This is probably should not be a linear relationship, but the battery weight falls within this range so it’s close enough for me. The good thing about Excel is, it provides an equation from a few dots on the graph. I got that from my charger, when I charge it fully at 4.2V per cell, I know what capacity was used in the previous flight. I then work out “mah / second”, which is the speed of power consumption, and we can draw a graph from this. The column “Actual Capacity Used” is not really needed, but I collect it just to make sure my data is valid. I always land the tricopter when the voltage alarm beeps, which is when the voltage reaches 3.5V per cell. This is the data I collected from 6 test flights. In my example, I used a 2200mah 4S Lipo Battery as a reference, and tested the flight times under different load weight (0g, 110g, 220g, 340g, 405g, 515g – all these weights are physical items I can find in the house that’s why the uneven numbers). You can of course collect some other data as well to help you identify what is the max load your multicopter can take, for example, the throttle value, current etc. Basically the data we need is flight times under different loads. Of course, this is only an estimation, but it does give you an rough idea what battery to go for, and save you from spending too much money and time to try each type.įirst of all, you need to get one battery first, and collect data using it. All you need to do is to put in the data of that battery in the excel spreadsheet. By using this model, you will be able to calculate the flight time of any battery. Build Mathematical Model to Estimate Flight Time To do that, we need to create a mathematical model. These graphs tell you some insights into which battery has the highest price/performance ratio, but it doesn’t tell you whether this is the best battery for your RC aircraft, quadcopter or tricopter. Also 4000mah might be a good choice too due to its outstanding value. Value, which is capacity per dollar (= capacity / price)įrom the above graphs, if I am only going for best performance and not worry about the price, I would definitely go for 2650mah, 3000mah, or 3300mah.Density, which is capacity per gram (= capacity / weight), and.Listing batteries and dataįrom these data, you can create some very interesting and useful graphs, for example I usually do My tricopter has a max current draw of around 30A – 35A, and all of the batteries below meet the requirement. I usually just look at the motor datasheet, which should tell you what the current draw is at 100% throttle, times number of motors, and add some margin for other electrical parts, and you have the possible max current draw from your quadcopter. Max current supplied by the battery can be calculated by this formula: max current = capacity * C-ratingįirst, work out what would be the possible max current draw from your motors. It’s important to note, that the batteries you listed can supply enough current for the motors. For example I was looking for 4S lipo battery for my tricopter and here is the table I created. You can include their weight, price, etc in your table. List All Batteries and Create Graphsįirst, list all the batteries with different capacities, brands of the same cell number. Talking about Batteries, here is a tutorial on how to do LiPo parallel charging. This technique should be useable for any multicopters, including the 250 mini quad. I recently bought some 4S batteries for my FPV tricopter, I will use this as an example. There are techniques you can use to help with this selection task – creating graphs and mathematical model in Excel, which I found really useful when comparing various products of the same kind. The trade off between flight time and battery capacity, makes it more difficult to choose which battery should be used, rather than just “pick the largest battery available”. Apart from capacity, there is also C-rating you need to consider, which I shall explain later. But some people prefer the stability it brings with heavier weight, some would call it “flies like a tank” :). Also note that the heavier your copter gets, the less agile it will be. This is mainly caused by the weight of the battery. Eventually it will reach a point where it just doesn’t gain any more flight time with bigger battery (even lose flight time). Before we begin, make sure to read the basics of LiPo battery for drones.Īs the battery gets larger, the increase in flight time becomes ineffective.
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