A battery is energy source for your Unmanned Aircraft System (UAS) i.e. your drone. This battery should be good enough to help a drove fly for longer time, that’s what every pilot wants, isn’t it? The flight time i.e. the time spent by drone in the sky is dependent on the batteries. So, selection of drone batteries is the wisest choice one has to make.

Lithium Polymer or LiPo batteries have a lot of benefits such as light weight, high capacities, high discharge rates, etc. that have made them the best choice in consumer drones. They have a high energy density in relation to their size and weight, with a higher voltage per cell, typically 3.7 volts, so you can get the necessary power with fewer cells than other rechargeable batteries. However, the LiPo batteries have shorter lifespan and they can lead to fire if the battery gets punctured. So, they are very sensitive and need special care for charging, discharging, and storage.

There are so many features, specifications, and price tags for various kinds of LiPo batteries available in the market, but it’s always important to keep your budget balanced with the quality of batteries you’re going to buy. However, it’s not too wise to save money for some cheaper quality of batteries and risk your expensive drone into higher repair or replacement charges.

So, this article is mainly focused in terms of a drone user’s perspective with some guidelines and explanations about how to select LiPo battery for your drone.

How to Choose LiPo Battery for your drone?

To answer this question, you need to understand some key-terms of LiPo Battery and how these terms affect your selection, so let’s see them one by one.

1. Understanding Numbers on a LiPo Battery

The nominal voltage of a Lithium polymer cell is 3.7V. Above image shows battery model of Orange brand. This LiPo battery has 2000 mAh capacity. It has 1 cell with 3.7 V (voltage). 30C is C Rating of this battery. We’re going to discuss battery capacity, battery voltage, and C rating further in details.

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2. Battery Capacity

It is the number that shows how long a battery can supply power to a certain device. It’s indicated by mAh (milli amp hours) rating i.e. how much millli amps of current can be supplied by this battery in one hour.

Choosing batteries with higher capacities will surely give you longer flight time, but the batteries will get heavier and larger in size. This will be more discussed in battery size & weight.

If you know the current rating of your mini-quad, then convert mAh rating into Ah rating. Then, simply divide it with average current drawn in amps rating. Considering battery in the fig. 1, 2000mAh/1000 = 2Ah, i.e. it would take an hour to be completely discharged if you draw 2 A current from it. Suppose, if the current draw doubles i.e. 4 A, then the duration would be halved i.e. half an hour (2/4=0.5). If you draw 40A of non-stop current, this battery pack would only last 3 minutes (2/40=1/20 of an hour). This approach will give you just an approximate idea for flight time.

Professionals often suggest buying a battery with highest capacity for longer flight time. While making selection for a new battery always prefer to pick a size as per the specification of your device. Its weight should not exceed from the range that your drone cannot lift.

If you have a mini-quad then you might have noticed that its battery often ranges somewhere between 1000 mAh and 1800 mAh. 1300 mAh battery used to be the most preferable size. It offers impressive balance between weight and power capability.

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3. Battery Voltage (Cell Count)

It is also called as cell count. LiPo batteries exist in cells and each LiPo cell has a nominal voltage of 3.7V. We don’t normally refer to the nominal voltage of battery, but how many cells in the battery, or how many “S”. For example, 3S = 3 cells=3.7*3=11.1, so 11.1V is the nominal battery voltage, and thus we call a 11.1V battery a “3-cell” or “3S” battery.

You can increase the voltage of the battery using a series connection of the cells to form a single battery. However, to increase the battery current, cells are connected in parallel connection.

The cell configuration of the LiPo battery is as shown in the table given below. 

Let’s understand some more voltage terms related to LiPo battery.

• Cut off voltage: The cut-off voltage is the voltage at which a battery discharges completely. Discharging the battery below cutoff voltage 3V could cause irreversible performance and even damage to the battery. This means you should set your voltage alarm to 3.2 V or 3.3V.

• Nominal Voltage: The nominal voltage of the LiPO is 3.7V. It is also referred as storage mode voltage of the battery.

• Maximum/full charged voltage: The maximum/full charge voltage is the voltage at which a battery reaches its maximum voltage. If you charge the battery above 4.2V, it is dangerous and eventually causes a fire.

Actually you need not to follow any golden rule for battery voltage selection but you can make decisions via comparing data tables as well as efficiency. You might have observed that drone motors usually become much powerful and efficient when they are powered by higher voltage. But, then problem comes in maintaining balance with cost and weight of battery. If you can decide how much motors will be used by your device, then you can also decide about required current set up.

If you are going to buy new batteries, then always prefer those whose specifications are suitable with the need of specific voltage or current rating. There are few motors that follow very specific rating for voltage and current of LiPo batteries, hence you need to make proper decision for your investment. The higher voltage rating motors will produce higher power/RPM, but will have more weight too. In the selection of the battery voltage, make sure that your motors/ESC and other electronics are able to support the voltage of your battery.

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4. C Rating (Discharge Rate)

C rating is nothing but discharge rate of a battery. This rating helps users to know about the maximum current that a battery can discharge but without damaging itself. These figures are often considered good for quality measurement.

For example, if you are going to buy new batteries and any brand offers them with 2 different C ratings then you must prefer to pick one with higher C rating as it will be able to handle much higher discharge rate as compared to another with lesser C rating.

