Lithium-Polymer Batteries — Part 2

In part one we took a look at how li-poly batteries are really no more dangerous than NiMH, or NiCad batteries.  We also took a deep hard look at the myth that li-poly batteries kill airsoft guns… and found it to be a farce!  If you missed part one you can find it here.

Enough of the past, let us venture on into the future where before us lies the land of li-poly happiness and reliability!  Wait, did I just use li-poly and reliability in the same sentence?  You bet  your granny’s muffins I did.  We’ve already proved that you have to abuse them to create that great big ball of fire that will not only kill your battery, but swap your two ply toilet paper for single ply!  Now you’re asking, since they’re reliable and my toilet paper is safe, how do I take care of li-poly batteries?  Thought you’d never ask.

First let’s go over the general construction of a Li-Poly pack.  There’s really not much to understand here other than, like NiCad and NiMH batteries, it’s a group of cells wired / soldered together.  As usual, you have a power connector, but unlike the other battery chemistries, you also have a balancing connector.  The power connector shown in the picture here is a Deans connector.  I prefer Deans connections over the stock Tamiya connectors, but that’s another article for another day.  For now, just remember along side the power connector is also a balancing connector.  More on that later.

Myth 3 states:

Lipos require a lot of babying

Well, here’s the cold hard truth.  They don’t.  They do require a bit more effort to maximize your output and use, but the rewards of using a li-poly far out weigh the slight bit of extra work.  Let’s break it down into the main parts of battery maintenance.

Precautions

Really, there’s nothing new here.  Just like NiMH or NiCad batteries, don’t drop them, puncture them, set them on fire, stick them in a fire, overheat them, or wear on your forehead and play William Tell with a Barret 82A1 rifle.  One more thing, don’t leave a battery of any type charged without someone present.

Charging

Charging a li-poly battery does require a charger that… well, can charge li-poly batterie.  These are not as common as your NiMH or NiCad chargers, but there is an increasing number of them.  What you pick is up to you.  They sell some as cheap as $35 that are li-poly specific at HK airsoft stores, up to $130 chargers that can handle any battery type.  As far as chargers go, you really get what you pay for.  Having a charger that is able to tell exactly what the battery is doing every moment while charging, and adjust accordingly is a real benefit not only for li-poly batteries, but all battery types.  I personally use a Triton2 made by Electrifly.  This is a pricey unit but will handle any battery I could currently need for airsoft, and it has 10 memory settings.  But, that’s another review, so we’ll keep moving forward.

One optional, but highly recommended bit of equipment is a Balancer.  That sounds like a fancy piece of kit, but in reality it’s very simple, and pretty cheap (about $30 for the one I picked up and I’m sure there are cheaper ones).  A balancer (the little box on the right in the picture) makes sure all the individual cells that make up your battery pack are all charged to the same level.  This is important as you’ll find out later in this article.  Balancers work by taking voltage from one cell, and moving it to another till they are at the same charge level.  Easy.  For the most part, you just plug in the balancer to the battery, press one button and presto after a few minutes your pack is balanced and ready for charging.

Another piece of equipment you need is a Liposack of some sort.  This is just a precaution.  If your lipo has been damaged, and you are unaware and are trying to charge it, there is a chance it could ignite (just like any damaged battery).  Because lipos do ignite violently, the use of one of these bags is recommended.  Just place your lipo in the bag with the wires hanging out.  Hook it up to your charger, and charge.  If the battery were to fail, the bag would contain the fire for the most part, and vent out the excessive gas.  Again, the likelihood of this is pretty low, but better to be safe.

As far as charging goes, it will depend on your charger.  Mine just asks for the capacity of the battery and the voltage. Once I put those two numbers in, off it goes charging my battery.  With the Triton 2, my 2200mAh battery charges in about 1 hour.

Balancing

Some balancers work through the charger.  I use the Equinox balancer.  This one can be used with or without the charger.  The beauty of this is that it keeps the pack balanced while charging.

Now I said I would get back to the balancer and why you should balance your packs.  Here’s the deal.  Li-poly cells have a lower discharge limit of 3v for most manufacturers.  If you go below this, there is the potential to damage your battery and prevent it from ever charging again.  Let us look at an example.

Say you have a 2 cell pack.  That’s 7.4v total power.  Say cell one has 3.5v in it, and cell two has 3.1v.  What happens is that you can still run your pack, but cell two will dip below the 3v minimum, and could be permanently damaged.  If you balance the pack before you use it, or before you charge it, you’d end up with two cells that are each at 3.3v.  They will hit the 3v minimum at the same time.  This maximizes the capacity you can get out of your pack by running all the cells down at the same time instead of having to stop playing to charge backup because one cell is too low.

This all sounds complicated, but I’ll wrap it up in a neat package for you at the end.

Low voltage Protection

Remember what I said before about the fact that li-poly batteries need to be kept above 3v?  If you’re using a li-poly on a gun with heavy demands or for multiple days, I suggest checking the voltage on it periodically.  This is easy to do with a multi-meter.  Just use the balance tap to check the voltages.  If you want to make it even simpler, there are devices you can plug into the battery that will use led’s to show you the charge of each cell, and warn you if you’re getting close to the low end.  There are even units that will beep/buzz so that you have an audible cue if your battery starts to reach the bottom of the barrel and needs charging.  So no worries there if you don’t have a multi-meter or don’t know how to properly use one.

Storage

Storing a li-poly is pretty straight forward.  You can keep them all in a liposack for protection, but the concern here is that if one pack goes, all your packs go.  I’ve heard of people purchasing nomex socks and using them instead of a liposack, but a pair of nomex socks seem to cost just as much as a liposack.  My suggestion is to use a separate liposack for each battery and put them in a metal ammo tin.  Of course, if you’re willing to risk it, you could just store them in one liposack and toss that in an ammo tin.  Just weigh your cost vs. potential losses.

Summary

Okay, so let’s sum up what you’ve got to do with a li-poly battery to make it usable and use it.

  1. Charge It — Do this with a balancer if you have one.  Some chargers might have a balancer built in and you wouldn’t need to worry about a balancer.  Some balancers need to be used in a separate step.
  2. Balance your battery
  3. Put it in your AEG and abuse your enemies!
  4. Store it for use later.

If you stick to that, and keep that voltage above 3v per cell (easier than it sounds), then you’ll have a battery that will far outlast your competition… unless of course they read my articles too!

Stay tuned to part 3 where we talk about where you should and should not purchase your li-poly’s from, how to pick out a li-poly pack, and summerize the pro’s and con’s of using a li-poly pack.  If you’re good, I’ll even put together pricing for a entry and a high end lipo pack as well as a “starter” kit.

Part 3

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