Notes:
I bought this battery out of curiosity (SKU #156914 from Dealextreme). The battery
comes with a plastic box and is made up of two Li-ion cells (2×3.7V = 7.4V average voltage). Even though it looks identical
to other types in the same PP3 packaging, it has a few very important differences:
- Higher capacity: 2-3 times more than NiMH;
- Different charging voltages: the chargers for NiMH and Li-ion of this type are completely incompatible. NiMH are charged
at 10.5-11 volts (7 cells of 1.5V). Li-ion are charged at 8.4V (2 × 4.2V). Even though the connectors match up physically, the
Li-ion battery cannot be charged in a NiMH charger: attempting the latter could result in an explosion,
fire, or ruining of the battery!
- Different working voltages: this chart visualizes how the starting, average and ending voltages of the three common
types of chemistries in this package are completely disparate:

- Weight: The Li-ion is quite lighter in comparison to its NiMH equivalents;
- Protection circuit: This battery is not a "pure" 2-cell one; it has a protection circuit. It switches off the battery
out of the way when the internal voltage drops below about 6.1V. There's an upper limit as well (or so they claim), but
I haven't tested it, it should be around 8.5V.
- Self-discharge: virtually nonexistent
- Current capability: significantly more than NiMHs, see below
As I didn't possess a Li-ion charger, I found an useful circuit here, which
I implemented and tuned to have around 60 mA of charging current. I did all charges with that device
During the tests I found out that this battery has no problem with high currents. The standard discharges were performed
at 55 mA (C/10), but I also did an experiment at 330 mA and it had virtually the same capacity!
Test results

Unpacking discharge:
