Quote:
Originally Posted by jhautz
This is cool Brian. I always wanted to do this test myself but never really had a good enough multimeter to do it. Especially after a little experiment I did myself a couple weeks ago. I have actually been meaning to start a thread on this very topic. I have heard for a long time that they did have regenerative braking in just about all ESCs but never saw any proof of the fact.
I'm hopeing someone can answer why it is that I see 10-15% better milage when I run mechanical brakes? This is on the same truck on the same day on the same track with the same setup and batteries. I did some testing the last time I went out for a practice day and wanted to see what effect the mechanical vs motor brakes had on run time. I ran 2 5 minute runs with the mechanical brakes on 2 different packs, and then took the mechanical brake off, and charged the packs back up recording the amount of energy I put back in each one. Then ran two 5 minute runs with the mechanical brakes taken off and used motor brakes. I tried to drive just as hard with both brake setups and ran 2 trials on each just to add a little extra data.
But for sure, both runs with the motor brakes used more mah from the packs than the runs with the mechanical brakes did.
A day or 2 after I actually did this I realized I could have used my eagle tree to get better data. Next time I will do it that way.
I just dont get it, the evidence would support the opposite effect being true. Longer run time with motor brakes. 
Wondering if anyone has any thoughts? |
The motor is still using power to stop. In other words, ESC braking is not free. The 'regenerative' part is that it can recapture small (if not tiny) amounts of power in between the pulses while the braking power is applied. After all, a force is essentially being applied in the opposite direction to bring the car to a stop, just as it would if it was starting from a standstill. This is also why motor brake setups run hotter since the motor is working in both directions. Also, braking force is usually applied more abruptly than while accelerating. AFAIK, a single mechanism (the motor) can't function as a generator and a source of power at the same time. You must use power to brake the car. I'm not an electrical engineer, but I know a few things about physics and the forces that are present and being applied in this scenario simply can't be ignored.
Please correct me if I'm wrong here because our results coincide with jhautz and others that have found mechanical brakes to be more efficient. I'm not arguing that some energy isn't being harnessed or regenerated while braking, I'm saying that it does in fact use power to brake and that the overall net of the system is negative, not positive. Mechanical brakes are obviously using power as well (servo), but compare a servo's energy requirements to a 1/8th brushless motor's requirements and I think the picture becomes clearer.
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