C5 Aircross PHEV Hybrid Only - Which Auxiliary 12v battery controls?

[pogologo]

I have a C5 Aircross PHEV (2021). I am having the issue where if I don't use the car for 4 or 5 days it says electric mode isn't available (the electric battery is 100%) and I can only run in hybrid. After 2 or 3 decent runs where the engine runs at around 500rpm constantly it will kick back into electric only, which I am presuming is because the 500 revs are recharging the auxiliary batteries.

Reading around, it appears this is likely to be one of the two auxiliary batteries are at the end of their life. Which one is it though? I believe there is one in the boot and one in the usual position at the front. Do I need to replace both or just one?

Does this need to be done by dealer as it is a PHEV or is it just a case of disconnecting and reconnecting as you would a normal battery?

Thanks

[Sloppysod]

It's probably the one in the boot as this ones job is to power the hybrid system.

Little tip.... Try to drive at least 15+ miles a month, one trip, with a flat traction battery, this will make the engine run and recharge both batteries.

[pogologo]

Thanks. I do many miles on hybrid with both going but for some reason it will not kick in now.

Do you know if you can just remove the battery as usual?

[12bucklemydrew]

Afternoon,

Have you resolved this issue? I am having the same problem and reading online I have traced it to my Aux Battery. Not sure if it's something I can do myself though.

Thanks,
Drew