WW2 Airsofters guide to LiPo battery packs

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WW2 Airsofters guide to LiPo battery packs

Postby Kermit » Thu Dec 30, 2010 9:27 am

Ok boys and girls, welcome to the revolution – the power revolution. It’s time to dump those old NiCad and NiMH packs and swap to LiPo.

Why should I swap to LiPo?
Quite simply, for two reasons. 1: Energy density. You can fit a lot more grunt in a LiPo pack than you can in an equivalent NiMH or NiCad pack of the same physical size 2: Discharge rate (more on that later!)

Physical pack characteristics
The first thing to be aware of with LiPo is that individual cells are a nominal 3.7v per cell, unlike NiMH or NiCad which are rated as 1.2v per cell, meaning that the packs that you’re interested in are going to be the 7.4v twin cell packs and the 11.1v triple cell packs.
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LiPo packs are available in all shapes and sizes

mAh and Discharge Rates (“C” Rating)
LiPo battery packs are a little more complicated to choose than NiMH/NiCad packs. Capacity (in mAh) is straightforward. It’s the “C” rating where things get a little complicated. It’s a measure of the discharge rate.

Ok, some maths. The simple equation you need is C rating X Capacity (in Ah) = Discharge Rate (Amps)

So. A couple of examples:

11.1V Li-Po 1600mAh 15C = 15 x 1.6 = 24 Amps.
11.1V Li-Po 1600mAh 10C = 10 x 1.6 = 16 Amps

Why is this important?

The motor in every AEG pulls power from the pack (the amount required will depend on various factors – from the type of motor used, to the spring being pulled back by the gear train, to the ratio of the gears used). Say that it requires 18 Amps to work at optimum (100%) efficiency, and comparing that to the performance of the batteries used above, you can see that the 10C pack cannot provide the grunt required, but the 15C pack can. In short, the C rating is important!

It doesn’t finish there though, there is further nomenclature about how the pack is put together. LiPo packs are available in both series and parallel types. In short, if a pack is in parallel add the capacities together, if in series, add the voltage.

Examples with 1000mAh 3.7v LiPo cells:

3S – 3 cells in series = 1000 mAh, 11.v
3P – 3 cells in parallel = 3000 mAh, 3.7v
2S2P – 2 cells in series, 2 sets of cells in parallel = 2000 mAh, 7.4v

7.4v Vs 11.1v packs
It’s about to get a little bit more complicated. And once again, it’s down to discharge capacity. Say that you have a high-speed set up in your AEG - A Systema Turbo and a high-speed gear set, coupled to an M100 spring that requires 25A to run at optimum efficiency. Naturally, you want a battery that can provide the grunt that the AEG needs.

So what do you go for? an 11.1v 1500mAh 15C pack or the 7.4v 2000 mAh 30C pack?

Doing the maths, the 11.1v pack will give you a discharge rate of 22.5 Amps, whereas the 7.4v pack gives a discharge rate of a whopping 60 Amps. The upshot of this is simple. The 11.1v pack cannot provide the grunt required by our example AEG to work at optimum efficiency, whereas the 7.4v pack can.

Charging LiPo packs
Unlike NiCad or NiMH packs, charging LiPo’s is a more involved exercise. Each cell of the LiPo pack needs to be charged at the same rate. This is called “balanced charging”. You won’t be able to do this on your standard NiCad/NiMH charger, so you’re going to have to buy a charger that’s capable of working with an (unsurprisingly named) “balancer” so you can charge each cell to the same voltage. As each charger might work in a slightly different way, read the manual before charging your LiPo’s. Several times, and charge them at a relatively low rate, never more than 1C (unless the pack supplier says it can charge at a higher rate).
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Balancers can come as either separate items or part of an all-in-one charger/balancer

There are several safety precautions you should take as well. The first is that you should never, ever, put the pack on charge and then just leave it on its own. Keep an eye on it! The second is that you should always charge the pack on a hard non-flammable surface, and thirdly, use a LiPo charging sack. Should the worst happen, these fireproof envelopes will stop any fire spreading.
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Charge LiPo packs in a fireproof sack. Any decent RC shop will sell them and they should be around a tenner in price

Minimum Voltage
In simplest terms, you don’t want to let the individual cells in your LiPo packs drop below 3v per cell. The easiest way of doing this is not to lug a multimeter around the skirmish site, but invest a few pounds in a monitor designed for the purpose. Most RC shops will offer a selection of monitors designed explicitly for the purpose of checking the cell voltages on LiPo packs, and the simplest ones should only cost a few quid.

