A Guide To Understanding LiPo Batteries And Their Testers
Not all batteries are created equal. There are quite a few different battery technologies in widespread use today. If you watch the television for a few hours you'll probably see commercials for three different kinds. The three used most commonly today are NiCd, NiMH, and LiPo. Each of these batteries has its distinct advantage, but the focus of this article is the LiPo battery.
Once you understand the LiPo battery, how it works, and how sensitive it can be, you'll understand the importance of buying a LiPo battery tester. The tester is your eyes and ears inside the battery. It lets you know its condition, its charge, and roughly how much longer it has left to life. First, you need to learn the basics.
Just What Is A LiPo Battery?
LiPo stands for Lithium Polymer. That's a big word and nobody wants to use it all of the time, so somebody shortened it down to LiPo. It's nice and simple, but not to be confused with the form of cosmetic surgery that sucks fat from the body.
LiPo is a relatively new battery technology. It's the newcomer in a market full of tested and proven batteries and it has a lot to prove. It's lightweight, can hold a big charge, and it can discharge fairly quickly if you need it to. These are qualities that are rather desirable in the world of radio technology, remote controlled vehicles, and drone flying.
LiPo vs. Older Technologies.
Older technologies aren't necessarily “worse” than LiPo. They just trade one quality for another. The advantages of LiPo over NiMH or NiCd is that they are smaller and more lightweight, they have a much higher energy density, a higher voltage per single cell, and they can handle higher discharge rates. Basically, the same benefits that were mentioned earlier that makes them perfect for flying drones.
However, if you aren't flying drones, then you might still prefer the older battery technologies. Why? NiMH batteries tend to have a significantly longer lifespan than their new alternatives. Your average LiPo battery might last you 300 cycles of charge and discharge. A NiMH battery, on the other hand, can last twice as long if properly cared for.
LiPo batteries are notorious for being unstable. This is particularly true if they aren't properly cared for, charged, and discharged. This is one of the reasons why it is always a good idea to invest in a battery tester or battery monitor if you are using lithium polymer batteries. The last thing you need is for your drone to spontaneously combust during flight.
Another reason you need a tester is that LiPo batteries drop their voltage as they discharge. This can become a problem once they drop below a certain threshold. Some other battery technologies will maintain relatively the same voltage until they have completely discharged.
As you can see, there are some advantages and disadvantages when compared to other battery types. If you need lightweight, high-power batteries, then LiPo is a good choice. Just be sure to test them regularly, charge them properly, and take good care of them while they are still alive.
Confusing Battery Labels
If you tried to purchase a LiPo battery online without understanding how they are labeled, then it probably wouldn't make much sense. To understand the labeling you need to understand the most important qualities of any such battery: Cell count, capacity, discharge rate.
The series cell count is directly related to the voltage. The nominal voltage, or resting voltage, of a single LiPo cell is 3.7 volts. The minimum charged voltage is 3.0 volts and the fully charged voltage is 4.2 volts. When there are multiple cells in a series it causes the voltage to add together. Thus, a battery with 2 cells in a series would have a nominal voltage of 7.4 volts.
The number of cells in a series is labeled with a number followed by the letter “S”. In the two cell battery example above the label would read “2S”, which simply means 2 cells in a series. If there were three cells, then it would be “3S” and the voltage would be 11.1 volts.
If you're using these batteries to power an R/C vehicle or drone, then the voltage is going to directly impact the speed of the motor. The RPM, to be exact, is influenced by the voltage. A brushless motor is often labeled as having a certain RPM per volt.
The next consideration and labeling factor is the capacity. The capacity is increased by placing batteries in parallel or by using larger cells. The capacity of a battery directly affects the size and weight of the battery.
If there are two cells in a series, then if there are any batteries in a parallel they must be in sets of 2 series cells as well. To clarify, you can't have two cells in a series and then one cell connected in parallel to those two cells. You would have two cells in a series and then two cells in a series connected in parallel to those cells. This would be labeled as “2S2P” and would mean a total of 4 cells and a voltage of 7.4 volts.
The actual capacity of the battery is described in terms of milliamp hours. In simple terms, it refers to the total drain on a battery that it can take to discharge it within a single hour. In even simpler terms, the higher the number, the higher the capacity. 5000 mAH is considered a typical average.
The final labeling factor is the discharge rate. This is also called the C rating or the continuous C rating. To choose a battery with the right C rating you need to know the current draw of the device. You then use that number to find a battery capable of discharging fast enough to power the device.
Even The Best Lipo Battery Needs A Tester
Finally, if you purchase a LiPo battery, then you need to purchase a LiPo battery tester. They go hand-in-hand and help everything to run smoothly. You would not want to use inappropriate battery chargers either - use only the recommended models.