Is my GM supposed to cut out on moderate hills?

[bumper]

I just got my rear 36V GM installed and I am happy with the speed it is giving me.  On flats I can get up to 20mph with MTB knobbies.  I am powering it with a new 36volt nicad pack (8ah) from ebikes.ca.  My problem is this:

On moderate hills, the motor doesn’t give me a chance to pedal assist it.  I see my speedometer going down to 5-7 mph and it dies.  I release the throttle for a second or two, re-engage and it, starts back up. Is this normal?

This is a different experience from my old wilderness energy brushed front hub that would keep trying to pull you up at 3-5mph and then I would assist it by pedaling.

I read somewhere that brushed motors are better for hills, but I read so many good things about brushless that I got this GM motor (I admit I was attracted to the price). 

What do you think?  Should I get a new controller?  I checked all my wiring. I’m not that technically proficient so any suggestions should be for the “Dummies Guide” variety. Thanks.

[Dave]

I've got a 36V rear hub with SLA's, and it will choke on moderate to steep hills, but I don't give it a chance to slow down that much. I'll shift down a bit in anticipation of the slowdown and help out a bit with pedaling, and usually maintain 10-12mph on even the steepest hill on my route to work. I don't know all the electrical factors that are at work to make it cut out -- you'll need to hear from some of the members that are better versed in that -- but I do believe it's normal for the voltage to dip when the motor is under severe load, and if it dips below the cutoff voltage for the controller, that's what you get. I don't think it matters if the throttle is released or kept open; power will come back when the voltage jumps back above the cutoff.

[bumper]

Thanks, Dave.

I guess I can live with it.  I took it out on a moderate hill this past weekend (w/o cars buzzing to the left of me, ha-ha) and practiced some more.  I applied maybe 1/4 turn of the throttle.  This seemed to work w/o cutting out.  Giving it full throttle makes it cut out, but about 3-4 seconds later it engages again.  Even with this, I don't have to take my feet off the pedals. It just slows down a little bit.  Sort of like herky jerky.

It is hard to keep it constant on 1/4 turn because of the twist throttle.  It would be much easier with a thumb throttle, which I will purchase. 

My main beef was that I was not given a chance to start pedalling.  It just stopped.

[mitch_781]

Hello,
I have the same problem with the 48V motor hub on hill and also on flat.
I bought a battery that is 48V and 4,2Ah because I do only 20km. I also took a nimh battery because it is more ecological than nicd.

It is not working at all, the capacity is low and the nimh has a bad internal resistance (worse than nicd) and even with a battery full charged when I am going full throttle the controller cut because voltage is going under 40V.

I think you have the same problem, the capacity is a bit low and the voltage go under 40v so the controller cuts for a few seconds the time for the battery to go over 40v. If you go with a small assitance it is working beacause the voltage is still over 40v (it is doing this also on mine)

I think I will try to limit the throttle to 50% or make voltage control on the throttle to be always upper 40v at the battery.

If anybody has an idea to build this system ? a system cut limit the throttle to be at 40v at the battery and avoid the controller to cut

Thank you
For information a picture of the bike.

[Timex]

I experienced similar issues, but it was due to the fact that I was using low gauge wiring to my batteries.  If your wires are warm after a ride, then that should be a clear indicator that you need to upgrade the wiring. Using 10 gauge wiring will solve the issue for a 36 volt system, and I'm no expert but I'm guessing 12 gauge would be best for a 48v system. 

[johnbear]

I just got my rear 36V GM installed and I am happy with the speed it is giving me.  On flats I can get up to 20mph with MTB knobbies.  I am powering it with a new 36volt nicad pack (8ah) from ebikes.ca.  My problem is this:

On moderate hills, the motor doesn’t give me a chance to pedal assist it.  I see my speedometer going down to 5-7 mph and it dies.  I release the throttle for a second or two, re-engage and it, starts back up. Is this normal?

This is a different experience from my old wilderness energy brushed front hub that would keep trying to pull you up at 3-5mph and then I would assist it by pedaling.

I read somewhere that brushed motors are better for hills, but I read so many good things about brushless that I got this GM motor (I admit I was attracted to the price). 

What do you think?  Should I get a new controller?  I checked all my wiring. I’m not that technically proficient so any suggestions should be for the “Dummies Guide” variety. Thanks.

The low voltage cutout is set for sla's. The ebikes.ca nicads sag alot and are not great for the power of the golden motor. It is not the motor kit giving you the problem, it is the battery not able to provide the power required.

[tartosuc]

i exeperienced a similar problem,

motor was working fones for the past 8 rides, then this morning when I got to the moderate hill that I climb everytime, the motor started to cutoff...i had to turn around and get my car to go to work...on my way back the motor(even on flat gropud) was cutting at all time and then coming back to life for a few second..on/off, on /off etc...

any ideas?

[Leslie]

Yea SLA's 12ah and below have a voltage slump in them. Some brands are much better than others and some are designed not to have the voltage slump so bad....



I use diamec 18ah batteries and they weigh a ton.

Spec sheet.



Compare to 12 ah version.




As you can see the 18ah is better..

Try better these 18 ah specs with in the hour time limit and you solve some issues.  Its not impossible but remember you will only get batteries that discharge their potential closer to full DOD.

Attempting to improve things with the smaller designs will shorten battery life..

Weight is a bit of an issue when it come to the wife riding the bike and Ive had to move up to steal rims with 12 guage spokes..  I am giving up trying to make these batts work tied to the frame...

However they can give me up to 50 km range with some pedals and around 30km without until some ass in town jumped all over my bike and damed wreck half of a good 20 hours of work 3 times over.  I found a crack in one of the batteries soon enough and repaired it before the acid dried in it.

We use the bike for shopping mainly so I'm moding a baby trailer with an alloy floor underneath where the babies would sit and inline with the trailer wheel axle..  Nice low centre of gravity and balanced.

I will post pics and post the results...

There are a few tutorials regarding the maintainace of these batteries.  you can bring them up a little and get 6mth more life out of them by adding distilled water and moistening the fibre glass mats, gel or what ever is in them, EV's heat them more than what some manufactures design them for and they dry up fast, the acid becomes concentrated and long term damage is going to happen.

Remember you just need to moisten the solution absorbant not drown the cells, you will know if you go to far when they start pumping acid out the tops. and don't forget to replace the top shield before you charge them.

ONLY USE DISTILLED WATER OR ELSE THEY WILL LAST A MONTH AT BEST.