This is for informational purposes... if something like this has been posted already please feel free to move/remove/whatever. Batteries are kinda my thing, and while im comfortable working on guns, I just dont have the time to really do it anymore, but my electrical knowledge might come in handy for some people to really understand batteries.
I get a lot of questions about batteries and chargers and this is meant as a fast simple explanation without going into too much detail. This is geared specifically towards airsoft so I am not including many important things in electronics that aren't as important in airsoft.
Terms:
Voltage (V) - higher voltage means higher rate of fire and the ability to turn over heavy spring loads. Nickle based batteries are always multiples of 1.2V because that is the voltage of each cell. The cells are put in series (in a line within the circuit) and they are added together. For example the standard 8.4V battery has 7 cells, 9.6V has 8 cells, etc. etc. Important: voltage pushes, you can force higher voltage into a gun and it will break it (burn out the motor or fry wiring)
Amperage (A) - NOT the same as mAh! Higher amperage means higher rate of fire, better trigger response, and the ability to turn over heavy spring loads. This sounds very similar to voltage and its kinda like its cousin. Larger cells usually means higher amperage, higher quality cells almost always means higher amperage. To know what amperage does think of a taser; it could have 10 000V but since the amperage is so tiny (well below 1A) it wont kill you. An industrial chrome plating machine runs 3-5V but in the thousands of amps and it will literally cook you alive in an instant. Important: amperage is pulled, you can have a 5000A power supply but the gun will only draw its own maximum amperage.
Miliamp (mA) - 1/1000 of an amp
ROF - rate of fire
FPS - feet per second, totally unrelated to batteries. A low battery will not reduce your fps and a large full battery will not increase it.
awg - wire gauge, smaller number means thicker wire
mAh - milli amp hours, a measure of battery capacity. 1mAh = a 1 hour battery life at a 1mA draw current.
Chemistry:
NiCd (nickle cadmium) - lower amperage than NiMh cells of the same size, far more toxic, illegal in most of Europe, and has the memory effect. Far better performance in cold weather though.
NiMh (nickle metal hydride) - best bang for your buck. Good amperage output, same 1.2V cells, almost no memory effect, no where near as toxic. The standard batteries for airsoft but when its getting colder, say -10'C and below, they can start to give reduced ROF or not work at all.
Size DOES matter!
Larger cells means larger capacity and usually higher amperage. A large 8.4V pack will often give the same ROF to a gun than a mini 9.6V pack because of the amperage differences. Larger cells do better in the cold regardless of chemistry.
Also note that rechargeable batteries sold in normal stores for, say, a digital camera will NOT work with an airsoft gun. They are designed for low amperage requirements and wont work, period.
Thicker wire also means higher maximum amperage. A shock from rubbing your feet on a carpet can reach 10 000V so it should be obvious that high voltage doesn't require thick wire. Standard guns usually have 18awg wire which can carry ~16A. More powerful motors (high torque motors) will want more amperage to run at optimum. Many upgraded or higher quality guns will have 16awg wire which can carry ~22A which will increase trigger response and ROF. If you are going above 400fps it is highly advised to upgrade to 16awg wire if your gun doesn't already have it. More powerful springs will add more strain to the motor and thus it will need more amperage to run so just because your motor can't turn your mechbox over doesn't mean the motor is too weak, the maximum amperage your wire can carry might be too low but the motor wants more. Remember that amperage is drawn, you can't force it, so a bigger battery might not be the answer. Also remember that the amperage can only flow as fast as the slowest point. So even if you have a huge battery and crazy motor, if your wires are small the entire system will only run as fast as the wires will allow it.
