Battery Issues

[4thes]

We’ve been in Thailand for 2 weeks and left our Taycan 4S CT with family in Hampshire. The alarm went off, and the key wouldn’t open the car. Porsche Tech claimed it happened because the car hadn’t been used — but that seems odd since we’ve left it unused for three weeks in summer before without any problems. Thoughts?

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[tycanmt]

We’ve been in Thailand for 2 weeks and left our Taycan 4S CT with family in Hampshire. The alarm went off, and the key wouldn’t open the car. Porsche Tech claimed it happened because the car hadn’t been used — but that seems odd since we’ve left it unused for three weeks in summer before without any problems. Thoughts?

Two weeks is nothing. I had a Lithium battery die in an ICE Cayenne and during the course of getting that replaced under warranty Porsche people told me that they expect a vehicle (ICE in this case) to be driven at least every 6 weeks. Our Taycan can go many weeks without being driven but I do keep track of its battery level via the app and will turn it on, drive it a few inches in the garage every few weeks for peace of mind, charge it up a bit here and there. But any car should be able to be left for 2 weeks --- that's the normal length of a vacation.

 

[4thes]

Two weeks is nothing. I had a Lithium battery die in an ICE Cayenne and during the course of getting that replaced under warranty Porsche people told me that they expect a vehicle (ICE in this case) to be driven at least every 6 weeks. Our Taycan can go many weeks without being driven but I do keep track of its battery level via the app and will turn it on, drive it a few inches in the garage every few weeks for peace of mind, charge it up a bit here and there. But any car should be able to be left for 2 weeks --- that's the normal length of a vacation.

Thanks, that’s really helpful feedback! I appreciate the reassurance and the tips on keeping an eye on the battery, good to know two weeks is normally fine.

 

[tycanmt]

Thanks, that’s really helpful feedback! I appreciate the reassurance and the tips on keeping an eye on the battery, good to know two weeks is normally fine.

I should add that these cars have two batteries: the obvious big one that drives the wheels, and a second small one that's similar in purpose to the battery in an ICE car. There are two batteries for a mixture of technical and regulatory reasons. Anyway, the small battery (usually called the "12V battery") runs the car electronics. That load in modern cars is non-trivial even when the car is not driven. There are cell network modems sending telemetry for example, software tracking battery charge state and so on. That parasitic load will discharge the battery in a few weeks just like in an ICE car. Ok, so you might think "there's a giant battery in the car, just use that to re-charge the 12V battery". That's exactly what is done, which is why you can leave a Taycan for a long time un-driven and it'll be fine. BUT...initially this feature either wasn't implemented, or was screwed up such that it didn't always work. As a result there were Taycan that discharged their 12V battery in storage. I think this might be what the Porsche Tech is thinking of. That problem was supposedly fixed some time ago in one of the recalls, and only applied to earlier model years.

 

[4thes]

I should add that these cars have two batteries: the obvious big one that drives the wheels, and a second small one that's similar in purpose to the battery in an ICE car. There are two batteries for a mixture of technical and regulatory reasons. Anyway, the small battery (usually called the "12V battery") runs the car electronics. That load in modern cars is non-trivial even when the car is not driven. There are cell network modems sending telemetry for example, software tracking battery charge state and so on. That parasitic load will discharge the battery in a few weeks just like in an ICE car. Ok, so you might think "there's a giant battery in the car, just use that to re-charge the 12V battery". That's exactly what is done, which is why you can leave a Taycan for a long time un-driven and it'll be fine. BUT...initially this feature either wasn't implemented, or was screwed up such that it didn't always work. As a result there were Taycan that discharged their 12V battery in storage. I think this might be what the Porsche Tech is thinking of. That problem was supposedly fixed some time ago in one of the recalls, and only applied to earlier model years.

Thanks for explaining, that makes sense. Sounds like our car just triggered an old issue that’s mostly been fixed in newer Taycans. Good to know it’s nothing serious.

 

[tycanmt]

Thanks for explaining, that makes sense. Sounds like our car just triggered an old issue that’s mostly been fixed in newer Taycans. Good to know it’s nothing serious.

I don't think this happened in your car (2 weeks is still way too short), but rather it explains the response of the tech. They were referring to a no longer present failure mode. The actual failure mode is still unknown.

 

[Dee]

My 2020 Taycan can be left alone for at least 4 weeks.
I've even heard a few months.
It's just supposed to work that way.
So either you don't have all the updates or there's another problem.

 

[Isaac]

Thanks for explaining, that makes sense. Sounds like our car just triggered an old issue that’s mostly been fixed in newer Taycans. Good to know it’s nothing serious.

Last Jan i went through a spate of flat 12 volt battery problems even though it was plugged in to charge the 800 volt battery. In one case after 3 days of sitting in the garage. It was (in Jan) the case that the 12 volt battery would be charged 8 times while the car was idle by the 800 volt battery but not beyond 8. In other threads people guessed that something was causing the 12 v battery to drain and as someone said on this thread there is quite a bit of draw on the 12v battery even if idle.. The limit of 8 might have been fire risk related. So what to do? When you are back take it to the dealer. They or rather Germany seem to have a means of working out what caused the 12v battery to go below the range at which it will start/open the car. In my case it was chased back eventually to a faulty heater. Note also that there was a software update that allows closer monitoring of the 800 volt battery for fire risk and this update may also have raised the 8 recharge limit. Unfortunately restarting the car is not straightforward - see other threads - so probably will require Porsche to come out. For a while i left the bonnet open to be able to get to the recharge points if it happened again - the light in the frunk goes off even if left open so that would not drain the battery. Its a great car but these issues can be v frustrating and elusive.

 

[W1NGE]

Read the lay up guidance in the Owner's Manual for both HV and 12v battery. But 2 weeks is nothing and the dealership has grossly misinformed you.

12v battery has had a chequered history on the Taycan and the early issues supposedly software patched.

Could be a failing cell, interior light left on, bonnet light left on or some other voltage drop.

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