I'm wondering if I have a bad Multiplus unit. I have just installed a Multiplus on my boat during winter layup with lithium batteries. As I am checking the install to verify that everything works, I decided to try to plug into a gfci to see if it trips. My dock has a RCD (30mA) on the shore power pedestal and I would like to have this figured out before we launch so I am using a GFCI outlet as a test. Unfortunately, it trips the GFCI as soon as the charger function comes on and starts charging the batteries. I have a dedicated leakage current clamp, so I checked the leakage current on the main AC-in and all is fine when you flip the breaker to give the multiplus AC power. It registers ~1.2 mA with the multiplus on. However a few seconds into the startup sequence, the multiplus charger turns on and starts ramping the current to the batteries in bulk charging phase. During this time, I can watch live with my leakage current clamp as the charger starts up the current go from ~1.2mA to 30 to 40 -50 mA +, all based on what I limit the current to the charger in the VE Configure software (ie charging current 50, 60, 80 amps etc). If I limit the bulk charging to 5-10 amps I can keep the leakage low. This is with a double pole breaker in the off position on the AC-out portion so nothing is really connected as a load and both N and L1 are open on the AC-out. The only load is the batteries being charged on DC. In addition, if in the VE configure software I click the box to disable the charger, then it doesn't trip the GFCI, and it works as normal with low leakage current, but of course without the charger functionality. Also, if the batteries are near full and the charger switches to absorption, the leakage current falls considerably into the 10-25mA region based on the charger output. I have been staring at this for a couple weeks now and I've tried just about everything with disconnecting all DC loads except the batteries, isolating neutrals for the inverting loads, and measuring leakage at each point. Thoughts on what I haven't tried, and or how to test if the Multiplus unit itself is leaking current to ground during the charging phase? What am I missing?