Run time:
Higher mAh rating means higher capacity and longer run time. More extreme upgrades will require more amperage so will drain your battery faster. It is often said that 1mAh = 1BB but this can vary widely. Different motors are more or less efficient and use more or less power when performing the same amount of work. An AEG shooting 450fps might need 2mAh to fire 1BB on full auto and firing on semi reduces your efficiency even more. I have never drained more than 1500mAh in a single game, even with 450fps semi auto sniper rifles; only exception being support weapons. Generally a 1500mAh mini pack will get you through a game, if its early spring or late fall bring a backup. If its a large battery (2400mAh+) then unless you count your shots in thousands instead of hundreds of BB's in a day you are fine.THIS IS IMPORTANT cold weather will drastically reduce the life of your battery and you will need 1-2 backups depending on weather. For those of you at OP: Black Hawk Down you probably know this first hand. IMPORTANT: Do not store your batteries outside in cold/heat exposure if at all possible especially the night before an OP!
About chargers:
Wall chargers are crap! The ones that are an AC adapter with a wire and a battery plug will kill your batteries. You want something that has at least a simple brain in it. Later down the road you can pick up more advanced chargers and thats up to you. I have heard some good things about one called Superbrain and I personally use the "universal" tenergy charger. IMPORTANT: DO NOT USE A WALL CHARGER WITH A LIPO, LIMN, etc, most lipos that come with charger have a "smart charger" but not a balancer.
How to charge and discharge:
Batteries should never be charged higher than 1C. This is the amp hours of the battery which is the same as the mAh divided by 1000. So for example if you have a 3800mAh pack then 1C for that specific pack is 3.8A. This should be your MAXIMUM charge rate for that battery. Voltage doesn't matter as long as the charger you are using is rated for that voltage. You can charge lower but I usually just round down and have never run into problems. In the above example for the 3800mAh pack I would charge it at 3A. For a 1400mAh pack I would charge at 1A but you could do up to 1.4A safely. Charging at 1C for a battery that is totally empty would mean very close to a one hour charge.
NEVER DISCHARGE A BATTERY TO ZERO! This greatly reduces the batteries life. Any sort of simple resistor based discharger does exactly this, it does whats called dead shorting and drains the battery to zero volts. A nickle based battery should never be drained below 0.9V/cell; so for an 8.4V battery (7 cells) it should not drop below 6.3V. This is next to impossible to monitor but a smart charger with a discharge function does it for you (and some can be programmed for different cut off voltages.) As for discharging DO NOT DO IT AFTER EACH USE! A NiCd battery, even though it has the memory effect, should only be discharged every 4-6 charges, a NiMh will still get the memory effect so should be discharged after every 15-20 charges. Generally if I go to games regularly I discharge my NiCd packs once every 2 months and my NiMh packs once at peak summer and once before winter. It is also good to discharge and charge a pack if its been in storage for more than 3 months.
Storage of batteries:
Batteries should NEVER be stored drained. Always store them full if you are playing on a regular basis. For long term storage (3 months or more) its best to keep them at 70-80% full. For longer term storage (6+ months) do the same but store it in the back of your fridge (NEVER the freezer).
Battery Brands (by far not a complete list but covers the most common):
The good: intellect, ELITE, GP (not the same as G&P), Sanyo
The mediocre: G&P, STAR
The bad: Tenergy, no-name (like those that come with cheap Chinese guns)
The dreaded Lithium:
LiIo (lithium ion) - used in laptops and cell phones mostly. I have heard of people using them for airsoft but its incredibly rare. Just forget about them in regards to airsoft.
LiPo (lithium polymer) some people have been known to explode these batteries, but this is a HUGE misconception for the average player. The batteries provide insane amperage but the wafers (instead of cells) come in 3.7V increments so the only really viable batteries for airsoft are 7.4V and 11.1V. Since they have such an insane amperage the 7.4V batteries can give similar performance to a mini 9.6V nickel or 8.4V large.
LiMN (lithium Magnesium) If mistreated charged on a wall charger not designed for its needs) its the most explosive battery, but treated right its actually more stable than LiPo, same basic information as a LiPo just a bit more expensive and "safer" for the average player.
LiFe (lithium iron) these are fairly new, don't know that much about it, needs its own very specific (and often expensive) charger. Very similar to LiPo but not as explosive.
