12V battery after long stand-still

[Jazzik]

I have no doubt people will think it is a great idea to keep the Li-Ion battery on their care absolutely 100% charged all the time, when in reality that will kill the battery pretty quick.

Yep, my Smartphone has an option to limit charge to 85% to prolong battery life.

Fortunately, at Honda (just like at Toyota, by the way) they have equipped our hybrids with "brains".


When the indicator shows 10 green bars, the battery is charged to about 80%, with 3 bars the charge is still about 40% (and the ICE switches on to recharge the HV battery).
You will never manage to charge the HV battery to 100% or discharge it to 0%.

But of course, this topic was about our 12V battery (that's charged by the HV battery) so this is a bit off topic...

[culzean]

Even at 80% a Li-ion still not happy,  they actually like around 45% for max life...  So an EV battery likes to live between 40% to 80 %,  which is like having a fuel tank of 50 litres that you can only fill to 40 litres but not empty below 20 litres....

https://www.eyerys.com/articles/40-80-rule-battery-charging-dealing-lithium-based-chemical-problems

[Jazzik]

So an EV battery likes to live between 40% to 80 %,  which is like having a fuel tank of 50 litres that you can only fill to 40 litres but not empty below 20 litres....

Let me guess: You have a "pure ICE" powered car with at least a 50 liter fuel tank, which you fill to the neck and then empty it to half a liter... 

By the way... what's your point?

[culzean]

So an EV battery likes to live between 40% to 80 %,  which is like having a fuel tank of 50 litres that you can only fill to 40 litres but not empty below 20 litres....

Let me guess: You have a "pure ICE" powered car with at least a 50 liter fuel tank, which you fill to the neck and then empty it to half a liter... 

By the way... what's your point?

It does not damage my fuel tank if I overfill or run to empty.  Does an EV with a 100KW battery only actually have a 60KW usable battery ? ( 20 to 80KW ) with a 'limp home' button to access the last 20% in an emergency ? - I know there are algorithms in EV that allow more than 80 and less than 20 % to be used as the battery ages, which will obviously more rapidly age the battery as those areas get used...

[Jazzik]

It does not damage my fuel tank if I overfill or run to empty.  Does an EV with a 100KW battery only actually have a 60KW usable battery ? ( 20 to 80KW ) with a 'limp home' button to access the last 20% in an emergency ? - I know there are algorithms in EV that allow more than 80 and less than 20 % to be used as the battery ages, which will obviously more rapidly age the battery as those areas get used...

About the aging of the EV batteries:

Toyota bZ4X EV debuts in Europe – 1 million km batt warranty. https://www.wapcar.my/news/toyota-bz4x-ev-debuts-in-europe-%E2%80%93-1-million-km-batt-warranty-remote-parking-37521

71.4 kWh battery to be offered with 1-million km / 10-year warranty

and: https://insideevs.com/news/531990/toyota-bz4x-battery-capacity-durability/
Toyota announced, by the way of a broader conference about batteries and electrification, that its new electric cars will have significantly more durable batteries.

The target set for the upcoming Toyota bZ4X and following BEVs is 90% of initial battery capacity (and range) maintained over 10 years of usage.

...but since we are talking about the Honda Jazz Mk4 here, not EV or "pure ICE", my suggestion is:

[Bristol_Crosstar]

So an EV battery likes to live between 40% to 80 %,  which is like having a fuel tank of 50 litres that you can only fill to 40 litres but not empty below 20 litres....

Let me guess: You have a "pure ICE" powered car with at least a 50 liter fuel tank, which you fill to the neck and then empty it to half a liter... 

By the way... what's your point?

It does not damage my fuel tank if I overfill or run to empty.  Does an EV with a 100KW battery only actually have a 60KW usable battery ? ( 20 to 80KW ) with a 'limp home' button to access the last 20% in an emergency ? - I know there are algorithms in EV that allow more than 80 and less than 20 % to be used as the battery ages, which will obviously more rapidly age the battery as those areas get used...

We have an EV and it has a 37Kw battery of which 34Kw is usable so even when the dash is showing 100% charge there is 3Kw left, this stops it being overcharged and I think most other modern EV's behave in a similar manner. If it's filled to 100% you're not meant to leave it unused for any length of time so this is only done if you're planning a long trip the next day, for example. We normally use it for local trips only so wait for it to get down to 25% then charge it up to 75% and this works fine for us, we don't have to charge it more than once a week at most.

[PWV]

Applicable to the new mk IV Jazz ehev 202Omodel only.

The 12V battery showing 12.8V is fully charged, if it drops over 72 hours to 12.25 (about 50%) that is worrying!  This begs several questions:
1.  What is the normal parasitic drain on the Jazz 12V battery?
2.  Is it possible to minimise this eg by switching off some items?
3.  What is the effect of disconnecting the 12V battery (when leaving it for long periods)  and does it do any harm. 
4. Can a external charger be connected whilst the battery is still connected to the car or should it be disconnected?

Anyone got any reliable answers for the appropriate car.

[sportse]

Re point 2 , I don’t think so on the Jazz.

