Your LIPO Battery, treated properly, will keep your drone in the air for a long time
By Dino of Dinos Drones
One of the most important components your drone needs to fly is the battery that powers all the electronics. No battery, no flying. The type of battery most widely used today in radio controlled vehicles is the Lithium Polymer or LiPo battery. These batteries provide great power but can be expensive; however understanding a few basic properties of LiPo batteries and learning techniques to properly charge, store and care for your them will keep you, and your house, safe and give you many hours of use and hundreds of flights.
Look at your LiPo you may see something like this written on it:
EXAMPLE: 3S 11.1V, 1000mAh, 20C discharge/50C Burst, 3C max charge
What does that tell you? Hmmmm……..
LiPo batteries are made up of cells. The number of cells a LiPo battery has is labeled with an “S” number and/or by its Voltage (V). A 1S LiPo is a 1 cell battery with a voltage of 3.7V when discharged to 20% (more on this later). Most drones operate with a 3S or 4S LiPo. A 3S LiPo has 3 cells and a discharged voltage of 11.1V and a 4S LiPo has 4 cells and a discharged voltage of 14.8V. Here is a chart of the most common size of LiPos encountered in the drone world.
- 1S = 1 cell and 3.7V
- 2S = 2 cells and 7.4V
- 3S = 3 cells and 11.1V
- 4S = 4 cells and 14.8V
- 5S = 5 cells and 18.5V
- 6S = 6 cells and 22.2V
- 7S = 7 cells and 25.9V
TAKE AWAY: LiPos are made up of a number of cells (S rating). The voltage of 1 LiPo cell is 3.7V when discharged to 20%.
The milliamp hour (mAh) rating is the capacity of the LiPo. In the above example, 1000mAh is the capacity of the battery. This means that at a draw of 1 amp the battery will be fully discharged in 1 hour…… For our purpose this is how much gas you have in the tank. As this rating increases so does the size and weight of the LiPo. Typically, more mAh = more flight time. However, increased weight will lessen flight time. This is not a hard and fast rule as there are many other variables in play like the motor kv, weight of the drone, flying style, etc. To effectively increase flight time lighten your payload.
TAKE AWAY: more mAh, more time in the air but must be balanced with total weight of the drone.
The continuous discharge rating or “C” rating refers to how efficiently the battery provides power to the speed controller, motors and other electronics. Basically, this is how easy power is drawn from the LiPo. As the motors draw power the LiPo heats up. You will notice at the end of your flight the battery is probably warm. This is normal if the C rating is appropriate for the speed controller and motors. If you cannot hold it comfortably in your hand, it’s too hot and you need a higher C rated LiPo. A C rating that is to low will cause the motors and LiPo to work harder and produce more heat. Most Drones will operate with a C rating of 20C – 30C. The maximum burst rate is what the LiPo will deliver on demand but only for a very short period (1 second for arguments sake). For example when you increase throttle to 100% quickly to ascend fast. The motors will need a burst of energy to spin up to your throttle command.
TAKE AWAY: Use a LiPo with the same C rating as the LiPo that came with your drone.
TAKE AWAY: C rating to low, LiPo too hot.
The charge rating is the maximum charge rate of the LiPo. A charge rate of 1 x the mAh rating is a 1C charge rate; 2 x the amperage is 2C charge rate, etc. (for our purpose this is different from the above discharge C rating). Let’s simplify this. In our example, the mAh rating = 1000 or 1.0 amp (A). A charge rate of 1C is 1 amp (1 x 1.0A). This means, yep, 2C is 2A and 3C is 3A. But what if your battery is a 3800mAh LiPo? Just move the decimal to the left 3 places and you get 3.8A. A 1C charge rate for a 3800mAh LiPo is 3.8A, 2C is 7.6A (3.8V x 2) and 3C is 11.4A (3.8V x 3). I charge all of my LiPos at 1C. I only charge at 2C if I don’t have much time and I want to get flying. I do not charge at 3C. Faster charging rates will lessen the life of your LiPo.
TIP: Look at this as 1000.00mAh. To figure out the amperage of any mAh rating, just move the decimal to the left 3 places. So, 450 mAh is 0.45 amps, 5000 mAh is 5.0 amps, etc.
TAKE AWAY: the higher the charge rate the less time it takes to charge – The tradeoff is higher charge rates lessen the life of the LiPo.