LiPo monitors
We've already mentioned LiPo monitors and what they do, so we thought we'd have a look at three of the most readily available units.
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There are a wide variety of LiPo monitors available. The three we have here are all available for less than the price of average wine. Some use a simple go/no-go system of Green & red LED’s, some use a buzzer and some have a display to show the actual voltage of the cells

Hextronik - £2.95 - http://www.component-shop.co.uk
The cheapest of the LiPo monitors in this group, this unit is about as simple as it gets. Plug the LiPo pack (1S to 3S) in to the monitor and look at the little LED’s. If they’re green, all is good. If red, then that means they have just dropped to 3.3v (a little over the recommended safe minimum). If that’s the case its time for a recharge. As with all the monitors here it can be left permanently plugged in to your LiPo pack if you really want to, though given that it would be hidden away you wouldn’t be able to see it anyway. The only slight issue with this monitor is that the pins are a tiny bit too long. Nothing that a pair of clippers cant solve though…
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Simple Go/No-Go system using LED’s

Intellect-Battery - £4.25 - http://www.component-shop.co.uk
Slap bang in the middle of the price range, this monitor adds to the functionality of the lowest priced monitor by having an audible alarm built into the design. It can handle 1S to 3S packs, and when any of the cell voltages drops to 3V not only will the LED’s flash red, but it will also start beeping loudly at you. If you’ve got enough space inside your AEG or battery box to leave it attached to your LiPo pack then great. OK, it may just bugger up that stealthy ambush when your AEG starts shrieking at you, but at least you won’t have written off that forty quid battery pack!
6.JPG
Go/No-GO system with the addition of a buzzer

Un-named 7 segment display - £5.50 - http://www.component-shop.co.uk
This monitor is rather different from the others. Where the Hextronik and Intellect-Battery monitors just use a go/no-go system, this unit shows you the actual voltages for each cell on a large display. It can handle between 1 and 6 cells (1S to 6S) and cycles through each cell before showing you the total voltage of the pack.
7.JPG
Full display that cycles through the total pack voltage and the individual cell voltages

LiPo storage in the field
LiPo’s can’t handle quite the same level of abuse that a NiMH or NiCad pack can and hence need to be stored in a way that the cells wont be punctured, or the covering membrane split or torn. If you’re concerned about this, there, there are an increasing number of hard-cased LiPo packs appearing on the market (mostly, it must be said, from RC car suppliers at the moment) but you do pay for the added protection. As it is, most LiPo packs designed for Airsoft use are uncased. Put simply, we wouldn’t just chuck a spare LiPo pack into belt order where there is too much chance of splitting a cell when hitting the deck. After a quick look around the ‘Net, we found some Tupperware type containers that were of the right size to carry LiPo packs in.

Disposal of LiPo packs (damaged, and undamaged)
If your pack is finally dying of old age and overuse, then place it in a LiPo sack, and connect a discharger to it till it’s dropped to 1v per cell or lower. Once that’s done place the pack into a plastic container of saltwater for a couple of weeks (about 1/4 cup of salt for 1 litre of water will do the job) then dispose of it. If the pack is damaged, then skip the discharging and go straight for the saltwater – don’t just sling the damaged pack into a drawer and forget about it!

