...

Do you remember whether the green "ready" indicator (the car with the two-pointed arrow below it) has been lit?
If both the HV (aka traction) battery as well as the 12V battery have been only marginally charged when you took off and the car wasn't signalling "ready" might explain why it "died" on you.

Has this happened again?
Title: Re: Battery failure
Post by: CB72 on April 13, 2026, 04:17:01 PM: Is this battery problem ever going to be sorted, the Yaris has the same problem. Just putting a normal battery in the car might help. An ICE car can sit in the garage for ten years and still start. Isn't there a way to use the EV battery start the car when the 12v battery fails, I think there is a car that can do this, can't remember the model.
Title: Re: Battery failure
Post by: coldstart on April 13, 2026, 04:44:24 PM: Quote from: CB72 on April 13, 2026, 04:17:01 PM
... Isn't there a way to use the EV battery start the car when the 12v battery fails, I think there is a car that can do this, can't remember the model.
For security reasons the HV system gets completely shutdown when the car is turned off.
The 12V battery is essential to prime the HV system which then in turn cranks the ICE.

Even putting in a "normal" 12V battery as per your suggestion wouldn't cure the root cause (only delay its effects), mainly: Driving the car only sporadically and/or only for short distances which will eventually result in a depleted 12V battery.

If you have this kind of motion profile you wouldn't even get great fuel benefits from the (quite elaborate!) e:HEV drive train because the engine never really gets out of cold start conditions.
A true EV would be the better and more "fuel"-efficient choice for such a use case (but would probably suffer from an occasionally depleted 12V battery as well).
Title: Re: Battery failure
Post by: Kremmen on April 13, 2026, 05:14:26 PM: The draw on the 12v battery must be significant when the car is off and left for just a few weeks to deplete it

I know it's totally different but I've got smart devices round my house that are continually transmitting data that run for over a year on a couple of AAA batteries

I also remember my dad's A35 van that had a red/white light hung on the drivers windows top that was illuminated all night, as was often done in the 50's and 60's, and the van started without issue every morning

Imagine having a normal filament bulb wired to the Jazz 12v battery all night, it would surely flatten it
Title: Re: Battery failure
Post by: Lord Voltermore on April 13, 2026, 05:37:23 PM: Quote from: CB72 on April 13, 2026, 04:17:01 PM
Isn't there a way to use the EV battery start the car when the 12v battery fails, I think there is a car that can do this, can't remember the model.
I think there are one or two makes that have an override switch which, in an emergency, takes a supply from the high voltage battery ,converted to 12volts. . But some owners would continue to use this override switch over a long period rather than go to the trouble and expense of replacing a faulty 12v battery . Or in the event of the car not starting or behaving as expected they might , in desperation ,repeatedly activate the overide often enough to discharge the VERY expensive HV battery to the point that causes it damage.
Title: Re: Battery failure
Post by: CB72 on April 13, 2026, 07:06:16 PM: Hyundai and Kia have a battery reset button, once pressed you have to wait 30mins before starting the car, also you have to manually open the doors, not something you would want to do very often. You'd be off to the garage quickly if that happened regularly.
Title: Re: Battery failure
Post by: coldstart on April 13, 2026, 07:22:31 PM: Quote from: Kremmen on April 13, 2026, 05:14:26 PM
The draw on the 12v battery must be significant when the car is off and left for just a few weeks to deplete it ...

You are absolutely right when (or if? - the english language just has too many words for the "same" thing) the 12V battery was fully charged at the beginning!
(which it probably wasn't, if the car wasn't "active" for longer periods in the past)
Title: Re: Battery failure
Post by: Lord Voltermore on April 14, 2026, 09:48:37 AM: Quote from: coldstart on April 13, 2026, 07:22:31 PM
the english language just has too many words for the "same" thing)

I agree ,acknowledge, admit, concede, concur, grant ,recognise that English has too many words for the same, selfsame, matching ,identical ,indistinguishable, interchangeable, corresponding, equivalent word. ;D A thesaurus is not a dinosaur. :D.
Title: Re: Battery failure
Post by: Kremmen on April 14, 2026, 10:21:28 AM: There, Their, They're..... never mind
Title: Re: Battery failure
Post by: Fredbassett on April 17, 2026, 05:20:47 PM: Sorry for the delay in updating. I bought a new Bosch S4018 battery from Tayna for £55.43 and fitted it myself. (I think Quikfit wanted £135 to include fitting). The car is working fine now, so the original Panasonic factory battery after 4 years was dead. Considering the 12v battery doesn’t spin a starter motor I would have thought they ought to last 10 years!
Title: Re: Battery failure
Post by: MikeRO on April 17, 2026, 06:47:07 PM: Quote from: Fredbassett on April 17, 2026, 05:20:47 PM
Sorry for the delay in updating. I bought a new Bosch S4018 battery from Tayna for £55.43 and fitted it myself. (I think Quikfit wanted £135 to include fitting). The car is working fine now, so the original Panasonic factory battery after 4 years was dead. Considering the 12v battery doesn’t spin a starter motor I would have thought they ought to last 10 years!

I also recently had to replace the 12v battery and bought the same Bosch, no troubles since!
Title: Re: Battery failure
Post by: stani on May 01, 2026, 08:32:20 AM: So yesterday the same thing happened to me. I tried the update, it didn't take long, just a few minutes, the update wasn't available, just the manual, so I let it download, halfway through the download (via wi-fi), the main display went out and the driver's display showed various warnings about problems. I tried turning the car off and on again - nothing, everything was locked incl. the gear lever.

It's my first hybrid, I didn't know what it was, I thought the car had somehow locked up in the software. I called Honda Assistance, they don't advise anything, they send a tow truck, the tow truck doesn't advise either (even though they could), they just load the car up and take it to the Honda service center.

The mechanic told me that it was a dead 12V battery. Apparently there is a fuse in the car that says that if the 12V battery is discharged below a certain level, the car simply won't go any further. He told me that all I had to do was use a jump starter (which I have (https://clubjazz.org/forum/index.php?topic=17665.msg151105#msg151105) in my car, of course), and then drive the car to a place where the 12V battery can be recharged. A tow truck could have easily done it, and charged the battery only enough to put the car in "N" and load it. Because if they started the car, they would have lost money on the transport.
I was also told by the tow truck that they come out to "dead" hybrids quite often.

