Post by Tank on Mar 29, 2011 20:41:33 GMT -8
This was stole from AP
Battery Guide
Voltage (V): The most common battery voltages in airsoft are 8.4V (7-cell) and 9.6V (8-cell). The voltage of a battery can be figured by simply counting the number of cells and multiplying by 1.2. (As most of the cells used in airsoft are 1.2V rechargable cells.) This is simply a power rating, how big of a current your battery will provide. If you increase the resistance of your gearbox onto the motor, you may need to increase the voltage of your battery to be able to operate it.
milliampere-hour (mAh): I'm just gonna steal this from wikipedia, cause it's pretty much perfect. It's for ampere-hour (Ah) but it's applied the same way, just at a different scale.
Quote:
An ampere-hour (abbreviated as Ah) is a unit of electric charge. It is a common measurement of how long a battery will last (or in the case of a rechargeable battery, how long it will last when fully charged). The ampere is the SI unit of electric current. One ampere-hour is equal to 3,600 coulombs (ampere-seconds), and indicates the amount of electric charge that passes either terminal of the battery when it provides one ampere of current flow for one hour.
However, in reality, the available capacity of a battery depends on the rate at which it is discharged. If a battery is discharged at a relatively high rate, the available capacity will be lower than expected. Therefore, a battery rated at 100 Ah will deliver 20 A over 5 hours, but if it is instead discharged at 50 A (coulombs per second), it will run out of charge before the theoretically expected 2 hours. For this reason, a battery capacity rating is always related to an expected discharge time, which is typically 5 or 20 hours.
The relationship between current, discharge time and capacity is expressed by Peukert's law.
In general, the higher the ampere-hour rating, the longer the battery will last for a certain device. Installing batteries with different Ah ratings will not affect the operation of a device rated for a specific voltage.
The Ah rating of a battery is related to, but not the same as, the amount of energy it stores when fully charged. If two batteries have the same nominal voltage, then the one with the higher Ah rating stores more energy. It would also typically take longer to recharge.
The energy E available from a battery is approximately given by
* expressed in joules: E=3600CV
* expressed in watt-hours: E= CV,
where
C is the capacity in Ah, and
V is the nominal voltage.
This is only an approximation though, due to the fact that the voltage during discharge is not actually constant.
Water Bucket Analogy: Simply think of a bucket with a hole in the bottom. Think of the size of the bucket as the mAh rating of your battery, bigger the mAh, the bigger the capacity. Now think of the hole in the bottom as the Voltage of the battery. The bigger the hole (Voltage) the quicker and more powerful the drain of the bucket (mAh).
NiCd vs NiMH:
NiCd:
Pros -
Keeps Hi-Output as it drains.
Won't drain as quickly when stored.
Cheaper to produce than NiMH.
Cons -
Lower mAh (Negligible since it's different between NiMH and NiCd*)
Must be discharged before charging.
More toxic than NiMH.
NiMH:
Pros -
Higher mAh (Again, negligible*)
Doesn't need to be discharged.
Less toxic than NiCd.
Low Internal Resistance.
Cons -
As battery drains power output decreases
Drains quickly when stored.**
More expensive than NiCd.
*NiMH really weren't made to be used in hi-output applications. Since they lose output power as they drain you'll notice your upgraded replicas losing power at a constant rate until they can no longer cycle, this'll happen long before the battery is considered completely empty. An exception to this would be the newer model electric cars with NiMH batteries, but remember, they also have alternators keeping them at high capacity/power.
**It's safe to keep them in a freezer/fridge to slow their self-discharge. If you do decide to store your batteries in the freezer or refrigerator, make sure you keep them in tightly sealed bags so they stay dry. And make sure that you let them return to room temperature before using them again. And keep them away from your food!
Quote:
My personal opinion is that if you want a battery that will last you a long time in a stock replica, get a NiMH. But if you start increasing the performance of your AEG, you'll need a battery that can keep step. Don't let the mAh ratings fool you, they're applied differently given the chemistry of the cells and the application of them.
Battery Size: There are three sizes of battery packs available; Large, Mini, and Stick. Large batteries consist of Sub-C size cells which offer much less internal resistance than the A cells used in many Mini and Stick batteries, thus allowing for marginally better performance out of your battery. Mini and Stick batteries are used for replicas which don't offer enough space to house a larger one.
Tamiya Connector: Airsoft uses the same batteries that you'd find in model plane and RC kits, so they use the same connectors. But it's important to note that there are two sizes, both Large and Small. If your replica uses a large battery, it'll come with a large Tamiya connector, and vice versa, if your replica uses a mini or stick battery, it will come with a small Tamiya connector. (An exception would be replicas fitted with a crane stock or other custom battery housing.)