CARE & MAINTENANCE
I mentioned before that the discharged voltage of a LiPo cell is 3.7V. Actually, at 3.7V there is 20% charge left in the battery. To increase the life of your LiPo DO NOT discharge it lower than 20%. A fully charged (100%) LiPo cell is 4.2V (3.7V + 0.5V). DO NOT charge a LiPo cell past 4.2V. So, a 1S LiPo at 20% is 3.7V and at 100% is 4.2V. In the example the 3S LiPo has a voltage of 11.1V (3.7V x 3 cells) at 20% and a voltage of 12.6V (4.2V x 3 or 11.1V + 1.5V) at 100%. Combine this information with the mAh capacity and fully charged the 3S LiPo will have 1000mAh capacity at 12.6V. When discharged to 20% the LiPo will have 200mAh capacity (1000 x .20) at 11.1V. Therefore, the useable capacity is 800mAh (1000 x .80).
Your LiPo battery probably has multiple cells. Remember, each cell holds 3.7V at 20% and 4.2V at 100% (3.7V + 0.5V). So, a 4S LiPo at 20% charge will hold 14.8V and at 100% charge 16.8V. A LiPo checker (pictured on the right) is a valuable tool to help you determine the charge percentage of your LiPos.
Different kinds of LiPo checkers.
TAKE AWAY: Do not discharge your LiPo below 3.7V per cell (20%) or over-charge your LiPo past 4.2V per cell (100%).
Charging the LiPo is very simple and safe if you keep a few things in mind. ALWAYS use a LiPo specific charger. Many chargers available today will charge multiple types of battery chemistries. These chargers will have a feature to set the battery chemistry type. ALWAYS make sure it is set on LiPo when charging LiPo batteries. I recommend using a computerized charger with an information screen that gives you, at least, the values for voltage, charge rate and capacity (mAh). It is important to match these values in the charger to safely charge the LiPo. Many computerized chargers have built in warning systems and will not begin the charge cycle in the event the battery is hooked up and/or the charger is set incorrectly. Some computerized chargers will also have a feature to check the internal resistance (IR) of each cell in a multi cell LiPo. This allows for further monitoring the lifespan of the LiPo. IR will increase over time and multiple charge cycles….Just something to keep in mind.
ALWAYS FOLLOW THE MANUFACTURES INSTRUCTIONS AND RECOMMENDATIONS
This is what I do with my charge station:
• Plug the charger into the wall outlet
• Plug the battery charge cable into the charger
• Turn the charger on
• Plug in the battery (Battery Connector first then the Balance Plug)
• Select the setting for LiPo
• Select the charge rate 1C – 2C
• Select Balance Charge
• Start charging
TIP: When plugging in the battery charge cable into the charger. Connect the Ground (black) lead first and the Positive (Red) second. When unplugging, reverse the order. Unplug the Red lead first and then the Black lead.
TIP: Wait for the LiPo to cool down after a flight before charging it again… roughly 15 minutes cool down time.
TAKE AWAY: It is VITAL to set the chemistry, number of cells, mAh and charge rate correctly in the charger before beginning the charge cycle.
I balance charge every time I charge my LiPos. This means that as the LiPo is charged the computer charger will detect the voltage in each cell through the balance plug lead (little white plug with many wires attached exiting the battery) and match the voltages across all cells as it charges the battery to full charge. It is important to maintain the same voltage across the LiPo cells to efficiently deliver the power to the drone and extend the life of the LiPo. It is not necessary to balance charge LiPos every charge if you do not have the ability. However, it is good practice to balance charge every two cycles.
TAKE AWAY: Balance charge LiPo batteries.
BREAKING IN NEW LIPOS
It is important to “break in” new LiPo batteries. Every LiPo I buy, whether it comes with the aircraft or purchased separately, is put through a break-in process. This is what I do but you will get many different opinions depending on who you ask. However, my LiPos are well used but remain in tip top shape. My break in period is 6 cycles. When I receive a brand new LiPo the first thing I do is charge it to full charge and then discharge to 60% storage charge. This is called cycling the battery. Next, I determine the maximum flight time given by the manufacturer of the aircraft and divide that in two. For example, my drone is said to fly for 15 minutes without a gimbal and camera. So, 15 divided by 2 = 7.5 minutes. My first flight I slowly increase the throttle and take off and hover for 5 minutes and land. That’s it 5 minutes. The battery will probably be around 70% +/-. My next 3 flights I take off and hover for 7.5 minutes. Typically, each of these flights will not see the percentage left in the battery at the end of the flight below 60% and the percentage left will increase with each of these flights. This is what should happen. For the 5th flight I will hover and include very slow forward flight a few feet out and back and land at 7.5 minutes. My sixth flight will be a regular non aggressive flight. After that it’s flyin’ time!
