Won’t charge…dead battery shortly after……

[Sandiemandie]

Hi all, so here’s a thing……
3 year old hybrid behaved perfectly, then……it stopped charging the hybrid battery a week ago…..mmmmm, dealer said probably the cable.
Anyway after driving on petrol for a week, dead car…totally dead…

called the AA yesterday, they were apoplectic about the bonnet release then we remembered 12v battery is in the boot….totally flat….. it recharged pefectly, hey presto after battery reset the car fired up, but it has more error messages than you can shake a cat at!
Guess what, now it recharges the hybrid battery all fine too……
Dropped it at the Cupra garage this morning to see what they say and hopefully their computers can just reset all the error messages ( man said no error messages on obd apart from current dodgy when battery flat)

anyone else had issues with totally drained 12 v battery with no explanation?
anyone know if the 12v starts draining, the hybrid battery won’t charge?
Just asking ahead of the expected…”nothing to see here” from the garage…

will update once here back from garage (who’s specialist is currently out training :-( )

Cheers for any thoughts/experiences

 

[EdwinV]

Out of nothing the charging socket of the car would lock the cable and charging wouldn't start. Looked at the fuses but everything looked fine and also other charging stations and cables didn't work.
After a couple of days driving on petrol I got a notification when starting the car that my 12v battery was getting low.
I could start the car and went to a local garage and they tested the 12v battery with a device and it was fine.
I told them about the charging socket problem and the mechanic told me to drive home and test it again. For testing he had disconnected the 12v battery and it wouldn't be the first time disconnecting the 12v battery would solve these kind of problems.
I got home, connected my charging cable, the socket locked the cable and it was charging again.

A couple of weeks later the roof control panel wasn't responding. I couldn't turn the reading lights on and the sunroof wasn't responding.
I decided to disconnect the 12v battery to see if that would solve the problem... and it did.
Disconnecting the negative to the chassis was enough to reset everything in the car. When I started the car I got all sorts of error messages. They all went away in a couple of minutes. I haven't had any issues since this 'hard' reset.

 

[Sandiemandie]

Well that sounds all a bit familiar!! Cheers Edwin. Don’t suppose you ever found out why it did it?

 

[LetsForment]

There are a few threads on the forum about this, the general sentiment is too keep the 12v battery in good condition. And to keep the vehicle in hybrid mode for some time regularly.

Because you are charging the high voltage battery does not always mean the 12v is being charged too. And there are things the car does that only uses the 12v battery. Eg the high voltage charge relays.

 

[CupForm]

- according to VAG documentation, the 12V battery will charge while driving in Hybrid mode, driving in EV mode, and while charging the HV battery;
- the faulty roof control panel (reading lights, touch-buttons and sunroof control) is a well-known issue across the entire range of VAG cars using this module version;
- there's a known correlation between HV-charge faults and 12V battery failure, but not completely understood (or not seriously treated) by VAG. Sometimes the car doesn't lock the charging cable, or it will simply not charge - but once it startts doing that, it seems 12V failure is to be expected quite soon. The 12V battery disconnection solves the problem simply by resetting the HV-charging system. On the Octavia (same PHEV) I was able to identify on the diagram a fuse (in the engine compartment box) that will reset that system - someone reported back on the Skoda forum that removing that fuse solved the problem. However, on the Formentor fuse diagram I wasn't able to identify that particular fuse, even though I was expecting a very similar fuse layout between those two-three cars (Golf, Octavia, Formentor/Leon).

 

[mannbaker]

thanks for the feedback CupForm
Cars back from dealer, all warning lights cleared, car given the ok, what caused the drain who knows - they dont - but they did add one interesting tip........

They think that if you leave the HV charger attached to the car for an extended period of time (a day>!) after it reaches 100% charge, this can/may cause the 12v battery to throw a wobbly!

now as it happens i did precisley that a week before this happened which times almost perfectly with my car refusing to charge its HV battery, which potentially led to the full 12v drain a few days after, even though running on petrol for a few days.....

Coincidence? who knows - but at least I now know the warning sign in future thanks to your feedback above, and more importantly how to stop it before full dead 12v...

much appreciated Forum - thank you

p.s. and the interesting taxi ride in a Tesla to the dealer cheered me up no end after he told me in the riculous rain we had here 4 weeks ago, his Tesla died and £10,000 pounds worth of new (re-conditioned) battery later.............. aaahhh modern technology

 

[Seastormer]

thanks for the feedback CupForm
Cars back from dealer, all warning lights cleared, car given the ok, what caused the drain who knows - they dont - but they did add one interesting tip........

They think that if you leave the HV charger attached to the car for an extended period of time (a day>!) after it reaches 100% charge, this can/may cause the 12v battery to throw a wobbly!

now as it happens i did precisley that a week before this happened which times almost perfectly with my car refusing to charge its HV battery, which potentially led to the full 12v drain a few days after, even though running on petrol for a few days.....

Coincidence? who knows - but at least I now know the warning sign in future thanks to your feedback above, and more importantly how to stop it before full dead 12v...

much appreciated Forum - thank you

p.s. and the interesting taxi ride in a Tesla to the dealer cheered me up no end after he told me in the riculous rain we had here 4 weeks ago, his Tesla died and £10,000 pounds worth of new (re-conditioned) battery later.............. aaahhh modern technology

Hope you gave him a decent tip, no not to buy a petrol/diesel car instead, a cash tip.