Cheap Lithium ion batteries - help?

I picked up 4 Canon NB-4L batteries for 50p each, thinking that for the price they might be worth having.
However, I don't have a charger - any help with this?
I've got power and electronics and stuff.
3.7V 760mAh (Li-ion)

Picture of Cheap Lithium ion batteries - help?
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lemonie (author) 8 years ago
Oh yes, I'd want to measure what the thing was doing. But I was hoping for a schematic...

V-Man7378 years ago
Kiteman was on to something.
If they're the same voltage and material as a cell phone battery, you could hook up wires from the cell phone battery contacts to the battery terminals. Make sure the phone's 3 contacts are used with the battery's 3 terminals correctly. Your normal cell phone battery should be analogous to these batteries in the terminals (voltage, GND, voltage). That should help indicate where to connect. Your phone will view it as a different battery and charge it using its smart circuits.
If the contacts are recessed (like mine were when I did this), put small bits of aluminum foil in the recesses and tape wire leads to that.

It is probably advisable to use an old cell phone instead of your nice new one, just in case of some catastrophic FAILure.
lemonie (author) 8 years ago
OK, that helps a bit, thanks.

yourcat8 years ago
Li-Ion batteries take a two stage charging technique where the rated charge current is applied until the voltage gets to a set level (usually about 4.2V), then that voltage is held until the current drops to ~3% (~10% for LiPo) of the rated charge current.

This shouldn't be too hard to rig up, but if there's a bug in the system things could be pretty bad.
lemonie (author)  yourcat8 years ago
It's the rigging-up I was after advice on. The stuff I can't easily find on the internet.

Emsaid8 years ago
you can get the charger here pretty cheap.
lemonie (author)  Emsaid8 years ago
I don't really want to spend more money on the charger than I paid for 4 batteries, but thanks for the comment.

NachoMahma8 years ago
.  I didn't see anything helpful in the first 4 hits, but you may be motivated to look deeper:
Google Canon NB-4L +schematic
lemonie (author)  NachoMahma8 years ago
I already looked, I thought someone might know better.

Kiteman8 years ago
Would an old phone charger do the job?  There is circuitry in place to prevent over-charging of the battery, but I don't know if it's in the charger, the phone, or built into the battery itself.
Crack open the wire that goes to the phone, get at the wires and fashion a couple of probes to touch to the contacts of the battery.

Maybe fashion a simple docking-slot to hold the wires in place?
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