Which battery for your AEG? mAh, C-rating and voltage explained
every battery has three numbers on it and nobody ever explains what they do. so you just buy something, or you go off someone at the field shouting that you need 11.1V.
here's what airsoft AEGs actually need from a battery, what those numbers mean, and why that 11.1V tip is more dangerous than it sounds.
the three numbers
a LiPo says, for example: 11.1V 1300mAh 25C.
voltage (V): how hard the motor spins
voltage decides how fast your motor spins and how fast your gearbox cycles. more volts is faster trigger response and a higher rate of fire.
LiPos come in fixed steps because each cell delivers 3.7 V nominal:
- 7.4 V = 2 cells (2S)
- 11.1 V = 3 cells (3S)
NiMH is different, there each cell is 1.2 V, so you see 8.4 V (7 cells) and 9.6 V (8 cells).
note: a full LiPo cell is 4.2 V, not 3.7 V. so an "11.1 V" pack fully charged delivers 12.6 V. that matters for what your gearbox has to put up with.
mAh: how long it lasts
milliamp-hour is the capacity. simple: more mAh is more shots per charge. it has no effect on how hard your replica shoots or how fast it cycles.
practically:
- 1300 to 1600 mAh: enough for half to a full playing day at normal use. fits in most stocks and handguards.
- 2000 mAh and up: a full day, but bigger and heavier.
for most people 1300 mAh with a spare battery is handier than one big one. swapping takes thirty seconds.
C-rating: how much current it can deliver
this is the number that's least understood and matters most.
C-rating multiplied by capacity gives the maximum continuous current. a 1300 mAh pack at 25C can deliver 1.3 x 25 = 32.5 amps.
why this matters: an AEG motor briefly pulls a lot of current on startup. if your pack can't deliver that, the voltage sags and your trigger feels sluggish, even though it says 11.1 V on the label. on top of that, a pack pushed beyond its ability gets hot, and hot LiPos are bad LiPos.
rule of thumb: 20C is the absolute minimum, 25C to 30C is fine for a stock AEG. higher C-ratings than that add little for a normal setup, and the quoted values from cheap brands are often optimistic.
shape and connector
shape. check where the battery has to fit before you buy:
- stick / nunchuck: two thin packs, fits in a crane stock or under the handguard
- brick: a block, fits in buffer tubes and larger stocks
- PEQ format: fits in a PEQ-15 dummy box
measure your space. seriously, measure it. two millimetres too fat means you won't get it in, and forcing a LiPo is a bad idea.
connector.
- Tamiya (mini): the old standard. high resistance, loses energy as heat.
- Deans (T-plug): better contact, less loss. the de facto standard among people who know what they're doing.
- XT60: also good, more robust to plug in.
if your AEG still has Tamiya, switching to Deans is a cheap upgrade that noticeably improves your trigger response. ask someone who can solder if you don't do that yourself.
7.4 V or 11.1 V: the honest answer
this is the question it really comes down to.
7.4 V (2S) is what most stock AEGs can handle. calmer cycle, less stress on the gears and the piston. your rate of fire is lower, your trigger response is slightly slower.
11.1 V (3S) gives noticeably faster trigger response and a higher rate of fire. that feels great.
and then the heart of it: 11.1 V in a stock gearbox accelerates wear significantly.
what happens:
- the motor pulls more current, so your trigger contacts get a bigger spark. they burn in and oxidise. this is usually what fails first.
- the piston gets pulled back faster and the piston teeth take heavier hits. on a stock piston with plastic teeth they strip.
- when you release the trigger everything keeps spinning and the sector gear can catch the piston at the wrong moment.
- more heat in the wiring, in the motor, and in the gearbox.
i run 11.1V myself, but not in a stock gearbox. that's the whole nuance in one sentence.
when 11.1 V is fine:
- there's a decent MOSFET in it (which protects your trigger contacts and often offers active braking)
- you have a metal or reinforced piston
- the gearbox is properly shimmed and the motor height is right
- the wiring is heavy enough
without that list: stay on 7.4 V. a stripped piston costs you a playing day and a repair. i've written a separate piece about this, because it's the most common follow-up question.
so which one do i buy
for a stock AEG out of the box:
7.4 V, 1300 to 1600 mAh, 25C, Deans connector, in the shape that fits your replica.
buy two. one in the replica, one charged in the bag.
if your AEG has a mosfet and you know the internals can take it: 11.1 V, 1300 mAh, 25C.
charging and storing
this is not optional and a fire can genuinely start from wrong use. LiPos you charge only with a balance charger, at 1C, in a LiPo bag, and never unattended. for storage you set them to storage voltage, not full and not empty.
i've written a separate piece about that and i'd really read it before you hang your first LiPo on the charger. it's the one part of this hobby where a mistake can cost you your house.
common mistakes
- buying a battery without measuring the space
- skimping on C-rating and then complaining about slow trigger response
- putting 11.1 V in a brand-new stock AEG and being surprised after three playing days
- leaving LiPos fully charged in the cupboard until next season
- keeping a puffed LiPo in use. puffed is the end, take it out of service immediately
Also on Airsoft-FOB
- also available in dutch: Welke batterij voor je AEG? mAh, C-rating en voltage uitgelegd