Lithium-ION-POLY Batteries.... etc.

Hi All,
Most of my project seem to be things? that move, etc. I have for years always used rechargeable cells usually in the form of AA's. I have some old Nicads on their last leg and some new NimH! I think 2700mA being the highest I have.

But I have been taken by the Lithium 18650 cell a bit longer and fatter (but lighter?) then an AA at 65mmx18 but 3.7v and 3600mA is tempting, the other thing I notice is some are protected (by a small PCB, in the base) for over changing/discharging, over voltage, etc) and some are not...

It would be good to hear from someone who uses or has used these cells, the protected are more expensive as you would imagine, could you recharge the un-protected one's then with a good bench PSU with constant voltage and current limit?? it seems you must never use more then 4.2volts for the single celled 3.7v ones.

There again I could be wrong



PS. Yes I know Lith-ion and Lith-poly are not quite the same!

I use them a lot.
Pretty useful and longer lasting than NIMH.
However, you must not overcharge them , or over discharge them .
ie no more than 4.2 V when charging and no less than 2.8 V when discharging.
The protected ones are more foolproof.
Also, be careful of the stated capacities, as there are a lot of fakes, especially if you are buying them on Ebay
or from Chinese sellers.
Anything over 3300 mah , unless its from Panasonic,Sony or Sanyo, is likley to be a fake.

I found this webpage about charging LiPos useful.


I am an expert in lithium battery. You should get the protected one. Why? All are the same basically. They will have same capacity, same current, but the protected has a circuit to stop discharging when it's below 3.0v or so, and stop charing at 4.2v. If you bought those cheap 18650 battery charger. Its terminal voltage most of the time will supply more than 4.2 v. Without protection, you are overcharging your battery all the time. That is bad. Draining you battery below 3.0 v reduce its capacity.

I am an expert in lithium battery.

State your credentials please.