question about load and ease of spin

[GreenTeam]

Can anyone please break it down for me as to why an alternator that is cored, gets harder to spin as the more power its producing?
My partner was quite shocked and at a loss for words when a hoverboard motor was super easy to spin by hand and putting out about 8-12V@1-2 AMPS.
And, to show my other half why I am researching coreless designs for building, I swapped my multimeter connect to the 10A hookup.
Took a deep breath and SPUN SPUN like hell lol.....
So, can I have an explanation as to why the motor was near impssoble to spin while on the 10A circuit? Like, it was HARD to spin, before it was even spinning lol.....

[Adriaan Kragten]

I think that when your meter is set in the 10 A position, it is meant to measure a current of maximum 10 A. So now your meter is becoming a short-circuit and the torque for short-circuit is rising strongly at increasing rotational speed. If the generator is loaded by a certain resistor, there is a voltage drop over the resistor and a much lower current. As the torque is about proportional to the current, you will find a much lower torque for this condition than for short-circuit.

[bigrockcandymountain]

Yep, multimeter is a short when set to 10a.

  I went to test for voltage on a 240v circuit with my meter lead plugged in the 10a plug one time.  It blew about 1/2" off the test lead in a really bright fireball. 

[Scruff]

It doesn't have to produce a voltage until it exceeds the battery voltage. After that it is working. The resistance is the power being produced + losses.

Whilst under the battery voltage it cannot produce current to the battery as the higher battery voltage opposes it. It is simply idling while climbing Voc. MPPT uses a very similar principle.

hp = kW + system inefficiency.
note zero kw until battery voltage is exceeded.

If you swap the battery for a resistor the torque would be linear.