12 Volt Battery Failures in BYD Atto 3 and other EVs

Forums › Transport (cars, bikes and boats) › 12 Volt Battery Failures in BYD Atto 3 and other EVs

arthurgeek

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#303207 24-Jan-2023 16:16

A friend owns a Peugeot e-208 GT and he told me that his car broke down recently because the 12V battery had failed. The dealer managed to replace the battery, but this made me wonder whether other EVs have experienced 12V battery failures?

I then found that there have been a lot of breakdowns due to 12V battery failures in the new BYD Atto 3, which arrived in NZ around August 2022. Some members of a FB group have reported that the battery management system (BMS) of the Atto 3 has not been adequately charging the 12V battery and just about every day an owner reports that their Atto has broken down due to the 12V battery failing. Apparently BYD has explained that when the vehicles were being freighted to NZ the batteries discharged to lower than expected levels and that the BMS couldn't recharge the batteries back to full capacity. The BMS is apparently being upgraded to check the 12V battery more often and charge it up for double the amount of time, and an OTA is due out soon.

So, do all EVs have problems with keeping the 12V battery fully charged, and if so, what are the main reasons why this is happening? Should EV owners invest in a battery charger and a jump-starter and check the state of charge of the 12V battery regularly?

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meow
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#3026741 24-Jan-2023 22:55

I know a few people with BYD Atto 3's who have never had an issue. Also, the issues on the pages are a very very small percentage of owners who have the Atto 3 and not all will be experiencing the issue.

Also note that there is a post (https://www.facebook.com/photo/?fbid=5918547241544910&set=gm.500986602146988&idorvanity=353628693549447) indicating this is caused by a software issue that will be corrected soon.

I'm personally a Tesla owner and have never had issues. I know many people with EV's who have never had issues either. I've heard about more battery issues from ICE cars than I have from EV's due to the fact with ICE cars the battery gets considerably more load and once that fails you are not going anywhere. I know with the Tesla the low voltage battery can fully die and the inverter will power the entire car allowing you to still drive.

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Batman

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#3026801 25-Jan-2023 06:29

in my leaf when i do climate pre conditioning it uses the 12V battery - basically everything the car does when the "engine" is not "started" drains the 12V. even when plugged in. so i don't precondition! lol

maybe that's the issue?

i don't know .... just a thought

arthurgeek

10 posts

Wannabe Geek

#3026802 25-Jan-2023 06:58

michaelmurfy:

I know a few people with BYD Atto 3's who have never had an issue. Also, the issues on the pages are a very very small percentage of owners who have the Atto 3 and not all will be experiencing the issue.

Thanks Michael, and that's very interesting info about your Tesla. With regard to the number of Atto 3 owners who have experienced breakdowns due to 12V battery issues, a recent FB posting quoted an email sent to owners from BYD which said that: "There are a small number of customers experiencing flat 12v batteries in their vehicles (By small, approx. 1 per day)."

Now 1 per day, or 30 possible breakdowns per month is a relatively small number, but over the period the Atto 3 has been on sale, this could amount to about 150 vehicles that have been affected.

CYaBro

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#3026803 25-Jan-2023 07:03

Never had an issue in our gen1 MG ZS EV and 23k of driving.

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RunningMan

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#3026808 25-Jan-2023 07:18

The 12v battery serves the same purpose in an EV and ICE vehicle - it provides the intial energy to get the vehicle to a state ready to drive, and provides a resevoir of energy to run the accessories. A flat or defective 12v battery will give the same problems in an EV to an ICE - you probably won't be able to get the vehicle going, and all the accessories (including remote/electric door unlocking) won't work. The 12v is then charged via an alternator (modern ICE) or DC:DC converter (EV).

BYD may have identified a specifc issue with theirs under charging a little, but no, it's not a common issue any more for an EV than any other vehicle.

