Quadcopter batteries – What is LiPo?

About LiPo batteries

Quadcopter batteries are made of lithium polymer which is the best choice as these batteries are as light as they can get. To answer the question,” what is lipo battery,” the answer is that it does not have a liquid electrolyte inside. A solid polymer makes up the electrolyte in a LiPo battery. The polymer can also be a part of the construction of the electrode. The former is the actual LiPo battery while the latter could be a Li-ion battery but both are known as LiPo in many cases. While both Li-ion and Lipo are identical in the way they are thin and flat compared to a cylindrical shape, the energy potential of the latter is better than the former. Also important in the context of a quadcopter is that the discharge of power has to be quite fast when compared to other standard utilizations. With a rechargeable lithium polymer battery, you also have to pay equal attention to the maximum charging voltage and the maximum charging rate. If you do not take care, you might damage the lithium polymer battery.

Some technical details

First, let us look at how many batteries you need for your quadcopter and all of its functionality. If your design calls for a 1s battery, it is one 3.7 Volt battery while a 2s stands for two 3.7 Volts batteries connected in series. So,  a 11.1 lipo battery equates to 3.7 plus 3.7 plus 3.7, i.e. three batteries of 3.7 Volts potential each being connected in series. Each 3.7 Volt Lipo battery in itself has thrice as much potential as those batteries that are made of Nickel metal hydride. The mAh value stands for the capacity of the battery in terms of microampere hours. 1000 microamperes make up an Ampere. So, a battery with 3000 mAH will discharge 3000 micro Amperes per second for a duration of one hour. The battery might also be able to discharge faster. The lipo battery discharge rate will be specified with a 2C or a 3C rating. This is known as the lipo c rating. This means that a 2C rating is
equivalent to twice the discharge which will lead to the operational time halving from one hour to half an hour. You might not be needing an Ampere discharge but maybe less than an Ampere, say 100 micro Amperes which is 0.1 Ampere in which case you will get the discharge to spread out to ten hours. When you need higher Ampere discharge as with your quadcopter, you will end up using up the charge in a matter of minutes. Say that you are drawing 10 Amperes in a battery that has a 3000 mAh capacity. It will discharge 3 Amperes per second for an hour but when you discharge 10 Amperes the capacity will last only for 0.3 hours or when multiplied by 60 to give it in minutes will be 18 minutes. You can go in for a high discharge rate of close to 50C if your quadcopter needs it.

Looking at a few most popular models available on Amazon

Tenergy 3.7V 380 mAh LiPo battery is a direct replacement for Hubsan X4, Syma X11, WLtoys V252, Walkera Super CP, Mini CP and Genius CP. Its dimensions are 40x21x7.5mm. The maximum constant discharge current is 5.7A at 15C rating. The constant charge current is 0.76A at 2C rating.

The DJI Phantom Aerial UAv Drone Quadcopter replacement. it is a 2200 mAh LiPo battery.

If you are looking for a 11.1 lipo battery, check out the Floureon 11.1V 2200 mAH Li-Polymer RC battery pack with XT60 Plug
Connector. It is compatible with DJI Phantom, Walkera E22. The 3S cells with a voltage of 11.1V have a discharge rating of 25C.  The dimensions are 108x28x25 mm.

BTG 3.7V 250 mAh battery charger is compatible for charging JJRC H20, Syma X11, X11C, Hubsan X4 and Ladybird Quadcopter. It is another popular product among quadcopter enthusiasts.

Important notes

It is absolutely essential to use the right charger for charging your quadcopter battery as you need to maintain the charge current that is specified with the battery. You also need to follow the recommendations with regard to charging the battery after a flight by giving it the required time to cool down. The same goes with regard to using different sources for charging the battery.  Batteries can get heated and even catch fire if you have not followed the recommendations. Hence, it is always prudent to not leave your battery to charge and get on with another task without keeping the battery under your observation at all times as it gets charged.

With regard to the time taken for the charger to be recharged and whether you need to recharge even when it has not been fully recharged, there are a lot of inputs that you can pick up from the community of other flyers. However, you should never take risky recommendations such as shortcuts for increasing the time taken to charge. Actually, it is always a safe tip to not go for the highest rate of charging but to keep it at a slow pace. In fact, it might also be better at times to not fully charge the battery but to keep a buffer. This will contribute to longer life of the battery. The battery will last anywhere from 100 to 200 cycles of charge and discharge while some may even go up to 500. Of course, you should never overcharge your battery as well. The same applies to over discharge. As a result, you might need to pick up a battery that serves your purpose perfectly rather than making a battery that is not up to the mark to go that extra bit. If you do so, you will surely be left with a situation of needing to buy a new battery.