The mechanic told me that every time I enter the infotainment system (update, set up, tune the radio, etc.) the car must be started (or in EV mode - so that the engine can start right away), otherwise the 12V battery will discharge. And since it's really small, it will discharge pretty quickly.

It's quite disappointing to me that the 12V battery can discharge so quickly and cause such problems.
Title: Re: Battery failure
Post by: Kremmen on May 01, 2026, 08:37:53 AM: I'll post again that if a car lead/acid battery becomes completely flattened then the alternator or whatever can't fully recover it. It only performs a stage 2 charge

Had the same in a Metro where the lights were left on and even after a 200 mile trip the battery still discharged overnight

The mechanic explained about the stage 1 and 2 charges

I wonder if a CTEK can perform the factory stage 1 charge that keeps batteries alive on forecourts until bought and fitted ?
Title: Re: Battery failure
Post by: Lord Voltermore on May 01, 2026, 10:43:53 AM: advanced smart chargers can do a desulfation cycle that can restore badly discharged batteries . I think it uses very rapid charging pulses to blast away any sulphur crystals that have formed on the lead plates.

Some more basic, cheaper, smart chargers may not include this function.
Title: Re: Battery failure
Post by: 5thcivic on May 01, 2026, 05:31:41 PM: My Lidl charger specifications has a charging graph showing the test ramp from 7.5V to 10.5V with 0.8A as a pulse waveform described as "Recharge / desulphation".

My Maypole charger has an initial process "Battery condition diagnosis & recovery with pulse charging" but with no mention of desulphation, but that is a much older charger so maybe not described at that time. My understanding is the pulse charging is the important step.

The Lidl will not work below about 3V and the Maypole below about 7V. My second Civic had a recall on the microprocessor in the fuse box which had faulty software which could drain the battery. The one time this happend the Maypole could not revive it. I still kept my old analogue transformer charger, and 15 minutes on this put enough charge in for the microprocessor charger then to take over. The free recall then fixed the issue.
Title: Re: Battery failure
Post by: coldstart on May 02, 2026, 07:49:52 AM: The IKEA-style manual of my CTEK 5 Start-Stop charger says it does only work on batteries which have at least 2 volts left.
I don't see this as a large limitation as it is clearly intended for car owners with activated batteries and not for manufacturers that have to prime brand new batteries.
Title: Re: Battery failure
Post by: Jazzik on May 02, 2026, 12:47:03 PM: I am reading this topic (and several others) about (alleged) problems with 12-volt batteries.

What kind of battery chargers are suitable, simple ones or advanced smart chargers...? And what about (long- or high?) jump starters... Problems, problems. :(

But... we don't drive a Toyota Yaris or anything like that, do we? ;D

We have been driving our Jazz for 4 years and 8 months now, about 37,000 km (23,000 miles). So that is 660 km (410 miles) per month. Not really a lot of kilometers, then, and it also regularly sits idle in the garage for some time. The longest period of inactivity was 10 (ten!) weeks.
In the cupboard in the garage, a battery charger from Lidl has been gathering dust in its original packaging for about 10 years now—new, never used. But the offer was so attractive, I just had to buy it! :P
A jump starter, or whatever it’s called: I never even thought about buying one...
And guess what: this morning the Jazz started, just like always, without any problems after 6 days of inactivity. :-*

And now comes my first question: who among you has ever been unable to start the Jazz due to a dead 12-volt battery?
And question number two: was the battery perhaps discharged due to your own fault then?
Title: Re: Battery failure
Post by: sebastiand on May 02, 2026, 01:02:54 PM: Quote from: Jazzik on May 02, 2026, 12:47:03 PM

The longest period of inactivity was 10 (ten!) weeks.

10 weeks is pretty good to me (above expectation). I wanted to know if this happens you know after 4 weeks of no usage, something like that.

In my Outlander (2014 diesel) i left it in a garage for 84 days (was not using the car at this time) and it started without any issue, of course it has a bigger battery and Mitsubishi is very strict with killing all the power when the car is off.
Title: Re: Battery failure
Post by: Kremmen on May 02, 2026, 02:00:53 PM: If you perform mainly longer journeys then your 12v will be fully charged when you park and a lengthy period will be OK

If you just perform short journeys of less than 5 to 10 miles then the 12v may not be fully charged and may run flat if left

So some here will have no problems whilst others may have issues, horses for courses

Look at your usage and decide if it needs a boost every now and again

In mine I used to do a regular 60 mile return trip with a few days gap every month (ish) and after 2 weeks of being parked I'd put the CTEK on and is usually took around 5 hours to fully charge
Title: Re: Battery failure
Post by: Jazzik on May 02, 2026, 02:29:16 PM: But my questions are:
Who among you has ever been unable to start the Jazz due to a dead 12-volt battery?
And question number two: was the battery perhaps discharged due to your own fault then?
Title: Re: Battery failure
Post by: Jazzik on May 03, 2026, 02:58:49 PM: More than 24 hours (https://www.youtube.com/s/gaming/emoji/7ff574f2/emoji_u1f553.png) later... No one at all? :o
Title: Re: Battery failure
Post by: Lord Voltermore on May 04, 2026, 09:45:53 AM: I can give a negative answer. In nearly 5 years of owning a small portable jump starter in case this happens I have never needed to use it.
Title: Re: Battery failure
Post by: stani on May 04, 2026, 10:09:29 AM: It is a bitter irony paradox that although the Jazz provides information and warnings about all sorts of things, it says nothing about this very important issue — the impending failure of the 12-volt battery…
Title: Re: Battery failure
Post by: Jazzik on May 04, 2026, 01:21:36 PM: Quote from: stani on May 04, 2026, 10:09:29 AM
the impending failure of the 12-volt battery…

(https://www.cheesebuerger.de/images/midi/konfus/a018.gif)

As long as it remains merely a threat of a failure, your Jazz always starts without any problem, right? That's why I wondered who has actually fallen victim to this (alleged?) 12-volt battery problem.
Title: Re: Battery failure
Post by: exAudi on May 04, 2026, 02:40:32 PM: It happened to me just after getting car when I was exploring/setting up the audio and other features with the power by accessory option; car in garage.

Complete ignorance on my part as to how limited the 12V battery was in comparison to all my previous ice cars😖

I had to put the battery on charge (via existing CTEK) in order to resume normal operation😀.

Already discovered clubjazz so absorbed lots of useful advice on the subject.