Tesla are slighly different in some ways as if things like sentry mode are active (with a corresponding continuous 12v draw) they will charge the 12v from the traction battery even with the car off in most circumstances. There's a moderately famous report from James May of being locked out of his Tesla because the 12v went flat.

So yes, you do need to check the 12v occasionally, but no more or less than an ICE vehicle. It's no different to all the other bits on a vehicle that aren't directly related to the motive power - electronics, suspension, wheels, tires etc.

SteveXNZ

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#3026817 25-Jan-2023 07:44

I’m one of the small but significant number of Atto 3 owners who’s had a 12V battery failure out of the blue. I was able to get going immediately with a lithium jump starter and my dealer swapped the battery out that day, so no major issue, but it has generated considerable noise and speculation on the Atto FB pages both here and Australia, and other EVs have a similar problem so it’s not isolated to BYD.

After investing in a battery monitor I think we have four key root causes working together:

The 12V battery in an EV is small (low Ah rating) as it doesn’t need to deliver cranking amps to a starter motor. Anything to save weight in an EV is a good thing, but it means there’s not a lot of reserve capacity
There is a constant current draw even when the car is turned off just to keep the comms and sensors running. In particular I’ve noticed there is a heavier than normal draw when the charging cable is plugged in waiting for a scheduled charging session to start. There seems to be significant interaction between the car’s BMS and the EVSE over this period
While in transit from China some batteries have degraded. Yet some unfortunate owners still have problems after their battery has been replaced
The BMS is not aggressive enough in checking the state of the 12V battery and recharging it from the traction battery. BYD are releasing a firmware fix for this issue in early February. This will increase the frequency of checks and top-ups, but doesn’t mention whether the low voltage threshold (around 11.5V) will be changed. In ICE-land a battery reading under 12V is suspect, but EVs with their lighter current draw may be able to get away with a lower voltage threshold in normal use.

BYD also claim there is a compatibility issue between the Atto and some EVSEs. This doesn’t ring true to me, but I have little evidence either way. In my case I have a Wallbox Pulsar which is recommended by BYD dealers, yet I still had a problem.

So my recommendation to EV owners is to keep a lithium jump starter handy. They are much more convenient than jumper leads from another car, and they’ll start an ICE too. Not a lot of point checking the battery as in normal use it will range from 12.6V after charging to 11.5V after a period of inactivity.

Operationally, don’t keep the charging cable plugged in unused for long periods, and minimise other battery demand, eg by keeping the key fob well away from the car when parked.

lchiu7

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#3026957 25-Jan-2023 13:30

It is a known, albeit lowish frequency on the ATTO3.

BYD has acknowledged the potential issue and sent out this comms to registered owners (extract here)

What is the issue?

During shipping some of the 12v batteries discharged to lower than expected levels, causing some vehicles to be unable to recharge batteries back to full capacity.
Some “Home AC Chargers” (Not the emergency charger provided) have compatibility issues with the ATTO 3 and are draining the battery

What is BYD Auto NZ doing?

Our next OTA update includes changes to the battery management system, meaning the cars computer will check the battery twice as often as it is currently and charge it for double the amount of time. We expect this to roll out to customers during the first week of February.

So they know about the problem and have taken action

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jonathan18

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#3026998 25-Jan-2023 15:13

SteveXNZ:So my recommendation to EV owners is to keep a lithium jump starter handy. They are much more convenient than jumper leads from another car, and they’ll start an ICE too.

I have a lithium powered jump starter in the boot of my car, left over from my ICE ownership days, but TBH I’ve not researched whether these work with the 12v lithium battery Tesla now ship in their cars. Can anyone confirm whether there’s anything different in jump-starting these?

