911Jeff

The 12v battery doesn’t charge when you are charging the car. It only charges when you are driving (or directly charging it with a charger like a conventional car).

daveo4porsche

the 12V battery is maintained by the “big” battery - other than bugs in Porsche’s software - the main computer monitors the 12V battery and will/should engage the big battery to charge the little battery when necessary - it does not directly charge from external power - rather it goes through a DC/DC converter that converts high voltage (400/800V) to 12V DC power suitable for the little battery - I believe you can “see it” if you add the battery voltage to the “information” display on your dash display

when the 12V is normal I often see 13.2-13.7 volts displayed by this information line - but occassionally it’s bumped up to 14.7 volts (or slightly more) - I believe this is when the 12V battery is being charged by the big battery - but that’s only speculation on my part.

dgtarga

I understand the Taycan's main battery will maintain a charge for prolonged periods when the car is stored - e.g., for three months, and that it's advisable to store the car with a SOC of about 50%. Under those conditions, will the "big battery" continue to monitor and maintain the 12V battery, or is it best to use a battery maintainer with the 12V battery if storing the car for a few months? Thanks.

991carreradriver

It is not necessary or recommended to charge the Lithium 12v battery with an external charger, except in the case of an emergency due to an exhausted SOC. When storing the car, the computer monitors the 12v battery and charges automatically as needed. There should be a sufficient SOC in the main battery to facilitate this. I have read a minimum of 50% and have seen recommendations as high as 80%.

GT Rennsport

It is important to also document that the 12V lithium ion battery is rarely every fully discharged, but rather there is a protection switch inside the battery that will cause it to shut itself down if it senses a current draw that could potentially drain it to much, this is a function of a microprocessor inside the battery.

With that being said, it would be important to think about what would cause a current draw. What come to mind for me is excessive use of the Porsche Connect app while the vehicle is charging, especially in situations where the car has limited connectivity to the LTE signal that is required to communicate.

Should the 12V battery get disconnected? The answer is both yes and no. All lithium ion lightweight batteries have microprocessors that will disconnect them in the event of a current draw. This is not native to the Taycan. While it is a bit of an inconvenience in a Taycan to have to restart the battery, it is not unique to it. I have seen the same issues in BMWs, VWs, Teslas and other cars with lithium ion lightweight batteries.

amelen

While that would be ideal, having my car sit for a while and not being used, I decided to monitor the 12V battery and have noticed it dropped to 13v after 5 weeks. I spoke to a few folks at Porsche and they recommended I use a battery tender, which I hooked up now. To note, the car still started fine at 13v, but dropping further would probably cause issues.

nycebo

I'm curious that Porsche recommended a battery tender for the 12v battery. I had wondered about doing the same thing periodically.

daveyator

My wife had an issue with our 1 week old Taycan. She turned it on and got a message that said “battery charge too low to support PCM at this time”. Off then back on did no good. But after letting the car sit (I.e. had lunch) the car was fine. If as said above the big battery monitors the little one how did that happen? Where on earth did you hook up a tender? Couldn’t see anywhere to do that.

amelen

I got this image from a thread in another forum if it's helpful.

911Jeff

Is the 12 volt lithium battery LiFePO4 ? Apparently there are different types that use different maintainers.

Whoopsy

Just leave the Taycan plugged in if the car isn't used for long periods. The computer will monitor the big battery and cycle it and also the 12V, if it sees the 12V is low the big battery will charge up the little guy.

it works the same way as on the 918. Keep the car plugged in and let the computer do its things. You can't damage the big one by keeping it plugged. I had my 918 parked for over a year, but plugged in the whole time, no dead 12V and the car starts right up.

Porsche's system work very differently than the Tesla system, where the user has to be the one doing the monitoring on battery level.

There was report of a little bug in the Taycan software that could drain the 12V all the way to dead battery, think it was Dave4porsche that reported it. But overall it's a non-issue for most.

daveo4porsche

ummmm - this “non issue” was a major thrust of the last round of software update - thankfully porsche has fixed it - but the april/may/june software update made available to Taycan owners contained fixes for multiple causes of potential 12V battery drain issues, and also required software updates of the PMCC to avoid interactions with that device that could also drain the 12V battery - given the severity of the issues Porsche felt it necessary to fix this in software - hardly a non-issue for “most”…

https://www.teslarati.com/porsche-ta...investigation/

there was also a series of Technical bulletins regarding this - it ultimately required Porsche to make changes to multiple systems to avoid this bricking your Taycan and finding it dead in the morning…things are better now

also I believe the “good to know app” recommends if you’re storing the taycan to have it unplugged and between 30-70% battery if it’s not going to be driven for several months - I don’t know of any EV vendor that recomends leaving the their EV plugged in during extended periods of non-use.

Whoopsy

The meaning of me using 'non-issue' is because of the fix Porsche issued.After the fix is applied it is a 'non-issue' for most.

Whoopsy

And having the car plugged in all the time is just the same as using a 12V battery tender on any other car. It doesn't mean the car is constantly charging, it just mean having electricity on standby for the computer to sort everything out.

I do 12V tenders for my normal cars, and keep my EVs and hybrids plugged in while they aren't being used, be it the 918, the Panamera turbo S, the Taycan or the e-Tron. Modern cars have onboard concierge to manage, why not take advantage of them.

whiz944

Of curiosity, which 12V battery tender do you like? My 944 is the worst of my ICE cars as far as vampire drain goes. It can only go a few days before the battery starts to have noticeable issues. (My GM cars can go for weeks by comparison.) So I used to use a small motorcycle battery charger with it, but recently bought a smarter Schneider charger/tender (6 amp charging/3 amp tending.) The Schneider is supposedly better matched to the AGM battery I have in the 944 than the older unit. But I was watching Lenos Garage where he really likes the CTEK tenders. One video showed him receiving a whole pallet full of them. I guess with a collection of 200+ cars and motorcycles, he'd need a few...