Quote:
Originally Posted by Kos-Mos
Physics 101...
Electro-magnet coils produce a magnetic field proportional to the CURRENT flowing through and the number of turns. (Higher number of turns = higher resistance = lower current).
Current is measured instantly. That is why batteries are rated in mAh or milliamps-hours, the the amount of current that can be sustained for 1h before the pack is empty.
The rate (or C) of a battery is the maximum current it can give. For example, a 1400mAh NiMh 2/3A battery (mini packs) can deliver around 10C, so roughly 14A at MAX.
A better battery for example a 4500mAh NiMh Sub-C (large packs) can deliver around 10C also (limited by the chemistry), roughly 45A at MAX.
Given both packs are 8.4v, the same mechbox and motor, the magnetic field of the motor running on the larger pack will be more than 4 times stronger. That directly results in more TORQUE.
The problem when a motor struggle to accelerate is that it will ask for that MAX current for a longer period of time. The curve of required current vs. speed is logarithmic (starts at +infinity, dropping VERY fast to almost nothing), so if you prevent the motor from accelerating by starving it, it will generate more heat for a longer period (we talk milliseconds, but the "cycle" only lasts a few hundread milliseconds anyways).
So the larger the battery, the better. Contrary to what youtube seems to say, running your AEG on a car battery won't break it any faster than running it on a 11.1v LiPo. In fact, the car battery will put a lot less stress on your motor.
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Thanks for the awesome explanation. This backs up many observations I've made over the last year but couldn't explain with my weak knowledge of the physics involved.
For what it's worth, I've got a ZIPPY brand battery coming in from Hobby King this week that's 7.4V, 6000mAh and 35C. Should push everything in my stable pretty effortlessly, though it's fairly certain none of my motors will be asking for anything close to 210A