Summary
LiPo battery packs are certainly not the fire-breathing destroyer of AEG’s that some people make them out to be if they’re treated with respect and common sense – and if your AEG is capable of working at 100% efficiency. If internal parts get damaged, then don’t blame the LiPo, blame your choice of internal components. They self-discharge at far lower rates than NiCad or NiMH packs. They are far smaller than NiCad or NiMH battery packs required to give a similar level of performance, and the price of the packs is generally very reasonable. Am I converted? You’re damn right I am – but I will always treat them with respect.
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LiPo packs are available in all shapes and sizes
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Re: WW2 Airsofters guide to LiPo battery packs

Postby Steiner » Thu Dec 30, 2010 9:40 am

Brilliant, Jay! :good:
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Re: WW2 Airsofters guide to LiPo battery packs

Postby Kermit » Thu Dec 30, 2010 11:09 pm

Feel free to do whatever you want with it matey. It could do with a bit of editing really, but I did throw it together at 0-dark-thirty this morning :lol:
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Re: WW2 Airsofters guide to LiPo battery packs

Postby Snake-DK » Thu Dec 30, 2010 11:24 pm

Kermit wrote:It could do with a bit of editing really, but I did throw it together at 0-dark-thirty this morning :lol:

Which brings me to that you are repeating yourself a little in the two sections quoted below:

Kermit wrote:Minimum Voltage
In simplest terms, you don’t want to let the individual cells in your LiPo packs drop below 3v per cell. The easiest way of doing this is not to lug a multimeter around the skirmish site, but invest a few pounds in a monitor designed for the purpose. Most RC shops will offer a selection of monitors designed explicitly for the purpose of checking the cell voltages on LiPo packs, and the simplest ones should only cost a few quid.

LiPo monitors
OK, by now we should all know the deal. In simplest terms, you don’t want to let the individual cells in your LiPo packs drop below 3v per cell. The easiest way of doing this is not to lug a multimeter around the skirmish site, but invest a few pounds in a monitor designed for the purpose. Most RC shops will offer a selection of monitors designed explicitly for the purpose of checking the cell voltages on LiPo packs. Some are better than others, and we’ve grabbed three of the simpler designs to take a look at.


Otherwise it is a really great guide, especially considering it is late-night work.
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Re: WW2 Airsofters guide to LiPo battery packs

Postby Kermit » Fri Dec 31, 2010 12:08 am

Yeah, just noticed that. Will edit it when i get a little bit of time :)

**edit**

Done!
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Re: WW2 Airsofters guide to LiPo battery packs

Postby Waldiebeast » Tue May 24, 2011 10:50 am

The only problems with lithium-polymer batteries are that the ROF is a bit too quick for a 1940's gun. That's just my opinion
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Re: WW2 Airsofters guide to LiPo battery packs

Postby greedo1980 » Tue May 24, 2011 12:27 pm

Waldiebeast wrote:The only problems with lithium-polymer batteries are that the ROF is a bit too quick for a 1940's gun. That's just my opinion


Thats why I use 7.4v lipo batteries with discharge ratings of at least 28 Amps :D

You'll get a similar ROF to a good quality 8.4V 1500mah NiMH, but in a much smaller pack, with tighter trigger response and it will more than likely see you through a full day of skirmishing.

While I'm on this thread, the AGM MP44 is worth a mention. That gun must be power hungry and require a higher than normal discharge rate to cycle the gearbox. Mine is nothing special - has an M100 spring in it, and fires out at roughly 340fps.

I would be lucky to shoot 500 BBs with one fully charged 8.4v 1500mah NiMh stick battery but I have yet to drain the 7.4v lipo I have stared to use with the gun. Specifically I use a 7.4V 1400mAh 20C (28 Amps discharge) stick lipo and it definitely improves the experience of skirmishing with that gun.

It could just be my gun of course, but I have heard another trigger shy player say that they only got half a day out of their NiMh sticks with their MP44, so maybe it is something to do with the motors AGM used in them.
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Re: WW2 Airsofters guide to LiPo battery packs

Postby Waldiebeast » Tue May 24, 2011 1:09 pm

greedo1980 wrote:
Waldiebeast wrote:The only problems with lithium-polymer batteries are that the ROF is a bit too quick for a 1940's gun. That's just my opinion


Thats why I use 7.4v lipo batteries with discharge ratings of at least 28 Amps :D

You'll get a similar ROF to a good quality 8.4V 1500mah NiMH, but in a much smaller pack, with tighter trigger response and it will more than likely see you through a full day of skirmishing.

