Would 8.4V 3600mAh or 4200mAh battery be considered "pushing it" for a stock gun?

[Cottoni]

Hi, I've recently ordered some Airsoft Guns from A&A and when I was searching for some information about the Intellect 8.4V 3600mAh or 4200mAh large connector battery to use on my TM M1A1 Thompson, I found some confusing and conflicting information whether or not I should go above 2000mah for a stock gun.

Some people argue that it's NOT recommended to go above 2000mah for a stock gun, and 3600mAh and above batteries would be considered "pushing it" which could potentially cause damage to the gun's internal parts.

Others say that the MAH has no maximum: the more the better as long as the battery cells fit in the gun, and that you should get the biggest battery you can fit in your gun, because the MAH does not matter. What really matters is the voltage.
Some even say that higher amperage batteries can increase ROF (???)

I would really appreciate some insights from you guys about which of the two arguments is actually true for Airsoft guns.

I do not have any plans to upgrade my guns any time soon, if ever. So i am not concerned about that.

So is it safe to use an Intellect 8.4V 3600mAh or 4200mAh battery in a TM Thompson or any other stock gun?

Thanks

[Greylocks]

The voltage is correct, the amperage allows the battery to last longer. The only problem you would face is that some of the larger amperage cells are physically bigger, so they may not fit well inside the gun. Going to a high voltage is a problem, so you dont have to.

Such batteries are not a danger, but they are overkill.

I have NEVER run out of power with an 8.4 1700mah battery.

High MAH is like having a large gas tank for a small engine instead of only 10 liters. Same power for longer. However, 3600 and 4200mah is like bringing your gas station with you. No real reason, they also cost more.

A lot of this is in the FAQ section, since it's been discussed before. Check it out.

[mateba]

+1 for the 4200.
It will allow more room for upgrades (better amp ceiling) but I wont damage your gun until then. You might get a slightly better ROF but thats shouldn't be the goal with an 8.4v regardless of how high its mah is. Having the ability to have a high amp output battery can be handy especially if you want higher rated springs. Your motor will be able to draw more, while a 1700 will draw 20-25 a 4200 will draw 35+. Greylocks is right though, you wont have to charge to 3 or more days or play. If you don't upgrade it pointless unless you play a 24+ hour event. Although even if its a large "gas tank" it still weighs the same and is the same size so its really just a better "gas tank."

get a mosfet

[ThunderCactus]

Slightly higher ROF? lol
A 7.2v 4200mah battery has the same ROF as a 9.6v 3000mah and I know form personal experience. True it's like having a bigger gas tank, but it's as if the gas tank is above your carb and your fuel pump is gravity (when your battery has 1400mah left in it you'll notice a difference in ROF as opposed to when its full). Even an 8.4v 3000 is fast for a stock gun, but as long as you get a good piston, it all comes down to how fast you want it to fire, and double torque up gears can slow it down to normal ROF. Something around 2200mah is really all you need, thats a good 3500 shots depending on your gun.

[CDN_Stalker]

Current is drawn, it's not pushed. Your rate of fire (and rate of wear) will increase (if you are using a small mAh battery right now) because your motor can draw current up to it's maximum potential for work, but you won't kill your gun because of the higher mAh.

[Crunchmeister]

As said by others, the voltage is all you have to be concerned about other than the physical size of higher capacity batteries. As long as the battery can deliver the right voltage, that's all you need to be concerned about. the mAh rating is nothing more than the storage capacity of the battery.

And like others have said, a higher capacity battery will be great for future upgrades. Installing anything above stock in your gun (torque-up gears, stiffer spring, etc) will draw a bit more current from your battery, draining it more rapidly.

To use the gas tank analogy - you may be able to drive 500 km on your 50 l gas tank. Add a 2500 lb trailer to the back of your vehicle, and you'll only get 400 km out of that same tank. Having a larger capacity tank will allow you to get that same 500 km between fills. Without the trailer, the bigger tank will have no perceivable effect on the performance of your car except allow you to travel farther on one fill. Same with the battery.

As for longevity, I managed to get about 3200 rounds out of my stock CA M15A4's 2500 mAh battery, which far exceeds what I'd need for a day of gaming. Even once I get the spring and piston assembly upgraded, I should still see over 2500 rounds out of a single charge. So to me, there's no real practical use for a 400 mAh battery in a typical airsoft gun.

[CDN_Stalker]

Actually one can't use the gas tank analogy. If the motor draws current to do it's work, a mini battery (say 600mAh) will be able to supply X amount of current, giving it a headroom (limit) of a certain amount. If you have a higher amount of current able to be drawn, the motor will draw more up to a certain point, causing it to work faster. Hard to explain properly, but there was very noticable difference in my MP5 with a 110 spring in it when I went from my 8.4V 1400mAh battery and hooked up my 8.4V 3300mAh battery from my MP5SD. More current was available from the larger battery, and my motor took full advantage of that fact.

It IS true though that your battery will last longer, that's just common sense, because it's known as current capacity. I can easily go two to three games without charging my 3300mAh battery. That's about the only way the gas tank analogy works.

[ThunderCactus]

With a 4200mah battery, you can chop it down to a 7.2v and not only will it give you the same rate of fire as a 8.4v 3000mah battery, but because its now a 7.2v you'll have a slower drain as well. And a 7.2 has NO trouble running a 380fps gun lol

[mcguyver]

Originally Posted by ThunderCactus

With a 4200mah battery, you can chop it down to a 7.2v and not only will it give you the same rate of fire as a 8.4v 3000mah battery, but because its now a 7.2v you'll have a slower drain as well. And a 7.2 has NO trouble running a 380fps gun lol

What?

