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Lithium polymer batteries, more commonly known as LiPo, have high energy density, high discharge rate and light weight which make them a great candidate or RC applications.
By learning the basics about LiPo batteries, you will be able to read and understand their specifications.
tattu 1300 4s.jpg600x600 56.3 KB
Battery Voltage and Cell Count (S)
LiPo batteries used in RC are made up of individual cells connected in series . Each cell has a nominal voltage of 3.7V . Therefore battery voltage is often referred to as how many cells in the battery (aka “S”).
1S = 1 cell = 3.7V
2S = 2 cells = 7.4V
3S = 3 cells = 11.1V
4S = 4 cells = 14.8V
5S = 5 cells = 18.5V
6S = 6 cells = 22.2V
For example, we call a 14.8V battery a “4-cell” or “4S” battery.
Voltage affects brushless motors RPM directly, therefore you could use higher cell count batteries to increase your quadcopter’s speed if your motor/ESC and other electroincs support higher voltage.
But a battery with more cells of the same capacity is heavier since it contains more cells. To make a 4S 1000mah battery, you could simply combine two 2S 1000mah, or one 3S 1000mah with an 1S 1000mah.
Nominal voltage for LiPo battery cell is 3.7V. However it’s not the voltage of the battery either when it’s fully charged or fully discharged. The number is come up by manufacturers, and It’s near the middle of safe voltage range, so I guess that kind of makes sense.
LiPo battery is designed to operate within a safe voltage range, from 3V to 4.2V . Discharging below 3V could cause irreversible performance lost and even damage to the battery. Over-charging above 4.2V could be dangerous and eventually cause fire.
However it’s advisable to stop discharging when it reaches 3.5V for battery health reasons. For example for a 3S Lipo, the max voltage is 12.6V, and you should land when the voltage reaches 10.5V (at 3.5V per cell).
LiPo Battery Capacity and Size
The capacity of a LiPo battery is measured in mAh (milli-amp hours). “ mAh ” is basically an indication of how much current you can draw from the battery for an hour until it’s empty.
For example, for a 1300 mAh Lipo, it would take an hour to be completely discharged if you draw a constant 1.3A current from it. If the current draw doubles at 2.6A, the duration would be halved (1.3/2.6=0.5). If you draw 39A of current non-stop, this pack would only last 2 minutes (1.3/39=1/30 of an hour).
Increasing your battery capacity might give you longer flight time, but it will also get heavier in weight and larger in physical size. There is a trade-off between capacity and weight, that affects flight time and agility of the aircraft.
Higher capacity could also give you higher discharge current as you will see in the next section.
Note that, 1000mAh = 1Ah.
C Rating (Discharge Rate)
Lipo batteries for quadcopters these days all come with a C rating. By knowing the C rating and capacity of a battery, we can in theory calculate the safe, continuous max discharge current of a LiPo battery.
Maximum Discharge Current = C-Rating * Capacity
For example an 1300mAh 50C battery has an estimated continuous max discharge current of 65A.
Some batteries come with two C-ratings: “continuous” and “burst” ratings. The Burst rating is only applicable in short period of time (e.g. 10 seconds).
Although C rating could be an useful tool, it has become mostly a marketing tools nowadays.
If C rating is too low, the battery will have a hard time delivering the current to your motors, and your quad will be under powered. You could even damage the battery if current draw exceeds safety rating.
When C rating is higher than what’s required, you won’t gain much performance improvement. Instead the battery would be heavier and you will be carrying extra weight that reduces your flight time.
Discharge Lead (Main Connector)
Rule of thumb, the battery connector should match the one you are using on your copter. If you don’t own a quad yet, choose one, and stick with it.
All Lipo batteries come with 2 sets of wires/connectors: a balance lead and a main lead or discharge lead(Except for 1S batteries which only have a main lead). There are quite a few different connectors used in LiPo batteries. The main differences are shape, weight and current rating.
1S Battery Connectors
LOSI
Pico blade
JST-PH
1S connectors are tiny and have very low current rating. They are commonly used in brushed micro quadcopters.
2S-6S Battery Connectors
You will find a lot more different types of battery connectors in this category, in fact not all are listed here. But majority of them are not used that often so you don’t need to ever worry about them. For mini quad, the most popular connector is probably the XT60. for smaller one, usually use the xt30.