In my previous Toyota hybrids you could disable the keyless entry and start system to save power when storing the car. They automatically switch into a low power mode anyway after a week or so of not being used but by doing this it saved some extra power.

I couldn’t see the equivalent setting on the Jazz.

[John Ratsey]

There's some relevant discussion at https://clubjazz.org/forum/index.php?topic=13275.0 .

Also, I never bother with disconnecting the battery before connecting an intelligent charger.

[Bristol_Crosstar]

Applicable to the new mk IV Jazz ehev 202Omodel only.

The 12V battery showing 12.8V is fully charged, if it drops over 72 hours to 12.25 (about 50%) that is worrying!  This begs several questions:
1.  What is the normal parasitic drain on the Jazz 12V battery?
2.  Is it possible to minimise this eg by switching off some items?
3.  What is the effect of disconnecting the 12V battery (when leaving it for long periods)  and does it do any harm. 
4. Can a external charger be connected whilst the battery is still connected to the car or should it be disconnected?

Anyone got any reliable answers for the appropriate car.

I have charged my Crosstar's 12V battery with a 2V trickle charger without disconnecting the battery and this hasn't caused any problems.

[Kremmen]

Same here.

I remember a post last year that indicated a CTEK problem when the negative lead was not connected directly to the negative terminal.

I had that twice where even after many hours, the CTEK was stuck on the final orange light and refused to go to green finished.

I changed it to the negative post and it completed within minutes.

[Lord Voltermore]

Applicable to the new mk IV Jazz ehev 202Omodel only.

The 12V battery showing 12.8V is fully charged, if it drops over 72 hours to 12.25 (about 50%) that is worrying!  This begs several questions:
1.  What is the normal parasitic drain on the Jazz 12V battery?
2.  Is it possible to minimise this eg by switching off some items?
3.  What is the effect of disconnecting the 12V battery (when leaving it for long periods)  and does it do any harm. 
4. Can a external charger be connected whilst the battery is still connected to the car or should it be disconnected?

Anyone got any reliable answers for the appropriate car.

I  cant give expert answers.  But the relatively small 12v 'utilities' battery discharging fairly rapidly happens to many hybrids and ev's, not just the jazz.
I have just been out and checked mine, it was reading 11.8 volts  ,despite a long run only a few days ago.  The car started  without problem at which point the voltage goes up to 14.4 volts - ie being charged by the HV battery.

Others have reported similar  , I am hoping its normal and does not cause long term problems for this type of battery.    But its a bit worrying when compared  conventional car 'starter' batteries which are regarded as discharged when below 12.4 volts.

Modern cars have a relatively high parasitic drain.  The alarm system, various computers and I think the car sends out a constant signal to detect the proximity of keyless entry transponders.

I cant comment on disconnecting the battery.  I wouldnt do it.

Leaving a charger  connected long term  may be ok as  long as it is a modern 'smart' charger  that can detect and adapt  to the specific battery type and state of charge . But not a conventional 'trickle' charger that you may have had for years.   It shouldnt be a problem clipping direct to the battery terminals whilst its still connected .  If you plan to do use a charger regularly its better to fit permanent leads with a special connector block that connects to the same on the  charger lead.  Quick and simple. You could even arrange it so there is no need to lift the bonnet.  Many smart chargers include this connector. 

A car that gets regular use  will probably be ok.  But if you want to prepare for the possibility of a flat battery, after a long stay in an airport car park for instance  , you could consider a  small power bank type jump starter that are small enough to keep in the car  . Like this 
https://www.ebay.co.uk/itm/234467400292?_trkparms=amclksrc%3DITM%26aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3Dea69b24a589a4e2fb355fbc1ecc059fb%26pid%3D100675%26rk%3D3%26rkt%3D15%26sd%3D124881738405%26itm%3D234467400292%26pmt%3D0%26noa%3D1%26pg%3D2380057%26brand%3DUnbranded&_trksid=p2380057.c100675.m4236&_trkparms=pageci%3A6f03c39d-ae7f-11ec-b585-22014976eb4d%7Cparentrq%3Ad002575f17f0a0f310e647b5fffaa65e%7Ciid%3A1

When I was looking  back in October these were available from about £22.   There are currently (excuse pun)  not many under £30.   I dont know if prices will drop again once demand drops in the summer.

[Kremmen]

I wonder how many of us double/deadlock the car ?

I also wonder if the same still applies that double locking shuts down additional systems and presumably helps the battery ?

[PWV]

Thanks for all responses, and in advance for future responses.
Thanks to John for the link.
Nothing definitive some contrasting experiences.
I pick up the car in June and will be reading the manual.
The telematics issue is a good point, I hadn't decided whether to authorise it or not.

[Jazzik]

Maybe double locking shuts down additional systems and prevents the battery from losing voltage quickly? I really wouldn't know, but...
I always double lock the Jazz, as I did the Yaris Hybrid (also "famous" for its small 12V battery). Next to that I always switch off the key, to avoid scanning and to save the key's battery.
Never had any issues with the battery (or any other issue ). Never measured voltage, never used a charger (which is gathering dust in the garage). It was and is getting into the car, safety belt, pressing the brake and starting.

So... whoever knows the answer, please post it here!