I posted something like this once upon a time (I think on the old Foxden forums) but I lost track of the original so I will just type something up quick.

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

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.

Of 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. The BB Bastard chargers are a simple brick charger with a delta peak sensor to detect when the battery is full and will stop charging. These are made by Tenergy and though they aren't the best out there they are adequate for airsoft and wont break the bank. Later down the road you can pick up more advanced chargers and thats up to you. I have heard good things about one called Superbrain and I personally use a Duratrax ICE competition charger.

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.)

Old batteries versus new:
I try to never buy used batteries as the vast majority of airsofters don't know how to take care of them and horribly mistreat them. I also try to NEVER buy batteries from airsoft retailers since they may have been sitting on a shelf for a year, two, or more and since they are shipped with next to no charge this means they have been sitting dead for years with an improper charge. Many airsofters will say bad things about good battery brands because they bought that brand from an airsoft retailer and it was toast out of the box or shortly there after. I buy my batteries from http://www.cheapbatterypacks.com and they have a very rapid turn over since they serve such a large customer base. I have never had a battery arrive dead from them and even after conversion and shipping (since they are a US retailer) they are very close to airsoft retail batteries.

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 hard of people using them for airsoft but its incredibly rare. Just forget about them in regards to airsoft.

LiPo (lithium polymer) – known to explode but this is a HUGE misconception. They 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.

LiFe (lithium iron) – 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.

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.

As stated by Lutnit,

I had a lipo blow up on me in the last weekend, the battery was drain down too far. But I tried to trickle charge it back at .5 ma.

Other then that I have had no problems with lipo batterys, been using them for 1.5 years now.

Get a LiFe! (also known as Lithium Iron, LiPo Iron, Lithium Iron Polymer, LiFePo, etc.)

HaZarD and I have both been doing some research on these batteries independently and I figured might as well post something here explaining them a little.

The name stands for Lithium Iron Polymer and is a different chemistry type to Lithium Polymer and is NOT compatible with chargers for use with any previously mentioned battery chemistry. Now there might be new chargers on the market that can do LiFe as well as others but unless it specifically says it can do LiFe (LiPo is NOT the same) then you need to buy a new charger.

They are close to LiPo batteries in the way they work but are not as dangerous. Now its easy to avoid a LiPo exploding with just a little know how but the risk is still there as well as the risk of puncture (which results in the battery flaming out.) LiFe batteries have a much smaller risk of this and are generally considered as safe as NiCd or NiMh but not quite that safe. They will still "flame out" when punctured but it is more of a smokey smoldering instead of the big explosive flames of a LiPo. The smoke from the pack burning is still HIGHLY TOXIC and can cause you to need an emergency room visit if you inhale the smoke and can fairly easily result in death or permanent disability. This is no different from LiPo batteries except apparently there is less smoke (I haven't seen a LiFe battery go up so I can't say from experience.) In that they are still toxic they are more dangerous than NiMh batteries which are quite safe and NiCd are only as dangerous if you throw it on a fire or try burning it in some other way (it wont burn itself.)

Generally speaking for airsoft purposes a LiFe battery is the same as a LiPo but safer. They have roughly the same capacity and drain rates but the voltages do differ and that's a key point; LiFe batteries are available in 9.6V! That's right the native voltage for many airsoft brands is possible with LiFe batteries where LiPo's where only capable of 7.4V and 11.1V since each cell is 3.7V so the pack must be a multiple of that. LiFe battery cells are 3.2V each so are available in 6.4V (not really that airsoft useful), 9.6V (awesome!), and 12.8V (a little high even for 500fps upgrades.)

If you dead short them (drain them totally) they have a high likelihood of just being permanently dead where as a LiPo that is dead shorted has a chance of exploding when you try to charge it again. Just like a LiPo though you need to avoid puncturing the cells so you want to be gentle with them; no hammering them into your stock or forcing them into a foregrip with all your weight.

