Batteries

[FlightChief]

Hello, Just trying to get a better handle on batteries. What I'm a bit dim on is the difference in the numbers and what sizes I can go to. For instance, I'm looking to buy a battery or two for my Flyzone Calypso.
Flyzone Calypso uses a Tigre connector so I was looking at the adapter. The Calypso comes with a 1330 mAH 15c 11.1v. I'm studying up on the Lipo batteries and trying to figure what changes I can make with batteries, difference in discharge rates , capacity etc. Can anyone suggest a battery from the Motion RC selection that they had success with?
Any help is appreciated. Thanks

[Guest]

Re: Batteries

Welcome to the MotionRC Forum, FlightChief!

Enter the SKU "EPR13003" in the Store's search field to take you to our 11.1v 3s 1300mah 25c lipo. It is perfect for that airplane of yours and will give you a bit more "punch" without unnecessary added weight or cost.

Your larger question cannot be answered comprehensively without a long explanation, but I'll try to generalize:

Battery capacity and discharge ratings are part of your power system (motor/esc/battery/prop) that benefit from optimizing the balance between several factors. Be mindful that the point in all these separate systems is that they operate in a RELATIONSHIP. So understanding each aspect is important, but ultimately it is understanding their intertwined relationship that will really unlock the details of power system optimization. By that I mean giving the most power, for the longest time, for the lightest weight, flying the intended performance envelope, for the lower cost and the longest life cycle. These considerations vary whether you're flying a foamy glider, or a warbird, or a hotliner, or a turbine jet.

So, to your question about battery's capacity and discharge rating.

Think of a battery as a gas tank. The size of the tank is analogous to the "mAh" rating of a battery. This is how much gas, or in the battery's case, electrical energy, is stored inside the tank. The larger the mah rating = the larger the tank = more energy, but also = more weight. For any given aircraft, there is a balance between weight and battery capacity. Too heavy/high capacity a battery, and you'll be at full throttle the whole time just to stay aloft, and an overburdened aircraft with high wingloading will fly like a brick. Conversely, too light a battery/low capacity a battery, and your flight times will be very short.

In this "tank" analogy, the discharge rating would be the size of the hole in the tank which leads to your engine (your ESC and motor/prop). The larger the hole, the more gas ("energy") can potentially flow to the motor at an any given time, if you needed it to. So the higher a discharge rating, the more Amperage it can supply to the motor without getting overburdened. Too large a motor/prop, continuing to pull more gas through the pipe/hole than can fit, will cause the tank to begin to break down. We see this in batteries as "puffing", which is a visual sign that the gas tank and it's hole/pipe was/is breaking down.

Discharge ratings are given in "C", and multiplying that number by the capacity of your battery gives a theoretical ceiling of amperage tolerance. So, for example, your battery is 1300mAh, or 1.3Ah. The C rating is 15c. Multiplying 1.3 by 15 = 19.5. So the maximum Amps you'd want to pull through that battery comfortably is around 19.5 Amps. MotionRC sells, for example, a 1300mAh 25c battery, which equals ~32.5 Amps. That's quite a bit more! And the thing to notice is, let's say your motor/prop/esc combo pulls 15 amps, tops. So one might be tempted to observe, "well, both batteries can provide more than 15 amps at full throttle, so they're just as good as each other, right?" To which I would respond, no, because consider that, at 15amps, the first battery (15c) is nearing 80% of its maximum output --it's running fairly quickly. But the second battery (25c) is operating at less than 50% its maximum --it's barely jogging.

All this means that, generally, the higher the discharge rating (given in "C") in a battery, the better, because this means your battery can handle more amperage/current flowing through it. However,
as with the tank, bigger isn't always better: If your battery has too high a C rating (meaning its pipe from the gas tank to the esc/motor is too large), than the ESC can get doused/overflowed with too much energy at once. This is seen as an increase in amperage. Increasing the Voltage of a battery using the same size prop will definitely increase the amperage in your system, which may overload the ESC. So, a balance once again must be struck.

So to summarize, as I stated in the beginning well designed RC power systems strike a purposeful balance between these and many other factors to provide the best performance envelope for a given aircraft. Good manufacturers will pay attention to packaging or at least recommending a motor which spins a certain prop a certain speed which draws a certain max of Current from a certain sized ESC capable of handling that current, powered by a battery (tank) with a large enough hole/pipe to provide that Current while still allowing reasonable flight times on an unburdened aircraft throughout its intended flight envelope.

My short answer to you is: For your particular model, just buy a 25-35c 1300mah lipo and you'll be happy without breaking the bank and won't have to change any components or even adjust your CG more than a tiny amount.

One final note:

There are MANY more details behind what I've written, but as an oversimplification, I hope it makes at least basic sense, and encourages you to read more on the topic. Other related topics would include a battery's Internal Resistance, Burst Ratings, and The Reliability of Manufacturer's Published Discharge Ratings (i.e. are they real figures, or just artificially inflated? Which brands' discharge figures are the most consistently accurate?). I believe MotionRC's batteries are a "great value", which I define as having reasonably low internal resistance, an ACCURATE published C rating, and all at a good cost and convenient availability.



'Hope this was helpful,
Alpha
MotionRC

[FlightChief]

Re: Batteries

Thanks for the Welcome. And thanks for an even better description and explanation on batteries.
Been reading alot on LIpo batteries and this will help. I''ll prbly take you up on the battery suggestion.

Thanks again.