Subsequently fitted a battery voltage indicator (decided on relatively expensive Ansmann one as have their excellent 1.5V/9V cell chargers) which simply plugs into car 12V socket. It gives good indication of state of 12V battery when I first power up and confirms charging when engine/HV battery running.

Most recently I have got myself a NOCO GB20 to give back up when out and about.
Title: Re: Battery failure
Post by: 5thcivic on May 04, 2026, 03:15:23 PM: 3 Civics, a Jazz and an E, never needed one yet!
Title: Re: Battery failure
Post by: stani on May 04, 2026, 03:54:35 PM: I was also looking for information about possibly replacing the 12v battery in the Jazz.

If the information is correct, it's not very happy...

The Honda Jazz uses the Japanese B19R format, not the European LN0.

The B19R has the opposite polarity (right +), does not fit the height of the holder, does not fit the shape of the foot, compared to the LN0.

The only supposedly correct battery for the Jazz allegedly is: GS Yuasa YBXAGM35R (B19R, AGM, right +)
Title: Re: Battery failure
Post by: coldstart on May 04, 2026, 03:55:03 PM: Quote from: Jazzik on May 04, 2026, 01:21:36 PM
Quote from: stani on May 04, 2026, 10:09:29 AM
the impending failure of the 12-volt battery…
As long as it remains merely a threat of a failure, your Jazz always starts without any problem, right? That's why I wondered who has actually fallen victim to this (alleged?) 12-volt battery problem.

Well, I do insure against all kinds of things that (hopefully!) will never affect me!
So, in the big picture of total costs, the expense for a CTEK and a NOCO GB20 doesn't bring me to ruin.
However, it gives me peace of mind!

Whilst I (so far) never had to use the NOCO jump starter I admit to periodically hook up the Jazz to the CTEK charger during the cold season (shorter and less frequent rides with more power drawing accessories active like heated seats, heated steering wheel and rear demister).
Title: Re: Battery failure
Post by: JB on May 04, 2026, 04:37:53 PM: Two came up at Yuasa only posted to show fitting time top right.
https://www.yuasa.com/uk/ybx5054
https://www.yuasa.com/uk/ybx7054
£59 difference between the two.
Title: Re: Battery failure
Post by: stani on May 04, 2026, 05:49:03 PM: I read about a similar problem with a 12V battery on the Czech Honda forum 3 years ago, it was about the HRV (here (https://www-honda--club-cz.translate.goog/forum/viewtopic.php?p=1212509&_x_tr_sl=cs&_x_tr_tl=en&_x_tr_hl=cs&_x_tr_pto=wapp#1212509) and here (https://www-honda--club-cz.translate.goog/forum/viewtopic.php?p=1212516&_x_tr_sl=cs&_x_tr_tl=en&_x_tr_hl=cs&_x_tr_pto=wapp#1212516) - it is translated into English). I only remembered it now.
Title: Re: Battery failure
Post by: 5thcivic on May 04, 2026, 08:17:12 PM: Bosch S4018 ?
Title: Re: Battery failure
Post by: stani on May 05, 2026, 05:28:25 AM: Quote from: JB on May 04, 2026, 04:37:53 PM
Two came up at Yuasa only posted to show fitting time top right.
https://www.yuasa.com/uk/ybx5054
https://www.yuasa.com/uk/ybx7054
£59 difference between the two.
Copilot: Both are classic flooded lead-acid batteries (SLI), not AGM, and they are not in the B19R format that the Jazz 2025 requires.

Quote from: 5thcivic on May 04, 2026, 08:17:12 PM
Bosch S4018 ?
Isn't it AGM? AGM is very important...
Title: Re: Battery failure
Post by: John Ratsey on May 05, 2026, 08:39:31 AM: My 2022 HR-V had a flat battery due to a bug in the perimeter control system (the vehicle didn't power down properly when locked) but my 2020 Crosstar and the current Jazz have behaved themselves despite not moving for a month or more during the winter months. However if the vehicle does move, it's for a decent journey.
Title: Re: Battery failure
Post by: Jazzik on May 05, 2026, 12:05:20 PM: Quote from: stani on May 04, 2026, 03:54:35 PM
I was also looking for information about possibly replacing the 12v battery in the Jazz.
I really wonder why you would do that. A bit VERY early, isn't it?
In your profile I see: My Honda: Honda Jazz e:HEV 2025
In Dutch, there is this proverb: "A person suffers most from the suffering he fears." This means that the fear of potential problems is often worse than the problems themselves (which often never become reality).
Title: Re: Battery failure
Post by: Lord Voltermore on May 05, 2026, 12:09:07 PM: Even conventional cars with full sized batteries needed to crank and start their ICE engines are vulnerable to flat batteries these days , unless they are used regularly for long enough journeys to top up the battery. (Or trickle charged etc) .

All modern cars have computer systems etc running 24/7 and many are 'connected' to various mobile networks etc. This small but constant draw can discharge a full sized, fully charged battery in a surprisingly short time . A bit like having to keep mobile phones and computer devices charged. Even in the 'good old days' car batteries unused for long periods had to cope with normal parasitic draw etc. Now they still have this plus all the new stuff.

Maybe I am biased having had no problem with the small 12v battery in 5 years (admittedly replacing the car at 3 years) If it does let me down I have a back up plan (jump starter power bank) . If that doesnt work I'll call for assistance. (assuming I kept my mobile phone charged. ;D)

I really dont think its that much of a problem . It doesnt need to crank the ICE. . If and when I need to replace the 12v battery ,and Yuasa really is the only compatible choice, at least its a very well regarded brand.
Title: Re: Battery failure
Post by: stani on May 05, 2026, 12:51:50 PM: Lord Voltermore: but this is a serious damn problem.

I can’t imagine this happening out in the middle of „nowhere.”

I’m not sure whether my previous post (https://clubjazz.org/forum/index.php?topic=18298.msg158063#msg158063) was understood correctly (perhaps due to my poor English – apologies), but this is honestly the worst issue I’ve encountered with the Jazz so far.

Now I know that in such a case it is necessary to use a jump starter power bank and drive somewhere to recharge the battery.

But as I wrote, the car completely locks up without any prior warning. The engine, gear lever, brakes, and traction battery are blocked. Main display off. In the end, I couldn't even lock the car.
The only thing that "worked" was a series of lockout warning messages on the driver's display.

As I wrote, this is my first hybrid, I didn't want to get involved in anything myself, so as not to mess something up even more. The Honda service is 3 km from me, the car is under warranty, call Honda Assistance. Honda Assistance couldn't help, they called a tow truck, which took my car to a Honda service center - the easiest and fastest solution to the problem at that moment and everything is free. It wasn’t until I went to the Honda service centre that the mechanic clarified and explained everything to me.

