So, you hear people talk about their sweet, decked-out LiPo battery with 5 million mAh and wonder, like I did, what these freaks were talking about? Well, I am now one of those freaks, and here I go, talking about it.

Ok. Whew. You should know when I start in this that I've spent most of my airsofting life obsessed with batteries, so I love it when questions like this happen. Here's a quick rundown of battery basics:

Battery terminology:

Voltage: A somewhat steady reading of the...well, let's say "power" here...higher voltage will cause a motor to spin faster. Most standard batteries have 7-8 cells in them at 1.2V apiece, making the standard battery either an 8.4V or a 9.6V. A lot of people upgrade their guns to a 9.6V battery to up the rate of fire...probably the safest level is 8.4, but I've had no issues with 9.6V...but then again, we're not talking about this are we? When battery cells are fully charged, they are typically above 1.2V apiece, lending themselves to higher total pack voltage, faster rate of fire, etc...so don't trust what a gun does on a full charge. Run with it for awhile and see how it operates on a less-than-full battery to see its "typical" operation.

Milliamp-hours: this is the "mAh" that you see on your battery. It corresponds to current and capacity depending on what you're looking at. If you look at your wall charger, you SHOULD see the same thing. On a battery, this tells you how long the battery will last. Let's say you have a battery with 1000mAh. This means that if you attached it to something requiring a 1 milliamp per hour drain, you could run it for 1000 hours, or if you had something requiring a 1000 milliam per hour drain, it would last an hour. Of course, airsoft guns require more like 3-5 amps per hour (read: 1000 milliamps = 1 amp) meaning if you just held the trigger in place, your battery of 1000mAh would last something like 12 minutes. Of course, with current run-off, continuous grounding, etc., the lifespan is not that long, but we're generalizing here.

Battery materials:

