Catastrophe After One Week

[voxel]

VW is replacing all 12V ID.4 batteries with lithium based ones and Tesla is shipping new 3s and Ys with 15V lithium ones. The argument I’ve heard is that the DC to DC converter from HVB to LVB is pushing too many amps for regular 12V batteries and toasting them. Unsure how much that’s is true but EV carmakers are moving to lithium 12V/15V LVBs. EV6 sounds like it is suffering from many 12V failures too.

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[Jbkimmel]

This is a good starting point, but it's a little misleading with the MME because if there's any load on the system (like the frunk light), it will measure pretty low. And even at rest with no load, the voltage seems to get pretty low before the DC/DC converter kicks in, so low voltage alone doesn't necessarily mean the battery is unhealthy.

So how low can it go before I should worry that it’s an actual problem with the battery holding the charge? Thanks.

 

[OWG]

This is a good starting point, but it's a little misleading with the MME because if there's any load on the system (like the frunk light), it will measure pretty low. And even at rest with no load, the voltage seems to get pretty low before the DC/DC converter kicks in, so low voltage alone doesn't necessarily mean the battery is unhealthy.

But we are discussing what happens over an extended period of just sitting (chip hold, or oadesign's sitting for 41 days).

Do we know what SoC the vehicle is in when built? When it was parked? If the HVB is significantly discharged that will have some impact on the HVB's ability to maintain the LVB.

The bright side is that AGM tolerate deeper discharges than flooded batteries, sulfation caused by sitting discharged for protracted periods is a real concern. Fighting Sulfation in AGMs - Practical Sailor (practical-sailor.com)

 

[generaltso]

So how low can it go before I should worry that it’s an actual problem with the battery holding the charge? Thanks.

I've seen mine dip down as low as 11.9V. But then the DC/DC converter kicks on and brings the voltage back up. If the voltage doesn't come back up, then you have a problem.

 

[generaltso]

Do we know what SoC the vehicle is in when built? When it was parked? If the HVB is significantly discharged that will have some impact on the HVB's ability to maintain the LVB.

No, we don't. We also don't know if the cars are put into transport mode when they're parked or if the LVB is even left connected. I just think it's a leap to assume that if a car has been sitting on hold for a couple of months it automatically means the LVB is likely toast. It's possible, but not so likely that everyone should be demanding a new 12V battery just in case.

 

[Jbkimmel]

Before this discussion, I had no clue that a 12V battery would be anything other than 12V - and I would have thought that sulfation had something to do with wine. Steep learning curve!

 

[67 Stang Convertible]

You may want to get a 12V meter and keep it plugged into the socket under the armrest. Many of us keep one. A quick glance and you know the state of your 12V battery.

Like this one:
https://www.amazon.com/Charger-Adapter-AINOPE-Cigarette-Compatible/dp/B08138GVMH/ref=sr_1_6?crid=8XD8ICR98T9P&keywords=12v+cigarette+lighter+meter&qid=1641564539&sprefix=12v+cigarette+lighter+meter,aps,91&sr=8-6

(yeah I couldn't find one on Amazon without USB plugs LOL).

Great tip. I just ordered. Thx!!!

 

[bruceski88]

No, we don't. We also don't know if the cars are put into transport mode when they're parked or if the LVB is even left connected. I just think it's a leap to assume that if a car has been sitting on hold for a couple of months it automatically means the LVB is likely toast. It's possible, but not so likely that everyone should be demanding a new 12V battery just in case.

Mine sat in my garage for 3 weeks that was between 35F. and 55F for 3 weeks while we were out of town. Went into deep sleep and when we came back it was still at 80% charge. Woke up and and everything was normal. Was impressed because my Honda CRV can become non functional in the same amount of time if it isn’t on a battery tender

 

[ARK]

What I don’t quite understand is how the LVB battery could die while the vehicle is on and moving.

I understand the concept of a battery being unable to hold a charge where, for example, after you jump an ICE and drive around a lot, you turn it off, and have a totally dead battery again the next day. But even with an ICE vehicle like that, I’ve never heard of the 12v battery dying while the vehicle is being driven.

Even if the AGM battery was having trouble holding a charge, shouldn’t that just mean the HVB had to be unusually active in constantly trying to top off the 12v battery?

Is there something unique about AGM 12v LVBs that makes them so unlike normal lead-acid batteries, where they can die in the middle of use?

Or could it be something different about how a HVB charges a LVB versus how an alternator charges a battery in an ICE, where the car might not realize the LVB is dangerously depleted and fails to send power from the HVB to the LVB even while moving (basically, a software issue)?

 

[chrisGT]

VW is replacing all 12V ID.4 batteries with lithium based ones and Tesla is shipping new 3s and Ys with 15V lithium ones. The argument I’ve heard is that the DC to DC converter from HVB to LVB is pushing too many amps for regular 12V batteries and toasting them. Unsure how much that’s is true but EV carmakers are moving to lithium 12V/15V LVBs. EV6 sounds like it is suffering from many 12V failures too.

I think they install them because they are small and light so it saves weight and space.
I had a Taycan with a Lithium 12v Battery and it was not a pleasant experience. Let's just say that there were at least as many bricked Taycans as MMEs because these batteries were tiny and very easily discharged by the various software bugs. This is one of the noumerous threads about it in the Taycan forum. Also the first Taycans had Li batteries with a firmware bug (firmware inside the 12v battery) that was not computing correctly the state of charge so they where bricking on after the other. Porsche replaced 575 of them in the US (Porsche campaign WLE3).
Last but not least you should not use your regular jump starter to jump an Li battery because of fire risk.

