How to avoid 12v battery anxiety

[Dee]

Thats not what the video shows or advice from my Porsche Centre with regards leaving car for extended periods.

Do they know it can destroy your DC/DC charger in your car or any other electronics?
Do you think dealers are the best advisers?
Do you know what a Taycan 12V battery costs to replace?
Or even the DC/DC charger?
Do you think your warranty will cover the 12V battery?
Or a fried DC/DC charger that got a trickle charger attached to it?
Do not fuck with Taycan electronics, seriously.

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[eddieterry]

Yes quite impressed with the technician at my local Porsche Centre.

I really don’t think Porsche would recommend it if what you say is correct but we will have to agree to disagree.

I did check that it would not affect my warranty (12 Volt is obviously not covered but DC / DC charger is).

Even the user guide shows how to charge the 12 Volt in detail - no suggestion of disconnecting battery from car. They even suggest it for long term use if away from car for extended time - if that was going to have the consequences you suggest I don’t think it would be a recommendation.
I respect your view but it flys in the face of documented recommendations from Porsche.

 

[eddieterry]

 

[Vercingetorix]

Victron chargers have Bluetooth and adjustable parameters.
https://invertersrus.com/product/vi...iKYgtk9hpt87NeqcJ4pzMCmLgIvzZCjIByIPuA4r0P819

 

[rb33gl]

Porsche has offered me no other option than to keep the CTEK charger trickle charging the 12v during periods when I'm away for more than 2 weeks. I'm not aware of any software updates that addresses this, but will ask when the car goes in tomorrow for another fault - resetting the data connection.

 

[rb33gl]

This was my wiring job for the CTEK connection

 

[eddieterry]

This was my wiring job for the CTEK connection

Yes I copied your method for the CTEK connection and it has made it very easy to connect without having to take the plastic cover off.
I did get Porsche Tonbridge to check my 12 Volt and also to make sure all software was updated and they could not find any problem but I still occasionally got the 12 Volt low message. The car was charging as it showed 14.2. If I get it again I will just plug in CTEC (Technician said that this would not cause any problem).

 

[F1Ruaraidh]

I am (now) the happy owner of a Taycan 4 Cross Turismo MY23.
I haven't always been happy and I'll explain how that changed.

I went away for about 3 weeks and left my car in the garage. Upon my return the 12v battery was completely dead and I found myself completely locked out.
It's a familiar story. But I have no dashcam or anything else that would potentially drain the battery. I also disabled all of the 'comfort' features so the car didn't spend any unnecessary battery time waiting for something to happen. And still the car died.

I had the car brought to the Porsche dealer in Dublin and they tested the battery, which was absolutely fine. They did, however, apply some new software updates. I'm sure someone will comment that their battery was fine after 2 months, etc. and that's great for them. But that didn't apply in my case and, judging by the number of posts on the web about dying 12v batteries, I'm not alone. At any rate, I vowed to never have to put my car on a flatbed again..

I've spent hours reading forums and watching videos about how to make things better, and one thing I've concluded is that there is no 'right' answer. Not only are there variations between Porsche models, there are also differences between Taycan models. What works in the UK/IE may not apply in the US and vice versa. What works for a 2021 model may not work in a 2023, etc.

So here is the list of things I do to allow me to sleep at night knowing I never have to worry about a dead 12v battery again. These are generic steps that should work in nearly all cases.

• Buy a trickle charger. I bought a CTEK Lithium XS (you must use a charger for lithium batteries - lead/acid chargers won't work..)
• You can see if the auxiliary charger (ciggy) port in the console between the front seats works but it didn't for me in my MY23.
• Use the CTEK eyelet connecter to hard wire the charger to the battery in the froot. It really isn't obvious where to connect it because you can only see the front half of the battery when you take the plastic cover off. I went to the Porsche dealer seeking their advice and they very kindly installed the cable for free. I turns out that you need to also remove the second plastic cover to expose the rest of the battery and appropriate connectors. You need to remove the windscreen wiper to do this but is was a small job. I do have a CTEK extension cable but the standard cable is long enough to hang out past the main plastic cover. However, the extension cable could be useful if you don't have a garage, allowing you to route the cable to somewhere accessible from the outside so you can shut the froot/frunk.
• I'm fortunate to have a garage to park my car in, so I always leave the froot/frunk open.
• Always keep the CTEK charger in the car within easy reach - not in the boot for example.

Now if I ever find myself in the unlikely situation of having a dead 12v battery, then the following steps are needed:

• unlock the car using the emergency key in the fob. It only works if you insert the key flat side up. Turn the key to the right 90 degrees, lower the handle so it engages the lock mechanism and lift again to unlock the door.

