mah fuel gauge

just started getting hardware programming little green. been long time web programmer have little
understanding of programming.

i got ardiuno uno start messing device programming.
i'm looking create mah fuel gauge.

here why want this.
i fly remote control helicopters fueled lithium ion batterys.
lithium ion batterys not discharged on 80% of capacity.

i fly timer on transmitter. fly 5 min , land.

if practice autorotations or stationary hovering piros discharge 50% of lithium
ion battery. if fly hard , heavy on controls go on 80% on capacity in 5 min.

so thought nice keep track of milliamps consume durring flight.

my larger helicopters can peaks of 100 amps while smaller 1 peaks of 50 or 60 amps.

i start project on smaller one.

it takes 1350 mah 25 volt lithium ion (lipo).

once 1080 mah used lipo have land.

i thinking use acs715 ardiuno uno testing @ first.

i hardware portion of , have seen several examples on internet.

but i'm trying head around calculations in code.

to amp reading shunt think this,

sensorvalue = analogread(analoginpin); 
outputvalue = ( ((long)sensorvalue * 5000 / 1024) - 500 ) * 1000 / 133;

133 sensors mv per amp of current.

so "outputvalue" milliamp reading @ 1 instance.

so if in loop , take reading every (10 ms) , add amp readings
i should total milliamps used?

i feel missing here.

i think need take milliamp readings , compare them total time milliamps used in flight.

of course next step getting data aircraft operator later.

thanks in advance

mike

if consuming (say) 500ma , 600ma later (10ms later) perhaps assume average 550ma 10ms or 550ma * 0.01 seconds = 5.5mas (and divide 60 minutes , 60 hours).

you need careful because discharging @ higher currents harder on battery. or put way 100mah @ current of 1 amp different 100mah @ current of 50amps.

i wonder if useful, , lot easier, monitor battery voltage. , conscious shunt impact performance of motors. , not easy measure tiny voltage drop across low ohm shunt.

...r

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