You should be able to stack a few button cells in series. My keychain Laser pointer uses three little batteries. The print on 'em is pretty small but they appear to be AG3 (AKA LR41, V3GA, or 192) 1.5V with dimensions 0.309" Dia X 0.143" thick each and three together weigh approx 0.07 oz. Voltage appears to be 1.5 volts, so you would need a stack of 6. Don't know their internal resistance, but the stack is probably not different enough from a 9v alkaline cell to matter.PhantomVirus wrote:Those radio shack clips are cheap and work well. I am in the process of building a police car with my son with blinking red/blue LED's all driven off of a 9V battery.
Will post pics as this thing evolves.......it is a bummer that the auto blinking LEDs are only 9 volt and I have to use that huge honkin battery.
Incorporating a 9v battery into a car that might actually place is going to be a huge challenge.......
R
The service life of smaller batteries will be a lot shorter that the "big honkin" 9v battery, but how many seconds does it need to flash to finish the runs in a typical derby? Wikipedia gives 25–32 mA*Hrs for the Alkaline version, and longer for the more expensive silver oxide version.
Fabricate your own "holder" by drilling a hole about 0.345" in diameter in your car and set of contact wire at each end plus a "plug" to hold the batteries and contact wires together. Note that the interior of the hole should be lined with an insulating paper if the batteries are to be left in the car. Otherwise, the resistance of the wood, as high as it might be, will drain the batteries over time.
The AG0 size is about 15% smaller, but has a much shorter life span, 10 mA*Hr.
I found some specs on alkaline and silver oxide button cells at http://en.wikipedia.org/wiki/List_of_ba ... lkaline.29.
By comparison, the "big honkin" 9v batteries, described at http://en.wikipedia.org/wiki/List_of_ba ... angular.29, have a capacity of "honkin" 565 mA*Hr.