LiPo Batteries – Breaking the Myths

Lithium Polymer batteries (often seen as LiPo or Li-Poly) are rechargeable lithium-ion batteries that use a polymer electrolyte instead of a liquid electrolyte. Nowadays, you can find LiPo batteries used in several things from RC cars to cell phones, electric/hybrid vehicles to wireless headsets and more. 

One of the great things about LiPo batteries is the amount of energy that can be delivered while still being in smaller, lighter weight package (when compared to NiMH (nickel–metal hydride) or NiCd (nickel–cadmium) batteries). In addition to the small footprint with a powerful punch, another plus side to LiPos is the discharge curve; which can give you a longer runtime at peak performance before draining to a critical level.  

The Bad Side of Good – LiPo Myths

Over the past couple years, I have seen and heard many different things about LiPo batteries and during this time I have also seen and heard many myths interjected about them. 

LiPos are Super Dangerous

Let’s be honest here, if you are able to find a high energy battery that can take the absolute worst abuse ever without any danger, you are probably sitting on a pretty big payday. All batteries have an element of danger to them and almost all batteries can be used safely if they are not abused. Yes, LiPos can catch on fire and explode, but then again, so can NiMH and NiCd. Usually, when you see LiPos catching on fire/exploding it is because they have been severely mistreated, they have been overcharged, over discharged, punctured, left in a hot car or shorted. Because of the stigma (of LiPos “are dangerous”), a lot of people avoid upgrading from NiMh/NiCd to LiPos. 

At the end of the day, if you use some common sense and do some research, you’ll be able to run LiPo batteries without any issues. 

LiPos are TOO Powerful for my [Stock] AEG

This is partially correct and incorrect. The concept that LiPos are too powerful for an AEG airsoft gun is completely wrong and is disingenuous. However, certain precautions must be taken before attempting to use a LiPo on an AEG; specifically, you have to protect the trigger contacts. 

LiPos are more efficient at delivering higher amounts of current than stacked cells of NiMh and NiCd. Because of this, some people tend to think that LiPo batteries (at a similar voltage as the factory NiMh/NiCd battery that comes with the AEG) will burn out their motor or do damage in some other way. As far as the current (amperage) is concerned, this is not true; it just won’t be under a higher demand. Allow me to try and explain: 

For an example, if your AEG motor requires 24A to run at 100% of its potential, it will only attempt to draw a maximum of 24A from the battery (does not matter what type of battery it is). A basic ‘quality’ brand NiMh stick (of 8.4v @ 1600 mAh) has a “C” rating of around 12C. Using a little math, 12 (battery C rating) * 1.6 (value of Ah (1600 mAh = 1.6 Ah)) = 19.2A, means that the NiMh can only discharge a maximum of 19.2A continuously. A LiPo battery (of 7.4v @ 3300 mAh) has a “C” rating of 30C; using the same math (30 * 3.3 =), the LiPo battery can discharge a maximum of 99A continuously. In the end, with the supplied information, the NiMh will only be able to run the motor at 80% of its potential, whereas, the motor will only be using roughly 1/4 of the LiPo’s maximum discharge capacity to run the motor at 100% of its potential continuously.

Hopefully, I didn’t confuse anyone with trying to explain that. 

How to Protect your Stock (or Mildly Upgraded) AEG when using a LiPo

This subsection is directed towards those who are not afraid to upgrade their AEG. For those that are not comfortable with messing with the guts of their AEG, just take it to an airsoft shop and tell them that you want your AEG upgraded with a MOSFET so that you can use LiPo batteries. 

There are a couple things that I will suggest here and that is

  1. Upgrade your AEG’s wiring to at least 16 AWG ((American wire gauge) or 1.3mm for everyone using the metric system).
  2. Either invest in a MOSFET or Microcontroller or Make a MOSFET yourself (I will not be covering a “How to make an airsoft MOSFET” in this post).

Unless you spend a good amount of money on an AEG, chances are that the factory wired it with some cheap 18 or 20 AWG wire (sadly I have seen 20 AWG wire used in the past). Beefing up the wiring is nothing bad at all, the only thing that may suck is trying to put it all back together with the thicker gauge wire. 

Why do you need thicker wire? With more current delivery, thinner wire will get hot and I mean HOT. According to basic DC gauge charts, 24A should require 12 AWG wire for a device that is running at 100% for long periods of time. Since most of us run out AEGs in quick bursts for relatively short amounts of time (10-30 minutes of gameplay per round), we can get away with running 16 AWG. 

As for the MOSFET or Microcontroller, you need one to pull the higher current away from the trigger contacts. Basically, with higher current, every time you pull the trigger, the contacts will arc; this causes premature wear on the contacts and deposits carbon on them which will eventually cause them to stop working as they should. A MOSFET or Microcontroller can remove the high current from the trigger contacts by design and the way it’s wired. Basically, you have the battery that plugs into one side of the MOSFET/Microcontroller, on the other side, you have the wiring going directly to the motor and then you have two other (much smaller gauged wires) coming from the MOSFET/Microcontroller that is wired to your trigger contacts. (See image below)

When wired like this (and you’ll have to excuse my crappy drawing skills), the MOSFET or Microcontroller detects the closing of the trigger contacts, then through some magic electronic wizardry, the MOSFET uses that closing of the contacts to trigger a flow of electricity to the motor. In this method, the higher current stays away from the trigger contacts, thus eliminating arcing, carbon deposits and premature wear and tear. 

My suggesting to you if you want to run a LiPo battery and/or protect the trigger contacts, just hop on Evike, Red Wolf or another airsoft vendor and pick up a Gate Microcontroller. They’re relatively cheap, they have a warranty, some of the work is already done for you and you can also get some other features like Active Braking, circuit protection, et cetera.

