Regenerative braking limits

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GaryB
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Last seen: 6 years 3 months ago
Joined: Saturday, December 18, 2010 - 15:17
Points: 21
Regenerative braking limits

If a forum already exists for this, please let me know. Don't mean to repeat questions or concerns.
Concern: a brushless, permanent magnet wheel (hub) motor attached to free wheel rear axle.
Battery fully charged to begin with.
From the top of a long hill (mountain like peak), the car goes downhill by gravity WITH THE THROTTLE AT ZERO
ACCELERATION and reaches a speed (say) of 70 mph. -
The motor, then, is acting like a generator (for example, as in regenerative braking). -
BUT the batteries are FULL already. They will not accept any more current charge.
The motor (generator) will still be generating considerable voltage (EMF) due to the relative
motion of the coils and the permanent magnet. They are permanently attached between the turning wheels and
the axle with no clutch, etc. -
How would a "controller" handle this excessive voltage (emf) that is generated? -
Would the voltage build up enough to cause arcing in the motor or breakdown of the
insulation on the wires? - Would the motor "burn up" under these conditions.
Am i really stupid and missing something here? -

Thanks,
Gary B

colin9876
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Last seen: 7 years 1 month ago
Joined: Thursday, October 23, 2008 - 11:37
Points: 289
Re: Regenerative braking limits

It really just doesnt happen.
In the unlikely event that you start your journey off at the top of mount everest ....
The reality is you only get at most 3% back in Regen.
Anyway cells drop a little when theyve been taken off charge, and just taking a vehicle out of the drive will use up more Joules than you get back from your first downhill slope!

Oh and voltage doesnt 'build up then arc' in the manner you describe lol!
If a voltage produced through Regen cannot be dissipated it then reduces the braking force of the Regen. You can test this by spinning a DC motor, then spinning the motor with the +ve and -ve wires joined. When the current can flow the resistive force is more!

strawhistle
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Last seen: 3 years 7 months ago
Joined: Monday, March 10, 2008 - 08:43
Points: 340
Re: Regenerative braking limits

I believe , if there is no room in the battery the controller makes a switch to OPEN circut and the motor would have no resistance to impeed the speed !!! LaTeR

thank GOD I wake up above ground !!!!

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