Battery Specifications

Capacity

• The capacity of the battery refers to how long it can be run for and is measured in mAH

• Some companies might just say 1.5, which means 1500mAH.

• mAH is milliamp hours, which indicates how long it will last before it is discharged.

• Placing batteries in series will only combine their voltages, but the total current output is the same (Placing 3 1.2V 2850mAH batteries in series will result in a battery of 3.6v 2850mAH)

• Placing batteries in parallel will only combine their current, but the total voltage is the same (Placing 3 1.2V 2850mAH batteries in parallel will result in a battery of 1.2v 8550 mAH)

• For example, with a 2000mAH you can draw 2A for 1 hour, 1A for 2 hours, or 20mA for 100 hours

• Lithium ions/polymer batteries are rechargeable and used in higher voltage and current output machines (laptop)

• Drawing current from a battery  will drain its full voltage to its nominal voltage, to its discharge voltage

• A larger capacity battery provides longer flight times but the added weight restricts the performance by increasing the craft’s momentum and making it respond more sluggishly

Cell Count/Configuration

• Cell count is related to the voltage of the battery (2s, 3s, 4s cell count)

• 4s1p means 4 cell in series and 1 in parallel (pre much not parallel, see the pic below)

• 5s is 18.5V (uncommon for races, not widely used)

• 4s is 14.8V (most common for FPV racing)

• 3s is 11.1V (lower RPM’s, used in smaller drones)

• 2s is 7.4V (used for tiny drones, indoor ones and for drone goggles and radios)

• 1s is 3.7V

Batterh Chemistry Selection

• Battery must be selected wisely to achieve an ideal balance between performance and flight time

• Lithium batteries are most common due to high energy densities and high discharge capabilities

• two common chemistries: Lithium polymer (LiPO) and lithium polymer high voltage (LiHV)

• LiPO cell has a fully charged voltage of 4.2V compared to a LiHV cell which has a voltage of 4.35V at full charge. A LiPO has a resting or nominal voltage of 3.7V versus a LiHV which has a storage voltage of 3.8V.

• A LiHV battery will initially provide more power but abruptly drops in voltage when discharged

• A LiPO has a more linear discharge making it easier to qualitatively gauge the remaining flight time.

• Battery voltage is the potential energy difference between the positive and negative terminals.

• A higher FPV Drone Battery voltage allows more power to the quadcopter without increasing the current or amp draw (p = vi).

• more battery voltage allows the motors to spin with greater speed (RPM) 

• 4s LiPO provide balance between speed and weight

C Rating

• C rating is the discharge rating

• Higher C rating is better, with lower internal resistance

• How fast you can discharge a battery without damaging it

• C rating dictates how much current a battery can continuously supply in a charge cycle

• The higher the C-Rating of a battery, the more current the pack can continuously supply.

• If a battery is forced to supply more current than dictated by its C-Rating for a significant period of time, it can damage the battery by causing the cells to puff, reduce overall longevity, cause excess heating and occasionally cause a LiPO fire

C-Rating Formula:

Maximum Safe Current Draw (mA) = Battery Capacity (mAh) * C-Rating

Maximum Safe Current Draw (mA) = 12000 mAh * 30C

Maximum Safe Current Draw (mA) = 360 000 mA or 360A

• most batteries can temporarily exceed their rated continuous current draw safely for around ten seconds.

• a motor-propeller combination quoted with a maximum current draw of e.g. 40A would actually be suitable for use with the 1300mAh 100C battery as the average current draw from that motor would be 30A (0.75 * 40A) which is below the calculated maximum continuous current draw per motor of 32.5A.