12v battery problems - again

[timc3]

Got the same issue here. Currently deciding whether to tackle it myself or call out Porsche assistance.

Sponsored

 

[Scandinavian]

Got the same issue here. Currently deciding whether to tackle it myself or call out Porsche assistance.

If you have a booster it is very easy to start the car.

There is a good instruction on the forum if you search.

Once it is back operational, just drive it for an hour and it should charge the 12 volt battery.

If you have a 12 volt Lithium charger even easier. No need yo drive it

 

[simcity]

If you have a 12 volt Lithium charger even easier. No need yo drive it

Might need to put the Lithium charger into “bypass / recovery” mode to overcome the under-voltage protection of the lithium battery BMS if that’s kicked in. Charger might not ‘see’ the battery otherwise if it’s severely depleted.

 

[Scandinavian]

Might need to put the Lithium charger into “bypass / recovery” mode to overcome the under-voltage protection of the lithium battery BMS if that’s kicked in. Charger might not ‘see’ the battery otherwise if it’s severely depleted.

True if you have not started it by the booster, which I meant.

Still a SW issue I guess that it does not use the HV battery to charge. Or perhaps my car had done the max no of cycles.

If you look at the discharge curve of a Lithium battery it certainly suddenly falls off a cliff edge.
Could this be triggered by a sudden drop in temperature?

 

[simcity]

True if you have not started it by the booster, which I meant.

Still a SW issue I guess that it does not use the HV battery to charge. Or perhaps my car had done the max no of cycles.

If you look at the discharge curve of a Lithium battery it certainly suddenly falls off a cliff edge.
Could this be triggered by a sudden drop in temperature?

That roll off discharge characteristic is just the nature of the beast with lithium batteries and why the BMS is so crucial so it know precisely where it is on / before the cliff edge.

 

[Kbmore22]

If you have a booster it is very easy to start the car.

There is a good instruction on the forum if you search.

Once it is back operational, just drive it for an hour and it should charge the 12 volt battery.

If you have a 12 volt Lithium charger even easier. No need yo drive it

I know you can open the car door if the 12v battery is dead but I’m wondering if you can get into the trunk. That’s where I’m keeping a Noco boost but if my car is ever dead, would I even be able to get to the trunk to get it?

 

[tchavei]

I know you can open the car door if the 12v battery is dead but I’m wondering if you can get into the trunk. That’s where I’m keeping a Noco boost but if my car is ever dead, would I even be able to get to the trunk to get it?

If you mean the rear trunk (not the frunk) you should be able if you can fold the rear seats to crawl into the trunk. I made a couple of kids around 12-16 years ago just for that possibility ?

Jokes aside, I'm planning to keep the booster somewhere inside the cabin. Not sure it fits the glove compartment so maybe under a seat?

 

[Scandinavian]

I know you can open the car door if the 12v battery is dead but I’m wondering if you can get into the trunk. That’s where I’m keeping a Noco boost but if my car is ever dead, would I even be able to get to the trunk to get it?

Not sure you can open the rear trunk? That has electric motors etc. I opened the front bonnet with the booster.

I keep the booster in the main cabin just so I can get yo it easily. That Is what has been recommended.

 

[rb33gl]

That made me chuckle. You're so right.

Anyway, @800v explained it perfectly here:

https://www.taycanforum.com/forum/threads/dash-cam-and-12v-battery.13972/post-210566

What I believe Porsche should do is just not limit it to 5 cycles and keep draining the main battery until it reaches the critical 10%. That way you could have the car parked for a year and still be able to drive off to the nearest public DC charger. My two cents.

I completely agree with this.

The 12v battery in a Taycan has to do a different job to that in an ICE car. When the car is at standstill, it must continually monitor a myriad of different systems, not least respond to a ping from Porsche's servers when you access the App. So there is probably a fairly constant discharge that requires replenishment from time to time. It can only get this from the main battery.

Porsche's algorithm for this is neatly summarised by @800v , referred to above.

This shows the 12v is charged back up to 50% when its state of charge falls below 8Ah for a maximum of (5, increased to 8) times. I cannot see why it imposes an arbitrary limit. Given the importance of the 12v battery to making everything in the car work, why is there any limit at all? As long as there's 10% or even 20% charge in the main battery, it should always be giving priorty to making sure there is enough in the 12v to keep things going. This is not some artificial number, it is a line of code somewhere that Porsche have introduced into the management of the batteries.

I've had the hassle of rebooting the 12v after it died twice, and one near miss. Sure, you can go through the procedure of using the manual key to unlock, removing the fuse cover, hitting the terminal with 12v (from where?) to open the trunk, tapping the terminals with another 12v from a car or jump starter that happens to be lying about, before recalibrating the front windows. This might get a tad tedious after every 2 weeks of non-use.

I reported this to my OPC and they had no concerns about my battery. They thought it was due to a) low mileage, b) it being 'fairly normal to lose charge' over 2 weeks, c) keyless entry (which I don't have) discharging the battery, d) use a trickle charger.

The Good to Know App isn't that helpful either. It says

The need to repeatedly provide power from a power supply or repeated charging of the 12-volt lithium battery under normal operating conditions may indicate that the 12-volt lithium battery is damaged.

Or simply update the software?

 

[Raphie]

Stupid question: where is the physical key And where is the physical lock hidden?

 

[Dee]

Stupid question: where is the physical key And where is the physical lock hidden?

There are no stupid questions.

The key is in your fob.
You can pull it out with your claw. ?
The lock is under the door handle (physically pull the handle up).

 

[Raphie]

ThnX found both.
does the charger still work once you get the door open? So can you fix it via the left or right charger? Or does it all start with the 12v?

 

[Dee]

ThnX found both.
does the charger still work once you get the door open? So can you fix it via the left or right charger? Or does it all start with the 12v?

Nope.
It al starts with the 12V battery cuz that will engage the main relais.

 

[simcity]

This shows the 12v is charged back up to 50% when its state of charge falls below 8Ah for a maximum of (5, increased to 8) times. I cannot see why it imposes an arbitrary limit. Given the importance of the 12v battery to making everything in the car work, why is there any limit at all? As long as there's 10% or even 20% charge in the main battery, it should always be giving priorty to making sure there is enough in the 12v to keep things going. This is not some artificial number, it is a line of code somewhere that Porsche have introduced into the management of the batteries.

Actually it’s a maximum of 30 minutes of charging or the small battery reaches 50% SoC - whichever comes first.

So it’s entirely possible the 12v battery is at less than 50% SoC when the charging cycle finishes.

 

[timc3]

Might need to put the Lithium charger into “bypass / recovery” mode to overcome the under-voltage protection of the lithium battery BMS if that’s kicked in. Charger might not ‘see’ the battery otherwise if it’s severely depleted.

I think I need to do this. The charger has been attached for 24 hours at least and hasn't charged, I presume because the minimum state of charge.

My NOCO charger has a force mode - perhaps I should try that?

Sponsored