I have read somewhere that cars equipped with belt integrated starter generators often don't use these and the 48V battery for cold starts due to, IIRC, issues with belt slippage. Instead they use the 12V battery. Does anyone know if this is the case for the 2024 150hp mild hybrid?

 

Connected to this, if the mild hybrid almost always (or 100% of the time if it doesn't use the 12V battery for cold starts) uses the 48V battery for starting, then you should not require an EFB or AGM battery, am I right?

Edited 8 December, 20241 yr by beneix

1 hour ago, beneix said:

you should not require an EFB or AGM battery, am I right?

The 12V battery is required for all the 12V systems in the car - lights, infotainment system, heater fan, central locking, alarm, etc.

8 minutes ago, PetrolDave said:

The 12V battery is required for all the 12V systems in the car - lights, infotainment system, heater fan, central locking, alarm, etc.

Yes, but EFB or AGM batteries are really only required in start/stop vehicles that put a heavy, repeated load on the 12V battery. If this is not the case with the mild hybrid, it should only require a normal 12V battery, not the more expensive EFB or AGM types.

11 minutes ago, beneix said:

Yes, but EFB or AGM batteries are really only required in start/stop vehicles that put a heavy, repeated load on the 12V battery. If this is not the case with the mild hybrid, it should only require a normal 12V battery, not the more expensive EFB or AGM types.

I read your question as ANY 12V battery!

@beneix I can see your point if, in fact, the 12 volt battery is not (or rarely) used for actually starting the ICE. Is this actually the case?

There is possibly still an argument for using at least an EFB for the longer inherent lifespan. 

When the 12V battery in my Mk4 drained somehow the car wouldn't start, so apparently the 12V battery is needed for the engine to start. 

On 08/12/2024 at 14:51, PetrolDave said:

The 12V battery is required for all the 12V systems in the car - lights, infotainment system, heater fan, central locking, alarm, etc.

 

3 minutes ago, strudlovina said:

When the 12V battery in my Mk4 drained somehow the car wouldn't start, so apparently the 12V battery is needed for the engine to start. 

Add to my list of 12V systems the engine ECU.

1 minute ago, strudlovina said:

When the 12V battery in my Mk4 drained somehow the car wouldn't start, so apparently the 12V battery is needed for the engine to start. 

That makes perfect sense; the 12V battery is required for all the electronics, which I would assume include the circuits that tell the ISG and 48V battery what to do. What remains to be confirmed is whether the 12V battery is ever used to provide the actual power to the ISG.

 

Incidentally, when your battery was drained, did KESSY stop working and if so how did you get around that?

I should edit my post to say 'Crank Engine' instead of 'Start ICE' - but too late for edit.