7.4 Lipo Battery Advice

[Bar1975]

So, I keep reading that a 7.4V lipo is basically the same as a 9.6 NiMh battery. I have a few questions on the subject.

Does the 7.4 lipo offer a better trigger response and snappier actions than the 9.6V though? Otherwise why would you ever use the 7.4 lipo?

Is the 7.4 lipo harder on the trigger contacts, wiring, etc? (Is this a general rule of thumb for all lipos or just starting at the 11.1V or higher voltage versions?)

In regards to increased wear and tear (when not fully lipo ready) that a higher voltage lipo brings does the 7.4V minimize this?

I would like to upgrade a couple of stock guns i have with these 7.4V Lipo's if they are easier on the gearbox than higher voltage lipos but offer some of the same benefits of a lipo (a general snappier response all around)

As a note: i have a fully upgraded M4 running a 11.1V LiPo and love it... have had no issues outside of trigger contact wear and tear (i know i need a Mosfet but doing ok without so far)

[MaciekA]

As I'm sure you suspect, most of your questions generate a "it depends" style answer

Originally Posted by Bar1975

So, I keep reading that a 7.4V lipo is basically the same as a 9.6 NiMh battery.

That really depends (1!), but my "lazy" answer is no. They may act similar in the first 50 shots in a workshop environment into a chrono, but the discharge curve of these batteries is really different over time, and their reactions to heavy load as well as temperature changes are different as well. The 9.6 to 7.4 comparison is a really loose rule of thumb that experienced players and techs use to explain the relative strengths and weaknesses of these battery chemistries to people who just want a quick answer. As you will see below, there are some 7.4V batteries that can pull loads that many 9.6V NiMHs can never dream to handle.

Originally Posted by Bar1975

Does the 7.4 lipo offer a better trigger response and snappier actions than the 9.6V though? Otherwise why would you ever use the 7.4 lipo?

It depends (2!) on several factors. I have a 7.4V, 20C, 610mAh Rhino LiPo battery lying around that I like to use for testing:



Hobby King says 30C burst can be sustained for 15 seconds. At 30C then battery is discharging at 18.3A (30C * 0.610A). Is that still more juice than a bigger size 3200mAh 9.6V NiMh stick? Unlikely. I don't see "C" values written on NiMH batteries, but I've heard 12C as an example, that would give you 3.2A * 12 = 38.4A. So it is possible to come up with contrived examples of where a NiMH battery is "better" than a LiPo (when it comes to airsoft that is, charge-discharge considerations are different if you're building an electric vehicle for example).

LiPos are all about how much energy you can pack into a small space. Hobby King claims the nano-tech line "approaches 7.5 kw/kg", which is pretty exceptional. Wikipedia says NiMH batteries contain from 0.5 to 1.0 Mega Joules (MJ) per Litre. Lithium batteries are listed at starting around 1MJ/L and ranging all the way to 4.3MJ/L. Whatever the numbers, a lithium battery occupying the same amount of volume as a NiMH battery is always going to have more juice.

Lithium batteries also discharge differently over the life of a charge. Check out this graph:



As you can see, with a LiPo, you get a more stable, sustained voltage, or shelf, over the course of the charge (i.e. imagine getting a very stable consistent RoF all day long). Towards the end of the usable charge is a sudden falloff, at which point you know it's time to recharge. With a LiPo, your RoF will be consistent most of the day, then at the end of the day it will suddenly drop off. This is a useful signal. You can install mosfets or alarms that detect this slightly quicker than your ears sometimes do. NiMH batteries tend to fade in a more linear fashion from their highest voltage down to their lowest voltage. I'm sure you've been on the field and heard a guy's RoF getting slower and slower and slower... And people around him are saying "dude your battery is dying". That's typical of NiMH.

For trigger response and generating extreme torque in general, you are going to want to choose the LiPo that gives you the highest discharge, or C value. You could have several LiPos that look the same except that they differ only in the C value and they would give you very different characteristics. Some examples:

• 7.4V 2000mAh 15C = 30Amps. Enough for most airsoft rifles pulling M110 springs with 18:1 gears over a few hours of typical airsoft play.
• 7.4V 2000mAh 25C = 50Amps. Enough for almost most harder-firing airsoft rifles (eg: M120 spring with 16:1 gears). Should go for a few hours of typical airsoft play.
• 7.4V 2000mAh 65C = 130Amps. Will give extremely snappy trigger response all day long, and easily handle a M130 spring with 13:1 gears. Should last the day as long as a neo motor is used.

