If im running 4 motors that on their own they draw about 25-30A does that mean that i need a battery that has a maximum draw (mAh capacity * discharge rate) higher than 120A (30+30+30+30=120)?For the longest time i thought this to be the case, but i just realized it might not.
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@chris: Our standrd Arducopter kits draw way less than 25 amps a motor so almost any reasonably sized hobby battery will do for us as you say. Im guessing that Alan has a heavy lift or something else to use such thirsty motors that may need a bit more!!!
It is correct to add the current draws yes (assuming the motors are in parallel and I've never seen otherwise in RC). This means you have a theoretical current draw of around 120Amp.
Now the Lipo, which has a C rating (such as 20) which is how many times its capacity you can safely draw at once. So a 5000ma battery (which is 5 amps, 1000mah = 1Amp) X 20 = 100 Amps maximum draw. You may not be able to draw this for long, that depends on the maufacturer. They report C ratings differently.
The C rating is a rough guide to the cell quality/technology (rough!). A lower C rating (say a 5000Mah battery with a 10C ratin) would mean you could only draw 50Amps peak.
RE your last question. You are bang on the money! A 2000 30C battery can supply a maximum of 60Amps, the 5000mah will. This is assuming that your motors are actually drawing the current you state, and that isn't a theoretical maximum that will never be hit.
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@chris: Our standrd Arducopter kits draw way less than 25 amps a motor so almost any reasonably sized hobby battery will do for us as you say. Im guessing that Alan has a heavy lift or something else to use such thirsty motors that may need a bit more!!!
OK,
It is correct to add the current draws yes (assuming the motors are in parallel and I've never seen otherwise in RC). This means you have a theoretical current draw of around 120Amp.
Now the Lipo, which has a C rating (such as 20) which is how many times its capacity you can safely draw at once. So a 5000ma battery (which is 5 amps, 1000mah = 1Amp) X 20 = 100 Amps maximum draw. You may not be able to draw this for long, that depends on the maufacturer. They report C ratings differently.
The C rating is a rough guide to the cell quality/technology (rough!). A lower C rating (say a 5000Mah battery with a 10C ratin) would mean you could only draw 50Amps peak.
RE your last question. You are bang on the money! A 2000 30C battery can supply a maximum of 60Amps, the 5000mah will. This is assuming that your motors are actually drawing the current you state, and that isn't a theoretical maximum that will never be hit.
Hope that helps!
D