Dead 12 Volt Battery recharging and towing questions

[DMTonka]

I believe it’s a little unclear in the TSB still; it does not clarify if the 12v is only charged when the car is in drive or also when the vehicle is parked as the HV battery isn’t active?

OP I assume your charger is compatible with lithium ion? My c-tek has a button to reset the battery electronics if a battery state gets to low.

Yes, it is unclear if simply plugging in is enough to charge 12 volt or if it must be driven.

I am 100% embarrassed to say it was not designed to be compatible with Li-Ion batteries. It was all I had in the garage and I wasn't really concerned when I was just using it to "wake up" the system and turn off relays. In hindsight I can see I may have created other issues if the charging profile was not designed for Lithium Ion batteries🫣

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[Gino]

You are right to question depleting the 12V battery to zero. That is a killer for Li Ion batteries. I certainly would not do this by design.

You are totally wrong on saying the main battery should never get below 50%. The problem at low SoC is getting the battery cells into the lower voltage knee. This is below 20% or maybe 10-15% if there is a good buffer, which is what a number of posters have said. If you are in the voltage knee then you run into balance issues and one cell could get to zero before the others and wreck the cells. Hence dont take the 12V to zero but you can easily run the main battery down to 20%. Holding an Li Ion battery at 30% is a good way to store them.

I believe it’s a little unclear in the TSB still; it does not clarify if the 12v is only charged when the car is in drive or also when the vehicle is parked as the HV battery isn’t active?

OP I assume your charger is compatible with lithium ion? My c-tek has a button to reset the battery electronics if a battery state gets to low.

It appears to be keeping my 12v battery charged but I can't confirm this since there is no charge level indication for the 12v battery. I wish there was.
For now I'm just following Porsche's advice.
I didn't mean to say never let the main battery go below 50%. I was told by Porsche to never store the vehicle for weeks or months with the battery below 50% since it will negatively impact the 12v battery. If your keys are close to the car or you wake the car electronics up by going to the My Porsche app this will also drain the 12v battery over weeks or months.

 

[raharris]

It appears to be keeping my 12v battery charged but I can't confirm this since there is no charge level indication for the 12v battery. I wish there was.
For now I'm just following Porsche's advice.
I didn't mean to say never let the main battery go below 50%. I was told by Porsche to never store the vehicle for weeks or months with the battery below 50% since it will negatively impact the 12v battery. If your keys are close to the car or you wake the car electronics up by going to the My Porsche app this will also drain the 12v battery over weeks or months.

I follow this process as well; but not going as long as the OP. If our system follows the same process as the audi, seems like we might be good.

 

[raharris]

Yes, it is unclear if simply plugging in is enough to charge 12 volt or if it must be driven.

I am 100% embarrassed to say it was not designed to be compatible with Li-Ion batteries. It was all I had in the garage and I wasn't really concerned when I was just using it to "wake up" the system and turn off relays. In hindsight I can see I may have created other issues if the charging profile was not designed for Lithium Ion batteries🫣

Hopefully the dealer will see if a reset/charge of the Li-ion has any impact before you have to spring for a new battery.

 

[Gino]

Your manual is slightly different from mine. Hard to tell if the information is changing or if it is still a gray area and Porsche's own understanding of best practices are evolving with more real world usage and scenarios...

Oki

The Porsche Service Bulletin I referred to was first released on Oct 16, 2020 but the one I quoted was the last revision on Mar 14, 2022. I'm sure they are continuing to learn about their on board chargers at 120V & 240v as well as any issues they may be seeing with long term charging. I just wish these service bulletins were more transparent since I called 3 Porsche service departments in Southern California and all 3 service advisors said they had never seen this bulletin but were able to find it once I showed it to them. That's not good.

 

[Gino]

The Porsche Service Bulletin I referred to was first released on Oct 16, 2020 but the one I quoted was the last revision on Mar 14, 2022. I'm sure they are continuing to learn about their on board chargers at 120V & 240v as well as any issues they may be seeing with long term charging. I just wish these service bulletins were more transparent since I called 3 Porsche service departments in Southern California and all 3 service advisors said they had never seen this bulletin but were able to find it once I showed it to them. That's not good.

It's interesting how the advice has changed but still a bit vague. They don't say at what voltage you can trickle charge at. The dealers assume this to mean at 240V because who would buy a Taycan and not install 240V charging. Unfortunately for me I live in a townhome complex where my panel is in the house and there is no 220/240 in the garage which is across the main driveway. The association will not let me run 220/240 since I would have to dig across the community driveway to do it.
For now I have to charge at a station but I'm hoping to figure out another way other than to move.

 

[Gino]

Hi Gino,
The main batteries always held their charge, whenever I would plug it while storing it. The PCM indicated that the batteries would drop only 1-2% over several weeks of storage. I would still leave it plugged in for a few days with the expectation that although the main batteries were charged (to 50% per my profile setting) that plugging it in I was also allowing the system to keep the 12 volt batteries charged.

This was obviously not enough maintenance for the 12 volt system hence the tow truck visit yesterday.

The issue was not with the main batteries being below 50% because they always were in that neighborhood.

It wouldn't be a surprise to me if what I was told by my dealer was not accurate. I usually try to get to a Porsche Service Bulletin that explains everything in better detail.
I think possibly Porsche is being very careful about sending out service bulletins on their charging protocols, on board chargers and main battery packs because it appears they are looking at replacing many batteries if they say too much.
Now there are two NTSB recalls on 2021-2023 main batteries due to shorts immediately after charging to above 80% at a fast charger which could result in battery fires. One recall they seem to have data which shows this issue and the models/serial #s affected but the other recall is wide open since it includes 2021-23 vehicles which have had no signs of shorts so far.
Porsche is supposed to send out letters on May 17th to all the affected owners.
My Taycan is a little over 2 years old and I may end up having to bring my vehicle in to replace all or some of the affected LG battery packs.
If that happens, I assume I'll be driving a loaner for a month or two if they deem these battery modules unsafe.

 

[Tooney]

This list updated regularly by @rs38 is a good source for Taycan TSBs filed at US NHTSA.
(Find more TSBs your dealer hasn't heard of . . . )

 

[Gino]

This list updated regularly by @rs38 is a good source for Taycan TSBs filed at US NHTSA.

Thanks

 

[ChadLi]

I follow this process as well; but not going as long as the OP. If our system follows the same process as the audi, seems like we might be good.

I had the same problem with my eTron GT. Left the car at SF airport for 2 months, and 12v was dead when I got back. Had to use emergency key to open car. Dealer said they had to remove drivers seat to recharge. And of course, had to be towed on a dolly

I believe my problem was caused by the USB charger that I left in the power outlet. Very small power draw, but over 2 months….

My long-term solution was to add a charging harness with connections in the drivers compartment. If it ever goes dead again, I can recharge it myself with something like a Halo.

 

[Gino]

I had the same problem with my eTron GT. Left the car at SF airport for 2 months, and 12v was dead when I got back. Had to use emergency key to open car. Dealer said they had to remove drivers seat to recharge. And of course, had to be towed on a dolly

I believe my problem was caused by the USB charger that I left in the power outlet. Very small power draw, but over 2 months….

My long-term solution was to add a charging harness with connections in the drivers compartment. If it ever goes dead again, I can recharge it myself with something like a Halo.

I don't understand why they make it so hard to get to the 12v battery to charge it. Makes no sense.

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