[ternus]

The lesser-known instance of this is RV power. When you're running off small batteries and solar, you want to make the best use of the watt-hours you have, and that means avoiding the DC-to-AC-to-DC loop wherever possible. So you run 12V (or in newer models, higher voltage) versions of everything, upconverting as necessary.

[amluto]

I am really skeptical that 12VDC power distribution in RVs actually saves power compared to a high-quality (hah!) higher voltage AC or DC system. 12V is absurdly low and you can’t easily lose quite a few percent in resistive losses even with fairly large cables, and those large cables are quite unpleasant to work with and rather dangerous.

[ternus]

The vast majority of what you're running from RV DC are things like lights, fans, phone chargers, and other cigarette-plug-adapter type devices. My RV has a 12V DC fridge. For anything more - particularly air conditioning - you need AC for sure.

My inverter-charger is connected to my batteries with 4/0 cable. That wasn't fun to run.

[saltyoldman]

I tried using a microwave off the RV batteries, your inverter needs 4/0 cable. Very "fun".