Lithium-Polymer (LiPo) Battery Primer

[infected]

When most people think about using lithium-polymer batteries (lipos,li-poly,etc.) in their AEG's we often associate it with a nuclear explosion or some other mega disaster. Well fear no longer! After recently making the switch to li-poly batteries, I don't know that I could ever go back! In light of that, I've started a series of articles (probably 2 or 3), about using lipo batteries and debunking some of the uneducated thoughts regarding these power houses o'plenty.

Part one is a close look at two of the common concerns about li-poly batteries, and reveals the real truth behind them!

Links to Information about LiPo Batteries:
Part 1 - Lithium-Polymer Battery Primer

Part 2 - Li-Poly Primer

Part 3 - Li-Poly Primer

Part 4 - Li-Poly Primer

If you have any input I'd love to hear it, especially from you lipo lovers out there!

Difference Between LiPo and Li-Ion
LiPO batteries are typically rectangular because they are basically strips of lithium metal wrapped around some basic form, separated by polypropylene plastic. These types of cells are solid and dry.

They could be put into a cylindrical shape, but its just easier to fold it over rather than curl it, its a manufacturing thing...

Li-Ion batteries are similar in their design, but they are kinda slushy, since they are not dry (the batteries you go buyform the store of the AA-D sizes are of the same slushy consistency), they are typically packed into some cylindrical casing.

Calling the law of averages the law, here's the differences other than shape:

LiPo batteries were developed for high capacity AND high impulse, meaning that they are a large reservoir whose floodgates can pop open and then remain farily wide open.

LiIon batteries were developed for high capacity and long run times, not high impulse. The typical LiIon batteries i see are typically the "stick" type. These cells are meant for laptop batteries, they have a max safe current drain of about 3-5 amps, not the 20 an AEG needs.

I have seen these batteries burst into flames due to the high discharge rates our AEGs demand. If they don't then they just don't last long andyou will only get a few good charges out of them rather than the 1000's you will get form a Lipo.

Most all manufacturers of these LiIon batteries for airsoft also sell HORRIBLE chargers for them with only increase their chances of bad things happening.

You can get a hell of a 7.4v pack that is the same size as a mini, and it will act like a 9.6 of slightly more mah, in comparison to a nicd or nimh pack, simply because of that high impulse capability and high energy density.

Links to Where to buy LiPo Batteries
You can find them from any hobby/RC store to eBay as well as many airsoft stores now carry LiPo batteries.

RC LiPos
Cheap Battery Packs
eBay Banned
Gunner Airsoft
Red Wolf Airsoft <-- Questionable batteries IMO
WGC
Flypo

[IBICO]

I have used li-po for about 2 years now on my systema ptw without any issues..

[metalhead666]

I must say, that was a very useful article. Infected, you're articles have just been awesome lately. I'm not totally sold yet, but I'm starting to lean towards lipos now...

[infected]

I must say, that was a very useful article. Infected, you're articles have just been awesome lately. I'm not totally sold yet, but I'm starting to lean towards lipos now...

 

Thanks! I've had a bit more time to devote to them lately too .

[Mike_West]

OK, but you didn't explain how to properly care about the Li-Po batteries. And that's the best bit.

Anyway, am I understanding right that a 7,4v Li-Po can pump as much juice as a 8,4v NiMH?

[greg]

Well done, nice read.

 

Folks are indeed ignorant about lipos, but that's changing. As more & more folk go lipo, the rest of the heard will have to follow to keep up.

 

About a year ago I asked the question on these forums: "Why aren't we using lipos?". This was spawned by an RC heli flying pal who couldn't believe we were still in the dark ages.

 

The responses were mixed & although "Xaccers" gave some encouraging & informed info, the majority was negative.

 

I love to remind the 'holocaust brigade' that lipos are in the watch on your wrist, the phone in your pocket, the camera you hold to your eye & the laptop on your knees. If lipos were as volatile as they believe, there would be reports of maiming in the papers every day & Sony/Samsung, etc would be sued out of existence.

 

I love my lipos, they have enabled me to keep my guns light with a great delivery of firepower. Either upping my rof (without heavy cumbersome power stations) or helping to reduce trigger lag in semi auto sniper set ups.

 

They run cold & give you more power per cubic inch than you can shake a stick at. For a while I went only for the 11's in high power set ups, replacing 12v nimh's twice the size & delivering way more punch. Now I use the 7's in sub 350fps set ups to give fantastic rof's in the space you can only fit an 8.4 mini.

 

My latest effort involved upping a 290fps (lalax kitted) Mac 11's rof from 500rpm (std bat) to 1300rpm with an internaly mounted 20C, 7.4v 1350mah! Oh Yes!!! No external mini rubbish here.

 

Go-Go-Lipo.

 

 

Greg.

