Replacing my Converter/Charger - Help

BFL13 wrote:

Steve92004 wrote:
I have a question, if I put that 75 amp in the same spot as the old 30 amp with 15' of cable each way, what size cable would I need for it to work?

I was running some tests so you caught me at a good time to check that.

I have a PM3-75ADJ so same thing as yours for this part. I used my Honda 3000 to run it about 125v input. I put the trailer on whole house inverter and ran a kettle, showing minus 89 amps on the Trimetric. I used about 30 ft of #2 copper-aluminum jumper cable (that is two wires each 30 ft) and plugged in the 75 amper set to 14.8 volts.

Trimetric amps went back to minus 8 amps so that means the 75 was doing 81 amps, which is not crazy. Most of these converters will do more than their rated amps in that kind of set-up. On actual battery charging they have to work harder and do more like their rated amps or a tad over.

So--what is needed for 15 ft distance to get the 75 amps? I am thinking you could do it with #4 copper (not cu-al) based on that test I just did.

On that, instead of going fatter wire for more money, what would it matter if you used #4 cu and it only did 70 amps? That is plenty on a pair of 6s.

That's what I was thinking
The original is using the frame for the negative connection with just a jumper between the converter and the frame and another jumper between the negative battery terminal and the frame.
So that's less distance if I go the same route
I'm guessing I need a fuse somewhere close to the battery also right?
I spent half the day just cleaning up the rust, repainting, and mounting the new boxes