JST
Mainly 2S
XT30
Mainly 2S and 3S
XT60 Similar to the Above, only bigger Mainly 3S, 4S
XT90 Similar to the Above but even bigger
HXT-4mm
EC3
EC5 Similar to the Above but bigger
Deans (T)
However since XT60 is only rated at 60A, and mini quad are running at higher and higher current and voltage, we might soon see a change in the popular connector used. such as xt90, EC5 etc.
Balance Lead
Balance lead is mainly used for balance charge to ensure all cell voltages are equal. It also allows you to monitor the voltage of each cell.
The number of wires in a balance lead starts at 3 for 2S LiPo, and for every increment in cell count, the number of wires also go up by 1.
How to choose LiPo battery for quadcopters?
To choose the best Lipo battery for your quad, you first need to know your requirement, the preferred cell count, and what would be the max discharge current.
Find Out How Much Current Your Drone Can Draw
Once you have decided on your choice of motors and propellers size, you should be able to find data online related to that requirement. For example, I am going to use this motor with 5040×3 props, at 100% throttle it draws 36.7A.
The total max current draw for a quad of 4 motors would be 36.7 x 4 = 146.8A at 100% throttle. If you want to play safe, you could just use this figure and find the battery you want. But for me, I usually discount it by 10% and that’s 146.8*0.9 = 132.1A because of the considerations we mentioned.
Choosing the Optimal Battery Capacity for your Drone
Now you need to work out the battery capacity for the particular size of your quadcopter, and C rating required. Here is some general guideline I personally follow by the propeller sizes:
6 inch: 1500mah — 2200mah
5 inch: 1300mah — 1800mah
4 inch: 850mah — 130mmah
3 inch: 650mah -1000mah
Say if I was building a 5″ mini quad, and I want a relatively lighter build, I would go for 1300mAh (1.3Ah).
From there, I can calculate the burst C rating requirement using this formula:
Burst C Rating = Max Current Draw / Capacity
In our example, 132.1A / 1.3Ah ~ 102 C . Based on the specification of most LiPo battery manufacturer, the the continuous C Rating is normally half of the burst C rating , and that would be 102/2 = 51C .
What Brand Should I Choose?
Acehe, Tattu, Turnigy, Dinogy, Infinity and so on are some of the best brands out there. (sorry if I miss your brand please remind me know in the comment). Here, we recommend links about UAV lipo battery And Fpv battery.
By learning the basics about LiPo batteries, you will be able to read and understand their specifications.
tattu 1300 4s.jpg600x600 56.3 KB
Battery Voltage and Cell Count (S)
LiPo batteries used in RC are made up of individual cells connected in series . Each cell has a nominal voltage of 3.7V . Therefore battery voltage is often referred to as how many cells in the battery (aka “S”).
1S = 1 cell = 3.7V
2S = 2 cells = 7.4V
3S = 3 cells = 11.1V
4S = 4 cells = 14.8V
5S = 5 cells = 18.5V
6S = 6 cells = 22.2V
For example, we call a 14.8V battery a “4-cell” or “4S” battery.
Voltage affects brushless motors RPM directly, therefore you could use higher cell count batteries to increase your quadcopter’s speed if your motor/ESC and other electroincs support higher voltage.
But a battery with more cells of the same capacity is heavier since it contains more cells. To make a 4S 1000mah battery, you could simply combine two 2S 1000mah, or one 3S 1000mah with an 1S 1000mah.
Nominal voltage for LiPo battery cell is 3.7V. However it’s not the voltage of the battery either when it’s fully charged or fully discharged. The number is come up by manufacturers, and It’s near the middle of safe voltage range, so I guess that kind of makes sense.
LiPo battery is designed to operate within a safe voltage range, from 3V to 4.2V . Discharging below 3V could cause irreversible performance lost and even damage to the battery. Over-charging above 4.2V could be dangerous and eventually cause fire.
However it’s advisable to stop discharging when it reaches 3.5V for battery health reasons. For example for a 3S Lipo, the max voltage is 12.6V, and you should land when the voltage reaches 10.5V (at 3.5V per cell).
LiPo Battery Capacity and Size
The capacity of a LiPo battery is measured in mAh (milli-amp hours). “ mAh ” is basically an indication of how much current you can draw from the battery for an hour until it’s empty.
For example, for a 1300 mAh Lipo, it would take an hour to be completely discharged if you draw a constant 1.3A current from it. If the current draw doubles at 2.6A, the duration would be halved (1.3/2.6=0.5). If you draw 39A of current non-stop, this pack would only last 2 minutes (1.3/39=1/30 of an hour).