 

PS, Can I advertise 'Flight-Power' as used by the UK's top RC 3D heli flyers,,,,,,,,,,,arguably the very best lipos. They do a 30C 7.4v 2000mah which is the same size as an 8.4v mini & gives batter performance than a 9.6v 3600mah nimh subC!!!!

[tosuzu]

Whenever I think of lipo battery I think of either

 

A) Liposuction

 

Crazy *albatross* battery (been on a receiving end of an clone with and 11volt)

[infected]

OK, but you didn't explain how to properly care about the Li-Po batteries. And that's the best bit.

Anyway, am I understanding right that a 7,4v Li-Po can pump as much juice as a 8,4v NiMH?

 

Charging and maintenance is coming up in part 2. Yes, in hindsight, maybe that should have been part 1, but I wanted to peak people's interest first.

 

As far as the "juice" let's do the math.

 

Average 8.4v Nimh Mini 1400mAh battery discharges at best 12C

12C x 1.4 Ah = 16.8A

 

7.4v 2200mAh 25C Lipo battery (about the same physical size as the mini in the above example)

25C x 2.2 Ah = 55 A

 

Yeah, it is CAPABLE of putting out more juice, BUT will only put out as much as the motor and drivetrain demands of it.

[greg]

That's coming up in part 2. Yes, in hindsight, maybe that should have been part 1, but I wanted to peak people's interest first.

 

 

It's hardly rocket science, but I won't spoil part two as you are a far better writer than me

 

Again, thanks for picking up the mantle & trying to dispell the myth.

 

 

Greg

[pistonhead]

So a 11.1v lipo will not overpower motor and setup that demands a large 9.6?

[infected]

So a 11.1v lipo will not overpower motor and setup that demands a large 9.6?

 

Think about it this way. The motor is like your body and the battery is like food. Your body can work up to a certain point due to the physical limits of it's construction (muscle build, cardio levels, age and so on). To do so it requires food. Give it too little, and it won't give you 100%. Give it just the right amount and you'll get 100% out of it. Give it more than 100% of the calories it needs, and you'll get 100% still, and the extra is just extra and doesn't do any work.

 

So in short no.

 

A BATTERY CAN NEVER OVER POWER THE DRIVETRAIN OF AN AEG. (bold for emphasis, not yelling) This is because it's the MOTOR that determines the amount of power used, not the battery.

 

Again, you do need to have a setup that can run 100%. Very few manufacturers out there truly make a gun that can run at 100%. To truly have a gun that can run at 100%, you need to have:

 

The right shimming

The right engagement angle

Proper lubrication

Proper meshing of gears (usually a problem at the piston)

Properly adjusted motor height

 

These are things you need to be conscious of anyway, so adding a lipo is no big deal. I'll be covering building a 100% gun in the future.

[pistonhead]

Thanks again infected they should make you a mod or something

 

I overhauled pretty much my entire P90 mechbox so I believe it should be capable of 100%....

I lube my internals frequently

I'm no champion "shimmer" but I'll take the time to make sure I get it right...

motor height is perfect

 

would you care to explain "proper engagement angle'

[infected]

Thanks again infected they should make you a mod or something

Lord no. I was an admin of a forum in the past... it wasn't pretty (all that power.......)

 

I overhauled pretty much my entire P90 mechbox so I believe it should be capable of 100%....

I lube my internals frequently

I'm no champion "shimmer" but I'll take the time to make sure I get it right...

motor height is perfect

 

would you care to explain "proper engagement angle'

Engagement angle is the angle at which the first tooth of the sector engages the first tooth of the piston. I have yet to see a gearbox (CA, TM, UTG, Cyma, Echo1,G&G or JLS) have proper engagement angle. The angle found in most gearboxes points to the 1 o'clock position. Now DO NOT CONFUSE THIS WITH TIMING (that's a bunch of horse squeeze). What you want is for the first tooth of the sector to be as close as possible to the 12 o'clock position when it hits the first tooth of the piston.

 

To achive this, you'll typically need to put a spacer between the piston and piston head. This can be washers, shims, or what I'm experimenting with, sorbothane (to obsorb impact). That will push the piston back a bit to correct the angle. Plus, you'll typically need to remove ALL of the 2nd tooth on the piston, and sometimes just a hair off the 3rd tooth on the piston.

 

I'll be putting together a guide on that too, in fact I just filmed a short clip on it. Hopefully it's useable as I didn't narrate well I don't think.

[greg]

So a 11.1v lipo will not overpower motor and setup that demands a large 9.6?

 

It won't do the motor in & Infected is right, if all (ALL) the other parts can keep up, you'll be ok.

 

Be aware, a high capacity, high C rating 11.1 lipo is a lot of electricity & well capable of driving an airsoft motor to it's max. This means you may experience a ROF that is way above anything your gun has had before. Chances are, your piston will go bang due to excessive rof if your spring is less than an M100/110.