(Not that I’ve had a problem with mine; similarly, my wife’s never had a problem with the 12v in her Leaf, and that battery was in it when we bought it over four years ago. I do understand that not all Leaf owners have had the same experience, though!)

arthurgeek

10 posts

Wannabe Geek

#3027068 25-Jan-2023 16:44

SteveXNZ:

I’m one of the small but significant number of Atto 3 owners who’s had a 12V battery failure out of the blue. I was able to get going immediately with a lithium jump starter and my dealer swapped the battery out that day, so no major issue, but it has generated considerable noise and speculation on the Atto FB pages both here and Australia, and other EVs have a similar problem so it’s not isolated to BYD.......

Thanks Steve for your informative post. I've been following the posts on the FB group "BYD ATTO3 NZ group" and I think anyone who wants to fully understand the 12V battery problem (and several other Atto 3 issues) should read through the posts in this group. There is great support there and it's pleasing that BYD have taken a positive and helpful approach.

It's interesting that owners who often use the slow "granny charger" to charge up the main battery of the Atto 3 do not appear to have experienced 12V battery failures to the same extent as those who use fast chargers.

I agree with your recommendation to EV owners to keep a lithium jump starter handy, but perhaps this also applies to ICE owners?

arthurgeek

10 posts

Wannabe Geek

#3027071 25-Jan-2023 16:50

RunningMan:

The 12v battery serves the same purpose in an EV and ICE vehicle - it provides the initial energy to get the vehicle to a state ready to drive, and provides a resevoir of energy to run the accessories....

Thanks for your interesting post and I couldn't believe what happened when James May was locked out of his Tesla because the 12V battery went flat! I guess this could no longer happen with new Teslas on sale in NZ now?

arthurgeek

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Wannabe Geek

#3027072 25-Jan-2023 16:56

lchiu7:

It is a known, albeit lowish frequency on the ATTO3. ...

Thanks for this update. I was impressed to read that BYD sincerely apologised to affected owners and wished to assure them that they are working hard to resolve these issues.

Obraik

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#3027073 25-Jan-2023 16:58

Since early 2022, Tesla switched from the traditional 12v lead acid battery to a 15v lithium battery in all their vehicles, mostly to resolve the inevitable reliability issue that comes from the traditional batteries. If you have a Tesla with the Ryzen processor for its infotainment (visible in the "About" screen of your car settings) then you have this.

That's not to say they're immune to fault, but it should be a lot less than a lead-acid.

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RunningMan

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#3027079 25-Jan-2023 17:25

arthurgeek:I agree with your recommendation to EV owners to keep a lithium jump starter handy, but perhaps this also applies to ICE owners?

I think this is an overreaction. Atto aside, where there is a known issue and fix on the way, modern vehicle reliability is very high, and most stop accidental battery discharge by preventing you leaving lights on and powering stuff down when not needed. The 12v battery will have a finite life in any vehicle and eventually fail and need replacement. The jump start kit is just a sticking plaster solution instead of addressing the underlying issue - replacing a dead battery (or fixing the charging system). The older the vehicle/battery, the more likely it will fail soon so get it checked as the vehicle ages and replace as needed.

Of course, if you're venturing far away from easy help and completely reliant on your own resources to solve a breakdown, then it's not a bad thing to have on hand, but I'd probably rate having a spare tyre higher up the list, and a lot of vehicles don't have those any more.

afe66

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#3027220 26-Jan-2023 07:57

My leaf lasted 8 yrs on its original battery.

If the BYD battery is low from long shipment times, vcan you connect it to a 12v battery charger?

The advantage if using 12v systems is cheaper as shares the system with all those ice cars

arthurgeek

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#3027225 26-Jan-2023 08:11

afe66: My leaf lasted 8 yrs on its original battery.

If the BYD battery is low from long shipment times, vcan you connect it to a 12v battery charger?

The advantage if using 12v systems is cheaper as shares the system with all those ice cars

Yes, several BYD Atto 3 owners have reported buying 12V battery chargers so they can regularly monitor the state of health of the 12V battery and charge it up when necessary. Owners who have done this have apparently not experienced breakdowns of the 12V battery.

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