While I'm on this thread, the AGM MP44 is worth a mention. That gun must be power hungry and require a higher than normal discharge rate to cycle the gearbox. Mine is nothing special - has an M100 spring in it, and fires out at roughly 340fps.

I would be lucky to shoot 500 BBs with one fully charged 8.4v 1500mah NiMh stick battery but I have yet to drain the 7.4v lipo I have stared to use with the gun. Specifically I use a 7.4V 1400mAh 20C (28 Amps discharge) stick lipo and it definitely improves the experience of skirmishing with that gun.

It could just be my gun of course, but I have heard another trigger shy player say that they only got half a day out of their NiMh sticks with their MP44, so maybe it is something to do with the motors AGM used in them.


Oh, thanks for the advice. The trigger response on my STEN is awful so I might get a stick type lipo (7.4v). But then, I don't realise why AGM discontinued the version 1s with the lipo :?:
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Re: WW2 Airsofters guide to LiPo battery packs

Postby Yith » Tue May 24, 2011 1:13 pm

I'm fairly sure you can get a lipo in the stick mag versions as well...
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Re: WW2 Airsofters guide to LiPo battery packs

Postby No1_sonuk » Tue May 24, 2011 2:06 pm

Yith wrote:I'm fairly sure you can get a lipo in the stick mag versions as well...

Yes, you can. I do now that I use a skeleton stock. My gun came with the NiMh T-stock.
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Re: WW2 Airsofters guide to LiPo battery packs

Postby Joseph Porta » Tue May 24, 2011 10:19 pm

thanks for trying to make it simple jay, :good: but my head hurts! :slap:


im just going to stick to my mini 8.4 nimi packs , and just carry a spare in my pocket, so much easier than having to "think" batterys, just charge em both for 3 hours the night before a game, job done (and bin the buggers every 2 years) :D


i think im becomeing a luddite in my old age, i just cant be arsed with new tech, my pc is 8 years old, my mobiles still a brick, and i carnt be arsed with texts :lol:
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Re: WW2 Airsofters guide to LiPo battery packs

Postby Lord Elpus » Sun Sep 18, 2016 6:33 am

This is good info, .....I'll have to read it again....a few times! Just start changing over to mosfets for my weapons put a gates nano "hard" on my Mp40 mainly because of the useless trigger set up, (will change to micro switch later) but then put in 11.1 lipo,.....only doing 780rpm! I guess I best drop down to 7.4 lipo, emptied 110 rnd mag in a few seconds, have visions of carrying a sackful of mags around! Might change mosfet for programmable one, what does anyone reckon, 5 round burst?
Last edited by Lord Elpus on Tue Jul 23, 2019 4:43 pm, edited 1 time in total.
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Re: WW2 Airsofters guide to LiPo battery packs

Postby Lord Elpus » Sun Sep 25, 2016 6:11 pm

I was wrong about the rpm on my mp40....... It's doing 1083rpm! Just waiting for 7.4 lipo to arrive, then will check again.
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Re: WW2 Airsofters guide to LiPo battery packs

Postby Lord Elpus » Sun Oct 02, 2016 1:50 pm

Just noticed my typo, on my post, I meant rpm not Fps ! Tried the 7.4 lipo, still high rate, didn't put it on chrono, but if it is slower, it's not by much, I did put different gears in so I reckon that's what is giving high rpm.
So.......gearbox apart again! Whilst I want the longevity of the lipo battery( and fitment in the small bat box) and want to run burst choice, I don't need such a high rpm rate. Also the mosfet gives trigger switch longer life( no burnt contacts!), quicker trigger response,
Then do the front end, ( hop and barrel) I'll get it sorted .......one day!
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Re: WW2 Airsofters guide to LiPo battery packs

Postby dadio » Sun Oct 02, 2016 8:58 pm

11.1v lipo's are really only useful in MG'g ,otherwise its wise to have a low ROF or you just run out of ammo quickly , the ideal is to get close to a real rate of fire .
You don't see many white laser ww2 guns , with my modern stuff I run up to 35 rounds per second but nothing like that would suit ww2 other than an MG .
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