 

In which case go for a 7.4.

 

As said, Flight power do plenty of cells that will fit into an unmodified P90 battery compartment.

 

The 30C 7.4v, 2000 is stunning. If you must go 11.1 they do an 'Evolite V2' 20C, 11.1v, 2100mah which will just about squeeze in with a bit of dremmeling, to remove part of the battery compartment floor & widen the back end pf the inside of the battery compartment where it tapers toward the but.

 

 

Greg.

[Vercingetorix]

Question: I have a completely overhauled gun, wit only prometheus, and where prometheus wasn't possible, systema. Its got a completely settled in slightly underpowered PDI170, and putting out 380fps on the dot with .25s (yes, I know good compression ) If I were to put say, an 11v 5000-odd mah elite lipo pack in(currently runing an elite 1500mah 9.6v, but I have all the upgrades needed to handle high rof I think, prometheus standard gears, prometheus piston, systema 6mm bushings, promethus spring guide piston head and cylinder/cylinder head, systema switch, and one of infected's rival mosfet makers, and a systema magnum, with the tooth next to the pickup tooth on the piston removed, well lubed gears, and expertly shimmed gears), would be piston be going bang very often? I can do mine own internal work, so if the piston did go every few months I'd have no problem replacing it) Would the gun run semi reliably? Also, putting a lipo like this in a stock bag, like the stock magazine pouches, is that safe

? I ask because this is a "soft" surface which wouldn't necesarily cushion the lipo sufficiently from an impact.

 

Thanks man!

[greg]

There's only one way to find out!

 

I'd give it a go & I think you'll be ok. I find that 11's are ok for guns above 350-380 fps with a .2. Below that & the rof is too high, to give reliable piston service.

 

It would be prudent to provide some sort of 'hard' impact protection. Most lipos come in a soft type wrap designed to swell & therefore contain gas expansion should the problem arise. This is not however sufficient to protect the cells from hard impact. Falling onto a pile of bricks, or a 500fps bb point blank is a chance in a million, but could be enough to wreck your lipo. I doubt the thing would go nuclear, but the battery could be written off & need replacing. So some sort of hard casing.

 

Why do you need 5000 mah? I use an 11.1v 2100mah lipo in a similar set up (m120/425fps with .2's) & get over 5000 semi auto shots before the battery needs topping up. This is a compact battery & would probably not need to be externally mounted. I would expect to see a lot more shots per charge if it was auto.

 

 

Greg.

[galactica]

As a fellow LiPo enthusiast I'd also like to mention the very convenient charging arrangements. The chargers are small, light, don't get hot, and get the job done very quickly. And then the battery retains its charge for AGES when not in use.

 

I'd also like to put in a word for a MOSFET as a great companion. Mine allows me to retain a sensible ROF on a gun which has all the trigger response you'd expect from a 11.1v LiPo, and a 3-rd burst into the bargain

 

 

[infected]

Be aware, a high capacity, high C rating 11.1 lipo is a lot of electricity & well capable of driving an airsoft motor to it's max. This means you may experience a ROF that is way above anything your gun has had before. Chances are, your piston will go bang due to excessive rof if your spring is less than an M100/110.

 

Again, that's not because of the lipo, but because your system is running at 100%, but the rapid pounding of the piston will likely damage it if you're running a TM spring because of the low damping rate. Running an m100 or above will fix that possibility. Also, making sure you're engagement angle is right will do a lot to save your piston even in a non lipo gun.

 

There is no need for a 5000mAh lipo in Airsoft. I run with a 2200mAh in my SAW and it lasts me all day.

[Marlowe]

Yet another excellent article Infected. I'm considering moving to Lipos in the long term (particularly with my RPK in mind, as I'd like to move to real steel furniture, which would necessitate a move to stick batteries), and this certainly has addressed some of my concerns.

 

If it's okay, I'll sticky this.

[Vercingetorix]

another question.... If I were to compare a 10.8v 5000mah nimh pack and an 11.1v 3000-odd/2000-odd mah lipo, which would give me better performance? I don't care much about size as it'll have t be externally mounted either way..... Also, seeing as its a stock mag pouch, I think I ight take one of those G&P Readymag shells, cut it, make it wider, put a lipo-sack in it, and use that to house the lipo.... realism, and protection in one! When I get back to the states I'll pick up a lipo and shell and try this....

[greg]

Again, that's not because of the lipo,

 

Well actually it is.

 

But it's not specifically because it's a "lipo".

 

Any power source that has enough, er, 'oomph', to spin the motor to full capacity will do it.

 

It just happens that most good quality, high mah, high C lipos, will have the required ,,,,,,,,,,oomph.

 

The stronger spring does two things; the first is obvious, it slows the rof (compared to a weaker spring) & secondly (as I understand it), it returns the piston to the cylinder head rapidly enough to avoid premature engagement.

