4S Lithium Ion Battery for a Quadcopter using Samsung 21700 4000mAh 40T

(Last Updated On: February 16, 2022)

4S Lithium Ion Battery for a Quadcopter, Description:

4S Lithium Ion Battery

4S Lithium Ion Battery for a Quadcopter using Samsung 21700 4000mAh 40T- There are some major reasons why I decided to shift from Lipo batteries to the Lithium Ion batteries for powering up my Quadcopter Racing Drone. I will also talk about the mistakes which are made by almost every beginner, for example, you make a battery but not able to charge it or you make a 3S or 4S lithium Ion Battery pack, but you are not able to fly your Drone with it, you just increase the throttle and the flight controller is restarted, I have seen a lot of guys facing the same issue, so I will practically show you how to fix this issue. I will also explain step by step the complete process of making a 4S Lithium Ion Battery Pack using the Samsung 3.7V 21700 4000mAh 40T Lithium Ion Batteries and then I will practically share with you the test results and the flight time. So, it doesn’t matter whether you want to use 18650 lithium ion batteries or the 21700 lithium Ion batteries, the techniques and connections will remain exactly the same. So, in this article, you will get answers to all of your questions. Without any further delay, let’s get started!!!


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Samsung 21700 40T 4000mAh Lithium Ion Batteries

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EMAX 2nd generation 2600kv motors

30A ESCs

Flysky Fs-i6 Transmitter and receiver

5×4.2 inches propellers

Puda Rooster 230 Carbon Fiber frame

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Digital Oscilloscopes

Variable Supply

Digital Multimeter

Soldering iron kits

PCB small portable drill machines

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Why Lithium Ion Batteries for Quadcopter Drones?

The very first question that might pops up in your mind is, why Lithium Ion battery packs for powering up quadcopter drones? The answer is lithium-Ion batteries are cheap, durable, and gives you more flight time. If any of the cell is damaged, you can simply replace that one cell and again you can start using your battery pack.

While on the other hand the lipo batteries are very expensive, not durable at all, and gives you less flight time. If any of the cell is damaged, it’s hard to replace that cell and then the whole battery pack becomes useless. I am not saying its impossible to repair the lipo battery, but it’s hard to find the same rating lipo cell. In my case, I am not in favor of repairing a lipo battery, if any of the lipo battery is damaged I simply throw it away, or I remove the damaged cell and then use the other cells for powering up my controller boards and other sensors. Now, I am going to talk about the beginners level mistakes.

When I decided to start with the Lithium Ion batteries, the very first mistake which I made was, I built a 4S lithium Ion battery pack using 3.7v 18650 laptop batteries. I was really happy, I connected my 4S battery, I could hear all those beeps, so far everything was going as per the plan, but the things changed when I started to apply the throttle; the flight controller was continuously restarting and I was really disappointed. This was due to my mistake, as I was using lithium Ion batteries with low discharge rate. So, whenever you are going to purchase the Lithium Ion Batteries first check the Discharge rate. It doesn’t matter whether you decide to use 18650 or 21700 lithium Ion Batteries. So, if you have built your first lithium Ion battery and you are not able to fly your drone with it then simply go ahead and check the discharge rate of your lithium ion batteries.

4S Lithium Ion Battery

Anyway, the discharge rate of these 18650 Lithium Ion batteries is just 4 amps, so with these batteries I can never fly my racing drone. So, I didn’t stop here, I started searching for the 18650 lithium Ion batteries with current discharge rate of around 30A. Seriously I was looking for 18650 lithium ion batteries but then I found these Samsung 21700 batteries which are more powerful than the 18650 batteries. Samsung is always ahead of the game when it comes to high-drain batteries, and the Samsung 40T battery is a shining example of their innovation. These 3.7V 21700 4000mAh lithium-ion batteries offers 35A max discharge rate, making these 40T top choice for high-drain devices. So, let’s go ahead and make a 4S lithium Ion Battery pack for the racing drone.


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4S lithium-Ion Battery pack for LongRange Drones:

 In my previous article, I have already explained how to make 3S and 4S lithium Ion battery packs using a homemade Spot welding machine. Anyways, since most of the beginners have no spot welding machine so this time I am going to use the soldering technique. So, let’s go ahead and start making the 4S lithium Ion Battery pack.

4S Lithium Ion Battery Pack Connection Diagram:

4S Lithium Ion Battery

The positive of the first cell is connected with the ground of the 2nd cell. The positive of the 2nd cell is connected with the ground of the 3rd cell. The positive of the 3rd cell is connected with the ground of the 4th cell. This is the main positive of the battery pack and this is the main ground of the battery pack. These three wires are needed to be connected in the same order. If you connect these wires in the wrong way then you won’t be able to charge your battery and there are also high chances of damaging your balance charger. So, double check your connections.

4S Lithium Ion Battery


Next, we are going to connect all these 4 cells in series. I set my soldering iron temperature at 400 Celsius. For this soldering job I am using this Bevel or C series tip. Due to its large slightly curved surface it can hold more solder than most other tips and it can transfer more heat. I have a very detailed article on how to use different soldering iron tips.

4S Lithium Ion Battery

I connected all the 4 batteries in series as per the connection diagram. I carefully soldered the balance connector wires and then I used my digital multimeter for checking all the voltages.

The balance connector wires should be connected in the same order, this is really an important step, and all the wires should be connected in the correct order.

4S Lithium Ion Battery



My 4S lithium Ion Battery pack is ready. It’s been 2 hours and now the battery pack is fully charged. You can see all the 4 cells are equally charged. For the flight test results watch video given below.

4S Lithium Ion Battery

This was such an amazing flight experience as this was my first time using a 4S battery pack. This battery pack gave me 25 minutes of flight time without any issues and seriously, still I feel like I can fly this racing drone for more 10 to 15 minutes. So, in the end I highly recommend you guys should definitely try these Samsung 21700 40T 4000mAh Lithium Ion Batteries. You can also use 18650 lithium Ion batteries but don’t forget to check the discharge rate. So, that’s all for now.


Watch Video Tutorial:

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About the Author: Engr Fahad

My name is Shahzada Fahad and I am an Electrical Engineer. I have been doing Job in UAE as a site engineer in an Electrical Construction Company. Currently, I am running my own YouTube channel "Electronic Clinic", and managing this Website. My Hobbies are * Watching Movies * Music * Martial Arts * Photography * Travelling * Make Sketches and so on...

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