SpudFiles

I wouldlike to build a cannon like this http://www.spudfiles.com/forums/my-firs ... 21937.htmlI need to find an affordable 12v battery and charger combination that is small and compact, i would prefer to have an extra battery as well.

It's pretty common for most of us o use airsoft batterys, but I think thats a better option for people who own airsoft guns because I have no idea how much they cost

12v Cordless drill battery and charger

How about an RC battery?

A possibility is a small 12V lead-acid gel battery. For example;
http://www.allelectronics.com/make-a-st ... ERY/1.html
3.8" x 1.7" x 2" (that's pretty small), 1.21 lb.
$10 (+$7 shipping IIRC)

Can be recharged with a car battery recharger (or straight off a running car using jumper cables.)

Take a look at the other 12V batteries at AllElectronics.

You can also get chargers there (and not have to pay additional shipping).
http://www.allelectronics.com/make-a-st ... IES/1.html
$10

would like to avoid lead acid, just for weight

i was looking at milwalkee m12 but that is expensive

The local Ace Hardware started selling similar batteries to the ones listed on Allied Elec. They are off brand sealed lead-acid type and about half the price of Allied. I payed $12.99 for this one and they have almost every other size. In comparison to a nimh or nicd pack the only benefit is cost. The lead-acid pack is a bit heavier than two 6v nicd packs. So if cost is an issue maybe the lead-acid us a viable option. Also chargers were about $10-$15 for a wall charger.

Why does it need to be electric powered? Have you considered a manual pump built in to the launcher, it will be much lighter, quieter and will probably allow you to reach higher pressures in a small chamber that will give you better performance.

Because he does not have FOREARMS OF STEEL.

mark.f wrote:Because he does not have FOREARMS OF STEEL.

Well then he ought to self-pleasure more!

A quick note on batteries. They are rated in Amp Hours. A small 4 amp hour battery can provide 1 amp for 4 hours or about 4 amps for 1 hour or 20 amps for about 12 minutes.

How many shots are you planning and how long does it take to fill your chamber. Battery size matters.

The faster you discharge a battery, the less capacity it has, so on the 20 amp draw, expect less than 10 minutes run time.

The tiny battery in the post above is only 1.3 Amp Hours.. Don't expect it to run a 10 amp compressor very long.

Many NiCad or NIMH batteries have a much higher capacity in a smaller package and can provide high discharge current.

We built something along the lines you're proposing a while back. We used a Li-Po battery 3s-2500mah. Charges a 1lb propane tank to 100psi, and gets 25 or so shots per charge.

An inexpensive place to get rc gear,

http://www.hobbyking.com/hobbyking/store/uh_index.asp

For the math challanged, 2500 mah is 2.5 Amp Hours or about 2wice the capacity of the lead acid battery in the photo. The LiPo is able to provide a higher discharge current than the Lead Acid.