Battery failure

[Lord Voltermore]

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?

[stani]

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.

[exAudi]

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.

[stani]

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. 

[stani]

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?

[exAudi]

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.

[John Ratsey]

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.

[MikeRO]

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.

[stani]

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)?

[stani]

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 that EUFAB 16620 should be more accurate...But it only shows percentages.

Or KONNWEI KW208.
Or wireless ANCEL BM200 permanently connected to the battery.

[Lord Voltermore]

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!  (Ultra reliable of course    )   

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  A cup of tea will do. I am not a robot.

[stani]

Panasonic 44B19L MF.

Otherwise, I see that there is already a similar thread on the topic.

[Lord Voltermore]

This site shows the Yuasa reference number connection 

https://www.parts-honda.uk/honda-cars/assignment_spare_parts/31500TG5G01

[stani]

My search shows that "31500-TZB-E01" (Panasonic 44B19L MF) is for the 2021 Jazz Hybrid EXECUTIVE....
Is there a different battery for the Elegance?

[Lord Voltermore]

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.