Can I charge Ni-MH battery with modem power supply?
This is what you need to charge your battery from 12 V supply:







simulate this circuit &ndash; Schematic created using CircuitLab

This will charge the battery pack with about 380 mA. Note that Resistor R1 needs to be at least a 2 Watt resistor (3W, 5W and 10 W is also OK) as it must be able to dissipate some heat.

This is what some resistors look like: 

 

The 3 on the left are OK

The others are too small and not OK, they would burn out.

From left to right these look to me like 5W, 3W, 3W, 1W, 0.5 W, 0.25 W and 0.125 W resistors.