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 Post subject: Guide: Battery Basics and Chargers
PostPosted: Thu Feb 05, 2009 2:13 am 
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BATTERIES AND CHARGERS
by Moondog
Copied from Airsoft:101

AEG batteries come in 3 types:

NiCad (Nickel Cadmium) These batteries are the most common rechargeable batteries in the world. It is important that you discharge these batteries before charging them, or they will lose their capacity, also called the "Memory Effect”. These cells are common in older AEGs and cheaper clones.

NiMH (Nickel Metal Hydride) NiMh is a newer battery type that is quickly replacing NiCad. They can charge faster, have higher capacity, higher amperage and aren't effected by the “Memory Effect”. Due to their chemistry they also self-discharge continuously. Left alone, they lose half of their charge after 30 days. So you should recharge your NiMH batteries no more than a day or so before a game.

NOTE: NiMH batteries are now the most common type of standard rechargeable battery (AA or AAA). Due to their constant discharge, NiMH batteries are unsuitable for emergency devices such as smoke alarms, safety flashlights or emergency radios.

LiPoly / LiPo (Lithium Polymer) LiPoly are the newest type of rechargeable battery used in cell phones, laptops and digital cameras. Lithium Polymer batteries have twice the capacity at about half of the weight of NiCad or NiMH cells. They require a special computer controlled charger to avoid catastrophic overheating during charging which can cause them to burst into flame. AEG LiPolys come in either 7v or 12v packs. 12v packs require that your AEG have high quality wiring and a motor and gearbox that can handle high-speeds. ::Read more about upgrading to LiPo batteries::


MAH MEANS CAPACITY
A milliampere hour (mAh) is 1000th of an ampere hour (Ah). This is a measure of the amount of charge that a battery will hold and how long an AEG will fire before the battery needs recharging. Contrary to some misconceptions, higher mAh batteries do not require you to modify your AEG in any way nor will it damage your motor or wiring.


VOLTAGE AND ROF
The higher the voltage the faster your motor will spin and the higher your AEG's rate-of-fire (ROF). Most AEG's in their stock form are optimized for 8.4v but most good quality AEG's can handle a 9.6v battery without any additional modifications. Bear in mind, the faster the ROF, the faster the heat will build up in your gearbox and the faster your parts will wear out. Some upgraded AEG's use 12v packs (notably LiPoly), but this requires reinforced, high-speed internals. Some smaller AEG's and PDW use 7.2v packs.


LARGE AND MINI PACKS
Battery packs typically come in two sizes, large and mini. And they ca come in a number of shapes and configurations such as stick, nunchuck, crane, double-stick, odd-double and more.

Large Battery are typically comprised of Sub-C (SC) sized cells . They offer larger storage capacity and thus large battery packs can be 3600mAh or higher. Due to their larger physical size, only AEG's with full shoulder stocks or external battery holders/bags can carry them.

Mini Battery are typically comprised of 2/3 A-sized or 4/5 A-sized cells that can fit into smaller AEG's with collapsable stocks or no-stocks at all. Due to the smaller size of the A cells, capacity can be 1200mAh or higher.


BATTERIES AND TEMPERATURE
Batteries generate electricity through a chemical process that is effected by the temperature of the cells. At near sub-zero winter temperatures, batteries can produce insufficient current to operate an AEG. As the batteries are used/drained, they heat up. As the cell approaches empty or full, the cell reaches it's maximum temperature.


CHARGERS
Rechargeable battery charges fall into two categories, smart and dumb chargers.

Smart Chargers have built in microprocessors that can determine the condition of the cells, monitor the charge, and auto-shut off when the battery is fully charged. This can allow smart charges to vary the voltage and fully charge a battery in as little as 10minutes. Many Smart Charges can auto discharge NiCad batteries as well. Special smart chargers are required to charge LiPoly packs.

Dumb or Wall charges lack microprocessors and rely on a small 'trickle' charge to continuously charge a battery over time. It is vital that you monitor the battery periodically to make sure it doesn't become overcharged and heat up dangerously (and possibly ignite and burn). This online utility can help you calculate the maximum time to fully charge an empty battery. As a rule of thumb, if the battery becomes uncomfortably hot to hold, disconnect it; it's fully charged.

Here's an online utility to determine the maxiumum charge time for wall chargers: http://www.csgnetwork.com/batterychgcalc.html


DISCHARGING AND STORAGE
All batteries lose charge over time. Some batteries lose charge faster than others. If you've ever tried an old flashlight in a drawer and found it dead, that's because the Alkaline batteries in it slowly lost charge over time. NiMH, NiCad and LiPoly also lose their charge. NiMH loses its charge fastest and LiPoly the slowest.

NiMH batteries lose 30% of their charge per month so after 3-4 months your battery will be totally discharged, though after only about a month and a half, the charge may be low enough that it won't work an AEG. Storing your battery in a fridge will slow the self-discharge rate but not stop it.

NiCad batteries develop crystals in the discharge/charging process which can fool a charger into thinking it's fully charged when it isn't. This is called the 'Memory Effect' discussed above. That is why you must fully-discharge a NiCad battery in order to fully charge it. Any electrical device such as a flashlight bulb or computer motor that you can attach to a NiCad battery to run it down until it fully drains will function as a 'Battery Discharger'.

LiPoly batteries are more complex due to their chemistry. LiPoly batteries that are fully discharged can cause an odd chemical reaction which causes the metals to heat up. 'Fully Discharged' LiPolys can catch fire (which is what happened with some early computer laptops). So it's advisable to always keep LiPoly's partially charged. And never, ever store and forget them somewhere flammable (like a closet next to your clothes or a garage next to cans of green gas.)


VOLTS AND AMPS EXPLAINED
Electricity can be explained using a garden hose as an analogy.

Voltage is the pressure/speed of water shooting out of the hose. The higher the voltage the harder the pressure of the electricity shooting through the wires/motor. The difference between a 7.2v battery and a 9.6v battery is like the difference between a garden hose and a high pressure hose at a self-service car wash.

Amperage is the volume of water coming out of a hose. For example, you can squeeze a hose and reduce it's diameter and make the pressure (volts) increase but it is still the same amount of water coming out of the hose (amps). NiMH's with the same cell size and voltage as a NiCad will produce higher amps.

mAh is the measure of total capacity (as mentioned in the post above). Using the hose analogy, it's the water tank/reservoir that feeds the hose. How long this water lasts depends on how much water you use.


PROPER DISPOSAL
Remember, don't throw away 'dead' batteries because they contain highly toxic chemicals. Batteries in landfills eventually leak into the water table and can contaminate the drinking water of your town. Either put them in your Recycling bin if your city/town has a recycling program or drop them off at your local firehouse as they usually have drop-off bins for toxic materials and batteries.


WHERE TO BUY BATTERIES
You can buy your batteries from airsoft shops like Evike.com which generally know which battery packs can fit into which guns. Airsoft batteries originated in the RC world (Radio Controlled cars, planes, boats, etc.) so you can buy these cells from the same websites but they require you come with some knowledge of what battery you need.

www.evike.com
http://www.cheapbatterypacks.com
http://www.onlybatterypacks.com
http://www.batteryjunction.com

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