During break in by being mindful of the battery percentages after flight you can determine the total amount of flight time you should get once the battery is ready for normal flight. This is where the battery checker comes in handy. When you land DISARM the drone and check the battery percentage. Based on this and your flight timer in your radio you can estimate your total flight time. Another strategy is to fly the drone for 4 minutes and land. Recharge the LiPo and take note of how many milliamps are put back into the battery to reach full charge. Divide this number by 4 and you will get the milliamps consumed per minute.
TAKE AWAY: ALWAYS break in new LiPos.
There are many different opinions regarding LiPo storage. Ask around and everyone will tell you something different. The basic rule of thumb is to store LiPos at 50% – 60% charge and at room temperature. Some will tell you to store in the refrigerator but that takes up valuable space for other goodies! Do not store LiPos at full 100% charge or at 20% charge as this can be dangerous and lessen the life of the LiPo. LiPos do not like heat, so, leaving them in your car while going shopping is a bad idea and will lessen its life. I am very conservative in the care and maintenance of my LiPos and can tell you that outlined in this article are my methods and all of my RC Helicopter batteries, which are flown harder than the drone batteries, have lasted for over 100 flights and are still in great condition, balance perfectly and perform great! I start with quality LiPos.
My process is very simple:
• I storage charge all my LiPos at 60%.
• I charge my LiPos the morning of the flight. I never let them sit overnight fully charged.
• I always storage charge my batteries when I am done flying.
• If I charge a LiPo and do not fly it, I always put it back in a storage charge.
• I never store a LiPo at below 50% charge
• LiPos will naturally loose charge over time like any other battery. If my LiPos will be stored over long periods of time (i.e. winter months), I storage charge all batteries to 60% charge. I then monitor all LiPos and keep a log of the percent charge in each LiPo every other week or so. If any of them falls below 50% charge I cycle that specific LiPo. This means I charge it to full charge and then discharge it to 60% for storage. I also take note as this LiPo may potentially be going bad if it discharges quicker than all others.
• All of my LiPos are stored at room temperature.
• When using them outside I keep all LiPos in the shade i.e. under my car or tree, etc.
TAKE AWAY: ALWAYS Store LiPos at 50%-60% charge (storage charge) and in a cool place.
Here is a simple chart to help you determine what voltage equals the percent charge of your LiPo batteries.
Used with a LiPo battery checker, as shown in the picture above, will give you the information needed to safely maintain your LiPo batteries.
LiPo batteries by nature will deteriorate over time with multiple charge cycles. Using the information above you can charge your LiPos efficiently and maintain a long life of flying power. Keep in mind that LiPo batteries are volatile and must be handled in a safe manner. If they are mishandled there can be dangerous consequences. Over-charging, over-discharging can cause the LiPo to burst into flames. Charging and discharging outside the C ratings, or charging and/or discharging to fast, can cause a fire. Do an internet search and you will find multiple videos of flaming LiPos. If you drop your LiPo and dent it, I recommend not using it and getting rid of it. Dropping can shift the cells and cause an internal short that may not be noticed until you try to charge it and use it and it bursts into flames. Do not use a LiPo that has cuts in the outer surface. A crash can cause the LiPo to burst into flames. Approach a crashed drone very carefully and when it is safe disconnect the LiPo battery immediately and remove it from the drone. If it is too hot to handle toss it aside and let it cool. A good LiPo should be hard. If the LiPo is puffing and/or feels soft it is time to discard the LiPo. It’s less costly to replace a bad LiPo than your $2500+ drone. If in doubt, throw it out!
TAKE AWAY: DO NOT charge LiPo Batteries unattended.
TAKE AWAY: DO NOT over-charge or over- discharge LiPo batteries.
TAKE AWAY: DO NOT charge or discharge outside of the manufacturer’s C rating.
TAKE AWAY: Approach a crashed drone with CAUTION and immediately disconnect the LiPo.
TAKE AWAY: DO NOT use damaged LiPos.
REMEMBER THE 5 KILLERS OF LIPOS:
2. OVER-CHARGING (Voltage & Current)
3. OVER-DISCHARGING (Voltage & Current)
4. CELLS UNBALANCED
5. IMPROPER STORAGE
This is a basic illustration of LiPo battery care and maintenance. It is not intended to cover every aspect of LiPo care and maintenance.
As always, feel free to contact me if you have any additional questions regarding the care and maintenance of your LiPo batteries.
Happy Flying and remember to always Fly Safe!
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