how to choose the right battery?

[pomprocker]

Sorry, I'm still half asleep and feeling ultra lazy so i didn't feel like combing the forum for this...

How do you figure out what size battery you need?

I see some things with 6v, 7.2v, 9.6v etc.....

[want2learn]

If it's for a robot i'd say go with the voltage nearest to your motor specs. Regulate it down for your circuitry.
If it's for circuitry alone I'd still regulate it down but pick a battery closer to the total voltage required by your regulator i.e. 7.2or6.0 for NimH, 7.4 for lipo.
As for capacity, work out the total draw for your robot/cicuit and multiply it by the desired run time, Then look at capaities you can actually afford.

[cooldog]

battery caculator
http://www.societyofrobots.com/battery_calculator.shtml

energy caculator (might come in handy)
http://www.societyofrobots.com/energy_calculator.shtml

always check the main site

[pomprocker]

thanks guys!