$$$$ Chargers
I have to agree with the statements that it's better off buying a good quality commercial charger for NiCd and NiMh batteries.
But it’s really not hard, or dangerous, to build a charger for LiPoly batteries.
It can be done with 2-LM317 adjustable regulators, with heatsinks, a current limit power resister and a voltage reg pot. Total cost for a 1 or 2 cell, 1.5 amp charger is $8.00. The only thing you need to make it safe is an accurate voltmeter.
You will need a power source. You can use a car battery, a computer power supply or a wall wart AC to DC power supply. Anything that will supply 12 to 20 volts DC at the current you want.
This charger will charge a cell to “100%” safely. All it takes is time.
Here’s one I built for 145ma cells.
Jay