Originally Posted by L473ncy
Just charge it at 1C (1600mAh for 1 hour).
If you're really worried about it then charge a .5C (800 mAh for 2 hours). No need to charge it any lower. In fact it might be better to charge at 2C for 30 minutes if you need to grab the battery and leave the house to go to the game.
Now as for the batteries, are they high quality? Are they working? What charger are you using? Is it a "smart" charger or a "dumb" charger (typically the wall chargers you plug in directly into the socket that you get stock with your gun)? If it's charging for only 15 minutes before shutting off then there's a problem, is your battery warm/hot after this? If not then you're not charging at 4C.
Secondly, are you sure it's not a problem with your gun itself? ie. Motor maybe dying, gears shimmed badly, or motor height set wrong? It shouldn't be struggling to turn the gears. If it's fine for 70-150 shots then it's most likely a battery charging problem.
The charger is an Intellect smart charger. The batteries are G&P. The original 1C didn't go the entire hour - the charger gave a warning that the voltage was below threshold, which I assume means that the voltage wasn't high enough to push additional current into the battery. The pack under 1C did not get warm. I'm currently running a test charge at 200 mA to see if that makes a difference.
The gun is effectively new. I looked at the shims and gear free-play a few weeks ago, and they looked fine (had clearance, spun freely). The motor is mating 100% with the gearbox (no rattling or stripping sounds). The motor pulled strong, but started struggling like it wasn't getting enough juice. Another player had a spare battery pack, and that one lasted the entire day, which is why I think it's the battery or battery charging method.
Anyways, batteryuniversity helped explain some of the issues I was having, but not all. Other threads here seemed to indicate a "low & slow" approach may help push the current into the battery pack. I'll just have to see in a few hours where the test battery stands.