epm96 avatar image

Multiplus 3000 Split Phase Voltage Issues


I have two Multiplus 3000's in an RV split phase with 50amp shore power (two legs of 120v power in USA). The units are configured in split phase and are hooked up to a 12v lithium battery bank with 800 amp hours of power (8 batteries in parallel).

I am experiencing a weird issue, where one leg's input voltage from shore will drop down to ~100 volts and the other leg will increase to ~135 volts causing my surge protector to trip briefly then everything resets after 1-2 seconds and the cycle repeats. I've tested in multiple locations and this is occurring in multiple locations so i've ruled out the shore power actually being the issue (i think, open to suggestions but this has occurred in 10 locations. We also just replaced our surge guard transfer switch to check if that would fix or be the cause). The issue seems to occur extremely frequently (every 15 seconds) when running a 1500 watt or more load on either leg. We have tried both dynamic current limit and without and UPS function and without with no noticeable change. When the issue is occurring the units will switch from float to inverter and back in a fraction of a second I think because of unhealthy input voltage. We are running through the system checking for loose wires but don't expect to find anything but will double check.

Everything works fine on battery and when not connected to shore power.

I'm curious if anyone has ever seen this before and if it may be a firmware issue or a result of a split phase configuration issue? We are running the 430 firmware that came with the units and didn't want to upgrade without checking here first if anyone has seen this issue.

installationinput currentsplit phase
2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

1 Answer
Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @epm96

It sounds like you've lost the neutral connection somewhere, this can do a lot of damage! make sure it is always connected or if it is not available use an autotransformer to provide the neutral.

2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Thanks Daniel, I think i've isolated the issue down to a bad power cord reel that probably has a loose neutral contact somewhere in the reel. I isolated it down to that as i fired up our generator and noticed that everything works fine with the Onan using the same transfer switch, same wires etc all the way back excluding the shore power reel which I think is the culprit. Glad to know its not a config issue from what you are saying. I'll report back on what the new reel does/doesn't do!

It has been a little while, where you able to figure out the problem?

Hi @Optingoutofnormal

as written, the neutral connection was loose somewhere between shorepower and inverters.

optingoutofnormal avatar image optingoutofnormal Daniël Boekel (Victron Energy Staff) ♦♦ ·

I was just curious if the OP had actual confirmation of the repair.