BMC V4 motor

[oatnet]

I'm bad at being cheap, I keep getting what I paid for ! :lol:

-JD

 

[ebikerbythesea]

I hear you, but the problem with expensive stuff is that it's often that way because it's overpriced Current retail price of V4's a case in point. Sometimes it's a choice between nothing or just having to bite the bullet though!

 

[Sacman]

I totally missed this comment from Chris at Hi-Powercycles about pumping 50A continuous to kill the V4's motor last week. But 50A only gives part of the picture. Just so we better know how much continuous WATTAGE these motors can handle.... What VOLTAGE were you using Chris?

Oh yeah, and another thing, I have killed the BMC V4C and BMC V4T on 50A, so don't expect to be pumping 50A continuous up the steepest grades. Most people will not torture the motors as hard as I do, but still 50A on heavy hills for prolonged periods is not recommended for the BMC V4 motors...

 

[sandymac]

So, anyone out there with some testing on the new v4's?

I have been using a BMC 1000 watt V4 C with a 50A controller and 2 10Ah 24v (29.4v max) batteries in series. The batteries are rated at 50A continuous. In cold weather the system is fantastic and can manage 56 KPH on the flat with no pedalling. Dropping the speed to 48 KPH halves the watts shown on the cycleanalyst.
However, in warm / hot weather (over say 22 degrees C = 72 degrees F) I have a problem. To best describe this you have to imagine there is a fault in the twist-grip. If you go above a certain point the motor power cuts out, but the Cycleanalyst still operates. (I had one of the battery packs battery become too discharged once and everything cut out so I assume its not a BMS problem) if I relax the twist-grip and then put it back to just below the cut-out point the motor picks up again. If I hit a hill while holding the twist grip just below the cut out point, the watts can go from say 800w up to about 1300w without a cut-out. This seems strange to me if there was some over current protection. Has anyone else had this sort of problem? I wonder is it the controller or the motor or even the twist-grip? All advice welcome.

 

[teklektik]

...To best describe this you have to imagine there is a fault in the twist-grip. If you go above a certain point the motor power cuts out, but the Cycleanalyst still operates. ...if I relax the twist-grip and then put it back to just below the cut-out point the motor picks up again. If I hit a hill while holding the twist grip just below the cut out point, the watts can go from say 800w up to about 1300w without a cut-out.

I think that above the cutout point the throttle voltage may be too high causing a controller input voltage fault. You should be able to verify this on the stand - crank up the throttle and if the controller cuts out you have the problem. If so, I would guess it's most likely the throttle. Is this a hall throttle or a resistive throttle (Magura)?

 

[oatnet]

So, anyone out there with some testing on the new v4's?

To best describe this you have to imagine there is a fault in the twist-grip. If you go above a certain point the motor power cuts out, but the Cycleanalyst still operates. (I had one of the battery packs battery become too discharged once and everything cut out so I assume its not a BMS problem) if I relax the twist-grip and then put it back to just below the cut-out point the motor picks up again. If I hit a hill while holding the twist grip just below the cut out point, the watts can go from say 800w up to about 1300w without a cut-out. This seems strange to me if there was some over current protection. Has anyone else had this sort of problem? I wonder is it the controller or the motor or even the twist-grip? All advice welcome.

I had similar problems with cutouts on a BMC V3 and the 50a controller, but did not associate it with ambient temps. If I launched too hard, it would cut out, but if I nursed the throttle I could get it up to speed. I suspected the 50a controller had a lower throttle peak v threshold than other controllers I was used to, but I melted the halls testing on a steep hill before I sorted it out. Throttle translation via a CA V3 would give a handy way to diagnose and work around the issue.

-JD

 

[sandymac]

...To best describe this you have to imagine there is a fault in the twist-grip. If you go above a certain point the motor power cuts out, but the Cycleanalyst still operates. ...if I relax the twist-grip and then put it back to just below the cut-out point the motor picks up again. If I hit a hill while holding the twist grip just below the cut out point, the watts can go from say 800w up to about 1300w without a cut-out.

I think that above the cutout point the throttle voltage may be too high causing a controller input voltage fault. You should be able to verify this on the stand - crank up the throttle and if the controller cuts out you have the problem. If so, I would guess it's most likely the throttle. Is this a hall throttle or a resistive throttle (Magura)?

Thanks for your response.
That sounds like an easy fix its a BMC Half throttle (about 2012 vintage)

 

[teklektik]

Thanks for your response.
...
its a BMC Half throttle (about 2012 vintage)

Gee - that post was a year and a half ago!

You can try it, but a hall throttle is unlikely to cause that controller failure mode (throttle input fault). You might see it with a Magura or other resistive throttle.