In a “normal” car, it's easy to tell - the starter barely turns over, the dashboard lights go out - you take the starter power bank connected to the battery and the car starts.

Yes, maybe I was under the mistaken impression that the traction battery would somehow replace the small 12V battery if needed. Now I know that I will always have to recharge the small 12V battery before and after winter.

It's also possible that it was discharged because I drove very short distances in the winter with the heated seats on (But it doesn’t show the status of the 12V battery anywhere!). It could also be that it was already half discharged when I bought the car from the dealer where it had been sitting for some time.

But it probably drains the most during updates, when Wi-Fi is on, as the mechanic told me, you need to have the engine running.

But what annoys me the most is that you don't get any advance warning at all, as I wrote above (https://clubjazz.org/forum/index.php?topic=18298.msg158123#msg158123).
Title: Re: Battery failure
Post by: 5thcivic on May 05, 2026, 03:55:27 PM: Quote from: stani on May 05, 2026, 05:28:25 AM
Isn't it AGM? AGM is very important...

Not supplied with an AGM so if you've not had any problems don't need one?
Title: Re: Battery failure
Post by: Lord Voltermore on May 05, 2026, 04:15:12 PM: Stani. Its nothing to do with your english, which is very good. Its my fault for not connecting my comments to your post #19 on 1st May. When topic threads gets quite long long I tend to forget what has been said before (even by me ) :-[ I am sorry.

I've never had a 12v battery going flat so maybe lacked the empathy to appreciate just how stressful losing all display systems etc must be. Especially if you are in the middle of nowhere.

And its disturbing that an independent breakdown operative may be more interested in maximising their payment by taking you to a Honda garage rather than simply getting the car started so you can continue your journey.

Others have reported problems of a flat 12v battery if you spend too long listening to the radio, updating the systems, learning how to work stuff etc while in accessory mode rather than allowing the engine to start when it needs to . Honda should definitely take more trouble to explain this. Manufacturers seem reluctant to explain situations that might imply inadequate equipment.

It is tempting to think things could be solved by simply fitting a bigger battery. It might help and delay things for a while but eventually even a large battery could go flat and cause the same problems. I wonder if its even possible and has anyone ever done so? Or for about £20 Honda could fit an additional small motorcycle type 12v back up battery thats normally kept fully charged, and not used, but could be brought into use just to power up the computer systems if necessary. It could trigger a warning display that you have used emergency back up and need to consult a dealer as soon as possible , blah blah.

If your 12v battery has suffered premature damage due to sitting a long time at the dealership (maybe straight after a long period onboard ship from Japan) shouldnt Honda replace it under warranty?
Title: Re: Battery failure
Post by: stani on May 05, 2026, 04:45:27 PM: Quote from: Lord Voltermore on May 05, 2026, 04:15:12 PM
Others have reported problems of a flat 12v battery if you spend too long listening to the radio, updating the systems, learning how to work stuff etc while in accessory mode rather than allowing the engine to start when it needs to . Honda should definitely take more trouble to explain this. Manufacturers seem reluctant to explain situations that might imply inadequate equipment.
This should be in the manual in a red box.

And only one thing would be enough: for the system to report a drop in energy in the 12V battery early.
Title: Re: Battery failure
Post by: exAudi on May 05, 2026, 04:51:42 PM: In the meantime best to install a plug in 12V battery monitor. As well as the digital voltage display, mine also has little red and green lights for those who may not appreciate the actual voltage displayed.
Title: Re: Battery failure
Post by: stani on May 05, 2026, 04:58:25 PM: Quote from: 5thcivic on May 05, 2026, 03:55:27 PM
Quote from: stani on May 05, 2026, 05:28:25 AM
Isn't it AGM? AGM is very important...

Not supplied with an AGM so if you've not had any problems don't need one?

Copilot: “The Honda Jazz e:HEV must use an AGM battery because the hybrid system constantly cycles it, charges it through a DC‑DC converter, and requires stable voltage that a standard SLI/EFB battery simply cannot provide.”

1) A hybrid doesn’t start the engine using the 12V battery – but the 12V system powers absolutely everything else.
In Honda hybrids, the combustion engine is started by the traction battery, not the 12V one. The 12V battery supplies all control units, pumps, relays, sensors, brakes, airbags, infotainment, lights, and so on. It therefore needs extremely stable voltage, which AGM provides far better than SLI/EFB.

2) The DC‑DC converter charges the 12V battery differently from a traditional alternator.
Hybrids don’t have a normal alternator. The DC‑DC converter uses higher charging voltages, short charging pulses, and variable modes. Standard SLI batteries cannot tolerate this — they overheat, overcharge, and degrade quickly. AGM is designed for this type of charging.

3) The hybrid system constantly cycles the 12V battery.
The Jazz e:HEV frequently switches between EV, Hybrid and Engine Drive modes, powers electronics when the engine is off, and recharges the 12V battery in short bursts from the traction battery. This means the 12V battery behaves like a cyclic battery, not a starter battery — and AGM has far higher cycle durability.

4) AGM handles temperature changes and vibrations much better.
The 12V battery in the Jazz sits in the engine bay, where temperatures fluctuate and can get quite high. AGM batteries have lower self‑discharge, better heat tolerance, and greater vibration resistance. SLI/EFB batteries deteriorate quickly in these conditions.

5) Using an SLI/EFB battery causes system errors.
In the Jazz e:HEV, a non‑AGM battery leads to charging errors, stability control warnings, electrical faults, and in many cases the car refusing to start. The DC‑DC converter can also overheat. Honda’s service documentation is clear: only AGM is acceptable.