Either way, I DO NOT suggest running a LiPo battery on an AEG until you have a MOSFET/Microcontroller in place and you’ve upgraded your wiring (if necessary). 

LiPos Require A Ton of Special Care

This is also untrue; LiPos require around the same care as other rechargeable batteries. LiPos are not made out of tissue paper, glass nor are they a brittle and frail little old lady. You can pretty much handle them just like NiMh and NiCd batteries.However, there are a couple of things that you need to take into consideration if you want to maximize the life of your LiPo batteries. 

Inspect

Get into the habit of inspecting your batteries, even if they are brand new out of the box. This applies to all types of batteries; NiMh, NiCd, LiPo, Li-Ion, LiFePo4, and the rest. With LiPo batteries, make sure they are not puffy, rounded or swollen (see image below). Also, make sure that the casing (“shrinkwrap”) is not punctured. If you get a new LiPo and it looks like a swollen marshmallow out of the box, take it or send it back for a replacement; don’t even attempt to use it. I’ve handled hundreds, if not thousands of LiPo batteries over the years, both for hobby and in a professional engineering capacity and I can only recall a few that were unfit to be used.

Charging

When people share stories of LiPos going wrong, charging is one of the biggest reasons why things went sideways for them. A lot of times, the problems could have been completely avoided if they would have just bought a good charger (and understood how to properly use it). High quality chargers have the ability to charge different types and sizes of batteries, allow rapid charging in a safe manner, prevent overcharging and will perform balanced charging (balanced charging allows multiple cells in a battery pack to be charged equally; for example, it avoids charging one cell more or less than the other(s)). 

Also, keep in mind what your battery ‘charge rating’ is and avoid attempting to push more current into the battery than it’s rated for. For example, if your battery lists a 5C charge rating and it is 2000 mAh, you can technically push 10A to the battery during charge. However, as my personal preference, even if I could push 10A, I would most likely only charge at 2C (for this example), which comes out to 4A. Don’t be impatient with charging batteries. While it may take a little longer to top off the batteries, it’s still better than having to worry about potential problems or reducing the life of the battery.

If you need any assistance calculating “C”s and amperage, you can check out this page here.

On a side note, some people will suggest buying a LiPo charging bag (or sack) and some people will say that they are pointless. These are flame resistant bags that you place the battery in while charging or while storing. While I do understand that the charging bags may seem a little over the top for those who pay attention to their batteries, I still suggest getting one (or more if you need to) just in case Murphy’s law decides to try and kick you in the teeth. Even if you are cautious and inspect your batteries (of any type really), there is always the possibility that you won’t see or catch something. Personally, I would much rather keep a potential problem (such as rupture or fire) contained instead of just sitting on the countertop, in the open. 

Discharging

LiPo batteries (and even Li-Ion batteries) do not like to be discharged below 3V per cell. Discharging the batteries to a point below 3V will almost certainly kill the battery/pack and then you can be left with a doorstop. There are instances where you can rescue an over-discharged LiPo battery, however, since I have never needed to do this and verify the results, I do not feel comfortable posting the process on here. My suggestion is to either invest in a LiPo monitor (they are really cheap and are worth the purchase) or be extremely vigilant in noticing the drop in performance of the LiPo. LiPo batteries (as mentioned before) have a pretty steady performance then drop exponentially. If the performance suddenly drops during use, stop and replace the battery with one that is topped off. Do not attempt to continue running the battery as you would with a NiMh or NiCd. 

Electrical Shorts

As with any type of battery, you need to avoid electrical shorts. An electrical short is caused when any of the positive and negative wires in your power system contact each other unintentionally. 

You generally see this when someone either solders the male side of a Dean’s connector onto the battery leads (which leaves both terminals exposed), when someone attempts to solder new connectors onto a battery and has both leads bare and exposed, and/or when someone does not cover the solder connections with heat shrink tape or electrical tape. There is also the issue of someone attempting to build a circuit with a design flaw including a short, but that is a different subject altogether. P.S. Shorts can also occur due to impact damage. Inspect your gear to make sure that you don’t have any exposed wiring that can ground out on other wiring or on metal parts.

When using larger gauge wire, a short can cause the battery to discharge at a rate in which the battery is not capable of handling. During this rapid over-discharge, it will cause the battery to heat up and expand, increase internal resistance and create more heat. Once this chain reaction is in place, you will most likely witness the catastrophic failure of the battery due to heat and internal pressure; rupturing the pack and either producing extremely hot smoke/bubbling material as well as even producing a nice fireball.

Storage

In the end, storage is not as simple as throwing the LiPo on top of the refrigerator after an outing. You really don’t want to store LiPos in a discharged state as it may not recharge to its full state after long periods of time. This is also where high-quality chargers come into play. Look for a charger that has a feature to charge your LiPo for storage. This kind of charger will balance the cells and charge it to a voltage that is safe for storing. Also as I stated earlier, it’s not a bad idea to store your LiPos in a flame resistant charging bag. If something, somehow, decides to go wrong and a battery goes into catastrophic failure, you won’t really have to worry about it potentially burning something down. 

Also, if you have animals, a storage bag helps keep them from attempting to chew on the wiring; cats for some reason are neurotic and a bit retarded when it comes to stuff like this. They apparently get off on chewing on dangling wires, this also applies to small/dumb dogs.

Moral of the Story

At this time, almost nothing (at the consumer level) can touch the performance of LiPo batteries. If you use some common sense and remember what is covered here, you should have nothing to worry about while putting yourself into a position to run and gun harder and for longer. The initial cost may seem a little high when compared to NiMh and NiCd batteries, but the performance value that comes with LiPo batteries are worth the extra money. 

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