
Sep 14, 2012, 02:51 AM  

New Product
RC Electric Calculator App for Android
RC Electric Calculator App for Android:
RC Ecalc Pro  $1.99 It's basically an 8in1 calculator for electric powered model airplanes, helicopters, multicopters, cars, trucks and buggy's, if fact anything that uses rechargeable* batteries. (*As long as the voltage is known then any rechargeable battery including LiPo, LiFe, NiCd and NiMh batteries can be used for some calculations). US imperial units and metric units are catered for! One of the units used for the calculations in the app is the mAh (millamphours). All batteries have a mAh or Ah rating, this is the capacity of the battery or how much energy is stored. After you've recharged the battery your digital charger will show you how many mAh has been put back into the pack i.e. how much was used. This number is used to calculate a number of things in the app, like expected flight time using 80% of the pack or the average current used during the flight or run. If you know the current draw of your system additional calculations can be made. In the calculator all the calculations are made "onthefly" so no buttons need to be tapped, just input your values and the calculations will be made when enough data is available. The images should explain how it all works but feel free to ask any questions. etc Use RC ECalc Pro to calculate the following:  Average Current Used by the aircraft during a flight/run.  Average Discharge Rate (Crate) of the LiPo battery during a flight.  Expected Flight Time using 100% capacity of a battery.  Expected Flight Time using 80% capacity of a battery.  Realistic Flight Time using 80% capacity of a battery and 70% average throttle.  Power in Watts from Volts & Amps.  Volts from Power & Amps.  Current in Amps from Power & Volts.  Static thrust of a propeller in pounds or kilograms.  Power to Weight Ratio in Wattsperpound or Wattsper100gram. Examples: a) Fly (or drive) for 11 minutes and 20 seconds, then recharge your 2200mAh LiPo, when finished your charger states that 1720mAh was returned to the battery. This app will then calculate that the average current draw for the flight was 9.11 amps, the discharge rate was 4.1C and you used 78% of the rated capacity of the battery. (Img #1) b) How long can you fly your plane safely? It is recommended to fly using only 80% of the capacity of LiPo batteries to maximize their longevity so using the 9.11A average from the example above, the full throttle current draw (you will need to measure this) is 16A, input 2200mAh and 16A into the app and it'll calculate that you should be able to fly (at FULL throttle) for 6 minutes 36 seconds until the battery is 80% depleted or for 8 minutes 15 seconds (also at FULL throttle) until it is 100% depleted. (Img #2) A "Realistic" flight time for a plane is also calculated which works out to be 11 minutes and 47 seconds using 80% capacity and 70% average throttle, very close to the actual flight time in the first example. For helicopters and multicopters the flight time is very dependant on what style of flight, but you can use the calculator to calculate the expected flight time in a hover. Future plans: Add wing loading, cubic wing loading calculator, + suggestions? Disclaimer: The formulas used in these calculations come from various internet sources, with some variations added from my own experience. Your results may vary! While a lot of effort was put into ensuring accuracy, this app is not intended to be professionally accurate. Comments & suggestions very welcome. thanks, Graham 

Jan 02, 2013, 11:45 AM  

I think adding something like an ecalc to help a modeler with picking a motor would be cool. Enter in the desired kV, prop, battery size, etc. to see what performance would be.
Do you have a "try before you buy" such as a limitedfunctionality version? 
Latest blog entry: Thank you, veterans


Jan 02, 2013, 12:17 PM  

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Motor performance is very complicated, it needs a whole program to calculate results, I use MotoCalc for that (www.motocalc.com) 

Jan 02, 2013, 12:30 PM  

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There's me  the biggest scrooge of all ... I love frrebies .. but $2 is not much is it really !! How much time did you spend writing the app ? I agree about motor calcs  I gave up with online and usual motor calculators  fine for everyday sport .. but for me pushing limits  they didn't really work .. too many other factors coming in as speeds and limits went up ... I found real world got further and further away from calculated results ... such that I wrote my own excel sheet in the end. Which I have to say  unless you are flying same model and combo's as I that it was compiled for  is not much use to another. To prove a point ... I'll bag a copy for $2 shortly.... Nigel 

Jan 02, 2013, 12:44 PM  

I spent more time than I should've doing the app, should've been flying rather .
I originally designed it for myself to calculate a few things at the field while chatting about flight times, planes and performance. Most of my flying buddies didn't know how much Ah they put back into their batteries, let alone how much current they were drawing in flight or how long they could safely fly on a pack. Now anyone can work those out just by timing their flight and watching how much they 'put' back into the battery. Yup, the calc programs can only take one so far and most of the time only give a ballpark figure, which is about all one can expect given the variations that occur. My aim is to just take some of the guesswork out of flying performance. 
Jan 02, 2013, 12:57 PM  

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There's $1.99 on it's way ... app installing now. Happy New Year Nigel 

Jan 02, 2013, 01:36 PM  

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Understood about the motor calculation. Thanks for the reply! 

Latest blog entry: Thank you, veterans


Jan 02, 2013, 01:46 PM  
Joined Dec 2008
475 Posts

pardus,
I found an error on your Power Calculations Screen. You have Volts/Watts = Amps which is wrong. This should be Watts/Volts=Amps just like Watts/Amps=Volts. V x A = W W / A = V W / V = A You have the correct answer, just the wrong equation. Ampmaker 

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