For any kind of LI battery you will not want to use a charger without a balancer. A balancer charger is one that uses a small clip connector (not standard for other batteries) to regulate the voltage each cell receives individually. If you do not use this eventually your cells will become unevenly charged and eventually stop powering your gun, this may or may not be fixed by hooking that battery up to a balanced charger.
EXPLOSIONS! (and how to avoid them)
A LiPo battery will not explode at random, just like a can of gasoline will not explode sitting in a garage. When they are drained too low (below ~3V per wafer) they will expand and the pack will be obviously fatter. If you try to charge a pack this has happened to it MIGHT explode, not a sure thing. Also NEVER charge a LiPo above 1C as this can cause it to explode (and it really is an explosion, fire and black smoke and everything, just go search it on youtube.) There are voltage monitors you can hook up between the gun and the battery that will either start buzzing or cut off the power (depending on model) if the voltage hits 3V per wafer. If you use one of these monitors LiPo are as safe as any other battery. Also since they are so efficient you can fit 11.1V and 1200mAh into the stock tube of an M4A1, something that is impossible with nickel based batteries if you want a voltage higher than 3.6V (which wont even turn over a mechbox.)
HUGE MAJOR WARNING!
The smoke from a burning lithium pack of any type is incredibly toxic. If you are unsure of a pack, don't charge it. If you want to see if it will take a charge (or want to watch it explode) do it outside or in a garage and from a safe distance. Also don't throw them in fires; that's just dumb in general for any battery.
Additional information from your battery expert regarding connectors: Tamiyas are the most widely used connector for airsoft (because they are the cheapest) so although they are also the worst; consider that your chargers and lots of players on the field that could lend you a battery may be restricted if you switch to some other type of connector.
Bullets: The best connectors are actually called bullet-plugs and hardly anyone uses them (i have never seen one on an airsoft gun in real life) and are quite expensive. To be clear "Bullet" connectors is really not descriptive enough, and although I am thinking specifically along the lines of the Gold Bullets by Hyperion; to be fair there are quite a few "bullet" style connectors The most popular are the Hyperion gold bullet, the EC3, Powerpoles, and the Schulze PP35. While there are many variations (including the XT-60s) they are not as popular.
JST connector: This is a small power plug rated for up to 5 amps of continuous load. It is used on smaller battery packs for powering on board electronics. This is the "balancing" plug on a LiPO battery. I didnt mention this because there is no way that it would be used in an actual Airsoft gun capacity except to run the balancer on a lipo.
Traxxas Connector: As the name suggests, Traxxas battery connectors are used almost exclusively on electric Traxxas RC vehicles/boats but can be fit to any high current application up to about 100 amps. These are a nice connector that many say are one of the nicest to plug and unplug. They are a GREAT plug, rather expensive, and although ideal for airsoft plugs, they are honestly overkill for any airsoft application
DEANS: The next and also second most popular in airsoft is Deans. There are some misconceptions about what makes them better. It is NOT the design that makes them inherently better its the way that the connection is made. The design allows them to make a full contact with a "pole" (in this case actually a flat surface area) which means more surface area and a tighter fit. This means no arcing or loose connections (something that drastically decreases battery life in both charge and half-life). However, it is good to note that because of this decreased resistance you can actually achieve an aprox. ~2 shots more per second in ROF. While this does vary across guns, it's a generally accepted number. This may or may not mean anything for you, but for those looking for the highest performance it matters. They are second most widely used because of their ease of use, cost effectiveness, and better performance.
Basically the reason tamiya is bad is because of the loose fit and small surface area that makes "hard" contact. While this can be somewhat remedied by shrinking the size of the female adapter (somewhat tricky) in the long run its just going to get loose again. That being said, I have never felt the need to change all my batteries over to Deans as I deal with so many types of guns that its generally best if I have some extra batteries lying around with tamiya, and if you aren't going to fully commit to the change its more trouble than it's worth (imo).
Theoretically the best connection would be a hard solder, but that of course is completely unviable for airsoft (or most things that use batteries).
I hope this helps all the people out there with battery questions. - Sarge (JTAG)