Originally Posted by Bar1975

Is the 7.4 lipo harder on the trigger contacts, wiring, etc? (Is this a general rule of thumb for all lipos or just starting at the 11.1V or higher voltage versions?)

Again, it depends (3!). If you mix the 65C battery mentioned above with the hypothetical gun I've paired it with, you will have tons of arcing at your trigger contacts and your stock wiring will have trouble keeping up.

Originally Posted by Bar1975

In regards to increased wear and tear (when not fully lipo ready) that a higher voltage lipo brings does the 7.4V minimize this?

It depends (4!) hugely on the discharge characteristics of the battery. For example, let's assume you're using a neodymium motor, steel 13:1 gears and a piston with some nylon teeth, like the Lonex blue, and for the purposes of experimentation, you've shoved a small screw driver into your cylinder to cause an artificial jam. The 15C battery is not AS likely to shred a nylon piston tooth as the 65C battery -- both can probably do it, but you're more likely to notice and have time to prevent the shredding in time with the 15C battery. So the voltage of the battery doesn't necessarily "minimize" wear and tear, but it does factor into wear and tear, along with the other characteristics of a LiPo battery.

Originally Posted by Bar1975

I would like to upgrade a couple of stock guns i have with these 7.4V Lipo's if they are easier on the gearbox than higher voltage lipos but offer some of the same benefits of a lipo (a general snappier response all around)

If would say you're safe if you're buying 15 to 20C batteries, but beyond that you are going to eventually find the need to write another post on ASC. I'll see you then

[Bar1975]

wow.. i drank an entire beer reading that response.

ok.. so in a nut shell it's as i expected..

the lipo wins out as long as i'm not going crazy with it. (my plan all along was no more than 20C discharge rate)

thanks very much

[Kos-Mos]

Easy way out:

Buy a 7.4v 5000mAh LiPo pack for RC cars. They are usually around 25-30$ and fit the stock without modifications.

You won't damage your gun with that.

[ThunderCactus]

Careful with the contacs
Less voltage means less arcing (black residue) but more sustained heat, so higher chance of melting the contacts if you shoot like an LMG
There's also a lipo thread stoicky in the noob section

[Bar1975]

Hey guys.. i wanted to follow up on this thread.

I have a couple of new 7.4 Lipo's now and i've tested them with all my different guns using all my different batteries (11.1, 9.6)

Hands down the 7.4 lipo gives me the lowest rate of fire with every gun i own. So i am asking myself again what is the benefit of the 7.4lipo over a good quality 9.6NiMh? I get that lipos discharge differently and can potentially last longer throughout a day of gameplay.. but at the expense of gun performance?

I wanted the 7.4 lipo because i had heard that i should get the same results as a 9,6 but with some of those good lipo qualities (trigger response, etc) but in this case it seems to me like the better battery is the 9.6? (faster rate of fire, easier on the gearbox)

I have another 7.4 (Hobby King Nano-Tech Airsoft) on it's way.. this could be a better quality battery so i'll see how that goes.

[SuperHog]

The higher the voltage, the faster the motor revs for higher rate of fire.

9.6V is basically bullet proof as you can run them until the gun stop firing. With a Lipo, it can easily dip below the safety voltage before the gun stops firing thus damaging the Lipo permanently.

If you want the fastest rate of fire, then 11.1V Lipo for sure, but you need a Lipo monitor to prevent low voltage damage. If you want 11.1V then I strongly suggest MOSFET trigger upgrade.

[L473ncy]

This is way more than you'll need to know for airsoft but good to know anyways: http://batteryuniversity.com/learn/

tl;dr Lipo is lighter, more compact, and has more energy density.

A 7.4V 1500 mAh lipo for example is way more compact than an 8.4V 1500 mAh "stick" or nunchuck or whatever (made up of a bunch of 1.2V 1500 mAh Sub-C batteries or whatever).

[Oshiha]

Originally Posted by Bar1975

Hey guys.. i wanted to follow up on this thread.

I have a couple of new 7.4 Lipo's now and i've tested them with all my different guns using all my different batteries (11.1, 9.6)

Hands down the 7.4 lipo gives me the lowest rate of fire with every gun i own. So i am asking myself again what is the benefit of the 7.4lipo over a good quality 9.6NiMh? I get that lipos discharge differently and can potentially last longer throughout a day of gameplay.. but at the expense of gun performance?

