My onan MCCK generator is overcharging the start battery

Well done Sdowney. I am not to sure why you leave the low charge wire off. You have fixed your ONAN now so niceley, why not keeping it the way it was. You have cleaned now all contacts and printed circuit boards (pcb's) dry joints and you are happy that it is working. The low charge has a reason. Try to put you into the steps of the designer. If you are correct in removing the low charge, he would have removed it for you.

 

I am concerned with competition of gen charging combined with convertor-charger charging, how that will affect the outputs. If Onan charger vdc goes too high, that will suppress the more powerful convertor-charger output. Is what I am thinking.

If you have two sources of dc power at different voltage potentials, which one gets used?

of course setting onan output lower than convertor-charger output is much better than other way round. Still then worried that onan would slip its vdc output high again, and my house batteries will run down, which is what was happening. Onan can only output 10 amps. then I am out on water thinking convertor-charger is charging my batteries and it is not. the onan output when it was broken, was backfeeding way too high voltage onto the DC of the boat with the main engines off.

It could be with main engines on, which turns off the convertor-charger DC output, that the backfeeding would not occur. Then we sit there with very poor charging of house batteries even with gen running and convertor-charger running. Several times the engines barely started.

With this commentary in this post, I am speculating as dont know for certain.