If, like me you leave the froot open, then get the charger from the car, raise the bonnet, plug it in to the hardwired connector and you'll be ready to go in minutes. Otherwise you'll need to:

• Take the cover off in footwell to expose the fuses. In an Irish/UK version this is on the right side of the car (drivers side) and on the left everywhere else (also drivers side in a left-hand drive country). I won't go into detail on how to connect the charger to the pegs in the footwell as there are numerous videos showing how to do this. Use the alligator clips from CTEK and once connected the froot/frunk should open (using the key fob).
• Now that the froot/frunk is open you can simply connect your charger using the hardwired cable that's there and you're all set.

The driver of the recovery truck that took my car away said 'this happens all the time and not just to Taycans but also to Audi e-tron GTs'. AFAIK, Taycans and e-tron GTs share most of the same chassis so have the same 12v battery issues.
Thankfully I won't have to call him again - at least not for a dead battery.

Covid flattened me. I spent months in bed recovering. My car sat on the 7kW charger and didn't move.

It was there for 5 months. The 12V was fine.

Because it was an ancient Model S not a Taycan.

Didn't need any 12V charger. Having to trickle charge the 12V battery on an EV is laughable.

Porsche should be profoundly embarassed and fixing this with an OTA update but no. Apparently not.

 

[tophamn]

Covid flattened me. I spent months in bed recovering. My car sat on the 7kW charger and didn't move.

It was there for 5 months. The 12V was fine.

Because it was an ancient Model S not a Taycan.

Didn't need any 12V charger. Having to trickle charge the 12V battery on an EV is laughable.

Porsche should be profoundly embarassed and fixing this with an OTA update but no. Apparently not.

I have a colleague who needed to call out a rescue truck to a dead car after a 3 week holiday - a Tesla Model 3.

 

[F1Ruaraidh]

I have a colleague who needed to call out a rescue truck to a dead car after a 3 week holiday - a Tesla Model 3.

Accidents happen. It's not a design feature though.

 

[f1eng]

My suspicion is that there has been far more activity over the air than usual because of the HV battery concern.

Presumably Porsche had to monitor -something- on customer's cars to decide which letter to send - don't charge above 80% or not, and maybe this takes far more than the expected power from thew 12V but even then the 8 30 minute top ups automatically applied by the software either hasn't happened or isn't enough.

It looks like the CTEK charger allows up to 30 hours to get from discharged to 95%.

 

[F1Ruaraidh]

My suspicion is that there has been far more activity over the air than usual because of the HV battery concern.

Presumably Porsche had to monitor -something- on customer's cars to decide which letter to send - don't charge above 80% or not, and maybe this takes far more than the expected power from thew 12V but even then the 8 30 minute top ups automatically applied by the software either hasn't happened or isn't enough.

It looks like the CTEK charger allows up to 30 hours to get from discharged to 95%.

While charge remains in the HV traction battery, there is zero need to limit 12V accu charging events.

Put a disgnostic limit on it by all means "12V battery needs service" but to just let it go flat immobilising the car while there's plenty of HV charge available?!

Madness.

 

[anonymouse]

I have a colleague who needed to call out a rescue truck to a dead car after a 3 week holiday - a Tesla Model 3.

For clarity, what goes flat on a Tesla (unusual failures excepts) is not the 12V -- which it continually charges up from the big battery -- but the big battery itself. The Tesla's computer runs continuously so if it isn't plugged in, it loses a few percent of power each day - quite a lot more if "sentry" (the system that watches on the cameras for intruders) is enabled.

However if you plug a Tesla in, it will sit (as mine did during Covid) for six months quite happily -- although it will consume a bit of mains electricity as it keeps the big battery topped up. Sadly the Porsche is not so sensibly designed it seems.

 

[jdzions]

You obviously don't have all the necessary updates cuz this is really a thing of the past.
I'm sorry you experience this but all this trickle charger thing isn't necessary at all.
In fact, it'll screw up your build-in recharge system of the car.
Maybe even possible damage to your 12V battery and/or DC/DC charger which will result in more yellow or red circles on your dash.
Insist that your Porsche dealer update your car cuz this is just bad s/w version management of your dealer.

My purchased-brand-new in March 2025 has just fallen to this 12v battery stupidity, so unless my dealer didn't apply all updates when before they sold me the car, yes this is still a problem. Oh, and my dealer contact, spoken to in February 2026, acknowledged "yeah, this is still a thing".

 

[CrazyINP]

My purchased-brand-new in March 2025 has just fallen to this 12v battery stupidity, so unless my dealer didn't apply all updates when before they sold me the car, yes this is still a problem. Oh, and my dealer contact, spoken to in February 2026, acknowledged "yeah, this is still a thing".

you can refer to this post. There is TSB with new SW update to address the issue. Porsche finally has came up with solution supposedly. I doubt you had that installed as just came out

https://www.taycanforum.com/forum/t...ing-parked-for-long-period-jan-12-2026.33336/

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