The overall performance of a drone is highly dependent on its C rating, so drone professionals always prefer to pick their batteries after checking C rating. However, the higher the C rating, the heavier battery will be. And, heavier batteries reduce overall flight time of your drone. Now, you’ll think that this stuff is getting more and more complicated and it could appear difficult task to most of drone users. Let me simplify it for you. While buying a new battery unit, prefer to check the specifications of your motors and also check their maximum current rating. Here is a simple law that can help you to perform right calculation.

Maximum Continuous Amp Draw (Max. discharge current) = Battery Capacity X C Rating (Discharge Rate).....(1)

Typically the smaller the capacity of a Lithium Polymer battery, the higher the C rating needs to be and vice versa. By knowing the C rating and capacity of a battery, we can calculate the safe, continuous and maximum discharge current of the Lipo battery. Some batteries come with two C-ratings: “continuous” and “burst” ratings.

• The continuous current C rating: It shows how the maximum safe current your battery can discharge for long periods of time.

• The burst C rating: It shows the maximum current your battery can discharge for short periods of time (normally around for 10 seconds).

Burst C Rating = Max Current Draw / Battery Capacity.....(2)

Max Current Draw = Burst C Rating * Battery Capacity.....(3)

In the fig. 1, the C rating of the battery is 30. You could safely draw it at the 30 times more than the capacity of the pack. For 2000 mAh capacity battery rated for 30 C continuous, the maximum continuous current will be 2 * 30 = 60 Amps.....(from 1)

The same battery might have a 40 C burst rating, meaning the battery can safely output 2 * 40 = 80 Amps for short periods of time.....(from 3)

If the C rating is too low, the battery will have more time delivering the current to your motors, and your quad will be underpowered. You could even damage the battery if the current draw exceeds safety rating. When the C rating is higher than the requirement, you won’t gain much performance improvement. Also, the battery would be heavier and you will be carrying extra weight that reduces your flight time. In short, you’ve to maintain the balance of C rating here i.e. not too higher & not too lower!

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5. Battery Size and Weight

Let’s consider an example of quad copter. Suppose, you’ve chosen a motor having thrust of 500gm per motor (or 2Kg thrust in total). Calculating the weight of the frame, motors, ESCs, flight controller and other electronics, it goes around 1.2Kg. It leaves 800g-1000g that we can use for the battery, so try to find a LiPo battery of higher capacity which has weight around 800g to 1000g.

If you have batteries with higher voltage rating then it will, naturally help your drone motors to produce higher power. Eventually, high voltage batteries are heavier in weight; hence it will directly increase the overall weight of your drone. Prefer to pick a larger one in terms of capacity so that it can serve your drone for longer duration. Ability of a battery to allow maximum flight time in air also depends upon overall weight of the drone as with larger physical size, even a highly powerful battery will face some reduction in flight time. The size & weight of battery should be considered on the basis of drone type and its battery cabinet, so before buying a new battery for your camera, prefer to check your drone specifications.

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6. Connectors

Connectors not only provide you easy way to connect or disconnect batteries form devices but also help users to create new drones in future. Even though you can easily find so many varieties of connectors in market, but these connectors must be compatible enough with your drone type.

There are two types of connectors are used in LiPo battery. The main connector is a power connector and the other is balance connector. Only 1S batteries have one main lead. There are a variety of different types of connectors that vary in size, current rating, and ease of use. These are as shown in the image below.

Some of the most common connector products use Deans/T plugs, EC3 and XT60 connectors with unique specifications. Be sure to collect some information about your device compatibility and get a suitable product with right specifications. If a battery has two male pins are striking out, there is a chance to get bent and short together. That’s why; LIPO battery has a female connector for safety purpose.

For a normal drone, the most popular connector is XT60 connector. The XT60 is rated only at 60A. Sometimes, your drone has requirement of high current, then you better go for different connector. The current rating of connectors is as shown in the table given below.

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7. Best LiPo Battery Brands for drones:

• Orange LiPO: The Orange Lipo battery is perfect for drones. This is a well known brand in India and it is provided by Robu.in. Orange LiPo batteries actively work for a longer time. These have high power delivering capacity in a compact size.
  

• Hobbyking: Hobbyking have so many LiPo batteries to offer where some of the highly rated ones are: Bolt, Multistar, Graphene and NanoTech.

• Tattu: This is another great brand for drone community that offer batteries with large discharge time and great stability! Gens Ace is a factory owned Lipo battery brand in remote control product market & Tattu is the sister brand of Gens Ace. You can also buy it from Rcmumbai, Robokits, Amazon, etc.

• Infinity: This company is well known as a battery service provider for Banggood. Most of the batteries on their site are of very low price but they have very good performance. You can also buy it from Aliexpress, Amazon, and other online shopping sites for drone RC products.

• Revolectix: Although this company is well recognised for RC helicopter models but they are also the only retailers who manufacture LiPo cells.

I’m sure that you’ve got clear guidelines about selection of perfect LiPo battery for your drone. I hope this information is helpful to you.

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References:

• How to Choose Lithium Polymer Battery for your RC Drone – by Priyanka Dixit
• How to Choose the Best LiPo Battery for Your Drone – by Liza Brown