LiFe batteries also don't really care about temperature to a higher degree than LiPo. Both can be used in any normal Canadian weather but LiFe can be used in hotter conditions. LiPo generally don't like being above 35-40'C but LiFe can go to 50'C without any real issues. Both can be used to well below zero (-20'C before wind chill) so that's not an issue unless you are playing in Antarctica.

A short note on chargers...

As stated above the BB Bastard charger (which is the same as the one made by Tenergy) works for almost all airsoft purposes but has its limitations. It uses delta peak detection (detects the peak of the delta waveform) and this occurs when the battery is roughly 95-98% full. Now the main limitation of the basic delta peak charger (usually a brick with a red light that turns green when the battery is full, no display or anything) is that they often only work to around 3000mAh. If you are using larger capacity batteries then it will often false peak and only charge it 10-20%. A good way to see roughly how long it should take to charge is if you are charging the battery from almost dead take the mAh rating of the pack and divide it by the mA rating of the charger (most often 500mA on cheaper chargers.) This will tell you how many hours it will take to deliver that much capacity to the battery. If it is significantly less than this (say it says its done in 1 hour when it should be taking 5-6 hours for a large capacity pack) then the charger may be false peaking.

Duratrax ICE:
I personally use a Duratrax ICE competition RC racing charger. It can do 1.2-12.0V at 1-9999mAh, NiCd, NiMh, LiIo, and LiPo, charge from 0.1A to 8.0A in 0.1A increments and discharge at 0.1A to 10A in the same increments. I can set the delta peak sensitivity, it has a temperature probe so I can set it to cut off if the pack reaches a certain temp, I can monitor the mAh that has gone in/out of the pack, the current voltage, and see graphs of various kinds of information including temperature and voltage. I can set it to cycle several times with time in between if I am breaking in a new pack or trying to work an almost dead pack back from the grave without having to check it every couple hours. In general it is an awesome charger and its only draw backs are its price and the fact that it needs an external power supply. The whole rig will cost you ~$200-300 depending on where you look and not all power supplies are compatible with it so you might need to do some rewiring. Some people recommend using a modified computer power supply and generally this works but several serious RC car racers I have talked to say a computer power supply can actually cause false peak detection so its best to stick to a power supply designed for it. I'm using a power supply designed for a different charger but one that requires the same voltage and amperage so I just had to rewire it a little but didn't need to modify anything.

Note: Everything below this line has a built in power supply.

Duratrax General:
Duratrax chargers in general run the gambit in price and quality but are known to be fairly unreliable and to false peak a LOT. The ICE falls under a different classification all together with Duratrax and even they don't lump it in with their more common chargers. A Duratrax charger can cost anywhere from $40-100 generally and serve the purpose of a basic charger but keep those charge rates and times in mind to get a general idea of how much it has put into the battery.

Super Brain 989:
Another common battery charger that you might hear about on ASC from time to time is the "Super Brain 989." This is very similar to the Duratrax ICE but has a much smarter "brain" or computer in it that can solve some problems that an ICE can't. When I was buying a charger the 989 was retailing for around US$400 and the Duratrax ICE cost me about US$300 to my door (with the power supply) so that was why I made the decision. Currently the 989 retails for around US$180 and is probably your best buy. It has a built in power supply so no worries about that, just plug it into any standard North American wall socket and your good to go. It can do pretty much everything my Duratrax can and more. It can do 1.2 to 25.2V batteries and can even do Lead Acid and Gel Cell batteries so can charge your car if you really want to. I would buy one of these now if I didn't already have the ICE as I can charge my motorcycle battery with it! It even has a permanently set cut off for all Lithium based batteries at 1.2C so you can't accidentally blow up a battery by setting the charging voltage too high.

Prophet Plus:
I have never heard of this charger outside of airsoft but it is quite common. This charger is kinda like a general Duratrax charger in that it has few options, is fairly cheap (~$50 new shipped), and quite commonly false peaks. I have had two come across my bench at various times and I tested them out but never really did anything in depth. Its your basic middle of the line charger in terms of airsoft and will serve the purpose.

