Have a 4P Lifep04 set up and when genset begins charging its over 105ah. Then tapers after 10 minutes or so to around 70ah. 314ah Batts each set at 175ah each max charge. Not sure if it’s batts or generator slowing charging down. Note: when PV is up with sun… charging goes higher in combo. Genset regulator issue?
perhaps Amps not amphours???
Check the Charging voltage and cable drops.
You need to describe that in more detail. What device is used to charge the battery, and what is the system voltage? Do the charge controller and battery communicate with each other? AC or DC generator?
HI RL,
Charging is 120v via 7KW Nothern Lights marine generator thru an original 40 year old 7kw isolation transformer or 120 or 240 cabled shore power with 240 stepped down on its way to multiplus
Install. All cables exact lengths and properly crimped and torqued to spec. 14lbs.
2/0 cabling 12ft distance from batteries to multi.
Loads: (Due to leght of run, might need to go 4/0 for loads because I’m seeing an occasional “ripple” warning on Cerbo GX under higher loads when drawing over 2500 watts with dehumidifiers and microwave operating simultaniously. Zero cable heat issues.
Charging: charging at 100-200ah shouldn’t be an issue using 2/0?
I’m going to speak with northern lights and Wattcycle batteries regarding this “fading” charging issue. Possible Genset control issue. Batteries possible BMS
One thing of note is I had an issue with the Multiplus ii 8 months back(new in 2025)and changed out the circuit board sent by distributor. Updated all firmware and set all the parameters again. But charging has never, as new or now, held max charging profile(120ah) and even when batteries are well below fully charged, and the multi switches from bulk charging to absorbsion charging. If I turn the charging off and then back to on, it’s goes back to bulk again. A few times I’ve had to switch it off to on again due to this condition of bulk absorption. Batteries BMSs set to 175ah each max charge. So I find it odd that the multiplus ii doesn’t stay at maximum 120ah charging until batteries are full ever. Even at120ah charging, that’s only about 30ah each battery.
So I ask myself, do I have a cabling issue, a multiplus issue or a generator control board issue? And how to isolate each to sort that out.
With generator and PV both active, I’ve achieved 150ah of charging on a sunny day but PV is only 70-80amps of that when I would think the generator could easily send that number to 200ah(120ah multi /another 80ah PV) charging with pv on.
I’M GLAD the system is working but don’t understand why this fading charge is happening.
Happily afloat 
If this is a 12v set up, then try using remote voltage sensing from the multiplus to the batteries, and do measure the volt drop of the cables whilst charging.
One would expect the bulk charge to taper off as absorption voltage is reached, but bulk should be steady at near max current for the initial charge.