Find appropriate replacement for Magnum 2812 charger/inverter

DIY
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1

The 14 yr old motorhome I bought last summer has an older Magnum MS2812 inverter / charger. It has 6x 100 watt PV panels on the roof. Recently I replaced the lead-acid batteries with 3x 230AH LiFePo4, and replaced the AM Solar installed charge controller with Victron controller and DC-DC Orion.

While I upgraded the remote for the MS2812 to their ARC-50, and upgraded the control board in the charger to fully support the LFP charge profile, it is just not playing nicely. My Victron shunt shows a ‘trend’ line including repeated, but momentary, spikes of charger voltage to 15.76 volts. Amps are shown as 0.1 at that time. That scares me. How much of that can an LFP battery take? Temps were in high 30°F range; is it possible those spikes are just an artifact of the BMS switching on and off?

Unless I’m being Chicken Little, I think I need to pull that MS2812, and go with Victron. But where do I find a table or other reference to determine what’s appropriate?

2

You won’t damage the battery—it’s simply disabling the charge MOSFET because one cell is going over voltage. Can you adjust the charge voltage? Many new lithium batteries won’t reach 14.6V the first time they’re used. Often, one cell will hit 3.65V while the others stay around 3.45V, resulting in a total voltage of about 14V.

The time it takes to reach 14.6V depends on the balance current of the BMS, which is typically a few milliamps or up to 1–2 amps. Try lowering the charge voltage to 14V initially, then gradually increase it to 14.1V and beyond.