Stupid 5500 character per post limit.....

Piranha:
Though it costs more than the Prophet it is actually worse. I have had the chance to try one of these and it CONSTANTLY false peaked with even 1200mAh mini batteries and with almost no force at all one of the buttons broke. They retail for ~US$60 but as far as I know from my limited experience are not worth it.

SystemA Quattro:
SystemA tried to push their own smart charger and when they couldn't make it any good they just made it a gimmick by letting it charge up to 4 batteries at once. Reviews about it say its a hunk of junk and at a retail cost over US$200 its best to pretend it doesn't exist.

TLP:
Like Duratrax this company makes many different models of chargers in many different price ranges but are generally near the US$50 mark. They suffer all the same pros and cons of the Duratrax ones so I wont retype it all. This is one of the more common chargers used by airsofters.

i've used this charger for R/C batteries and never had a problem. it also does LiFe and Lipo. You need an external lipo balancer for it though. Has built in power supply but can use battery to charge also.

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these two chargers also charge every type and have a balancer built in, they also have built in power supply and ability to use battery.

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Bump with a couple notes and reminders based on what I have seen at games recently.

NEVER buy batteries from airsoft retailers of any kind. You have no idea how long its been sitting on a shelf dead (could be years) and that means its toast. Lots of good battery brands have a bad name on ASC because of this. The absolute best batteries I have ever used are from http://www.cheapbatterypacks.com since they have a very fast turn over and test all packs they make. They supply a lot of competition RC car and airplane leagues/teams/stores/etc. and know what they are doing. Getting packs made by a local RC shop can also be very good but often costs more.

If a gun comes with a battery (common with Cansoft) don't expect to be able to rely on it. Dirt cheap Chinese brand batteries are dirt cheap for a reason. Tenergy is one of the most common cheap brands and though sometimes they work great they have a high rate of lemons and failures. See above for good battery site.

No airsoft batteries contain "acid." People often talk about leaking "battery acid" from battery packs and unless you are running a lead-acid car battery in your gun, there isn't any. Yes there are chemicals in batteries which can cause skin irritation or even chemical burns but its not a true "acid" as most think about it. NiCd batteries have VERY toxic chemicals inside, NiMh batteries are generally safe and I have had fluid leaking from them end up on my hands accidentally and absolutely nothing happened (I washed with LOTS of water immediately.)

NiCd and NiMh batteries cannot explode (under normal circumstances.) People talk about exploding batteries and such but the worst a NiCd or NiMh pack can do is heat up, maybe smoke a little (melting plastic usually), and swell and get fat. Short of putting a fully charged battery in a fire or taking a blow torch to it a NiCd or NiMh battery will not explode.

LUTNIT Wrote:Duratrax General:
Duratrax chargers in general run the gambit in price and quality but are known to be fairly unreliable and to false peak a LOT. The ICE falls under a different classification all together with Duratrax and even they don't lump it in with their more common chargers. A Duratrax charger can cost anywhere from $40-100 generally and serve the purpose of a basic charger but keep those charge rates and times in mind to get a general idea of how much it has put into the battery.

Weren't you the person who recomended the duratrax "onyx 210" too me a couple months ago?

Was this in person or via the forums? I did not know Duratrax even made a series called the Onyx until I just looked it up now. No idea how they are.

I recommended it. They have great reviews and im sure it was the 220 model for NIMH 9.6v or under batteries and if you plan to go LiPo I suggest the 230 model for you budget people.

The company has been around for 30 years and has stuck to batteries and chargers the whole time. I have used their products 14 years ago and still trust them to today.

Also they make the ICE model and seeing how well that performs their 220 and 230 onyx models shouldnt be far off.