6) AGM is the only correct technology for the Jazz e:HEV.
Title: Re: Battery failure
Post by: stani on May 05, 2026, 05:02:12 PM: Quote from: exAudi on May 05, 2026, 04:51:42 PM
In the meantime best to install a plug in 12V battery monitor. As well as the digital voltage display, mine also has little red and green lights for those who may not appreciate the actual voltage displayed.
Do you have any specific recommendation – a link?
Title: Re: Battery failure
Post by: exAudi on May 05, 2026, 05:29:52 PM: Stani. I bought an Ansmann one. They are £18.90 on Amazon at present. Not the cheapest but I was happy to pay for quality. Already had Ansmann cell battery chargers for many years.
Title: Re: Battery failure
Post by: John Ratsey on May 05, 2026, 05:37:54 PM: Quote from: stani on May 05, 2026, 04:58:25 PM
3) The hybrid system constantly cycles the 12V battery.
The Jazz e:HEV frequently switches between EV, Hybrid and Engine Drive modes, powers electronics when the engine is off, and recharges the 12V battery in short bursts from the traction battery. This means the 12V battery behaves like a cyclic battery, not a starter battery — and AGM has far higher cycle durability.
I struggle to comprehend why cycling the charging of the 12V battery is sensible, if true and not a AI hallucination. The 12V battery won't last very long when powering, for example, the heated seats.
Title: Re: Battery failure
Post by: MikeRO on May 05, 2026, 06:52:39 PM: I think it's AI hallucination. The original battery that came with the car is Panasonic 44B19L-MF which is a standard flooded battery. The Bosch S4018 is a suitable replacement, I've been running with it for 6 months now with no issues.
Title: Re: Battery failure
Post by: stani on May 05, 2026, 07:15:25 PM: Quote from: MikeRO on May 05, 2026, 06:52:39 PM
I think it's AI hallucination. The original battery that came with the car is Panasonic 44B19L-MF which is a standard flooded battery. The Bosch S4018 is a suitable replacement, I've been running with it for 6 months now with no issues.
Of course, AI can talk nonsense. For the Honda Jazz 4G (2020 - 2026)?
Title: Re: Battery failure
Post by: stani on May 05, 2026, 07:28:02 PM: Quote from: exAudi on May 05, 2026, 05:29:52 PM
Stani. I bought an Ansmann one. They are £18.90 on Amazon at present. Not the cheapest but I was happy to pay for quality. Already had Ansmann cell battery chargers for many years.
Is it the Ansmann 1900-0019? Do you have it plugged into the 12V socket permanently?

Edit: I read in a review (https://www.amazon.co.uk/product-reviews/B00I3ZGV9I/ref=acr_dp_hist_1?ie=UTF8&filterByStar=one_star&reviewerType=all_reviews) that EUFAB 16620 should be more accurate...But it only shows percentages.

Or KONNWEI KW208.
Or wireless ANCEL BM200 permanently connected to the battery.
(https://play-lh.googleusercontent.com/UCltKuRPMqphlwzzb2w2BnQZ8XWjm_EYgRRx44G1KH1Lrb_wQs5lkqK9fXczOtY5g7Q=w5120-h2880)
Title: Re: Battery failure
Post by: Lord Voltermore on May 06, 2026, 10:09:31 AM: My 2024 car also has Panasonic 44B19L MF fitted as OE. A google search on this reference number comes up with various Yuasa batteries for sale , which is not surprising as Yuasa own 80 % of Panasonic's battery division. And the official Honda part number for a replacement battery gives a Yuasa reference number
.
A google AI search for 'best type of 12v battery for a hybrid '(in general) does indeed say AGM battery. For a number of reasons, including for safety 'as they are often inside the passenger compartment.' Which is NOT case with the Jazz. Google AI also says that many hybrids use standard flooded batteries and you should check usage.

If Co pilot specifically mentions the Jazz e:hev as being fitted with an AGM battery its wrong .

Its not surprising AI is sometimes wrong. It searches a wide range of sources, including posts on this forum. Including some comments made by me! :o (Ultra reliable of course ;) ;D :P )

So it appears Honda do regard a flooded type battery of sufficient performance and quality as suitable OE for their hybrid car . But the question remains , have they fitted it as a cost saving measure. Or is there an AGM battery out there that would physically fit, work all the cars systems equally well without problems while also giving better charging performance. ?

Or if you stick with flooded type are there fully compatible alternatives (including Yuasa) available more cheaply than paying full Honda price?

My brain hurts. I need a recharge :D A cup of tea will do. I am not a robot.
Title: Re: Battery failure
Post by: stani on May 06, 2026, 10:20:17 AM: Panasonic 44B19L MF (https://www.honda-parts.eu/eu/car/parts/battery/battery-44b19l-31500-tzb-e01).

Otherwise, I see that there is already a similar thread on the topic (https://clubjazz.org/forum/index.php?topic=13275.0).
Title: Re: Battery failure
Post by: Lord Voltermore on May 06, 2026, 10:25:38 AM: This site shows the Yuasa reference number connection

https://www.parts-honda.uk/honda-cars/assignment_spare_parts/31500TG5G01
Title: Re: Battery failure
Post by: stani on May 06, 2026, 10:34:29 AM: My search (https://www.parts-honda.uk/honda-cars/assignment_spare_parts/) shows that "31500-TZB-E01" (Panasonic 44B19L MF) is for the 2021 Jazz Hybrid EXECUTIVE....
Is there a different battery for the Elegance?
Title: Re: Battery failure
Post by: Lord Voltermore on May 06, 2026, 10:50:00 AM: I think it will be the same. The more you search the more the anomalies and confusion :-\

As the Mk4' become older more owners will be looking for a compatible replacement 12v battery at a reasonable price. If anyone is successfully using one please post details.
Title: Re: Battery failure
Post by: Jazzik on May 06, 2026, 11:05:11 AM: I hope there isn't going to be an outbreak of some kind of "Toyota 12v battery panic illness"(https://www.cheesebuerger.de/images/midi/muede/f048.gif) here?

My two questions were:
1. Who among you has ever been unable to start the Jazz due to a dead 12-volt battery?
2. Was the battery perhaps discharged due to your own fault then? (Meaning: fumbling around with electricity consumers without having te car in "ready"?)
Title: Re: Battery failure
Post by: exAudi on May 06, 2026, 11:55:14 AM: Yes Stani that’s the Ansmann that I have permanently plugged in to the 12V socket. Not as if I use the 12V for anything else.

As regards accuracy, I have checked it against my Martindale meter and it’s correct to 2nd decimal.

Hopd this helps.
Title: Re: Battery failure
Post by: 5thcivic on May 06, 2026, 03:51:14 PM: Please don't rely on AI answers for your facts. Many many electronic, camera, hi-fi, and other technical questions I put into google for instance the first paragraph is more often wrong than right.
Title: Re: Battery failure
Post by: JB on May 07, 2026, 12:00:07 AM: Original battery Panasonic £177-38
https://www.honda-parts.eu/eu/car/parts/battery/battery-44b19l-31500-tzb-e01
https://www.bike-parts-honda.com/honda-motorcycle/assignment_spare_parts/31500TZBE03
£79 more than Yuasa heavy duty, £89 more than standard Yuasa
https://www.yuasa.com/uk/ybx3202
https://www.yuasa.com/uk/ybx5202
Title: Re: Battery failure
Post by: zdan on May 07, 2026, 03:34:09 PM: 10 extra quid for the yuasa heavy duty 5y warranty (5000 series) that sounds good.

