LIPO, or Lithium Ion Polymer Batteries are rechargeable Lithium Ion batteries with a polymer electrolyte and provide among the highest amounts of energy per unit weight of any battery available to use. This means that LIPO batteries find use in appliances and machinery that need to be, above anything else, light. Drones can reliably source a large amount of power without gaining too much additional weight through the use of LIPO batteries.
LIPO cells provide a nominal voltage of 3.7V and can operate safely between 3V to 4.2V. The voltage provided by the battery is simply the sum of the individual voltages of all the cells.
How is this relevant to drones? Well, the voltage supplied by the battery directly translates into the ability of the battery to turn the propellers, i.e., the speed of the motor is directly proportional to the voltage supplied by the battery. More powerful batteries can produce more powerful drones.
The KV rating of your drone puts this in perspective. It is the rpm provided/volt by the battery. A 1000 KV drone at 10-20V means that the motors can rotate at 10,000 rpm with 10V and 20,000rpm with 20V.
A battery with a higher Voltage and KV value is superior to those with lower values.
Capacity and C Rating
Battery Capacity is a measure of the amount of energy the battery can hold. It is measured in milliAmpere hours (mAh) and is the amount of current that can be drawn from a battery such that it would be drained from fully charged to fully discharged in one hour. A 1000mAh battery can supply 1000 mA (or 1A) for an hour before it is completely drained.
Another useful rating that most batteries will display is the C rating (discharge rating) which is the multiple of the total capacity at which it is still safe to draw current at. It is usually provided as both a ‘continuous’ and a ‘burst’ C rating. Continuous C Rating informs the pilot about the maximum current they can draw safely for a prolonged period of time, and Burst C Rating indicates the maximum current that can be safely drawn for short bursts of time, usually 10 seconds or less. A 2000mAh battery with a Continuous C rating of 20 can safely draw (20 x 2000) 40,000mA (40A) of current without damaging the battery for a prolonged period of time, and if it has a burst C rating of 40, it can draw upto (40 x 2000) 80A of current safely for short bouts.
A battery with higher capacity and higher C rating is better for performance. Higher capacity allows the drone to fly longer before needing to be recharged, and a higher C rating allows the drone to draw on more power safely. If the C rating is too low, the drone will not be able to draw sufficient current to spin the motors at a required speed, and if it does so anyway, it runs the risk of damaging the battery, and possibly the drone, irreversibly. However, it is important to note that increasing the Capacity and C Rating results in an increase in the weight of the drone, which may then reduce the flight time and power of the drone. Higher C Rating than recommended for the drone will not provide any improvement in performance and only weighs it down.
How do I Select a Battery?
Higher Voltage, Capacity and C Ratings are ideal, but will inevitably increase the size and weight of the drone. Ensure that you know the total size of the battery that can physically fit into the drone, as well as the maximum weight of the battery the drone can tolerate. If the drone has four propellers with a 500g lift, it can carry a total of (4 x 500g) 2kg. If the rest of the drone weighs 1.5kg, the battery cannot be heavier than 500g. Do not choose any battery that exceeds any of these limits.
Next, calculate the total current draw the drone requires, both from the motors as well as other components. Compare this to the maximum discharge rate of the battery. It can be calculated by:
Maximum Discharge Rate = Capacity x C Rating
If the maximum discharge of the battery is insufficient for the drone, it should be rejected.
Select the battery with the highest Capacity that can meet these requirements.
Finally, ensure that the LIPO battery has the right connector. Different connectors support different discharge currents. The connector on the battery should match the corresponding connector on the drone, and must be compatible with the amount of current you intend to draw from the battery.
And that’s it. Select the best LIPO battery for your drone, plug it in and you are ready to fly!