IDEA...charging house battery(set) underway.

BFL13 wrote:

wwest wrote:

BFL13 wrote:
The OP is mis-informed about the batteries boiling out when at low SOC and accepting lots of amps. I ignored that part of the OP to concentrate on the inverter/converter match etc.

Maybe the OP could post a diagram of his intended set-up so we could help with the details to get it so it would work. Especially since some people here already have done something like that.

"OP's house battery set is two 6 volt deep cycle (golf cart) batteries in series. Encountered almost complete boil off twice, both times ~300 mile drive immediately after only running on batteries for a weekend.

Alternator will source unlimited(***) AMPS as long as the battery set internal resistance is low, deep discharge.

*** In my case 90 amps in cruise mode.

Alternator output = 14.9 volts, house battery = 10.5 volts

4.4 volts X 90 amps = 396 WATTS, 200 watts/battery.

A lot of HEAT.

Not understood. I regularly charge at 14.8v and with two 6s at 50% to get them back to 90% I have used 70 amps charging where it stays at 70 amps for about half an hour to get the batts to 65% SOC, then amps taper for an hour and a half to get to 90%. Total time is two hours. Nothing "boils over"

If your house battery is at 10.5v it is totally dead and could be recharged from that (but not often or they will be toast!) so the time at constant amps of the charger would be longer. No boiling over. Why would it do that?

I have seen with batts that are really , really low, that at first they won't take many amps at all but after a while they start taking more. Kind of a reverse taper going higher. After a while the amps peak and you are back to normal and the amps then taper back down as normal.

Perhaps something exceptional happened there, which needs to be addressed, but don't take it as being normal. You normally recharge at 12.1v or about 50% SOC. What is all this 10.5v?????? Holy cow!