which is most battery efficient

Whenever you pass electrical power through a device whether it be an inverter, transformer or just a plain wire, there is a loss of energy to be tolerated. Therefore it is always best to be as direct as possible.

So, to directly answer the question ...... Run the Engel direct from 12 volt.

Is that direct enough?

Cheers
Allan

M and J

Interesting question.

I have already demonstrated my lack of knowledge re Engels but here goes again.

The compressor in the Engel actually runs on 240V AC. The Engel contains an inverter that supplies this current.

From a US site:

"Power Inverters

Never use a commercial inverter or converter to operate your Freezer Fridge on AC, as these devices do not hold the required constant frequency. These electrical supplies generate high ripples or surge voltages that could result in damage to your Freezer Fridge."

Bob