I have installed a DC to DC converter, actually 2 as you can connect them in parallel. The first one was not quite large enough so I added another one. The next model up was physically too large so I stacked these ones. So now 2 Victron 12v to 12v 9amp converters. Typically the one converter was charging at about 5amps depending on battery voltage. But if the auxiliary battery is a bit low there is now more capacity to charge up quicker.

I did a torture test running the compressors off the auxiliary batteries & the charging briefly got up to 19.5amps. The batteries are actually for the fridge. One controller was briefly outputting 11.5amps so I was a bit concerned with the 20amp fuse!

So the maximum amps is ok. The typical maximum will be around 12amps. When the batteries are charged it is about 3amps.

The DC to DC converters are at the bottom stacked one in front of the other, slightly offset vertically so I can get to all the terminals. Above is the 100/20 MPPT solar controller, it has heatsinks front & back for hot weather as they start running less efficiently above 40°C.

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Im always impressed with your mods - may they long continue Jules