All batteries are composed of cells assembled in rows. The starting point of a battery is it’s cell. For an NiMh, the cell is always rated at 1.2 volts per cell and for a LiPo it’s starts at 3.7 volt.
A battery is composed of two characteristics: The voltage and the amperage. The higher the voltage, the faster the motor will turn, therefor the harder the gun will shoot. But be careful, A battery that is too high of a voltage could damage the piston and the components of your gearbox.
The Amperage (mAh) is the concentration of energy stored in milli-amperes per hour. You can generally find batteries with amperage’s of 600mAh, 800mAh, 1100mAh, 1600mAh or 3300mAh.
A battery with an mAh of 1200 will deliver 1.2amps for one hour. The higher the number the longer it will last.
NiMh batteries are safer and are usually used by beginners. To break them in before use, they must be fully charged then discharged in order to complete a full cycle for the memory of the battery. It is also not recommended to overcharge the battery as it could damage the cells. This is why it is highly recommended to purchase a smart battery charger so that the charger will automatically shut off once the battery is fully charged. NiMh batteries should be changed every two to three years.
LiPo batteries are newer and a big advantage to the sport of Airsoft. They are significantly lighter and smaller than the NiMh batteries. A 7.4v LiPo would have the same performance as a 8.4v NiMh.
You do not need to cycle a new LiPo battery and it will not lose it’s memory cell. The downfall of a LiPo is that they are very fragile. They can be damaged if they are pierced or even damage from a drop to the ground. A damaged LiPo would have a bloated cell and therefore must be discarded. They must be charged with a balanced charger. Since the cells are attached to one another, the batteries cells are charged equally, which is why we use a balanced charger.