Our AscTec UAVs use LiPo batteries due to the high energy over weight ratio. This leads on the one hand to a great flight performance together with long flight times of over 10 minutes. On the other hand, these batteries need to be treated quite carefully, since they have the potential of getting ignited in certain conditions. Furthermore they are quite sensitive to temperature changes. The following list shows some important information about our LiPo batteries:
- LiPo batteries do not suffer from a memory effect, hence it is no problem to discharge them e.g. only half and then recharge them completely.
- Do not short circuit LiPo batteries, they have a very high discharge rate.
- Do not discharge the LiPo batteries exhaustively. If the voltage level drops under a certain value, this can damage the batteries.
- Disconnect LiPo batteries if you are not using them, because the connection can still lead to a little discharge, even if the UAV is not switched on.
- If you intend to store the LiPo batteries for longer time without using them, make sure they contain a certain voltage level. It´s best to store them approx. half-full in a cold, dry and non-inflammable place.
- The voltage level of the battery is affected by the actual drawn current. The following example graph shows this effect:
The colored keys on the right side of the graph refer to a discharge rate (C-rate). The C-rate signifies a discharge rate relative to the capacity of a battery in one hour. A rate of 1C would mean an entire 2.100mAh battery would be discharged in 1 hour at a discharge current of 2.1A. A 2C rate would mean a discharge current of 4.2A, which would lead to an empty battery already after half an hour.
In this diagram you can see, that the voltage level will drop when the battery is discharged.
Preparing your own battery
You need a 3s (three cells, 11.1V) Lithium Polymer (LiPo) Battery to operate all AscTec UAVs. For the AscTec Hummingbird we recommend capacities between 1500 and 2100 mAh. With a state-of-the-art 2100 mAh battery the vehicle is able to hover up to 22 minutes without any payload, and up to 12 minutes with 200 g of payload.
Make sure you prepare your battery such that it can definitely not get damaged by hitting the frame, even in a crash. Otherwise the battery could explode! Here is an example of how to mount a battery correctly:
The black foam on both sides prevents it from being hurt by the magnesium parts of the Hummingbird frame. Configured like this, the battery slides into the battery slot of the vehicle and holds inside by friction. Of course, there are also other ways to prepare your battery for a safe operation. This is only an example for the AscTec Hummingbird.
Lithium Polymer Batteries (LiPo) can be very dangerous if not handled correctly. Please read and follow the instructions of the battery and charger manufacturers ! Do never short circuit a LiPo battery and use safe connectors!