Teardown: Old APC Back-UPS units

A look at the output waveform, and how to change the charging voltage comes at the end of the video.
The old models in the video are BK300MI, BK500MI and BK650MI, all 230 V models. The new "horrifying example" one is a BR500!.
In the video, I mention line-interactive as a negative feature, which might sound a bit strange. The reason for this is that the power consumption of a line-interactive UPS is considerably higher than that of an off-line unit; APC's line-interactive models are usually rated for a 95 % efficiency while running on the grid, which is an extra 5 % loss - over 30 W in a large unit under load - for all connected equipment.
Unless your utility power has sags and spikes, to the point where an off-line unit switches to battery power frequently enough to wear the batteries at an accelerated pace, this extra consumption will not be worth it.