Ive done some research at http://www.airsplat.com/airsoft-batteries.htm and read most of the material on Ni-MH and ni-Cad and they come up with these 2 batteries:

NiCad: Lower Battery Capacity, High Discharge/Charge Rate / Inexpensive
NiMH: Lower Discharge/Charge Rate, Expensive

for a m249 would i want

high discharge/low battery capacity
low discharge/high battery capacity?

Little vague on the site when it came to what you want from an AEG...help

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Airsoft Gun Repair Technician

First Q, what kind of 249? M249, M249 mk2, M249 Para?

For any of the 249 varients, youre gonna want something with a very high mAH. At least 3000+. That way youll never have to worry about a battery running outta juice on the field. For the mk2, this is easy, as the stock fits a large battery. The other two use mini's. Voltage wise, 8.4v is more than enough to get a good rate of fire without shredding any internals. Stick to nimh as well.

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I agree, don't bother with NiCd. They take abuse better than NiMH but they're a dated technology and the energy density is much lower, which is why you don't see any Sub C NiCd cells over 2300 mAh or so. High capacity NiMH are certainly not low discharge. A few years ago that may have been true but the R/C community's demands for high performance, race-bred cells has turned out NiMHs that perform a lot better than NiCd equivalents. Intellect brand seems to be the current leader in the market.

I run a 7.2V 4200 mAh Intellect pack in my M249 and it's fantastic. Easy to find (Eliminator R/C has them in stock), tons of power, has no trouble pushing a 400 fps spring to 800 RPM which is more than an adequate rate of fire for me.

Whatever you do, do NOT get a high capacity 9.6V and run it in a stock gun. You can ask Zekk about that one and how long it took me to change his shredded piston.

Funny thing is, I upgrade all the internals except the gears. deepfire piston, systema Al head, M100 spring, systema spring guide with bearings...pretty solid internal upgrades. Even with these upgrades still would a 8.4v 3000+mAh be more then enough?

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Airsoft Gun Repair Technician

It wasnt just the battery that did it, it was a combination of the battery and hop up. If it was an 8.4, it woulda done the same, only not as quickly.

the ROF on a 9.6v is crazy high and not required. Youll go through ammo way too fast. 8.4 is more than enough for me.

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I'll consider looking into an 8.4v then. I appriciate the help in the decision making process, thanks.

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Airsoft Gun Repair Technician

So i Found a Intellect 8.4V 4200mAh - Large Type ( Ni-MH ) would be the best for my M249 MK2. but, when looking for a charger, all i find is 400-3000mAh chargers..are just normal 1.8A chagers that take 3 hours to charge it up good enough. Because I was interested into buynig a Fuzzy logic charger.. any suggestions?

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Airsoft Gun Repair Technician

DuraTrax Intellipeak ICE. Highly recommended. The 18A power supply is required to power the charger and comes separately.

wicked, from the reviews looks adept. Whats the name of the 18A power supply I canounldt read teh small print. or can i just get any 18A power supply?

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Airsoft Gun Repair Technician

Any power supply that will provide the requisite current will do, I think the ICE calls for 15A minimum. That's probably far in excess of what you need for airsoft; the charger will break in motors for R/C cars which takes about 10A continuous current. However since it's a requirement for the unit you're best sticking with what they recommend as it may come up as a warranty issue if you ever need repairs. Any good R/C hobby shop will carry power supplies too.