Battery Pack Monitor Boards

[dknguyen]

About those little PCBs on battery packs meant to do things like keep track of the charge going into and out of the battery for gas gauge purposes, as well as other pack information health and statistics...

Does anyone know how the power management on those things work so they themselves don't drain the battery empty? Are they just in sleep mode most of the time when the pack is not being drained or charged? Or is there a auto-switch of some kind that is keeps the board disconnected from the pack so it doesn't drain the pack?

 

[Nigel Goodwin]

They do indeed drain the battery, but are specifically designed for such current to be extremely low - however, if you're wanting maximum life in a long term intermittent operation device, then you don't want any battery pack devices leaking even small amounts of current.

I use an FET switch to turn power ON to a GSM modem when required, so I have the battery monitoring potential devider on the output of the switch, so it doesn't waste any power.

 

[dknguyen]

Okay. This is for a fuel gauge battery monitor that is only plugged in and used occasionally for short periods pf high power.

Maybe I'll use a double prong positive connector where one goes to the battery but the other goes to the board, with the intention that the load/charger has both terminals electrically connected so when the battery is plugged in, the monitor PCB becomes powered (by battery if it's the load or charger if its a charger). Then I don't have to worry about parasitic drain during storage since that's the only time it matters since the load power dwarfs it during use anyways.