Lipo run time.

[arrowskartax9]

Can anyone please advise me of the following.
I have a 31" mono with an astro flight 207d speed control that doesnt have low voltage cut off. The engine is a fdm cordite ss1 and i have twin 5000mah lipo batteries in series giving me 14.8 volts spinning a x440 octura prop all set up by Fine Design Marine. The question is, what would be the approximate run time with out running the batteries deadflat with the above setup?
Thanks, Chris.

[ozzie-crawl]

others may have better ways but what i do is run for exactly 60 seconds
then recharge the batteries and see how many mah were drawn.
just to keep it basic you dont want to use more than 80% of your capacity,in your case 4000mah.
if you say use 1000mah you know you have around 4 min run time.there is a calculator here that makes it easy,you can convert your mah used into average amp draw then into run time.
or you can buy a lipo shield that will work as a lvc for your esc.
here is the link for the calc,
http://www.offshoreelectrics.com/conversion.htm

[ReddyWatts]

Hope this helps.

FORMULAS


To calculate run times

Battery Mah rating (times) 0.06 (divided by) motor load in amps = run time

Example: 3300 MAH (X) .06 (divided by) 35amps = 5.65 minutes of run time

To calculate your average amps

Battery Mah rating (times) 0.06 (divided by) run time = average motor load in amps

Example: 3300 Mah rating (times) 0.06 (divided by) 5.0 minutes = 39.6 amps

To calculate your geared RPM.

Motor shaft teeth (divided by) prop shaft teeth = multiplier.

12 motor shaft teeth (divided by) 24 prop shaft teeth = .5 multiplier

Motor RPM (times) .5 multiplier = geared prop RPM

To calculate your gear ratio.

prop shaft teeth count (divided) by motor shaft teeth count = gear ratio.

24 prop shaft teeth (divided by) 12 motor shaft teeth = 2/1 gear ratio

Meaning your motor turns (2) revolutions for each prop (1) revolution.

To calculate motor horse power

amps (X) volts (X) efficiency (divided by) 746 = horsepower.

Example: A 540 10XL was using 65 amps X 21.6 volts X .91 eff. / 746 = 1.7hp

[ozzie-crawl]

thats the formulas i was thinking but keep forgetting, thanks reddy
was going to suggest they be moved to here,looks like the mods are on the ball

[arrowskartax9]

Thanks for replying guys i will work on your info.