I wanted the 7.4 lipo because i had heard that i should get the same results as a 9,6 but with some of those good lipo qualities (trigger response, etc) but in this case it seems to me like the better battery is the 9.6? (faster rate of fire, easier on the gearbox)

I have another 7.4 (Hobby King Nano-Tech Airsoft) on it's way.. this could be a better quality battery so i'll see how that goes.

It depends how much amps the 7.4 lipo is putting out. This lipo here is smaller then a Nimh, but is a 7.4v lipo regardless. It puts out a total of 16.5 amps. (15C x 1.1Ah).
Nimh batteries are generally 120mm (L) x 34mm (W) x 19mm (H). An intellect one is 9.6v 1600mah. Generally, they output 12C continuous. 12C x 1.6Ah = 19.2 amps. This is more then the 7.4 lipo.
Now, compare it to this lipo here . From the math above, the GensAce 7.4v lipo should be 55 amps continuos, 110 amps burst. And this lipo is smaller then an average NiMH! Now thats a difference. Also, you can see that a word "7.4v lipo" is pretty broad, ranging from 16.5 amps to 55 amps.
You have to remember that when comparing 7.4v lipos to 9.6v NiMH, you consider the mAh and C rating.

[Bar1975]

The thing is... i didn't want to go above 20C because the gun is running stock.

So basically unless im running a 20C+ lipo the NiMh batteries are just plain better. Anything less and im just loosing too much rate of fire to justify it.

i wish i knew that before buying two 7.4 lipos!!!

[Kos-Mos]

Discharge rating =/= rate of fire.
It lets the motor accelerate faster = snapy trigger response, same ROF.

Plus a sub 20C battery won't be much use when upgrading your gun.

[Gump]

Originally Posted by Bar1975

The thing is... i didn't want to go above 20C because the gun is running stock.

So basically unless im running a 20C+ lipo the NiMh batteries are just plain better. Anything less and im just loosing too much rate of fire to justify it.

i wish i knew that before buying two 7.4 lipos!!!

You can get a bazillion-C rated lipo for your stock gun, and you won't harm it IN ANY WAY. You'll only run into a problem with a highly 'C' rated lipo if you heavily upgrade the gun and then try to rely on the stock wiring and contacts, or if you have multiple drum-mags and tape your trigger down while you switch mag after mag.

This thread needs some info from you so a proper lipo can be recommended (clearly, you chose a lipo that was not powerful enough, through no fault of your own).

What gun?
What motor?
What stock (or wherever your battery goes)?
What spring?
What length barrel?
What's the fps with .20's?
and most importantly, link us to what lipo you purchased.

I'm certain once you post the needed info, someone reading this will be able to recommend the maximum-sized, high 'C' rated lipo to fit into your gun.

[Bar1975]

My apologies... I've sort of combined a couple of my own threads here.

The point of this particular thread was to get some info on the use of lipos in stock guns (stock everything except Deans being added)

I have several stock guns and several heavily modded guns..

I wanted to run a lower power lipo in my stock guns because i was under the impression that despite being a lower voltage (7.4 vs 9.6) i would still get better performance from a lipo. It was recommended that a 15-20C 7.4 lipo would be a good/safe bet for my purposes.. i ran out and bought two of these things and to be honest im just not impressed with the overall performance. Trigger response doesn't seem overly better (if at all) and the ROF is significantly lower than my 9.6

Now where i have mixed threads is by adding in details of a heavily modded MP5K i have (separate thread) that just can't seem to pull a sp120 with a G&P M120 motor and one of these new 7.4 lipos (again i thought for sure the lipo would solve this problem but it seems the only battery that will consistently pull this gun over is my 11.1 lipo.. to solve this im going to get a higher torque motor and hopefully the 7.4 will work then)

Anyways.. I have two new lipo batteries.. i will use them. Can't hurt to have a few extra batteries kicking around when I'm quickly approaching almost 20 guns!!

[Gump]

Originally Posted by Bar1975

...to solve this im going to get a higher torque motor and hopefully the 7.4 will work then)...

I'm afraid that won't work either. Its not about power consumption, its about power delivery. Don't spend the money on a motor. Sell the batteries on the forums, and buy the correct power rating for your application.

[Bar1975]

what power rating does the higher torque motors require?

I'm looking at the SHS High/Ultra Torque Motor or the Lonex A2

With either of those what is the minimum battery power rating i should be considering? Ive been told the 7.4 20C batters can pull either of them (using a SP120)