Charging issue

[Tracyandkimo]

Charging problem. Just got back to boat which is on the hard for past 4 weeks hooked to shore power. BMS showed 100% charge at first but boat was unplugged for 1/2 day to move on yard and then put back on shore power. Charge had dropped to 85% and when plugged in showed +16amps going in from the 2 Cristec chargers (40 & 60 amp chargers). Charge only went up to 87% at 13.8v before charging dropped to 0-1amps. It’s holding there w BMS showing no net draw or charge. So it’s holding the state of charge against the draw of refrigerators etc. but not raising any further. Both charger’s indicator lights show “charging”. Completely overcast so can’t tell if solar will raise charge further and I can’t run alternators since we’re on the hard. 840amp hrs of 2 1/2 yr old AGM’s. Where do I start?

[Pete7]

I would start by measuring the battery voltages now whilst the chargers are on and in an hours time with the chargers off so that the surface voltage has time to dissipate. Use a volt meter.

Pete

[CharlieJ]

You do know that LFP batteries should be stored at approximately 50% state of charge. Constant floating does them no favors.
I don't know where Cape Charles is. What is the ambient temperature there?

[HeywoodJ]

Originally Posted by Tracyandkimo

...840amp hrs of 2 1/2 yr old AGM’s....

Originally Posted by CharlieJ

You do know that LFP batteries should be stored at approximately 50% state of charge. Constant floating does them no favors.
I don't know where Cape Charles is. What is the ambient temperature there?

Perhaps the use of “BMS” tripped you up?

I’d suggest that there isn’t really a problem. A long time at float, the chargers probably saw enough voltage that they stayed at float. The BMS is slightly confused. If you’re going to be on float for a long time in the yard just ignore it. If you can’t, drain down the batteries far enough that they have to go through a full charge cycle.

[CharlieJ]

@HeywoodJ #4

Perhaps the use of “BMS” tripped you up?

Absolutely did! OP, belay my post #3.

[smac999]

Guessing he means battery monitor not bms.

If the voltage is at 13.8v as stated and current is 0. The battery is full. Manually reset the battery monitor back to 100%

I would test a drain again to see what happens. But this time pay attention to it.