The Beginners Guide to Drone Batteries and Battery Chargers
The batteries used in drones are mostly of Lithium Polymer (LiPo) type. These batteries are very light-weight, have an excellent energy density, very high discharge rates are possible and have low self-discharge rate. LiPo batteries are best suited for drones due to high current requirements of UAVs, in particular for racing drones. Although, LiPo batteries do not require much maintenance but still need some care and precautions. The most important thing to keep in mind is that drone batteries are sensitive to low voltage when discharging and sensitive to a high voltage when charging. To avoid both of these, never drain your battery below 80% of its rated voltage and never use a cheap battery charger. If you keep flying your drone at low voltage, your flight time might increase, but the maximum number of recharge cycles (Life) of your drone battery would decrease.
Three Key Terms (Energy, Power and C-Rate) used for Drone Batteries:
1., 2. Energy and Power of a Battery:
Power is measured in Watts while energy in Watt-hours (Wh). However, for LiPo batteries, we use another term called the capacity of the battery (which I measured in mAh). It is an indirect way of expressing the energy. Now the question is how these two relates to each other, i.e., the energy units Wh and the capacity unit mAh? The relationship is this:
Wh = mAh/1000 times Voltage.
However, it should be noted that the voltage varies during a drone flight and therefore this cannot be estimated very accurately.
3. C-Rate of a LiPo Battery
Without going into the physics of this, I try to explain this with an example. If a battery having the energy of 5000 mAh discharges at 1C (C-rate of 1), it will provide 5000 mA for one hour. If the same battery is operating at 2C, it will provide 10000 mA of current for 0.5 hr. Also, if this battery is operating at 0.5C, it would deliver 2500 mA of current for 2 hours. Some quadcopters have high amperage requirement, and the battery should be able to cope with this. The discharge rate is expressed as multiples of C, such as 2C and 3C, etc.
How to Calculate the Endurance of a Battery:
If we know the energy (or capacity) of the battery (in mAh) and how much current our drone draws (in mA). The time of flight can be calculated as below:
Endurance (in minutes) = (Battery Capacity in mAh)/ (Current Drawn by Drone in mA) times 60
Visual Inspection to Ensure the Health of a Drone Battery:
One of the leading indicators of the health of a LiPo battery is its shape. The battery should feel stable and firm in hands. There are few things you must inspect every time before you install the battery. These are the presence of any deformation, dent, any leakage, stain, any camber or burr on the sealing parts. These are the signs of the poor health of the battery and may adversely affect the performance. If these signs are present, the batteries are not fit for any commercial use and must be replaced.
Battery Chargers: What to Look for and What are the Options
Lithium Polymer Batteries are mostly charged to no more than 4.2 Volts and should not be depleted to less than 3.0 volts per cell. The battery chargers usually come with the battery but can be used interchangeably.
When it comes to battery charging, we all love to charge our batteries as soon as possible. However, for this purpose we might have to buy a special battery charger hub. These battery charger hubs can charge multiple batteries but varies in specs and can be broadly divided into two types.
- The charger hub which can charge multiple batteries but you can only “put” multiple batteries into this charger. The charger first charges the first one then the second and so on.
- The battery charger hub which can charge multiple batteries simultaneously. These charger does not wait for the first battery to charge. Instead they charge all of your batteries at once.
Why we Must Always use a High-Quality Charger
As described earlier, since LiPo Batteries are very sensitive to high voltage when charging, therefore, if the charger is not maintaining the voltage properly, there would be a potential fire hazard. Most of modern battery chargers have balancing functionality. As we know LiPo batteries have more than one cells. We want to charge all those cells up to the same voltage. Our charger should be able to handle this by stop charging the cell that is fully charged to the desired voltage and keep charging the rest which are not yet fully charged. This is called balancing. If the battery has 4 cells, usually there would be as 4 red cables in the connector to battery charger if it has a balancing functionality.
Recommendations for Charging Drone batteries:
- Understand the settings of the battery charger and use the appropriate settings for your LiPo.
- Always charge on surfaces that will not catch on fire, such as ceramic, stone etc.
- Charging leads must be connected correctly.
- Do not try to charge a deformed, punctured or damaged battery.
- Always have a fire extinguisher near the charging area.
- Always use Lip Charging safety bags to charge LiPo battery packs.
- Never leave charging batteries un-attended.
Maintaining accurate documentation of Drone Batteries:
It is critical that you must label all of your UAV batteries and maintain the logbook for them. After each flight, the time of flight should also be recorded on the UAV logbook. This will give you an estimate of when you might expect to discard the battery if you see any signs of deterioration.
Charging Times of Batteries of Some Popular Drones:
Following Table shows the charging time of the batteries of some popular drones:
Battery Charger/Charging Hub
No of Batteries
|1||Phantom 4 Series 160 W Battery Charger||1||NA||53 to 58 mins||Buy on Amazon|
|2||DJI Phantom 4 battery Charger Hub||3||One at a time||3 hr 30 mins||
Buy on Amazon
|3||Mavic 50 W Battery Charger||1||NA||1 hr 20 mins||Buy on amazon|
|4||Mavic Battery Charging Hub (Advanced)||4||One at a Time||4 hrs 10 mins||buy from dji|
|5||DJI Spark Battery Charger Hub||3||At the same time||90 mins||Buy from DJI|
|6||DJI Phantom 3 , 100W Battery Charger||1||NA||67 mins||BUY from DJI|
|7||DJI Inspire 1, 180W Battery Charger||1||NA||58 to 68 mins||Buy from DJI|
Commonly Asked Questions about Drone Batteries and Battery Chargers:
1.Are Drone Batteries Interchangeable
While selecting a different than the original battery of your drone, you should take few things into consideration. The voltage is the most important and then the capacity should be the same. If you want to use a high-capacity battery for your quadcopter, you might consider modifying the drone. It is doable but it needs extra skills.
2.Are Drone Batteries Allowed on Planes
If you are travelling with batteries, the best approach is to ask the airline but in some countries, there are three types of situations you might face.
- If all of your batteries are below a certain capacity, you can bring them with you. (<100 Wh)
- If the capacity of any battery is beyond a threshold, you may need to declare it. (>=100 Wh but < 160 Wh)
- If any battery is beyond the maximum threshold, you won’t be able to carry it on a plane. (>160 Wh)
3.How long Drone Batteries Last
If you treat them properly, these batteries can last 200 to 400 cycles.
4.What are the Smart Drone Batteries
Smart or intelligent batteries are those which have some intelligent features due to which less maintenance is required. The intelligent features make sure that you do not overcharge the battery. Other features also include self-discharging and going in to hibernation mode when depleted or not used for extended period of time. These batteries have a small processor inside which implements the safety features. It stopes charging when a cell is fully charges. For ordinary LiPo batteries you have to make sure that the battery is not overcharged. The price difference between intelligent and ordinary LiPo batteries is huge and of the order of 1:8 or more.
5. What are common storing and shipping recommendations for quadcopter batteries.
Since the fundamental characteristics of Lithium Polymer batteries are such that the capacities of these batters, decreases over time. Therefore, we impose storage conditions regarding temperatures and the state of charge. You can store LiPo batteries in fully-charged state for a reasonable amount of time (for 10 days or so) but for extended periods, the battery should be stored at 50% charged state to stay safe. For shipping, the recommended value is 30% charged.
6. How to measure the health of the UAV batteries.
One way is to charge the battery fully and note the capacity in mAh. Now divide it with the rated capacity and multiply by 100 and you will get the percentage of capacity left in the battery.