We have had similar problems with battery/ inverter start-up, as well as red warning lights with EG4 batteries mentioned in previous posts. Fortunately, our batteries seem to be working well lately, but I’ve experienced the same issue with the SS 48 volt, 25 amp charger. The charging process took a little longer than expected, but the indicator lights on the charger go from flashing red to flashing green. No yellow lights at all. Near the end of the charge cycle, the voltage went from 55.2 to 58 volts in just a few minutes before I turned the charger off. I don’t think we’re getting a full 1400 watts of charging power, but can’t prove it. Whenever I charge batteries with the generator, I bypass the inverter completely by turning the AC input breaker to the inverter off, the inverter AC output breaker off, and the inverter AC bypass breaker on. That way, 100% of the power from the charger goes directly to the batteries.
I’m curious when you say that your house is drawing 3-5 amps according to your magnum. Are you leaving the breaker settings in the inverter/charger in the normal position when charging from your generator? When I charge batteries from the generator, I turn off the inverter AC input breaker and turn off inverter AC output breaker and turn on the AC bypass. The inverter will then be in bypass mode and the house is running totally on the generator. The charger will then charge batteries with no AC load connected to the inverter. If you don’t take the inverter off line when charging with an external charger, it seems like the built in charger in the magnum would be charging at the same time as the external charger. I’ve been charging this way for years since my magnum integral charger failed when it was new and I didn’t want to dismantle it to return it. I recently bought the 48 volt, 25 amp charger and EG4 LiFePo4 batteries and the charger seems to work reasonably well. Maybe not 25 amps, but close. I could be misunderstanding your set up, but I thought I’d throw in my 2 cents anyway.
