do not "measure the current of the battery"
it will be several hundred amps and will blow your multi meter.
V = IR
measure voltage and resistance, that will give you current.
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Mechanical engineers build weapons, civil engineers build targets

measuring the resistance of the battery is also a bad idea. I did that once and blew a resister in my multimeter (back in the day there was no protection). Still seems to work fine with the charcoal in there
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They say that he crossed the fine line, from insanity to genius.

Hmm that would explain why my lsat ones terminals(prog thingies) well just melted of the plastic setion and the screen went black
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A journey of a million miles begins with a single step followed by a hell of a lot of other steps so get walking

yey time for me to ask more electrical questions

why do people say when you double the volts you 4 times the power out put of the motor?? does p = I V?? so doubleing volts would double out put not 4 times??

also to run a 400 watt drain for 1 hour at 12 volts you need 2000 amps right??
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A journey of a million miles begins with a single step followed by a hell of a lot of other steps so get walking

V= IR

therefore I = V/R

and P=VI

substituting the above for I

P=V ( V/R)

-> P= V*V/R

so a double of the voltage for the same resistance is P = 2*2/R =4

which is 4 times the power compared to the original voltage.

Your second question is a bit ambiguous. To run the 400W load for 1 second will require I=P/V = 33.3A . Now to run the same load for an hour will require 33.3A delivered every second for an hour. This will require at minimum a 33.3Ah battery at C1 ratings. If you want to know the total amps consumed, then it's 33.3Amps/second * 3600 seconds/hour = 120000Amps delivered every hour.
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They say that he crossed the fine line, from insanity to genius.

thanks for that i had the right idea but was applying it wrongly
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A journey of a million miles begins with a single step followed by a hell of a lot of other steps so get walking

Ummm i don't get those figures at all?

a 400 watt load at 12 volts = 400 watts(watts equals watt hours) divided by 12volts equals 33.333333333 amps so thats 33.333333333 amps for one hour

where do you get 20,000 amps from? to run a 400 watt load at 12 volts for one second uses .555555556 amps so thats about half an amp a second not 33.3333333amps a second unless i missed something and you meant a 400 amp load which is 4800 watts at 12 volts but would only need to suply 400 amps at 12 volts for one hour .

Last edited by Totaly_Recycled on Fri May 30, 2008 10:50 pm; edited 1 time in total

Ummm, no one said 20,000... I said 120 000 Amps, and cerberus said 2 000.

The only reason I pointed my funny answer out was that 120 000 Amps for 1 second at 12V is the same amount of power as for 33.3A at 12V for an hour. I was trying to work out where the 2 000 came from.
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They say that he crossed the fine line, from insanity to genius.

sorry meant 120000 just typeo'd and missed the 1 on the front lol

Why are you getting 0.55A from?

Power is in Joules/second, Amps are in Coulombs/second and Volts are in Joules/Coulomb.

Watt hours doesn't equal watts, watt hours is a measure of energy, while watts is a measure of power.
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They say that he crossed the fine line, from insanity to genius.

Mike is right the amps is 33.3Amps which is coulombs per second.
watts (the unit of power) is joules/second
Watt hour is joules/ Second *3600
as there are 3600 seconds in an hour. my brain is 2 dead to test mikes acual canculations but the logic sounds about right 2 me.

quote:

---

Originally posted by cerberus3112:
also to run a 400 watt drain for 1 hour at 12 volts

---

thanks for all the info. I went back and re read my post and started laughing i don't even know how i got those numbers thanks for that.ill be a bit more careful next time i do calculations.

i have no idea why I as trying to find out how many amps were used each second or even how many amps over the hour were used each second .... I blame bad thinking XD .(and a mix up with power and time)
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A journey of a million miles begins with a single step followed by a hell of a lot of other steps so get walking

I think Totaly_Recycled was pointing out where you said 120000 Amps every hour rather than using the units A/hr or W/hr.

"If you want to know the total amps consumed, then it's 33.3Amps/second * 3600 seconds/hour = 120000Amps delivered every hour."

If he is drawing 33.3A then he would need a 33.3A/hr battery. That would equal 400W/hr or 1440kJ of energy per hour.
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needing some electronic help of my own,

tinkering with my brushless setups and both appear to have changable "govenor mode" settings. i tried it on my big inrunner and the only difference it seems to make is that it is less sensitive around the deadband when on?

any idea what a govenor mode does? does it just compensate for motor speed or something to that nature?
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