This is one of those parts of battery technology that has gone through some rapid development, so we will have to start with the oldest technology and move to the newest...at least when it comes to airsoft:
NiCad: Nickel-Cadmium. Among the first material combinations used for rechargeable batteries, this technology has been around for decades. If you ever had a portable phone in the late 80s or early 90s, it was 99% likely to be NiCad. These batteries were nice to have, were reliable, lasted a good long while, and saved a ton of money from alkaline batteries. However, they had one major flaw that made them trouble with airsoft: battery memory. You probably never noticed this issue with portable phones until one day your phone no longer charged, but in Airsoft, it's a big deal. Battery memory refers to the amount of charge (in mAh) that a battery can store up. With NiCad batteries, if you ran a battery to about half its capacity, then charged it up, the battery would memorize the lowest charge as its penultimate lowest charge, effectively reducing the life of your battery by half. So airsofters, without knowing it, would charge their batteries with some capacity left and ultimately lower the effective mAh of their battery. There are ways to recondition batteries to return the life back to them, but without getting into the nitty-gritty details, suffice it to say it was not 100% effective and battery life still took a (permanent) hit. Airsofters with these batteries are always advised to fully discharge their batteries before recharging them.
NiMH: Nickel Metal-Hydride: This is the most popular battery type out there at this present time, because most of the research and development of rechargeable batteries, both in Airsoft and in RC applications, has gone into this for the last couple decades. NiMH batteries have the capacity and voltage of NiCad batteries, without the significant issues related to battery memory. Battery memory issues are not COMPLETELY devoid from ANY rechargeable battery, but are certainly much less pronounced than NiCad and most airsofters will tell you it's safe to recharge a battery without fully discharging. If you ever encounter an issue with a NiMH battery, try discharging it fully and recharging it. Usually does the trick.
Li-Ion: Lithium-Ion: This is probably a good place to talk about cell shape. It is important to remember that rechargeable batteries were first intended to replace consumer alkaline batteries, which explains why in those battery packs you own, the cells are cylindrical, with a negative pole on one end and a positive on the other. It's a perfect setup for stacking batteries end-to-end and easy to assemble packs. When lithium batteries came to the forefront of battery technology, they were still in the "cell" (read: cylindrical) form. Nothing wrong with that, but because of the significant change of materials (nickel to lithium) along with other things that need not be discussed here, the voltage of these cells came out to be 3.7V. What's worse is that you can actually buy AA shape batteries that put out 3.7V instead of the 1.5V of an alkaline battery. Whew. BIG no-no. Additionally, these cells, while producing greater voltage in the small packages, did not necessarily provide the mAh necessary to run airsoft weapons. This isn't to say they wouldn't make great airsoft batteries, but you'd have to probably produce parallel-series batteris, taking 9 cells, in order to have a reasonably better-quality battery pack than standard NiMH batteries. Don't get me wrong here. Li-Ion cells are good batteries, and you'll actually find them in several laptop battery packs. For some reason, they didn't catch on very well in the airsoft world. One reason was the volatility of these batteries. Because of the energy density within the cells, overcharging had a much more dangerous impact than overcharging NiMH batteries. That leads us to
Li-Poly (LiPo): Lithium-Polymer: These batteries are essentially the holy grail of battery packs, and that explains their expense. Truth be told, LiPo batteries are actually Li-Ion batteries with a polymer-laminate casing, making them flexible, rectangular, and, for lack of a better word, flat. The volatile substances that were so prone to damaging cells in the cylindrical format were now housed in flammability-resistant housing and spread out thin for better heat transfer. Because you could have higher volume in the rectangular casing, battery capacity skyrocketed, to the point that you can essentially house an 11.1V battery pack with 4000+ mAh in a battery pack the size of a standard small NiMH 8.4V pack. This spells a number of things for airsoft. The higher voltage means higher wear on internals, requiring better quality gearboxes, shim jobs, more efficient motors, etc. The higher capacity means smaller weapons can pack a bigger wallop. Anyone who's gone toe to toe with AEPs with LiPo batteries know firsthand that the rate of fire on those little puppies is awe-inspiring, to say the least. LiPo batteries are still volatile, and require specialized charging and discharging gear. They also require internal voltage monitoring hardware that is capable of cutting off all juice below a certain voltage threshold, in order to make sure the pack doesn't explode. Yes I said explode. Google LiPo explosions and you will see what I mean.

Charging Batteries:

Now, what's most important for charging is the charger's mAh versus the battery's mAh. If your battery has 1000mAh capacity and is FULLY DISCHARGED, then a 300mAh charger would have to take 3 1/3 hours to fully charge it (300 * 3 1/3 = 1000). It's very simple math. Complicating the process of battery charging is a number of variables.

First off, you probably do not have a fully discharged battery, unless you discharged it by a.) hooking it up to a airsoft battery discharger or b.) made an electrical rig designed to drain batteries, like a 9v light bulb. Second, the charging of a battery is not linear...if you look at the charging of a battery, you get your full 300mAh charge happening during the sweet spot between 20% and 80% capacity, but in the time before 20% and after 80%, things slow down. Batteries are physical objects with physical limitations, and charging is not an exact science.

THIS IS WHY PEOPLE SUGGEST A SMART CHARGER. The main reason is that smart chargers detect when charging slows down and will either cut off the circuit or run what's called a "trickle charge" when the battery has reached full capacity. If you were to keep the battery plugged in overnight to a basic wall charger, it would keep trying to pump 300mAh into the battery, severely over-charging the battery to the point that it will get very (I mean very) hot. Not only does this suck to try to pick up, but it physically messes with the battery to the point that you lose capacity. Double suck.

HOWEVER, all of that being said, it is typically safe to just run the little calculation (take the mAh of the battery and divide by the mAh of the charger, that is the # of hours you should charge) and charge off of that. You may not reach maximum capacity, but unless your battery has a 50% or greater charge left in it, you won't be endangering your battery.

I suggest ALWAYS discharging your battery first. Some people have spare motors lying around that they hook the battery up to, or the light bulb, or even get chargers that do the discharging for them. Then there's no question as to how long to charge.

Mo