I bought a couple of Lithium Ion batteries on sale for $0.05 a piece. The are for a sony camcorder or something. I was wondering how I might charge them. I see there are chargers and chips to charge lithium polymer batteries. This battery seems to have 3 contacts on it. How do I tell which is which?
My Lithium-Ion cells are 1800mAh, 2000mAh and 2200mAh. That is their rated capacity, C. They all have a charging current that drops very low when they are fully charged.Not sure what 3% of rated current means. If 3% of C rate, would be okay but charger will likely timeout on a lot of still useful batteries. An older battery may not drop to this level. Do 3% C termination without failsafe 2-3 hour timeout would be foolish.
There is a way to charge a "c rate" LI battery in about an hour, it uses what we called "dual rate" charging where you have two different voltage set points and the charger is limited to C rate max anytime the battery is below the set voltages:Many consumers got used to 1 hour recharge times for their cellphones, electric toothbrushes, and such when Ni-Cads were being used.
NiMH extended this time slightly. LiIon need at least 2 to 2.5 hrs to recharge. Even a 'ruggidized' LiIon that claims it be recharged at 0.8 or 1.0 C does not improve the recharge time to any significant degree. The 4.2v limit still applies and at higher charge rate it just reaches the 4.2v sooner but with less achieved charge. At 0.5C charge rate it will be at about 85% charged when it hits 4.2v, at 0.8 C charge it will be at about 70-75% charged. So all you end up with is spending more time in the top-off charge period at 4.2v. (and you have stressed the battery more using the higher charge rate)
Re the comments by Dean Huster:
Install a 10,000 mA-Hr battery and meter it as if it is 2,000 mA-Hr battery.
Will recharge in 15 minutes.
Li-Ion have no memory effect and no detrimental effect due to partial recharging. They actually have much greater longevity health if never charged above 60% state of charge.
LI's have a higher internal impedance than NI-CD or NI-MH of comparable A-hr rating, hence the cells heat up more powering high current applications. The NI cells impedance is so low you can pump out incredibly high currents. Remember the old soldering irons run off two sub-C Ni-Cad cells? They ran the cells at like 10c discharge rate (use them up in a few minutes) because the design is basically a dead short across the batteries through copper wire which gets hot enough to melt solder. LI's would not be happy doing that....."Something" in the circuit of my electric RC model airplane throttles down the motor speed while it is flying. Then the Lithium-Ion battery is pretty warm and the motor is hot. The motor speed control circuit is warm. The battery is just two cells with the thermal detection circuit removed.
After a rest (maybe a cool-down) then the battery will continue to power the airplane for another powerful long flight.
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