Instructables

Any objections to my battery charging solution?

I bought some cheap 360 battery packs on the internet and big surprise they don't work.  The problem is that the built in charging circuit charges the packs to around 2.26v when my controller wont turn on until closer to 2.5v.  My idea is to use the indicating LED (that came as part of the pack) that has a forward voltage of around 2v to drop the 5v charging voltage down to 3v and charge the packs to that voltage.  Theoretically when the packs reach 3v the LED will not be able to sustain the forward voltage and will turn off stopping current flow to the batteries and thus stop charging.  I have a lot of knowledge about electronics, however my knowledge of batteries and their sensitivities is just about nill so I thought I'd ask here before I rig this together and get an idea of the likelihood of the batteries blowing up.  I've attached an image of the proposed circuit any knowledge would be greatly appreciated.


Picture of Any objections to my battery charging solution?
frollard1 year ago
If just nimh cells inside I see no risk in trying it while supervised - perhaps the charge circuit is crapped out. If lithium, I'd just chuck/recycle them and get something better.
double_g (author)  frollard1 year ago
Thanks for the input frollard!

I'm pretty sure they're NIMH it didn't say it was one of those auctions where they said the batteries were "3600 MHz" I assume they meant 'mah' but who knows maybe I just desoldered the world's smallest super computer. I have it charging now seems to be working, I'll post back when its fully charged.
double_g (author)  double_g1 year ago
Well I'm going to call this a success. The batteries charge quickly to around 2.8 v which seems to be enough for the controller to play on. Since at around this point there isn't much voltage left for them to charge on they start charging really slowly so I don't think I'll probably ever get to full voltage where the LED would shut off but it's nice to know that the circuit should theoretically stop charging if left plugged in long enough.

As a side note I really should have put a current limiting resistor in series with the LED so I didn't burn it out. Fortunately the resistance in the line as well as the internal battery resistance seems to limit the current enough.