I've got an idea how to test if your chargers work. although i havent done it, i want to try, but havent got around to it.
ALL chargers charge at higher voltages than its batteries, so use a multimeter to check the output voltage.
using the equation R=V/I, where V is the voltage, and R is the resistance, I would be the current (must be in amps. if it is in mA, divide by 1000). check the amperage of the charger (I), should be on the label of the charger. then, use the equation to find your multimeter reading minus batteries voltage (V), ie; V=reading-1.5. When you find the resistance, go to radioshack or wherever and buy resistors that add up to the resistance (R). you want a variable resistor as well, then whilst varying the resistance, measure the voltage across the resistors.
find the voltage when the charger stops charging. if its above your expectations, either chuck it, or set a timer on it everytime you use it, checking the status of the batteries regularly during charging to prevent overcharging.
to check how long it takes to charge a battery, use t= Q/I, t is in seconds, Q is most likely in mA h. Check the amperage of your charger, and divide it. Do note what everything is measured in. if it has a small 'm' as in mA h, it is 1/1000 of an A h. CHargers usually give current in mA. Alternatively, and much simpler, you might remember how long to charge the batteries.
Batteries can usually handle overcharging for a while. dont test it, just dont panick too much if you forget to unplug the charger an hour later.
an example is a plugpack which says 720mA, and measured 12.40V.
recharging 1800mA 1.2V rechargeables. (i expect the voltage to be slightly higher, say 1.5V.)
12.40-1.5=10.90V
R=V/I
R=10.90V/(720 mA/1000)
R=10.90V/0.720A
R=15.138888888 ohms
R=15 (go buy a resistor around 10 ohms, and a variable resistor)
attach variable resistor with the resistor in series, ie end to end like a chain.
attach the set of resistors to the charger.
put a multimeter at the charger.
turn on the multimeter and charger.
twist the variable resistor until the charger turns off. take the last known voltage, say, 1.45.
CLose enough, the chargers fine. if its something like 1.53, id personally say thats too far.
say it was at 2.64V. its obviously broken, but i want to keep the charger.
t=Q/I
t=1800mA h/720 mA
t=2.5 hours.
at most, id give it a little bit more since its charging so fast, +- 45 min?
charge for 2hours 30min
and at max 3.25 hours = 3hours 15min
but check the voltage. this time is only a guide. if your batteries reach 1.5 volts, its good enough to turn off, and so check how long the charger was on. keep this time for future reference
hope this helps some people!
feel for you heartbreak. except, i checked my batteries, luckly!
Edit: Sorry everyone, big mistake, you must reread
