@owashii@plush.city do you know if your UPS is double-conversion or not? a double-conversion UPS *always* goes through the battery, which means that there's literally zero interruption when power is lost, but also that the output inverter is a limiting factor no matter what, whether wall power is available or not
that sounds like it's what your problem is
-F
@owashii@plush.city offline and line-interactive UPSes just switch mains power directly through when they do have power, and switch a relay when mains power is lost; this means that when power is lost, the output loses power for a few milliseconds, but this isn't a problem for most things since they're designed to deal with AC that keeps dropping to zero momentarily anyway
-F