Kt regen settings

anon4

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May 9, 2017
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I'm tempted to try a stronger regen braking setting but the kt manual states that levels stronger then setting 1 can damage the motor. How true is this? Also it says something to the effect of stronger braking recovers less energy. Eh? Surely strong regen would recover more energy as long as you keep moving, or is it all just wasted as heat? How much is too much?
 

Andy-Mat

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Oct 26, 2018
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I'm tempted to try a stronger regen braking setting but the kt manual states that levels stronger then setting 1 can damage the motor. How true is this? Also it says something to the effect of stronger braking recovers less energy. Eh? Surely strong regen would recover more energy as long as you keep moving, or is it all just wasted as heat? How much is too much?
I'm tempted to try a stronger regen braking setting but the kt manual states that levels stronger then setting 1 can damage the motor. How true is this?
The possible damage could occur when a higher current is drawn, than the copper wire winding of each phase, can safely handle. I certainly cannot say anything that could be considered better than the manufacturer. If you ignore that, you may end up with an overheated and defective motor, so my advice would be to do exactly what they say....
Also it says something to the effect of stronger braking recovers less energy.
Do they mean regen braking, or normal braking? Normal braking would burn off in heat in your disk brakes, that energy that could have been recovered by the electronics.
If they meant regen braking, maybe they mean that not all the energy gets channeled back into the battery possibly. I am very unclear as to exactly what they are trying to say at this point.
Surely strong regen would recover more energy as long as you keep moving, or is it all just wasted as heat? How much is too much?
Theoretically yes, but the wording they/you use, is difficult to make sense of, sorry. I suspect that energy, over and above what can be replaced back in the battery, could be wasted as heat. The question is where?
A guess, but most likely in either the motor, the controller or the battery (assuming controller is in the battery!).
But putting a short across the 3 motor windings though, would produce very heavy braking and heat up the motor windings at the same time.
Or a "short" across the motor, but with a low value resistance (x3) is more likely and safer for the windings.....
Such shorts are used with many motor types to stop a motor quickly, in good quality electric drills, both mains and battery do this for example. Its always a good idea when buying a drill, to check that this happens. Also on other portable tools, saws for example....
Its called "Dynamic Braking" an it is used also in heavy locomotives, railcars and similar.
See here:-
Dynamic braking is the use of an electric traction motor as a generator when slowing a vehicle such as an electric or diesel-electric locomotive. It is termed "rheostatic" if the generated electrical power is dissipated as heat in brake grid resistors, and "regenerative" if the power is returned to the supply line. Dynamic braking reduces wear on friction-based braking components, and regeneration lowers net energy consumption. Dynamic braking may also be used on railcars with multiple units, light rail vehicles, electric trams, trolleybuses and electric and hybrid electric automobiles.
I am guessing as to what they do on an e- bike, but those are the usual electric motor possibilities.
I hope this helps a little, but only the designer will know what he did for certain.
It would be interesting (for me at least), to insert an ammeter (possibly "fiddly"), (center off with a needle meter, as in cars of the 60's), in the battery circuit, to see if TRUE regen is used or not, that is, does energy actually get sent back to the battery, or just wasted as heat somewhere?
This also may prove interesting to read:-
The way the brake on cordless tools works is slightly different than in corded models; when the switch is released, the motor terminals are shorted together, causing a slight spark and the motor to stop almost instantly. This is because the smaller motor size produces much less inertia.
If the manufacturer is worried about damage to say the motor, I would guess they are using resistive dynamic braking and simply heating up the motor....
Aren't I negative, sorry!!;):mad::cool:
Regards
Andy
 

danielrlee

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May 27, 2012
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torquetech.co.uk
The same rules apply with regen as when you are using the motor to generate motion. There are two ways you can damage a motor; physical damage to the motor axle due to torque and heat damage due to copper losses (IR²).

The KT manual is referring to copper losses. Efficiency drops as regen strength increases, since a larger proportion of the energy is turned into heat in the motor's windings. This is no different than if you were to increase motor current when using the motor for forward traction.
 
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anon4

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May 9, 2017
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I believe it's true regen (at least to a degree) as it shows a charging animation on the display and the voltage does increase if you use it for long enough, there is very little actual braking force felt. I guess the only way to know is to cautiously test the stronger settings and monitor the temperature of everything. But before I get brave I will need some torque arms, my dropouts are ebike spec but I think strong electronic braking might be pushing it. I probably won't even try tbh just curious, the gains are small anyway I'd have better luck turning the pas down to get more range (and resist using the throttle hehe)
 

vfr400

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Jun 12, 2011
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Basildon
I'm tempted to try a stronger regen braking setting but the kt manual states that levels stronger then setting 1 can damage the motor. How true is this? Also it says something to the effect of stronger braking recovers less energy. Eh? Surely strong regen would recover more energy as long as you keep moving, or is it all just wasted as heat? How much is too much?
You can forget about that. instead, you need to worry about the torque on your axle. The regen torque is much higher than the motor driving torque, so you need really strong reinforced drop-outs.

The next problem is the current going into your battery. Ebike batteries are not designed for high charge currents. You can blow the mosfets in the BMS if you go too high. That used to be quite common on steep downhills.
 

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