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 AIRSOFT 101: BATTERIES

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zarj

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Number of posts : 26
Registration date : 2009-03-16
Location : dungeon

PostSubject: AIRSOFT 101: BATTERIES   Thu Mar 19, 2009 7:46 pm

Airsoft 101 : Understanding batteries

With the ascension of electric guns in the sport of airsoft, batteries have evolved to offer the player a number of choices. Understanding how batteries work, and how they effect a gun’s performance will help you make the right purchases.


Batteries + Automatic Electric Guns (AEGs) :

Basic battery terminology; Voltage, Miliamps, Current, Resistance and Short Circuit.

The voltage of a battery (7.2v, 8.4v, 9.6v, 10.8v, 12v) directly effects how fast a gun will shoot. The higher the voltage the faster the rate of fire (ROF).

Stock guns work well with 8.4volt batteries while 9.6v requires the gun to have upgraded internals (note this may be supplied from the manufacturer, such as some CA and G&G models).

Typically, though, the metal used in stock gears and plastic bushings cannot withstand the strain and speed a 9.6v battery forces the internals to go through. Cheaply made ‘teeth’ on gears strip. The motor, on the other hand, is usually not in trouble. A Tokyo Marui EG 1000 motor, stock, can handle voltages from 7.2 -> 10.6 without burning out.

Only uncommon and expensive gears can really handle the awesome power of a 12v battery. In fact, most 12v players know their gun will only last so long and budget for regular gear replacements. The ROF with a 12v battery can exceed using high-speed gears or motors. But there is a price, literally.

High speed gears or the use of a high speed motor, increases the ROF while allowing the gun to utilize a 8.4v battery. Some owners have fine-tuned their mech boxes and shimmed their gears to a high tolerance, well done upgrades can allow for high-speed parts to be used with a 9.6v battery, but it is risky and stripping gears is common… on the other hand, the ROF is eye-opening. I would not recommend over a 9.6volt battery with high-speed parts.

Miliamps refers to the batteries storage capability. The higher the number the longer the battery can supply energy. Many guns are forced to use small batteries as their storage compartments are small. More on Miliamps later…

Current is a measure of the flow of electrons from the battery to the electronics. Ampers or amps is the measurement used to gauge current. Airsoft players usually only deal with Current when their batteries are being charged. NiCad and NiMh cells deliver a very high current due to their low internal resistance.

Electrical resistance is a measure of the degree to which an object opposes the passage of an electrical current. Wires, motors, and circuits all contribute resistance to a battery.

Short circuit. This is when the energy from a battery travels an unintended path. Lets say a wire in the handle of a G3 gets exposed and touches the metal body of the gun’s frame. Immediately, the battery energy is moving through the gun metal and no longer through the proper wiring. There is suddenly less resistance, the current (flow of power) jumps up and the battery dangerously heats up. Fast.

More obviously, the player smells something burning, and in a bad case scenario the battery literally melts, destroying the stock, possibly damaging the motor, and potentially injuring the operator. What stops shorts? A fuse. Properly selected wiring. And some basic examining of your gun/battery from time to time. Water can be a serious concern. Shorts are not uncommon.



A closer look at Batteries:

There are two types of batteries commonly used to power airsoft guns, NiHm and NiCad. (NiCad = Nickel Cadmium / NiMh = Nickel Metal Hydride)

The quality debate between the two battery choices is ongoing. I will outline pros and cons for both styles, followed by personal experiences and a glossary.

The quick and easy: NiCad vs NiMH

The main difference between the two battery types is the fact that NiMH batteries (the newer of the two technologies) offer higher energy densities than NiCads. In other words, pound for pound, NiMH delivers approximately twice the capacity of its NiCad counterpart. What this translates into is increased run-time from the battery with no additional bulk to weigh down your gun. NiMH also offers another major advantage: NiCad batteries tend to suffer from what is called the "memory effect". NiMH batteries are less prone to develop this dreaded affliction and thus require less maintenance and care.

On the other hand, NiCad batteries deliver an even voltage during an entire charge while working in an AEG, while NiHm batteries are like classic powercells in that they get slightly weaker as their charge is drained. This means right up until the battery dies, the NiCad will be providing full power, while NiHm cells become less efficient once 75% drained. In big batteries like 2000 -> 3000mAh bricks, I have personally found the dying charge of the NiHm to be negligible. But were I using smaller 300 ->800mAh battery (ie in an MP5 front grip battery) then perhaps I would reach the 75% spent mark much quicker. The drop in output power is not always severe, but is noticeable. Note that some would consider the near constant voltage of a NiCad a drawback, as it makes it difficult to detect when the battery charge is low; this is usually a minor concern.


The Details explained: NiCad

NiCad batteries have gained a bum reputation for their Memory Effect, which can reduce their voltage and capacity with age. This means that improperly charged and discharged the battery will ‘remember’ a non-optimal state and will not deliver the voltage or lifespan it was meant to provide. On the other hand, if you take some time and take care of your NiCad battery it will not fall prey to the memory problem and will indeed outlive most other batteries.

