12v Battery Needs Charging - 2025 petrol car

[trew]

Yesterday I bought a new/used Formentor (7 months old, 4k miles). Last evening I got the 12v Battery Low warning. Is it safe for me to charge the battery with a modern charger, while it's still connected to the car? I don't want to disconnect the battery, unless someone convinces me it's okay.

 

[James_R]

If the charger is suitable then yes, you can charge the battery whilst it's still on the car.

If the vehicle is a PHEV then you need to charge it through the engine bay points like in the picture I have attached.

If it's a normal I.C.E engine then the live needs to go onto the battery positive terminal and the earth on the earth point on the bulkhead like in the picture attached.

If the issue persists, I'd speak to your supplying retailer to look into the battery possibly being defective.

 

[trew]

Cheers mate. It's not a PHEV, it's got a proper nice ICE engine. I've just come from a PHEV and I do not regret putting that charging cable away for the last time!

 

[Syphon]

Yeah as mentioned on your introduction post I've had to charge mine a couple of times now and once had the tech's out as it was dead. They said the battery health was good so didn't need replacing. Now I just keep one eye open with it.

 

[trew]

Yeah as mentioned on your introduction post I've had to charge mine a couple of times now and once had the tech's out as it was dead. They said the battery health was good so didn't need replacing. Now I just keep one eye open with it.

I took a trip to my local (trusted) mechanic this morning and asked him. He confirmed that, with a decent charger, he would foresee no issues charging the 12v in my car without disconnecting the battery.
I didn't want to go back to the main dealer, for fear of them trying to take a load of money off me, unnecessarily. That's what dealers do, isn't it lol?

 

[James_R]

I took a trip to my local (trusted) mechanic this morning and asked him. He confirmed that, with a decent charger, he would foresee no issues charging the 12v in my car without disconnecting the battery.
I didn't want to go back to the main dealer, for fear of them trying to take a load of money off me, unnecessarily. That's what dealers do, isn't it lol?

It's my favourite part of the job...

Image of a non PHEV on charge.

 

[trew]

It's my favourite part of the job...

Image of a non PHEV on charge.

That's brilliant information for a noobie - thanks mate.

 

[trew]

If I charge the 12v battery at home, does it get recorded in the car's system and logged so it can be read by an OBD2 reader?

 

[James_R]

That's brilliant information for a noobie - thanks mate.

No problem at all.

 

[James_R]

If I charge the 12v battery at home, does it get recorded in the car's system and logged so it can be read by an OBD2 reader?

Some historical data will be stored in the CAN gateway but it's not interrogated during diagnostic work.

 

[trew]

Update - I charged the 12v battery in situ, without disconnecting anything, using my little charger - and it was absolutely fine. Took about 2 hors, from 20% to full.

 

[Tell]

What is the thinking on the battery. Duff batteries fitted, faulty alternator or too much activity going on when the cars switched off which drains the battery. We know hybrids have issues if people drive them too much on the hybrid battery, the other battery doesnt get any charge but these are not all hybrids...

I'll stick to my trusty 2 litre diesel . As well the SS you can't turn off on these latest generation ones without a pre flight mode process, then it seems you can't get the props spinning without wheeling out the charger .