9 months is all of last winter and a long time for an OK battery, to now not be OK, especially if its a few years old.

Have another full battery check, in particular the CCA level - this is the maximum amps the battery has to turn the engine over. I've just had a new battery on an 8 year old Yaris. It was reading a healthy voltage and no problems when charging, but the CCA was only 55% of a new one, which is why it was struggling to start.

Edited by daveyjp on 23/03/2025 at 15:12

Thanks for your replies both. I've had the battery fully checked and it's shown as being in 'good condition' but needs charging which is strange as just a few days previously, it had had the best couple of runs in quite a while - nearly an hour each way so I would have thought that would have charged it so maybe there's another problem with something draining the battery?

This is a common problem on PSA cars of this era - it will be the battery protection unit (BPGA) which sits in front of the battery. There's probably a fault code for protection relay stuck open or something if you scan it. Almost certainly once it does decide to start, it does so normally without struggling - likely you get a warning about faulty fog lights as well?

The part is not that cheap (c£300) but it's plug and play, no coding required. Seemingly you can get cheap ones from AliExpress, but not sure I would trust them....