Originally Posted by djmarchand
The only reason to have a big charger is if you want to charge with a genset while on the hook. You want to limit genset running time so a big charger (up to 25% of the AH house capacity if flooded cells, more if AGMs) is needed.
When I replaced my shore charger, I wanted the largest charger my Honda generator could comfortably power without the need for a full RPM generator operation. My loads run 150-180 AH per day on a 660 AH house bank. I settled on a 55A charger.
The generator can handle 13.3A and the peak load for this charger is 13A but I knew most charging would be well below this level so it seemed like a good fit. The charge level is less than 10% but in the real world, after an hour or so, the charge current drops below 50A for my lead acid batts so any extra capacity would be unused from this point on in the charging cycle. When the charge load drops to about 15A +/- (approx 80% battery charge), I stop the recharging.
Without an engine run, I find that I run the Honda 1.5-2 hrs in the morning and evening...breakfast and dinner...to maintain the house bank between 60% and 80%. If I run the engines for a couple of hours repositioning the boat, I generally won't need a generator top off charge.
One big savings on my battery bank has been a revised operation for me. I no longer routinely run my microwave on my inverter. If I need to conserve electrons, I start up the Honda 2000 for the microwave operation. This puts the load on the generator and provides some battery charging at the same time. It works well for me 80% of the time. If I'm underway, I just run the microwave from the inverter.