 

[Jbkimmel]

Great questions, ARK - I hope someone enlightens us both on that. In part because my service rep just told me the battery is reading normal on their diagnostic device. They jumped it in order to drive into the shop, observed no problems or warnings, and now want to keep it over the weekend (outside) before taking another look on Monday. I guess I’m just skeptical that it didn’t even need a nice long charging and conditioning session, much less anytime else. Would a jump really be enough to make everything right long-term? ?

 

[voxel]

I think they install them because they are small and light so it saves weight and space.
I had a Taycan with a Lithium 12v Battery and it was not a pleasant experience. Let's just say that there were at least as many bricked Taycans as MMEs because these batteries were tiny and very easily discharged by the various software bugs. This is one of the noumerous threads about it in the Taycan forum. Also the first Taycans had Li batteries with a firmware bug (firmware inside the 12v battery) that was not computing correctly the state of charge so they where bricking on after the other. Porsche replaced 575 of them in the US (Porsche campaign WLE3).
Last but not least you should not use your regular jump starter to jump an Li battery because of fire risk.

In VW’s case I don’t think it weight savings reason. If they wanted to trim weight they’d re-engineer the steel hood which is insanely heavy. The ID.4s have suffered from random electrical glitches which I think VW suspects is low voltage from the current 12V battery.

For Tesla it could be new CPU related reasons. They put more powerful chips in the latest 3 and Y update (2022 models). There have been third party lithium battery drop ins for Tesla for a while now.

 

[chrisGT]

In VW’s case I don’t think it weight savings reason. If they wanted to trim weight they’d re-engineer the steel hood which is insanely heavy. The ID.4s have suffered from random electrical glitches which I think VW suspects is low voltage from the current 12V battery.

For Tesla it could be new CPU related reasons. They put more powerful chips in the latest 3 and Y update (2022 models). There have been third party lithium battery drop ins for Tesla for a while now.

For VW, I think it makes sense to have all EVs in the VW-group to use the same 12v electrical system and reuse components and software.
I know Porsche started using Li batteries in 911s almost a decade ago, well before the Taycan, and the reason was weight savings (22lb savings) and not electrical related.
https://www.porsche.com/usa/aboutporsche/pressreleases/pag/?pool=international-de&id=2009-11-23-02

 

[Mach-Lee]

What I don’t quite understand is how the LVB battery could die while the vehicle is on and moving.

I understand the concept of a battery being unable to hold a charge where, for example, after you jump an ICE and drive around a lot, you turn it off, and have a totally dead battery again the next day. But even with an ICE vehicle like that, I’ve never heard of the 12v battery dying while the vehicle is being driven.

Even if the AGM battery was having trouble holding a charge, shouldn’t that just mean the HVB had to be unusually active in constantly trying to top off the 12v battery?

Is there something unique about AGM 12v LVBs that makes them so unlike normal lead-acid batteries, where they can die in the middle of use?

Or could it be something different about how a HVB charges a LVB versus how an alternator charges a battery in an ICE, where the car might not realize the LVB is dangerously depleted and fails to send power from the HVB to the LVB even while moving (basically, a software issue)?

There isn't anything that special about an AGM that would cause this, I think it has to just be faulty programming that isn't always turning on the DC/DC converter when it's needed. Ford has been using AGM batteries in other cars (like the Escape) for a while now without major issues.

If you have an alternator suddenly fail, your car will die while driving about 20-30 minutes later. It's rare but I've seen that happen. Another potential failure is a cracked bus bar inside the battery, this will cause a loss of power going over a bump when the crack opens, but the battery will appear and test totally fine afterwards. But if you smack the battery (carefully) it can drop out. Hard to diagnose.

Great questions, ARK - I hope someone enlightens us both on that. In part because my service rep just told me the battery is reading normal on their diagnostic device. They jumped it in order to drive into the shop, observed no problems or warnings, and now want to keep it over the weekend (outside) before taking another look on Monday. I guess I’m just skeptical that it didn’t even need a nice long charging and conditioning session, much less anytime else. Would a jump really be enough to make everything right long-term? ?

They can't replace the battery under warranty if it tests good. Personally I'm not convinced the batteries are actually bad in most cases, I think it's the charging system not maintaining the battery at a high enough charge level sometimes for unknown reasons. These batteries seem to be fine after charging them. Cold seems to exacerbate the low charging problems. Even if you car is fine on Monday, I would encourage your dealer to submit a concern report in PTS regarding the incident so engineering gets a record of it. I think we need a TSB fix for this issue so it has to get reported up the chain.

Not sure if you saw this, but I reccomend you do a long charge when you get your car back to be safe. https://www.macheforum.com/site/threads/how-to-recondition-service-your-12v-battery.11069/

If you're worried about being stranded again, I recommend you buy a Gooloo jump starter and familiarize yourself with removing the funk panels to access the jump points. I've verified they have enough initial power to jump start successfully unlike other brands like NOCO which use a lower voltage that isn't as effective.

Last thing you can ask for are updates. I don't have any definitive information that the 12V charging has been updated for Job 2 vehicles yet, but it wouldn't hurt updating the powertrain modules in case.

 

[kltye]

If you're worried about being stranded again, I recommend you buy a Gooloo jump starter and familiarize yourself with removing the funk panels to access the jump points. I've verified they have enough initial power to jump start successfully unlike other brands like NOCO which use a lower voltage that isn't as effective.

Interesting... I've used my Norco to jump my car when I accidentally drained the LVB while doing updates. Had zero issues starting up, though I might have bypassed the failsafes in order for it to work. At that time I assumed the LVB was so drained that the jump pack decided there wasn't actually a battery attached to it and so it wouldn't start.

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