What is ”LiPo” batteries ?
Lithium polymer batteries, henceforth referred to as “LiPo” batteries, are a newer type of battery now used in many consumer electronics devices. They have been gaining in popularity in the radio control industry over the last few years, and now are the most popular choice for anyone looking for long run times and high power. LiPo batteries have high energy density, high discharge rate and light weight which make them a great candidate or RC applications.
By learning this page, you will be able to know and understand their specifications.
Battery Voltage and Cell Count (S)
LiPo batteries exist in cells, each cell has a nominal voltage of 3.7V.
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 = 22.2VFor example, we call a 1 1.1 V battery a “ 3 -cell” or “ 3 S” battery.
If higher voltage is required, these cells can be connected in series to form a single battery. We don’t normally refer to the battery voltage, but how many cells in the battery, or how many “S”.
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 22 00 mAh Lipo, it would take an hour to be completely discharged if you draw a constant 2.2 A current from it. If the current draw doubles at 4.4 A, the duration would be halved ( 2.2 / 4.4 =0.5). If you draw 66 A of current non-stop, this pack would only last 2 minutes ( 2.2 / 66 =1/30 of an hour).
Battery capacity increasing might give you longer flight time, but it will also get weight heavier and physical size larger. There is a trade-off between capacity and weight/size, 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)
Nowadays, Lipo batteries used in quad-rotor aircraft have a C-rating. It is simply a measure of how fast the battery can be discharged safety and without harming the battery.
By knowing the C-rating and capacity of the battery, we can theoretically calculate the safety.
Continuous max discharge current of a LiPo battery.
Maximum Discharge Current = C-Rating * Capacity
For example an 22 00mAh 8 0C battery has an estimated continuous max discharge current of 176 A.
Some batteries come with two C-ratings: “continuous” and “burst” ratings. The burst rating is only suitable for a short period of time (for example, 10 seconds).
You should know, if the C-rating is too low, it will be difficult for the battery to provide current to the motor, then your quad will be out of power. If the current consumption exceeds the safe rating, you might even damage the battery.
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 Plug (Main Connector Type )
Based on experience, the battery connector should match the connector you use on the helicopter.
All Lipo batteries come with 2 sets of wires/connectors: a balance connector type (charge plug) and a connector type ( discharge plug).
Notice: Except for 1S LiPo batteries which only have a main lead.
There are quite a few different connectors to be used in LiPo batteries. The main differences are shape, weight and current rating.
1S Battery Connectors
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, common are: XT60 Plug, XT90 Plug, JST Plug, ect. For mini quad, the most popular connector is probably the XT60**.** Other majority of them are not used that often so you don’t need to ever worry about them.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.
Charge Plug ( Balance Connector Type)
Balance connector type (charge plug) is used for checking voltages of each cell. You need connect it to the charger while charging, because it’s extremely important to ensure all cell voltages are equal to avoid over-charging any cell.
The number of wires in a balance lead starts at 3 for a 2S LiPo, and that number increase by 1 for every increment in cell count.
Internal Resistance
Internal resistance (IR) can be used to measure how good a LiPo battery is. The lower the value, the better. Higher internal resistance reduces performance.
You should know that internal resistance increases over time and usage which is inevitable and irreversible.
LiHV
LiHV is a different type of LiPo battery, HV stands for “high voltage”. They are more energy dense than traditional LiPo battery, and allow to be charged up to 4.35V per cell.
the source from: https://www.tindlingshop.com/blogs/battery-knowledge/basic-knowledge-about-lipo-batteries