I'm still running the original 12v battery and 55k miles (September 2020). I wonder if I shall I change it now or wait till it stops working.

It read 12.45v the next morning before I started the car.
Title: Re: Battery failure
Post by: coldstart on May 07, 2026, 04:17:08 PM: Quote from: zdan on May 07, 2026, 03:34:09 PM
It read 12.45v the next morning before I started the car.
According to this source (https://powmr.com/blogs/news/lead-acid-battery-voltage-chart) your battery is at 70 to 80% charged (sealed gel technology).

As for battery technology: The Jazz's 12V battery doesn't have to actually crank the ICE, so buying an AGM replacement seems to me somewhat over the top and a waste of money.
Title: Re: Battery failure
Post by: Nollypra on May 08, 2026, 08:28:40 PM: Quote from: CB72 on April 13, 2026, 04:17:01 PM
Is this battery problem ever going to be sorted, the Yaris has the same problem. Just putting a normal battery in the car might help. An ICE car can sit in the garage for ten years and still start. Isn't there a way to use the EV battery start the car when the 12v battery fails, I think there is a car that can do this, can't remember the model.
No chance a modern car will start after being in a garage for 10 years! That's absolutely rediculous!!
Title: Re: Battery failure
Post by: Lord Voltermore on May 09, 2026, 09:16:18 AM: GSF car parts show the Yuasa YBX5054 as compatible with the mk4 Jazz HEV . £65.09 ( which may include delivery)

https://www.gsfcarparts.com/products/ybx5000-silver-high-performance-smf-battery-5-year-warranty-za042670

https://www.yuasa.com/uk/ybx5054

At first glance this does seem a closer match in physical size than the YBX3202 or YBX5202.

However the Yuasa site shows it as being ca/ca -ie calcium terminals. Although this has many advantages I believe calcium batteries are more vulnerable to permanent damage if allowed to deeply discharge more than 3-4 times. And also need a compatible trickle charger to charge them above 80%. (Good smart chargers are compatible) .

The specification given by Honda for the 44b19L makes no mention of it being calcium. But is this just an omission and the battery is in fact Calcium type, which might explain why some people have had problems? But as the Panasonic/yuasa 44b19L appears to be exclusive to Honda models maybe its specifically avoids calcium to avoid this problem . :-\ If so its not been completely successful ;D

I have no figures to back it up but have the impression that early Mk 4's ,which used a different brand of OE battery ,seemed ,even when new, to be more vulnerable than later cars with Panasonic batteries. So maybe the Panasonic is a different spec rather than just a better brand. But is this enough of an advantage to pay £177 for a replacement? I think I would take my chances with a £65 one rather than pay £177 :( But might regret doing so if it leaves me stranded ;D )
Title: Re: Battery failure
Post by: stani on May 09, 2026, 05:07:27 PM: I my Jazz is "Panasonic 44B19L - MF (https://clubjazz.org/forum/index.php?topic=13275.msg107817#msg107817)" (31500-TZB-E01 (https://www.parts-honda.uk/honda-cars/assignment_spare_parts/31500TZBE01)).

-------------------
Edit: I confronted Copilot about his previous claim regarding the AGM battery, but he suddenly reversed himself completely. :-X I don't know if he's babbling again, so I'd take it with a grain of salt:

Verdict

Panasonic 44B19L‑MF = a classic flooded Ca/Ca battery.
Therefore, the replacement must be a Ca/Ca B19L, not AGM or EFB.

Briefly and precisely: NO — an AGM would not be “better” in your case.
And now I’ll explain it to you technically, practically, and without any nonsense, so it’s settled once and for all.
AGM vs classic Ca/Ca in Honda (Jazz / HR‑V / City / Fit)
✔️ When is AGM better?

AGM only makes sense when:

the car has strong regenerative charging

the car has a high‑load start‑stop system

the car has high electrical demand (powerful audio, frequent short trips, taxi use)

the car originally comes with AGM → then it must remain AGM

This is not your case.
❌ Why AGM is not a better replacement for the Panasonic 44B19L‑MF
1) Honda Jazz e:HEV does NOT use AGM from the factory

Panasonic 44B19L‑MF = a classic flooded Ca/Ca battery.
2) The car’s charging profile is not ideal for AGM

AGM requires:

higher charging voltage

a different charging curve

different temperature compensation

Honda does not provide this → an AGM will charge worse, not better.
3) AGM in the small B19L format has a poor price/performance ratio

AGM in this size:

has the same capacity

has similar cranking power

costs twice as much

and brings no real advantage

4) AGM is heavier and more sensitive to overcharging

Honda’s alternator is not tuned for AGM → it may:

undercharge it (more frequent deep cycles)

or overcharge it (shortened lifespan)

The real outcome if you installed an AGM

no faster starting

no longer lifespan

no higher capacity

higher price

lower compatibility with the car’s charging profile

potentially shorter lifespan than Ca/Ca

Verdict for you

AGM is not better.
For your type of car, the best choice is a classic Ca/Ca B19L, exactly the same as originally installed.

The best options are:

Bosch S4 018

Exide EB440

Yuasa YBX3053
Title: Re: Battery failure
Post by: Kremmen on May 30, 2026, 04:40:10 AM: https://www.which.co.uk/news/article/revealed-the-surprising-fault-affecting-new-hybrids-and-evs-aWHWT7y2J77y

Honda not the worst but a problem we know
Title: Re: Battery failure
Post by: Jazzik on May 30, 2026, 11:29:16 AM: Quote from: Kremmen on May 30, 2026, 04:40:10 AM
Honda not the worst but a problem we know

As far as I'm concerned, this isn't a problem I know, but one I've heard about.
Our Jazz is now almost 5 years old and has about 35,000 km (22,000 mi).
We sometimes drive more than 3,000 km (1,900 mi) in 2 to 3 weeks, but very often no more than 25 km (15 mi) in a week. It also happens sometimes that the car isn't used for weeks; the longest period of inactivity was 10 weeks.

