Adding a capacitor to an AEG

[Thraxxx]

I was just wondering if this has been atempted or maybe its already in effect. Everywhere that I have read about the build of an automatic Electric Gun, they all state the same parts. Battery, Motor, Gears, Piston.

Now if you were doing a full auto non stop with a high-cap mag, gradually the amperage of the battery might not beable to keep up with the constant draw of the motor. In return your shots per second would drop as the motor wouldn't be spinning as fast as it did for the first 20 shots.

Now I could be wrong here as I am new to this but has anyone tested this out...if so, would a cap help compensate here to help stiffen up the power grid and keep that motor spinning at a constant rate?

[Kokanee]

How many rounds are we talking here? Because I have emptied an entire highcap out of my AK once for shits and giggles nonstop, winding as it was firing, and the battery kept things running just fine.

[Digital_Assasin]

Caps won't help in sustained fire. They would only help in delivering that extra umphf when the motor is drawing the most current at the begining.

Think of them as nitrous for a car. Quick power boost, but nothing sustained.

[Mysteryfish]

might not be terrible just for that reason, while the motor gets up to speed...

What would that be protecting though? Motor or battery?

meh, i burned through a 3000 round Cmag almost non-stop once with no problems

[spaceghost0]

This may shed some light:

http://www.airsoftmechanics.com/articles.php?aid=11

[mcguyver]

That article gives some basic intro into the use of capacitors. However there are some flaws in their reasoning for capacitor use that lend it to be a waste of time for an airsoft gun.

1) The motor used in an AEG is a universal motor (both AC and DC capable) that uses internal phase reversal via the commutator to achieve rotation. This will cause the DC output of the capacitor to also fluctuate, negating exactly half of it's potential.

2) The motor acts like an inductor (as the windings are basically inductors) and will exhibit the electrical characteristics of one. This means that during motor operation, the current going to the motor will lag it's voltage by a factor dependent upon the pure inductance of the windings and their resistance. This is a fixed value during motor load and a fixed value when the motor runs but is not under load. These values are different and may vary significantly.

Using the pure capacitance of a capacitor (as they effectively have zero resistance) to offset the motor inductance (known as "power factor correction") may lower the net current during motor load running, but may also increase current needs when discharging during motor running with no-load (half the time). You may in effect be taking the lagging current drawn by the motor and turn it into leading current drawn by the capacitor. So you gain nothing, except the added expense and effort of installing the capacitor in the first place.

Now we get into the other aspects of placement and safety. In most guns, there is simply no place to install the capacitors of a size that may even be useful. And then, there's safety aspects as well. If you use a polarized capacitor (which is required for DC circuits) and you accidentally reversed the polarity to it, it will explode. If you did this with a 25v 100mfd cap, there would be nothing left of the stock of your gun as the explosion will be significant. And you'd probably hurt yourself in the process.

That's why for our purposes, they are a complete waste of time.