How many / What kind of batteries to use for this?

Other Hardware Motors, Mechanics, Power and CNC
1

http://www.sparkfun.com/tutorials/199
This RGB LED wants 650mA per channel, and anywhere between 9 to 30 volts.

It works fine plugged into a 9V wall adapter, but I need to make it powered by batteries.
Would a series of C batteries work? If so, how many?

Thanks.

2

If only there were a magic formula to figure out how many 1.5 volt batteries it would take to equal 9 volts.

Oh! There is! 9 divided by 1.5 equals 6! Take that, Fermat! I'll take that Nobel Prize now, thank you.

Now, as to how long the batteries will last, you'll have to google for that, dividing the total mAh of the batteries by the load of the circuit.

3

dividing the total mAh of the batteries by the load of the circuit

Not quite that simple - a D cell could be rated at 14Ah, but try that as 14 amps for one hour.

4

AWOL:

dividing the total mAh of the batteries by the load of the circuit

Not quite that simple - a D cell could be rated at 14Ah, but try that as 14 amps for one hour.

Quite true. mAh ratings are often a 'marketing' specification. Unless the spec is accompanied with discharge rate and temperature one should take them with a grain of salt. :wink: