Brief:
The cheapest 12V sealed lead acid battery I've ever seen!!

Construction:
Parts list:

• 1 Tyco XFO ($10 from Dollar General)
• bullet connectors
• epoxy

I had this built in under 1/2 hour with basic hand tools.

1. Remove XFO from its packaging.
   
2. Remove 6 Philips screws from XFO charging station then remove front cover.
   
3. Locate and drill holes for female ends of the bullet connectors. I drilled mine level with the top of the battery on the side the wires are soldered to.
   
4. Clip and strip one battery lead between the circuit board and battery. Twist stripped ends together and crimp on a female connector.
   
5. Repeat with other battery lead.
6. Slide female bullet connectors about half way through holes from step 1 and tack with CA.
   
7. Reassemble field charger and epoxy female bullet connectors in place from the outside.
   
8. Crimp on male bullet connectors to battery leads of your launch controller so it can receive power from the XFO Field Charger.
   
9. Charge XFO Field Charger for 14 to 16 hours.
10. Fly all day long!

This battery will ignite motors using Quest Tiger Tails, Copperheads, Solar Ignitors (singles and clusters at least up to 5), and straight nichrome wire.

Summary:
Pros for this battery are its ability to be modified for rocketry use and still be used for its original purpose, length of time it can hold a charge under near constant use, and low cost.

Cons are its long charge time.