Why Regenerative Charging is Best Done Slow
See also Kite Car
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AWES Hackerspace: Why Regenerative Charging is Best Done Slow
Tomorrow kPower gets a used electric skateboard to test as kite regen vehicle. What can be expected? Its going to take time to fully charge the battery; a few hours, no matter how much kite power is available. Its more a function of inherent battery limitation than what the generator could do a max RPM with min torque, which is ideal groundgen performance. So I should hope to travel around 20kmhr for hours and arrive well charged, but not be able to fast charge.
Given hill-climbing as the max discharge mode, 25% recovery of battery energy, or more, the higher RPM but lower torque at which the energy is regenerated, as the linked video nicely reveals. The trick is not to stall the generator too much, or the ESC just dumps more energy into heating the gen coils rather than putting more in the batteries. Its also true that stalling the motor by reducing internal circuit resistance wastes energy in extra motor heating.
Why do batteries charge slower than they discharge? Physics Stack Exchange- "This is done by design, this type of battery (LiPo) is designed to have a low internal resistance in order to be efficient when driving high current loads. But it usually can't charge as fast without reducing the battery life because the electrolysis effects will decompose some molecules in the electrolyte and usually release a gas hydrogen, CO2 or other, which can't be recovered."
Will report soon how the kPower electric kiteboard goes.