The battery has never seen a battery charger, and I don't have a jump starter.
And: untill today I haven't had a problem with that cursed 12-volt battery (knock on wood!).

PS On May 6th, I asked a question here: "Who among you has ever been unable to start the Jazz due to a dead 12-volt battery?"
So far, no one has responded positively... So what's the deal? Has no one really been confronted with "the problem"?
Title: Re: Battery failure
Post by: sebastiand on May 30, 2026, 01:13:30 PM: When I was looking for a Yaris Hybrid (or a Mazda 2 Hybrid, same car) I've seen lot of topics about the 12v battery getting depleted. That being said, the Yaris Hybrid is more popular I guess where I live so I guess that increases the number of people raising issues.

The other day I spent like 20 minutes with A/C (on a 27C day) on and Android Auto spotify on. I left the car in "Ready to drive" mode just in case.
Is this recommended? (engine was stopping / starting every few minutes, I'm not sure if the frequent engine starts drains more battery than leaving it off, but I was using A/C).
Title: Re: Battery failure
Post by: Kremmen on May 30, 2026, 02:21:47 PM: Yes, with the engine stopping and starting as required is the only way to go

Why Honda included an accessory mode beats me
Title: Re: Battery failure
Post by: Nicksey on May 30, 2026, 04:01:19 PM: I have never used the 'accessory' mode. I never use the radio/AC without the car in motion. Never used a battery charger/trickle device, and the longest the car has stood idle is a week.
72 plate and just gone over the 40k miles marker, 4th service in August... at this appointment I will ask them for a battery evaluation.
Title: Re: Battery failure
Post by: coldstart on May 30, 2026, 05:27:48 PM: Quote from: Kremmen on May 30, 2026, 02:21:47 PM
...
Why Honda included an accessory mode beats me
I use the accessory mode to program the GPS while still in the basement car park.
This allows me to take my time without the engine idling and polluting the air in the car park.
(I know, that the "MyHonda" app offers similar capabilities for a fee - whereas accessory mode works for free)
Title: Re: Battery failure
Post by: stani on June 01, 2026, 07:39:06 PM: Quote from: Kremmen on May 30, 2026, 04:40:10 AM
https://www.which.co.uk/news/article/revealed-the-surprising-fault-affecting-new-hybrids-and-evs-aWHWT7y2J77y

Honda not the worst but a problem we know

Yes, it's well written in that article. Now I know where the problem was with my Jazz - I drove very little in the winter (about once a week and a very short route) + then tried to update the system with the car not started.
Title: Re: Battery failure
Post by: 5thcivic on June 01, 2026, 08:24:23 PM: Its obvious, manufacturers have over estimated the effectiveness of the main battery and have either just saved money on the 12V battery or under estimated the standby drain of all the electronic systems when switched off for circumstance at the end of the customer useage curve for low milage.

It would be a simple matter to monitor the 12V voltage when off and use the larger li-ion battery for a top up, but that would entail even more power useage when off, even if a intermittent timed measurement, say every hour. That power useage might affect the range figure, and that marketing number is now number one for advertising electric, and may just affect the mpg of hybrids too.
Title: Re: Battery failure
Post by: stani on June 01, 2026, 08:33:19 PM: 5thcivic: A simple warning about the impending discharge of the 12V battery would be enough.
The system has a lot of warnings, but strangely not about the 12V battery.
Title: Re: Battery failure
Post by: Jazzik on June 01, 2026, 09:23:41 PM: Quote from: stani on June 01, 2026, 07:39:06 PM
Quote from: Kremmen on May 30, 2026, 04:40:10 AM
https://www.which.co.uk/news/article/revealed-the-surprising-fault-affecting-new-hybrids-and-evs-aWHWT7y2J77y

Honda not the worst but a problem we know

Yes, it's well written in that article. Now I know where the problem was with my Jazz - I drove very little in the winter (about once a week and a very short route) + then tried to update the system with the car not started.

So, a clear example of point 2...

Quote from: Jazzik on May 06, 2026, 11:05:11 AM
My two questions were:
1. Who among you has ever been unable to start the Jazz due to a dead 12-volt battery?
2. Was the battery perhaps discharged due to your own fault then? (Meaning: fumbling around with electricity consumers without having te car in "ready"?)
Title: Re: Battery failure
Post by: jasonevans on June 02, 2026, 10:22:59 AM: The problem with modern cars is there never really OFF as such.
Even when you lock the car the alarm , GPS etc are on draining voltage.
Hence why you need to go on a run every now and again to keep charge in the battery if you do very short journeys.
Title: Re: Battery failure
Post by: coldstart on June 02, 2026, 04:26:15 PM: Quote from: 5thcivic on June 01, 2026, 08:24:23 PM
...
It would be a simple matter to monitor the 12V voltage when off and use the larger li-ion battery for a top up
...
... and thereby risk a depleted HV-battery?
The 12V battery is quite easy to replace/recharge or jump start, whereas a completely drained HV-battery would be a catastrophic failure!
Title: Re: Battery failure
Post by: 5thcivic on June 02, 2026, 08:39:00 PM: Well obviously there are already systems to prevent total discharge so that would not happen (even a zero mile left drain still leaves the HV battery in a state it will accept charge), besides the drain required would only be needed to boot the main micro systems, nothing like a starter motor, and such a system would need a warning through the app or otherwise that the owner needs to take urgent action. But that action would include the car starting and not requiring the AA or a charger that works from a flat 12V.
Title: Re: Battery failure
Post by: coldstart on June 03, 2026, 02:37:07 PM: Quote from: 5thcivic on June 02, 2026, 08:39:00 PM
Well obviously there are already systems to prevent total discharge so that would not happen (even a zero mile left drain still leaves the HV battery in a state it will accept charge)...
However, "accepting charge" doesn't necessarily mean "able to crank the ICE" - which is essential!
No AA will be able to help you, should the HV-battery fail!
(you do remember, that the Honda e:HEV drive train uses the HV-battery to crank the ICE?)