I think it's time for some simple Batteries 101.

The current rating on your battery is deceptive. It is given in "milliamp-hours", which mean the amount of milliamps your battery is rated to discharge in 1 hour. You are not running a flashlight, with a constant, continuous load for 1 hour. You are running a motor, which has some resistance, some inductance and some square-wave component with a measurable frequency. These factors, along with the in-rush current the motor "demands" from your battery during start-up, minus the counter-emf the motor itself generates, the load the motor is under and the time of cemf build up determine the the "draw" it has on your system.

If your gun is a stock gun, with a very light load, it may run fine on a 600 mah 2/3 "A" battery, at least for a while. The battery will be able to discharge enough current for start-up for a few hundred rounds, and will start to become depleted on a predictable geometric scale. When you increase to a 1700mah "A" battery, you will increase your effective "run-time" as the rating suggests, but you will not increase your start-up current capacity. This is due to the surface area of the cell's membranes and only so many ions can migrate between poles in a given area.

When you increase to a 1700 mah Sub-C pack, your run time may or may not increase a whole lot, but your start-up current has gone up big time. The membrane surface area has doubled and then some, so now more ions can migrate from one pole to another. This fact has been known amongst airsofters for some time as it's easy to see the performance difference.

If you take the sub-C sized battery and change the chemistry from NiCad (which is generally the lower rated ones) and go to NiMH (which is the 3000+ mah rated ones), will the NiMH packs be able to deliver more start-up current? Not always, and there are other mitigating factors as well. Temperature and charge procedures play a far more important role. NiMh hate the cold, and the colder it gets, the worse they perform. NiCad is the best of the common chemistries (NiCad, NiMH, LiPo) for cold weather performance.

The base ROF your gun is able to achieve is based solely 100% on the battery voltage. This is not even in question. The job of the battery is to be able to mainatin that voltage while under load, so that ROF is maintained. This means more surface are of the cells ("A" vs. sub-C) first and foremost. Second is the ability of the battery chemistry to be able to discharge the current in large doses to start the motor and to keep it running during periods of load-no-load at 15 times per second or more.

Will a 7.2v 4200 mah battery give you more ROF than an 8.4v 3000 mah battery of the same chemistry and cell size? No, absolutely not. The only way this is even remotely possible is if you have a defective 8.4v battery. But this is not a fair test, is it?

Science and common sense don't support the ROF increase in the 7.2v battery.

[ThunderCactus]

Well then would it be possible that intellect made their batteries fatter in the 4200mah pack? Because an 8.4v 4200 most definitely fires faster than an 8.4v 3000

[mcguyver]

Originally Posted by ThunderCactus

Well then would it be possible that intellect made their batteries fatter in the 4200mah pack? Because an 8.4v 4200 most definitely fires faster than an 8.4v 3000

OK. How about qualifying your statement a bit. Is the gun upgraded, with an increased motor load over a stock gun? If so, then there maybe a slight increase, but it won't be drastic. You will reach the limits of a sub-C pack at about 40 amps max, regardless of mah rating.

Now you are saying 8.4v 3000 vs. 8.4v 4200. If so this might be more acceptable that 8.4v 3000 vs 7.2v 4200. The cells in a 4200 mah pack are not any fatter, but do have better electrolyte concentration, giving them better run time as more ions are physically present. But it's surface are is the same, so the amount of ion migration is limited by the membrane surface area anyways.

[mateba]

Originally Posted by ThunderCactus

With a 4200mah battery, you can chop it down to a 7.2v and not only will it give you the same rate of fire as a 8.4v 3000mah battery, but because its now a 7.2v you'll have a slower drain as well. And a 7.2 has NO trouble running a 380fps gun lol

I think you should get a new 8.4v. You're basically saying a 8.4 provides the same performance and a 9.6v or better. The battery construction makes a difference and this may be the case for one or both of your batteries. Some batteries are constructed with "tabs" and some are soldered directly to each other. This affect internal resistance and performance. Age could also degrade the performance. If I knew a quick way to check their amp output I would tell you. Maybe someone else will chime in.

Nice catch mcguyver, you have a much better explanation than what I had in mind.

[mcguyver]

Believ it or not, there are variable battery testers that have been available for decades. They use them for tetsting all sorts of batteries, but their main use is for automotive batteries. I have a fixed tester meant for 1000 amp-hours, but this is way too large a load for a little airsoft battery.

The variable ones are basically a huge potentiometer. I'm sure a google search could find them, but I also suspect they won't be cheap.

You can make one yourself for a few dollars using automotive lightbulbs, 1157 to be exact. Put 4 of them in series, and connect both coils. Measure the DCR of the load, and calculate your load current using:

Current = Voltage / Resistance

The voltage you can measure with a simple DMM. To make it easy to test short-term discharge, install a switch in series (momentary) with the load, and depress the switch quickly (as quick as the DMM will capture the reading). This is not the 100% most accurate way to simulate a true motor load, but short of spending thousands on diagnostic equipment, it works pretty good.

If you want to simulate more load, add more batteries.

I built one of these years ago, and can e-mail you a picture if you want.

[ThunderCactus]

The 7.2 is brand new, and provides the same results as 2 other elite 7.2v 4500mah packs. I tested them against 2 intellect 8.4v 3600mah packs, which have the same results as my GP 8.4v 3000mah pack. So then the only explanation is that intellect and elite have bigger cells right?

[mcguyver]

You're comapring pack "A" to pack "B", then comparing pack "B" to pack "C", and using the perceived results to conclude a comparison between pack "A" and pack "C"?

Makes no sense at all, man!!