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I am trying to charge a 9V battery with a 24V generator so i need to bring the voltage down closer to 9V. what is the best way to do this? With resistors? and if so, what size resistors should i use?

The answer to your question depends entirely on the battery type.

What type of battery?

NimH?

http://en.wikipedia.org/wiki/Nickel%E2%80%93metal_hydride_battery

Li-Ion?

http://en.wikipedia.org/wiki/Lithium-ion_battery

Li-Polymer?

http://en.wikipedia.org/wiki/Lithium_polymer_battery

:)

just use a diode from the 24v geny giving half wave dc to quick charge the 9v If you use a resistor to slow charge it may need to be a big one on a heatsink ?

@jonnyaudio,

Depending on the type of battery, your suggestion could result in overcharging the battery with a consequent risk of overheating and - possibly explosive - cell rupture.