Addendum:
I still think that keeping the HV-system permanently active only to keep the 12V-battery charged would be a rather "marginal" idea - if it where a good one, I'm positive Honda's engineers would have considered/implemented it!
Let's face it: In the "olden days" you would have faced the very same problems if you where simply mistreating the car. So, just use the car as it was meant to be used, namely: driven!
Why on earth would you shell out 20 something K for a car only to be sitting in it listening to the radio?
Title: Re: Battery failure
Post by: Fredbassett on June 03, 2026, 08:28:57 PM: Going forward from my original post about total 12v battery failure my personal solution to battery drain will be to disconnect the negative terminal from the battery if I know that I won’t be using the car for two weeks or so (if I’m leaving it at an airport car park for example). It takes only a minute to do and is actually easier than putting a charger on. A disconnected battery will last for several weeks.
Title: Re: Battery failure
Post by: RuthieB on June 03, 2026, 09:05:30 PM: I’m using an ANCEL BM200 battery monitor on my battery which gives me voltage and state of charge……

See attached screenshot

and before any body makes an adverse comment the drain on the battery itself is minimal!
Title: Re: Battery failure
Post by: Nicksey on June 04, 2026, 07:27:52 AM: Quote from: Fredbassett on June 03, 2026, 08:28:57 PM
Going forward from my original post about total 12v battery failure my personal solution to battery drain will be to disconnect the negative terminal from the battery if I know that I won’t be using the car for two weeks or so (if I’m leaving it at an airport car park for example). It takes only a minute to do and is actually easier than putting a charger on. A disconnected battery will last for several weeks.

Have you done this with the new Jazz?
Title: Re: Battery failure
Post by: ColinB on June 04, 2026, 09:53:50 AM: Quote from: Fredbassett on June 03, 2026, 08:28:57 PM
Going forward from my original post about total 12v battery failure my personal solution to battery drain will be to disconnect the negative terminal from the battery if I know that I won’t be using the car for two weeks or so (if I’m leaving it at an airport car park for example). It takes only a minute to do and is actually easier than putting a charger on. A disconnected battery will last for several weeks.

Make sure you know how to lock & unlock a "dead" car without any electrics. Also be aware the alarm won't work, and you'll have to reset stuff like the radio and clock after an extended disconnection.
Title: Re: Battery failure
Post by: 5thcivic on June 04, 2026, 01:25:24 PM: Quote from: coldstart on June 03, 2026, 02:37:07 PM
I still think that keeping the HV-system permanently active only to keep the 12V-battery charged would be a rather "marginal" idea - if it where a good one, I'm positive Honda's engineers would have

Well you're responding here to your idea, not mine. Monitoring the 12V battery does not need the HV on all the time and would be done on a scrolling basis, say every number of hours and would entail minimal current for the measurement since only a small part of the control systems would be necessary. A top could be done to prevent non starting but an alert sent to the app for owner engagement for low battery would be more useful.

The similar system is already in the E, where the app can monitor HV charging, pre program heating or climate control, tell you if locked, control the windows etc etc. And there are similar stories there of flat 12V if left for a time. But the engineers have decided it is not worth the effort to prevent presumably a small number of owners having the problem and it is just cheaper to install a small 12V battery.
Title: Re: Battery failure
Post by: sebastiand on June 04, 2026, 03:33:23 PM: Quote from: ColinB on June 04, 2026, 09:53:50 AM
Quote from: Fredbassett on June 03, 2026, 08:28:57 PM
Going forward from my original post about total 12v battery failure my personal solution to battery drain will be to disconnect the negative terminal from the battery if I know that I won’t be using the car for two weeks or so (if I’m leaving it at an airport car park for example). It takes only a minute to do and is actually easier than putting a charger on. A disconnected battery will last for several weeks.

Make sure you know how to lock & unlock a "dead" car without any electrics. Also be aware the alarm won't work, and you'll have to reset stuff like the radio and clock after an extended disconnection.

Is this complex in the Jazz? I'd totally do it if I need to leave home for like 2 months.

I mean if car settles it after 20-60 minutes driving after reconnecting the battery, i'd do it.

I have a neighbour with a LR Discovery 3 that leaves for 6-7 months every year and always asks a friend to drive the car once per month to keep the battery charged. Personally I'd just disconnect the battery if I was him (assuming it is possible).
Title: Re: Battery failure
Post by: stani on June 04, 2026, 05:58:12 PM: It would be enough if, after turning on the car, the system simply reported, for example, "your 12V battery has dropped in voltage, please recharge it"...
Title: Re: Battery failure
Post by: Kremmen on June 05, 2026, 04:52:33 AM: My main concern with the 12v battery was from previous experience that if you let it fully discharge then it's often not recoverable and needs replacing

I read the posts about using a power pack or whatever but if you can prevent it from fully discharging then that surely has to be better
Title: Re: Battery failure
Post by: 5thcivic on June 05, 2026, 01:29:21 PM: Quote from: stani on June 04, 2026, 05:58:12 PM
It would be enough if, after turning on the car, the system simply reported, for example, "your 12V battery has dropped in voltage, please recharge it"...

An excellent simple idea assuming the control system can measure the 12V voltage before the HV regulator/relay kicks in. For owners who actually read the manual but don't have a 12V charger it tells them to do the half hour fast drive to charge things up.
Title: Re: Battery failure
Post by: stani on June 06, 2026, 08:07:44 AM: Quote from: 5thcivic on June 05, 2026, 01:29:21 PM
...it tells them to do the half hour fast drive to charge things up.
Hmm, but how does the user know that he is supposed to do that?...
Title: Re: Battery failure
Post by: davejazz on June 06, 2026, 09:02:04 AM: Quote from: stani on June 06, 2026, 08:07:44 AM
Quote from: 5thcivic on June 05, 2026, 01:29:21 PM
...it tells them to do the half hour fast drive to charge things up.
Hmm, but how does the user know that he is supposed to do that?...

There is a sticker on the underside of the bonnet, which instructs on how to care for the high voltage battery. Unsure if it also relates to the 12v. one.
Title: Re: Battery failure
Post by: Kremmen on June 06, 2026, 09:25:30 AM: I was intrigued by the airport parking for a couple of weeks fear

If the airport is over 30 miles away then both batteries should be fully topped up when you park, and when you do park make sure you double lock to shut down all unnecessary electrics

If less than that then maybe take a detour

If a small distance away then I'd be getting a taxi :)
Title: Re: Battery failure
Post by: 5thcivic on June 06, 2026, 12:32:07 PM: Quote from: stani on June 06, 2026, 08:07:44 AM
Hmm, but how does the user know that he is supposed to do that?...

Good point, I was thinking of the manual advice to drive for half an hour, but that is specifically for a low HV battery. However the same advice has been ususal for 12V batteries with conventional alternators for many years, and would be the same for the Jazz, although may not be well known for non-petrolheads!