I'm looking for any real world experience with 120V inverter/chargers for a boat with 24V lithium batteries in terms of overall efficiency including standby power. There are limited options here, so alternatively, would a 230V unit feeding an autotransformer for the 120V power be a better option.
I think the conversion from 240V to 120V is unlikely to be the most efficient route but my options for a pure 120V inverter/charger would be limited to a MultiPlus 24/3000, MultiPlus-II 24/3000, or a Quattro 24/5000. The 3000s wouldn't be enough power and I would need a pair of them while the Quattro would probably be used by itself.
I've seen the datasheets. A pair of MultiPlus-II 24/3000 would use 13W each for a total of 26W with a max. efficiency of 94%. The Quattro would use 30W with the same max. efficiency while supplying a bit less power. I don't know how accurate these numbers are in the real world.
It seems like a pair of the new 24/3000s is the best option with a bit of redundancy at the cost of complexity, space, and weight. Does anyone disagree?
The 230V alternative mentioned above would be a MultiPlus-II 230V 24/5000: 18W standby and 96% max efficiency, and I've already got an autotransformer onboard. But most of our loads are 120V (including all cooking) and I can't imagine the trip through the autotransformer is going to be the most efficient route.
