The battery monitor works as advertised. It does not come with good instructions, but those are easy to find online (search for 'tr16 battery monitor manual') and pretty intuitive. You can set the number of AH in your battery and the state of charge when it is full (or empty) by a long-press on the relevant button. One slightly annoying thing is that you can't turn off the lights manually, so as long as it is discharging it will keep the lights on.