Did some more reading and the Onyx series seems to be an improvement over their older series of charges that had false peak issues. I also chatted with my friends who do RC racing and they generally run into the false peaking when they are quick charging between races where they have 15-20 minutes to recharge. This results in them charging at 2-4C instead of 1C so is hell on their packs and causes the false peaks. If sticking to 1C or less the false peaking is rare with the old style Duratrax chargers and almost non-existent with the new Onyx series.

HaZarD Wrote:I recommended it. They have great reviews and im sure it was the 220 model for NIMH 9.6v or under batteries and if you plan to go LiPo I suggest the 230 model for you budget people.

The company has been around for 30 years and has stuck to batteries and chargers the whole time. I have used their products 14 years ago and still trust them to today.

Also they make the ICE model and seeing how well that performs their 220 and 230 onyx models shouldnt be far off.

It could have been the 220 you recomended; I went with the one that could charge my battery and was a little less pricey (I don't need to be able to charge 10cells if I'm only running a 9.6v) though if I had realised the 230 was capable of charging nimh AND lipo's I would have change my decision -- the store owner where I picked it up was adiment that you needed a special charger to charge Lipo's (and implied you couldn't get a charger that could handle Lipo's AND Nimh/Nicd)

Anyways, I was only asking because Lutnit expressed such a negative opinion on duratrax chargers

LUTNIT Wrote:If sticking to 1C or less the false peaking is rare with the old style Duratrax chargers and almost non-existent with the new Onyx series.

I have to say I'm glad to hear they've improved -- I've heard the name before but was mostly unfamiliar with the brand but it was recomended (by hazard) and I have absolutely no regrets, it's a great charger.

Something I forgot to mention originally...

The voltage ratings for battery packs are wrong (generally.) To refer to a pack as a "9.6V" pack is silly since it is rarely if ever at precisely 9.6V in reality. Everywhere but airsoft you refer to packs by the cell count so what we call a "9.6V" pack everyone else would call an 8 cell pack.

The voltage used to describe a pack is generally only seen when you are drawing near the maximum amperage from the pack or it is almost dead. Here are some examples of voltages I have seen from fully charged packs:
7 cell (8.4V) - 9.5V
8 cell (9.6V) - 11V
9 cell (10.8V) - 12.5V
10 cell (12V) - 14V
3 cell LiPo (11.1V) - 15V

And always remember that voltage is pushed, not drawn, so these voltages are being forced through your AEG. Since airsoft guns are limited to 12-15A draw and even then only with good wires, good connectors, and a better than most trigger contact you aren't drawing the max amperage of the pack so it will be operating at above its "rated" voltage. As an example a pack made of sub-C cells (a large pack in airsoft terms) can easily supply 25-30A and only at a draw of 20-25A will it actually be its "airsoft rated" voltage, and less of a draw and it will be above its rated voltage. Some LiPo packs are rated at over 100A which you will never EVER use in airsoft. One problem with the fluctuating values is as the voltage lowers as the battery is drained, the motor will attempt to draw more amperage to still turn over. Its an automatic thing related to the physics of electromagnetic fields and such so I won't go into it. This can cause it to try to draw more and more amperage until the fuse possibly blows. This could also lead to wires and battery connectors heating up (though they will rarely melt from this.)

In older SystemA PTW's low batteries can actually cause the circuit boards to fry and burn out as the motor tries to draw more amperage than it is designed for. The PTW's released more recently (I think 2007 onward) have a cut off where if the voltage drops to a certain point while firing (while under load) it will cut off power to save the sensitive electronics.

The voltage tends to drop off fairly quickly at first, then stabilize, then drop off again when the battery is closer to dead. This is why a freshly charged battery will give a higher RoF than its normal run speed and the RoF will drop as the battery is getting close to dead. Running your batteries till they can't turn the mechbox over isn't good for them as it puts a lot of strain on them and can reduce the number of cycles the battery can be used for. Its best to stop using a battery once the RoF starts to drop off the second time. I haven't used mini batteries forever and as such I have never run into this. The point of second drop off of a large pack is after a couple thousand rounds and since I don't hose that much I never run into it.