There are 3 tech parameters you need to consider when select a battery pack:
1. Output Voltage: The battery output voltage should meet your device input voltage requirements. Some device may only work under certain fixed voltage, such as 12V, 15V, 19V. Some devices may work with a wide range voltage, such as from 5V to 24V. Please check with your device manual or manufacturer to know the device input voltage requirement. If your device comes with a AC to DC power adapter, look at the power adapter label, it should have output voltage. This power adapter output voltage is the input voltage of your device needs.
2. Maximum output current: A battery pack can only output limited electric current at a given voltage. This maximum current should be larger than or equal to your device maximum current requirement. For example, if your device needs 12V input voltage, maximum 3A current, then a 12V battery with maximum 5A output current will work for it, but a 12V battery with maximum 2A output current may not work for it.
If you do not know the maximum current your device needs, check your device power adapter, it may mark maximum output current, such as 300mA, 3.5A. If not, it may mark output wattage, such as 60W, 75W, 90W.
Wattage divided by voltage is the maximum current. For example, a 60W 12V power adapter maximum current output will be 60/12=5A.
Maximum current output is just a capacity. The actual current output of a power adapter or battery depends how much the device needs. If a power adapter maximum current output is 4A, it only means the power adapter current output maximum capacity can be 4A, actual output current actually will be anything between 0~4A.
3. Capacity: Battery capacity will determine how long the battery can power your device. There are two major different ways to rate a battery capacity on market: Watt-hour (Wh) and Amp-hour (Ah). Some batteries may rate is mAh instead of Ah. 1000 mAh= 1 Ah.
We suggest using "Watt-hour (Wh)" instead of "Amp-hour (Ah)" to compare capacities of different batteries. Watt-hour or Wh, is a more accurate unit to show the power capacity than Amp-. Hour (Ah) that was used before. The Watt-Hour unit means the wattage that the battery can provide within one hour. If you see a battery capacity is rated in Ah or mAh, please ask the battery manufacturer the Amp-hour is under which voltage. For example, a 20Ah battery may is actually rated under 3.7V, which means its capacity is only 74Wh, another 10Ah battery may is rated under 37V, which means its capacity is 370Wh,so the 10Ah battery actually have 5 times capacity of the 20Ah battery.
Battery running time = Battery Capacity (Watt-hour) / Device Power Consumption (Wattage)
For example, if your device consumes 50W power, a 150Wh battery running time will be 150Wh / 50W = 3 hours.