The lithium battery is being used while driving in fact it is key to turning my 1 litre engine into a 155bhp speed machine😂 Nope. The 155ps peak comes completely from the engine. I think I am right in saying that both batteries are charged via the same system Not really. The 48V battery is charged ...

15.1 volts is fine. It suggests the 12 volt battery is depleted and a higher setpoint is being used to recover the state of charge. Once recovered the setpoint is reduced.

22mpg and 24mpg with the bum warmer off!

Kuga MHEV has a 2 litre diesel. The 1.5 litre Dragon is in very short supply: - https://en.wikipedia.org/wiki/Ford_Brid ... gine_Plant

Does it always charge at 15.1v? Try the 12 volt battery reset procedure to see if it makes a difference.

The Welsh Dragon died and the only sensible replacement was a Fox. The car in vastraffick blue is simply gorgeous.

Try the 12 volt battery reset procedure to see if it makes a difference.

This is the dc/dc module which converts 48 volt power to 12 volt power. Next time you open the hood look to the right and you can find it.

The BISG only creates and consumes 48 volt power. Its inverter converts high voltage AC to 48 volt DC. It does not provide 12 volt power. That is the job of another module called the dc/dc which supports all the cars 12 volt loads. OP said the alternator failed which implies the dc/dc module failed ...

The Puma ST 1.5 litre is not an mhev. The alternator on those do have a belt attached.