Increasing your battery capacity might give you longer flight time, but it will also get heavier in weight and larger in physical size. There is a trade-off between capacity and weight, that affects flight time and agility of the aircraft.
Higher capacity could also give you higher discharge current as you will see in the next section.
Note that, 1000mAh = 1Ah.
C Rating (Discharge Rate)
Lipo batteries for quadcopters these days all come with a C rating. By knowing the C rating and capacity of a battery, we can in theory calculate the safe, continuous max discharge current of a LiPo battery.
Maximum Discharge Current = C-Rating * Capacity
For example an 1300mAh 50C battery has an estimated continuous max discharge current of 65A.
Some batteries come with two C-ratings: “continuous” and “burst” ratings. The Burst rating is only applicable in short period of time (e.g. 10 seconds).
Although C rating could be an useful tool, it has become mostly a marketing tools nowadays.
If C rating is too low, the battery will have a hard time delivering the current to your motors, and your quad will be under powered. You could even damage the battery if current draw exceeds safety rating.
When C rating is higher than what’s required, you won’t gain much performance improvement. Instead the battery would be heavier and you will be carrying extra weight that reduces your flight time.
Discharge Lead (Main Connector)
Rule of thumb, the battery connector should match the one you are using on your copter. If you don’t own a quad yet, choose one, and stick with it.
All Lipo batteries come with 2 sets of wires/connectors: a balance lead and a main lead or discharge lead(Except for 1S batteries which only have a main lead). There are quite a few different connectors used in LiPo batteries. The main differences are shape, weight and current rating.
1S Battery Connectors
LOSI
Pico blade
JST-PH
1S connectors are tiny and have very low current rating. They are commonly used in brushed micro quadcopters.
2S-6S Battery Connectors
You will find a lot more different types of battery connectors in this category, in fact not all are listed here. But majority of them are not used that often so you don’t need to ever worry about them. For mini quad, the most popular connector is probably the XT60. for smaller one, usually use the xt30.
JST
Mainly 2SXT30
Mainly 2S and 3SXT60 Similar to the Above, only bigger Mainly 3S, 4S
XT90 Similar to the Above but even bigger
HXT-4mm
EC3
EC5 Similar to the Above but bigger
Deans (T)
However since XT60 is only rated at 60A, and mini quad are running at higher and higher current and voltage, we might soon see a change in the popular connector used. such as xt90, EC5 etc.
Balance Lead
Balance lead is mainly used for balance charge to ensure all cell voltages are equal. It also allows you to monitor the voltage of each cell.
The number of wires in a balance lead starts at 3 for 2S LiPo, and for every increment in cell count, the number of wires also go up by 1.
How to choose LiPo battery for quadcopters?
To choose the best Lipo battery for your quad, you first need to know your requirement, the preferred cell count, and what would be the max discharge current.
Find Out How Much Current Your Drone Can Draw
Once you have decided on your choice of motors and propellers size, you should be able to find data online related to that requirement. For example, I am going to use this motor with 5040×3 props, at 100% throttle it draws 36.7A.
The total max current draw for a quad of 4 motors would be 36.7 x 4 = 146.8A at 100% throttle. If you want to play safe, you could just use this figure and find the battery you want. But for me, I usually discount it by 10% and that’s 146.8*0.9 = 132.1A because of the considerations we mentioned.
Choosing the Optimal Battery Capacity for your Drone
Now you need to work out the battery capacity for the particular size of your quadcopter, and C rating required. Here is some general guideline I personally follow by the propeller sizes:
6 inch: 1500mah — 2200mah
5 inch: 1300mah — 1800mah
4 inch: 850mah — 130mmah
3 inch: 650mah -1000mah
Say if I was building a 5″ mini quad, and I want a relatively lighter build, I would go for 1300mAh (1.3Ah).
From there, I can calculate the burst C rating requirement using this formula:
Burst C Rating = Max Current Draw / Capacity
In our example, 132.1A / 1.3Ah ~ 102 C . Based on the specification of most LiPo battery manufacturer, the the continuous C Rating is normally half of the burst C rating , and that would be 102/2 = 51C .
What Brand Should I Choose?
Acehe, Tattu, Turnigy, Dinogy, Infinity and so on are some of the best brands out there. (sorry if I miss your brand please remind me know in the comment). Here, we recommend links about UAV lipo battery And Fpv battery.