How many batteries do I need for 21v lithium battery for electric tools

The right lithium battery size must meet your power needs and at a reasonable cost. Correct sizing offers many benefits, such as system efficiency, reduced strain on the supply, and extended its life. To size one, you need to know your power requirements. For instance, if your load draws 20 amps for 8 hours, you need at least a 160Ah capacity.

Using the formula, the battery capacity you need is 600 Ah x 1.2 x 1.05 =756 Ah. Round up this figure to size up your battery. The additional capacity will account for energy losses in the circuit or system. Standard lithium battery sizes range from as low as 50Ah to as high as 10,000Ah.

Standard lithium battery sizes range from as low as 50Ah to as high as 10,000Ah. Power systems typically follow a 12V, 24V, and 48V configuration. With this in mind, we can calculate the different amp hour ratings based on the required voltage by dividing total consumption by the voltage. Here, we used a 12kWh/12000Wh daily consumption.

Discharging from a battery has inefficiencies, lead around .88 and lithium .96 to .98. So, if you're using Lithium it's 1.2/.96=1.25 kW/hr With that number we can see the power consumed per day is 24 x 1.25 = 30 kWh. If you want enough power for 3 days, you'd need 30 x 3 = 90 kWh.

If you want enough power for 3 days, you'd need 30 x 3 = 90 kWh. As discussed in the post above, the power in batteries are rated at a standard temperature, the colder it is the less power they have. So, with batteries expected to be at 40 to supply 10 kWh, with this data you'd multiply by 1.3 to see you would need 13 kWh of batteries.

For instance, if your load draws 20 amps for 8 hours, you need at least a 160Ah capacity. In practice, though, the capacity is typically rated higher. A higher value means you will maintain the capacity whenever you power the load. Deep discharge cycles are not advisable even though Li-ion batteries can withstand them.