Quote:
Originally Posted by MaciekA
Wow, crazy. The exponential rise in temperature is really interesting, kind of like a vicious cycle. In a sufficiently-large R/C car I could imagine there being a few options for introducing a cooling system. I can't quite imagine what we would need to cool an airsoft motor in-situ. A grip designed hand-in-hand with a motor housing, with the housing having a dense array of fins. The question becomes.. where to dump that heat?
I have noticed fairly huge differences in heat output from different neo motors which pretty much have the same magnetic stickiness and torque when tested "in the lab". My JG Blue hardly produces any heat at all, while at the same time the SHS High Torque seems to get fairly warm -- but only the long version, where as the short version doesn't produce much heat.
I've gotten the impression, but haven't been able to solidly verify, that some motors seem to produce less heat if they've powered by a larger battery with a higher C value. I'd love to hear someone explain why the heck that would happen.
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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.