They included a couple of spare
fuses in the box with mine, so I presume they’re used serviceable. Do you have the programming cable? That might help with diagnostics. That said, the makers are pretty responsive to
email, so drop them a line.
I myself am running one as part of a fully integrated victron system. We leave out running at all times to keep the
batteries happy, as the bms fully controls all the
charging sources. (Also, our
water doesn’t turn hard in the
winter, and winter sailing is something that we definitely do).