Batteries
Battery is incredibly important to know the ins and outs of. It is the one thing that can ruin your drone and everything around it (your house). Battery is something we need to take serious or the consequences can be detrimental. In this article you will learn what you need to look for when buying consumer grade LiPO batteries, storage and charging procedures, and overall battery knowledge so you don’t burn your house down. Drones are one thing but the safety of everyone you live with is another. We will be talking about mostly LiPO batteries in this article (which is the most popular used battery for FPV drones).
Cells (S)
Each battery consist of cells. The more cells in a battery means the more voltage power it can output. The voltage direct impacts how many RPM the motors of the quad spin. RPM can be calculated by multiplying the voltage to the KV of the motors. Quads usually fly from between 1 cell (1S) to 6 cell (6S); 4 cell (4S) being the standard for 5 inch quads. Cells that go higher than 6 do exist and are usually found in electric skateboards or bikes. Each cell in a battery is 3.7v (storage/empty) and 4.2v (charged). In a 4S battery that means you will have a total 16.8v (charged 4.2 X 4 cells = 16.8) and 14.8v (empty).
mAh
mAh refers to the capacity of the battery. Essentially the higher the mAh the longer the flight times because of the higher capacity, but be aware there is a point of diminishing return. The higher the capacity the bigger and heavier the battery is. A typical 5" quad usually uses a 1000mAh - 1500mAh battery. Flight time will depend on your motor kv but expect anywhere from 2 minutes - 5 minutes. Another factor for flight time is dictated by how you fly. Racers can fly the same battery but half the flight time as someone who is cruising.
C-Rating
C-Rating is a unit of measurement for the discharge rate of the battery. The higher the C-Rating, the more current can be discharged resulting in more power/thrust. This also dictates how “sluggish” your quad can feel, so it’s important to understand the math behind C-Rating and pick appropriate batteries for your setup. More importantly figuring out if your ESC has a high enough amperage to take the battery discharge. To do that you will need to use the formula …
Maximum Safe Current Draw (mA) = Battery Capacity (mAh) * C-RatingExample would be 1300mAh 100C battery would have a current draw of 130A or 130000mAh (calculated using the formula). 130A will be divided by 4 ESC’s (cause all quads have 4 ESCs) which leaves you with 32.5A. This means any ESC over 35A will be capable of running the that battery. It is very important you calculate this to make sure your ESCs are compatible with the batteries before you buy them.
Don’t expect to just plug the battery in like your phone and come back 30 minutes later to a fully charged battery. If you do that, your battery will be a ball of fire when you come back. Charging LiPo batteries is an art in itself. It’s simple and safe if you follow all the correct steps. First, let's talk about charging batteries without a parallel board. This is when you charge one battery at a time which most of you will do to start. First and foremost with every single LiPo battery more than 1 cell, it always has to be BALANCED CHARGED. This means it will charge each cell equally till it reaches max capacity compared to charging one cell full at a time. Next is amperage. Every battery has a max amperage out and a max amperage in. For example if you have a small water bottle and you wanted to refill it, you can’t just dump a bucket of water on it and expect it to be filled. You will need to slowly empty the bucket into the tiny mouth hole of the bottle. Same with LiPo batteries. As a rule of thumb the max amperage you should charge your battery is the mAh divided by 1000. If you have a 1500mAh battery, the max rate you should charge is at 1.5A. However, the safe and better option to increase the longevity of the battery is charging significantly lower (given you got the time). Again if I had a 1500mAh battery I would charge it at 1A or 0.5A.
Charging with a parallel board is a whole new ball game. It is when you want to charge multiple batteries at the same time. Before charging all the batteries, we need to make sure they are all the same voltage or else you cannot charge without blowing something up. A cool way to make them all match each other's voltage is plugging in all the batteries (both XT60 and balance leads) you want to charge into a parallel board. Leave it for 10-20 minutes and then proceed to check their voltage with the cell checker. They should all be the same and now you can charge. What amperage should you charge at? Rule of thumb, if you have 4 x 1500mAh batteries you would charge them at a max amperage of 6A. I would suggest charging any amount lower than max to maintain the health and longevity of the battery.
Charging
Li-Ion
Lithium Ion batteries are a different breed of batteries. These are built for endurance and commonly found in house hold items. However, there are limitations with using Lithium Ion batteries. Their discharge rate is much lower than a LiPo and can break if you decide to draw too much amperage. Typically Li-Ion batteries sit around 30A discharge rate which is significantly lower than LiPo. Li Ions are perfect for endurance type flight such as long-range and mountain cruising. Just don’t get too carried away and start diving everything.