Apparently something is wrong with the charging circuitry. In the meantime while I'm figuring something out, we bought her a new OEM battery from eBay for less than $5 shipped. She used a spare cell phone in the meantime (which she doesn't like) to keep her going, but it is not a good long-term solution. So, I put on my little thinking cap as this was a challenge I was looking forward to taking on.
After much searching the 'net, I found a particularly useful web page:
What I liked about this one is that it doesn't use a dedicated lithium ion charger IC, which mostly seem to be SMD as opposed to through-hole. I don't have the tools/experience/knowledge to solder those kinds of components (yet), so was happy to find this circuit.
I already have half of the components required for the circuit, and it was only a couple of dollars to order the ones I didn't have, so I placed the order with DigiKey, and a few days later, I was ready.
First order of business was to breadboard the circuit based off of the schematic from the link above:
Then I needed an easy way to connect the battery non-permanently. I have a bunch of old cell phones in my 'junk bin', so I found one that might work, and disassembled it:
The part I needed is not shown above, but shown below after I soldered a couple of wires to the appropriate 'spring terminals' (not sure what they're really called):
Closeup of the soldered wires on the 'spring terminals':
Now we just need to connect the 2 wires to the breadboard:
And put the battery in:
Doh!! It doesn't work - FAIL! It only charges for a few minutes and not up to the voltage it should, so is no good. :(
I contacted the creator of the circuit and he gave me a couple of suggestions but it still didn't work. He ended up sending me a professional circuit board. When I got it, I soldered the components onto it:
So then I connected those 2 red/black wires from the top-left corner of the photo to the other 2 wires from my 'battery holder', connected the battery, and was another FAIL. :(
Not being the electrical engineer I would love to be, I didn't know what to do, or how to troubleshoot. I turned to one of my favorite online retailer of electronic components/widgets (Duh - Sparkfun!), and found the perfect thing. I wanted to avoid going this route (buying a pre-made product) as it costs more money and isn't as fun and educational as DIY. But, I had no choice.
Here's the board from Sparkfun with a Micro USB cable plugged into it (for supplying power) on the left, and a JST connector coming out on the right (to connect to the battery holder):
I know you probably can't tell, but this thing is small! It's so small I don't know if it's a good thing or a bad thing, but it works! When a battery is charging, there is a little red LED that lights up...when the battery is charged, it turns off. It's simple and small, and again, it works, so I'm very happy with it. Thank you Sparkfun. :)
To wrap this up, I performed a few more steps. I added a little bit of solder to the wire connections to make sure they stay together (circled):
Added some hot glue to keep the wires in place (they would never survive in my sister's bag otherwise):
Covered the bottom section with electrical tape in addition to the hot glue to help keep the poor wires from moving in her bag:
Then wrapped the exposed wire connections up with some electrical tape to avoid shorting the charger/battery:
All done! Instead of throwing her half-broken cell phone that won't charge the battery anymore into the garbage, she can now keep one charging/charged outside of her cell phone while the other battery allows her to actually use her cell phone!