"These batteries function quite well for the minigun. You can pull around a solid hour of use from them, before you start to feel the rotors of the barrels slow and chug a little. The one thing with these batteries is, is that you DO NOT want to fire them dry!!! That's the easiest way to kill off the battery, then your back to square one, which is buying a brand new battery.
If you do happen to drain it dry (which I did my very first time as it stated to do) it takes around 10 hours to fully charge it. So if your on your way to the field, be sure to charge it to capacity the day before. The best thing for these batteries, is to top them off after each use.