Li Ion batterys

[Silver Serpent]

Another option is to find someone with an old laptop battery pack and dismantle it. Many of them use unprotected 18650 cells inside the pack, with one big PCB for all of them. In most cases, only one or two of the cells are defective, so you're free to use the rest for sabers.

[Lawrs1]

good idea, how would you test to find out which cells are bad

[Silver Serpent]

*Disclaimer* I haven't done this myself, so take it with a grain of salt:

I'd pop the cells on the charger and bring them up to a full charge, and then give them a known load. Say, a P4 green @ 1000mA or whatnot. Measure the voltage. Right off the charger they should be around 4.2v. Use a stopwatch to measure how long it takes them to drain and calculate mAh from there.

I found this little nugget on another forum, and it may be useful for calculating battery capacity:

4.2V – 100%
4.1V – 87%
4.0V – 75%
3.9V – 55%
3.8V – 30%
3.5V – 0%

I'm sure some of the more experienced members here may know of a better way to test them.

[Kevin Starwaster]

Another option is to find someone with an old laptop battery pack and dismantle it. Many of them use unprotected 18650 cells inside the pack, with one big PCB for all of them. In most cases, only one or two of the cells are defective, so you're free to use the rest for sabers.

Sometimes you can find them at the dump if they have an electronics recycling section. (Or even if they don't but someone doesn't care and just dumps stuff)

[mrknify]

question; will testing them after fully charging will let us know if they are bad?

[Silver Serpent]

That would be the point of testing, yes. You want to be sure the batteries charge up to full, hold a charge without draining on their own, and have close to the correct mAh.

[mondas42]

I am having a problem. i have wired up my battery pack as per the advice given. when I connect it to the charger the charging light comes on for about a second and then goes off. When I reconnect it, the cherging light again comes on but quickly goes off. I know that the battery is connected correctly because when I connect it to a voltmeter it shows about 6volts but this quickly drops. any ideas?

[mondas42]

please any help with this. I charge it for about five seconds before the charger says that its fully charge, this gives me approx 4 seconds of LED light before it powers off, I dont know what to do to stop this???

[Silver Serpent]

Can you post a picture of your wiring? If you're only getting 6v from a li-ion pack, then it's definitely not fully charged.

[Zzan]

Can you give more information or pics of your battery pack?

Is this a pre-made protected pack?
Did you make it yourself from unprotected cells with the proper PCB?
Did you make it yourself from protected cells and add another PCB? (hope not cause this is wrong and bad)
Did you make it yourself from protected cells which you removed the protection PCB's from and then wired together with the proper PCB?

What charger are you using, is it a Li-ion charger? Are you charging batteries directly or through a recharge port? If it is a recharge port what does the wiring of it look like (pic, diagram)?