They work fine albeit not with a huge/fast balancing current. I use them all the time on 12ah and 24ah Headway Life packs. You will need to be charging for the balancing to work though, otherwise it will just slowly drain your pack down. I am not familiar with using it on LIpo per say, but for Life packs you would need to have the charger achieve 3.45 volts per cell or more for the balancing to actually occur. Thats where the inflection of the charge voltage curve starts (spikes upwards steeply). So for Lipo it will be at a different higher level... not exactly sure where that would be. Keeping it attached with the pack at rest in the hopes it will balance is, im sorry to say, an incorrect assumption/expectation... balancing just doesn't happen that way.
My 8s Life packs are connected to a relatively smart 24 volt SLA charger which throttles down when the HVC of the DB8 engages. I have used it with and without the HVC connected in line. If the charge current is low enough at the end of charge and the pack is fairly well balanced to begin with, then it will balance without the HVC... though I don't recommend doing that since it is likely you'll be overvolting a cell or two before the balance charge is done for most packs.
Also, when any single cells hits 3.75 v (for Life) the HVC kicks in, and there is a beeping HV alarm that occurs continuously until the pack finally balances up. Some complain about it, but it is a good indicater when it stops beeping that your pack is finally balanced up.
All in all, I really like it. It is useful if your charger plays/interacts nicely with it and you don't need all of the other features of a typical BMS... like current limiting. BTW it also has a LV alarm, but it may not be loud enough to do you any good when riding.