NiCad batteries self-discharge. Losing about 40% of their charge in 4 weeks. This is natural. Simply realize last months charge will not be sufficient for that big game tomorrow. Especially if you are using batteries with low storage (anything under 1500mAh).

NiCad batteries have a low internal resistance
They deliver a high current
They don’t overheat easily in use.
They can be charged quickly.
Used sensibly they have a life span twice that of NiMh batteries.

New NiCad batteries require a few charging and discharging cycles to come up to full power. When you receive your new batteries, charge them overnight. Next, allow them to drain. This is commonly done with a special (and cheap) battery drainer sold by Tokyo Marui and others. Never dry fire an airsoft gun to drain a battery! Once depleted, recharge the batteries fully. This procedure should be repeated two more times if you want to get the full output of your NiCads as soon as possible. Also ask you airsoft shop if the battery you are buying has already been pre-conditioned. Many are. Here we see slight ‘con’, this battery type needs some specific handling, not plug and play.

Do not overcharge NiCad batteries. Excessive charging heat will substantially reduce their life span. If you are charging your battery and it gets hot… unplug it, let it cool and begin the charging again. Also make sure you are not charging the battery with too high of an Amp setting. And of course, use the correct style of charger.

NiCads slowly lose their charge even without use. It is best to charge them up for an hour or so once a month. You can store NiCads indefinitely without ever charging them, but one must go though a lengthy conditioning cycle (or three) if you are bringing long-term storage batteries back into use.

NiCads can develop a “memory”. For example, if they are constantly drained only half way and then recharged they will lose some of their capacity. For this reason it is best to fully discharge them a few times a year so your batteries will retain their full capacity. *However, it is best not to drain NiCads fully. If you have a volt meter bring them down to approximately 1 volt. Using a Marui battery discharger I drain mine down until the LED light is barely glowing… but not dead.

No matter how much a manufacturer brags about how fast their batteries will charge, the fact is… the slower the charge the better! You can substantially reduce the life span of a NiCad battery by consistently charging at a high rate.



The Details explained: Ni-MH

Generally speaking, Ni-MH batteries do not suffer from the "memory effect" and thus do not require conditioning. Nevertheless, to ensure top performance, conditioning is recommended at once for every ten charges.

At room temperature, Ni-MH batteries, without usage, will self-discharge in around 30 to 60 days, depending on environmental condition. In other words, if you leave the batteries on the shelf for more than 30 - 60 days, you should recharge the batteries before using them. It is normal for batteries to be fully depleted of power after long term storage.

Another distinction of a NiMH battery is it's discharge path. The voltage and amperage of a NiMH starts high and does a good job of holding this rate for about 75% of it's battery use. Towards the tale end of the discharge, it will gradually diminish.

I personally like NiHm batteries for their easy of use. I do not need to condition them, they have no memory issues, have lots of miliamp storage for their size, and are essentially plug and play. Because most of my NiHm’s rate at 1500->4000 miliamps, I rarely see the issue with their loss of current once drained to %25. I’ve seven batteries, one is a NiCad.




Battery Charging:

1. Improper charging or using a charger that is not specifically designed to charge any rechargeable battery can cause their useful life to be shortened dramatically or in some cases actually damaging them permanently. Alkaline batteries, which are uncommon in airsoft can actually exploded if charged improperly.

2. Although a NiCad charger may seem to be charging NiMH batteries fine, this is not usually the case. NiMH chargers are specifically designed to prevent Hydrogen bubbles from forming on the battery plates and of course to charge them to their full potential. Please check your charger closely, and when in doubt… don’t.

Basically you should always use the type of charger recommended for your type of batteries. Most medium range chargers can do both style of batteries.

Slower is always better than faster.

Battery cycle. Cycle life is measured by the amount of times a battery may be charged and discharged. Every time a battery is charged and discharged, it uses one cycle. Cycle life is very important in battery applications such as laptop batteries and emergency light batteries. A NiCad battery has a cycle life of 500-1000 or more cycles. Where as a NiHm has a life-span closer to 300-500. While these number are dramatically different… It’s a little like saying a NiCad battery will charge up for 800 games, and a NiHm will charge up for 400. Even if you play weekly that’s 15.4 years vs 7.7 years.



The future!

There is an enormous amount of research conducted every year into better batteries. From electric cars to portable electronics to Laptop computers. Perhaps the most interesting cutting edge battery for airsoft is the Lithium Polymer style.

Read this, but be wary… damaged Lipo cells can actually explode in a fireball. People have lost cars and houses to this. Yipes!

http://www.rchobbies.org/lithium_battery_breakthrough.htm

Spec Sheet:

http://h1071118.hobbyshopnow.com/ProdInfo/Files/EFL-LiPoSafetyWarnings.pdf
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