Battery Guide
Voltage (V): The most common battery voltages in airsoft are 8.4V (7-cell) and 9.6V (8-cell). The voltage of a battery can be figured by simply counting the number of cells and multiplying by 1.2. (As most of the cells used in airsoft are 1.2V rechargable cells.) This is simply a power rating, how big of a current your battery will provide. If you increase the resistance of your gearbox onto the motor, you may need to increase the voltage of your battery to be able to operate it.
milliampere-hour (mAh): I'm just gonna steal this from wikipedia, cause it's pretty much perfect. It's for ampere-hour (Ah) but it's applied the same way, just at a different scale.
Quote:
An ampere-hour (abbreviated as Ah) is a unit of electric charge. It is a common measurement of how long a battery will last (or in the case of a rechargeable battery, how long it will last when fully charged). The ampere is the SI unit of electric current. One ampere-hour is equal to 3,600 coulombs (ampere-seconds), and indicates the amount of electric charge that passes either terminal of the battery when it provides one ampere of current flow for one hour.
However, in reality, the available capacity of a battery depends on the rate at which it is discharged. If a battery is discharged at a relatively high rate, the available capacity will be lower than expected. Therefore, a battery rated at 100 Ah will deliver 20 A over 5 hours, but if it is instead discharged at 50 A (coulombs per second), it will run out of charge before the theoretically expected 2 hours. For this reason, a battery capacity rating is always related to an expected discharge time, which is typically 5 or 20 hours.
The relationship between current, discharge time and capacity is expressed by Peukert's law.
In general, the higher the ampere-hour rating, the longer the battery will last for a certain device. Installing batteries with different Ah ratings will not affect the operation of a device rated for a specific voltage.
The Ah rating of a battery is related to, but not the same as, the amount of energy it stores when fully charged. If two batteries have the same nominal voltage, then the one with the higher Ah rating stores more energy. It would also typically take longer to recharge.
The energy E available from a battery is approximately given by
* expressed in joules: E=3600CV
* expressed in watt-hours: E= CV,
where
C is the capacity in Ah, and
V is the nominal voltage.
This is only an approximation though, due to the fact that the voltage during discharge is not actually constant.
Water Bucket Analogy: Simply think of a bucket with a hole in the bottom. Think of the size of the bucket as the mAh rating of your battery, bigger the mAh, the bigger the capacity. Now think of the hole in the bottom as the Voltage of the battery. The bigger the hole (Voltage) the quicker and more powerful the drain of the bucket (mAh).
NiCd vs NiMH:
NiCd:
Pros -
Keeps Hi-Output as it drains.
Won't drain as quickly when stored.
Cheaper to produce than NiMH.
Cons -
Lower mAh (Negligible since it's different between NiMH and NiCd*)
Must be discharged before charging.
More toxic than NiMH.
NiMH:
Pros -
Higher mAh (Again, negligible*)
Doesn't need to be discharged.
Less toxic than NiCd.
Low Internal Resistance.
Cons -
As battery drains power output decreases
Drains quickly when stored.**
More expensive than NiCd.
*NiMH really weren't made to be used in hi-output applications. Since they lose output power as they drain you'll notice your upgraded replicas losing power at a constant rate until they can no longer cycle, this'll happen long before the battery is considered completely empty. An exception to this would be the newer model electric cars with NiMH batteries, but remember, they also have alternators keeping them at high capacity/power.
**It's safe to keep them in a freezer/fridge to slow their self-discharge. If you do decide to store your batteries in the freezer or refrigerator, make sure you keep them in tightly sealed bags so they stay dry. And make sure that you let them return to room temperature before using them again. And keep them away from your food!
Quote:
My personal opinion is that if you want a battery that will last you a long time in a stock replica, get a NiMH. But if you start increasing the performance of your AEG, you'll need a battery that can keep step. Don't let the mAh ratings fool you, they're applied differently given the chemistry of the cells and the application of them.
Battery Size: There are three sizes of battery packs available; Large, Mini, and Stick. Large batteries consist of Sub-C size cells which offer much less internal resistance than the A cells used in many Mini and Stick batteries, thus allowing for marginally better performance out of your battery. Mini and Stick batteries are used for replicas which don't offer enough space to house a larger one.
Tamiya Connector: Airsoft uses the same batteries that you'd find in model plane and RC kits, so they use the same connectors. But it's important to note that there are two sizes, both Large and Small. If your replica uses a large battery, it'll come with a large Tamiya connector, and vice versa, if your replica uses a mini or stick battery, it will come with a small Tamiya connector. (An exception would be replicas fitted with a crane stock or other custom battery housing.)