 

& your dead right, sorting out the eng/ang definitely prolongs the pistons life in high speed full auto set ups, esp the lower fps ones.

 

 

Greg.

[CSC Maverick]

Ill gladly throw my 2cents in here. I was one of the first to get their hands on the gun you hear most often in a sentence with lipo: a KWA m4. Got it right around the new year (And I still dont regret that move ). I got, what else, a 11.1v, 1500 lipo battery. Freaking crazy. Instant trigger response, 20 rounds going downrange every second. Fast forward 7months to mid July this year. My gun hits some big problems. Open her up(well, the store tech did while i was there). The piston was at the breaking point, but pieces of it jammed the gears, causing two to strip teeth. We install prometheus torque up gears and a ca piston. The Ca Piston was a bad move. It goes in 200 shots. In light of this, the store has ordered me a 7.2v lipo battery. The battery is still the amazing trigger response, but with a 9.6v ROF. Also, I now have a deepfire polymer piston with titanium teeth, the last tooth being a half one for high speed, in the gun. Its been fine with the 11.1, but im still switching to the 7.2. If you guys want, I still have the broken gears and 2 broken pistons and can post pics of them. I'm selling the 11.1v lipo in the sales thread if anyones interested as well.

 

Even though I had some problems, I still love lipos. I just think the 11.1v is too strong. I dont want to be replacing gears/pistons once a year, And I dont have the bankroll to make the KWAs internals go from great to indestructable, so a 7.2v lipo is fine.

[greg]

another question.... If I were to compare a 10.8v 5000mah nimh pack and an 11.1v 3000-odd/2000-odd mah lipo, which would give me better performance? I don't care much about size as it'll have t be externally mounted either way..... Also, seeing as its a stock mag pouch, I think I ight take one of those G&P Readymag shells, cut it, make it wider, put a lipo-sack in it, and use that to house the lipo.... realism, and protection in one! When I get back to the states I'll pick up a lipo and shell and try this....

 

You would have to do a comparison to know for sure. My guess is the 11.1v lipo, but this would depend on its 'C rating' & capacity.

 

I have a 25C, 11.1v, 3300mah lipo & a 10.8V 3300 nimh (sub c). The lipo gives a faster rof & lasts about 30% longer.

 

Other examples I have are a 30C, 7.4v, 3600mah lipo, which gives similar rof to a 10.8v 3300mah nimh (Sub c). A 30C, 7.4v, 2000mah lipo (same size as an 8.4v mini), which gives the same rof as a 9.6v 3300mah nimh (sub c). A 20C, 7.4v, 850mah lipo (same size as a 7.2v 500mah aep battery) which gives the same rof as av 8.4v mini & lasts twice as long.

 

I would say that I wouldn't change to lipo, just for the sake of it. I use them for size & weight saving qualities. They allow an internally mounted, respectable power source, where an external mount was previously the only option. It is hard to compare like for like, but they are (as you can see from the above examples) approximately half the size of their nimh equivalent.

 

Also be aware that lipos do have their limitations:

 

1, They must never be run flat. This will in almost all cases write the battery off. I have heard that efforts are being made to improve this, but we are unlikely to see 'run flat' lipos for at least a year.

 

2, They will only last for about 100 to 250 charges. This obviously varies. Again efforts are being made to improve this & currently, you can expect at least 2 years (possibly 5), even if you use & recharge your lipo every week. In comparison, most manufactures quote 2000, charges for a ni-cad.

 

3, They are subject to physical damage. As already said, puncturing, denting, compressing &/or bending lipos will probably write them off. Although they are unlikely to 'go super-nova', this damage can cause them to swell, & warm up. If, (& only if) there is a puncture, venting gas, & a source of ignition, they can also catch fire. There is (as with any battery) the slim possibility that a severe trauma could cause gas venting, in combination with a short circuit, creating enough heat to self ignite. They should (like any battery) be treated with respect. If they swell, or heat up, at any time (including charging) they should be safely disposed of.

 

 

Greg.

[greg]

Just a thought:

 

Where have all the lipo-haters gone???

 

This time last year, the merest hint of lipo resulted in 3 pages of foot long rants, describing how entire cities were laid to waste because someone left a lipo out of the fridge or stared at it for too long!

 

Is this finally the wind of change?

 

 

Greg.

[MrBlanks]

I love to remind the 'holocaust brigade' that lipos are in the watch on your wrist, the phone in your pocket, the camera you hold to your eye & the laptop on your knees. If lipos were as volatile as they believe, there would be reports of maiming in the papers every day & Sony/Samsung, etc would be sued out of existence.

 

Most of those do not use Lithium Polymer batteries but Lithium-Ion batteries. Big difference.

 

However, technology is actually just starting to use them and implementing them in stuff. Popular products include iPhones and PS3 wireless controllers.