Battery Backup PCB -- How to discharge

Thread Starter


Joined Apr 28, 2004
Had an old battery backup die out. Ripped it apart to see the pretty innards, and figured I'd snag a few components off the board for keep sake to play with when I get back into labs. However, I want to make sure the board is not retaining any dangerous levels of electricity. Most of my measurements on several components have been under 100 mV and 30 mV. Do such boards retain lethal amounts of juice, or can I freely desolder components without zapping the begeezus out of myself?


Joined Jul 22, 2007
Did you try replacing the battery, before writing it off as dead? Check the fuse? I've had mine about 12 years now, replaced the battery twice. Still works fine.

Doubt you'll get much of a shock, least not any worse the sticking your fingers in an outlet... Seriously, the battery is 12 volts, unless you haven't unplugged it from the wall yet, that'll be the worst you'll see. I really hate getting shocked myself, but finding humorous to see my brother get zapped. Anyway, if you are seriously worried, just short the leads of the large caps. I don't remember any real huge ones in mine, and most likely would even be concerned if I was scrapping it.


Joined Jul 17, 2007
Is the battery removed?

If not, remove it.

If so, just hook up a resistive load across the board's connections for the battery. Use Ohm's Law to determine the proper resistance and wattage.

A light bulb of appropriate voltage rating would be a very good choice.


Joined Sep 8, 2007
also, capacitors arent perfect, they will lose their charge after a certain period of time. it sounds like youve had this sitting around a while, the caps might be fully discharged, or close to it, if thats the case.