I'm trying to piece together a system on a budget... I managed to find two Multiplus Compact 12 2000 80 120V units with the same part number and first four digits of the serial number, which means I should be able to use them in a split phase configuration. Both units were originally purchased from and programmed by Battle Born, but I've sourced them from different private sellers.
I'm new to the Victron inverter world, having only had limited experience with an Victron MPPT charger, but I do have plenty of experience with electricity and electronics in general, and I'm learning pretty quickly.
I bought an MK3 USB adapter, and presently have it hooked up to one of the Multis, along with a pair of 12V LiFePO4 batteries. I've confirmed its ability to pass through AC, invert with and without power assist, and charge the batteries. Everything seems to work fine, however...
I've taken note of a noise that sounds a lot like a faulty fan bearing. With the cover off, though, it's clearly not emanating from the fans themselves. A buzzing sound from the transformer can be heard, and gets louder on increased inverting/charging loads, but that's not what I'm talking about here. This noise seems to show up during lighter DC loads, for example as the battery charge tapers when the battery approaches full SoC. This is a video of the noise, most audible from 6 second mark onward. For the record, it's been updated to the newest firmware. (edit: with further testing, the noise disappears completely when the fans speed up, and reliably comes back when charge current is reduced--it seems to be related to the throttling of the fans, although not the fans themselves)
Perhaps unrelated, I also took note of a period when there were no loads attached, and the "AC Loads" indicated negative power draw of circa 30W.
Being inexperienced with Victron inverters, I'd appreciate if someone could let me know if these things are normal, or indicative of a (possibly latent) fault. It would also be nice to know if there's any kind of specific diagnostic testing tools, besides the built-in status LEDs.
Thanks in advance for any tips, feedback, or suggestions!
