Is the problem the Controller or Battery? Help!!!!

tboyle

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Aug 24, 2015
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I have built an electric bike with a battery pack that I made using a 60A BMS from BesTech Power, I have a 24Fet 80A max controller I got from GreenTime on Aliexpress and a motor from golden motors. I am having problems with the battery power cutting off after the first twist of the throttle. I am not sure what I should do to fix it. I recently have put it all together and when I first tried to run the bike I would twist the throttle and the bike would give a small jerk and then stop and would not do anything so I would unplug the battery and plug it back into the controller which it would than do the same thing so I finally after doing that a few times I would get the bike in motion and then twist the throttle and that seemed to get it going without killing the power to the motor. I have put it on a stand so the back wheel is not touching the ground to test a second battery pack I built but now even with no load on the bike it continues to have the same problem. The power is killed after one twist of the throttle and I have to unplug the battery which seems to reset something so it will work.

Please if you could give me some advise I would really appreciate it. Should I get a different controller? I tested two different battery packs and with the same result so I don't think that is the problem but I am very new to this so I am just guessing here. I am wanting to go fast so I want a good controller but don't want to spend over $200

Thank

TB
 
If you ease into the throttle, does it still happen? If not, it's the fact that your controller and motor demand more juice than your battery will supply.

Controllers are pretty lax in how they're rated. The "22A" controller I install most often peaks at about 50A, which makes all the difference to a battery.
 
Hi Chalo,

Thanks for responding. I just hooked it up and eased the throttle and I was able to ease on and off of it three times which was better than before but in the middle of the third twist it killed it again. Do you think the battery needs to be bigger? I am ordered some additional Samsung 25rs that should come in the next week or two and was going to make the battery a 48v 15amp 13S6P.

SHould I increase Voltage or Amps?

The Controller is 24fet 3000w 48-84V 80Amax bldc motor controller Greentime
Motor is 48V 3kw golden motor.

Thankss
 
I think if you had more battery, you might not face the same problem. But if you had a Cycle Analyst, which is cheaper than a battery, you would be able to limit the output power until the battery you have would do the job without interruption.
 
When it cuts out and you have to disconnect the battery pack to get it to work again, then the BMS on the battery pack is cutting power for some reason. Could be a low cell group hitting LVC. Could be the controller is drawing more power than the BMS is rated for and over current in the bms is shutting you off. But, with the wheel off the ground it should draw less than 2A, unless you don't have the right phase sequence. Could be a bad connection too.
 
For what it's worth, it could be one single cell in your pack that's sagging to the minimum cell voltage and tripping the BMS. You can't know that without opening the pack and probing all the cells for individual voltages. Short of that, all you can do is to make sure the pack sits on the charger as long as possible so that the balance cycle completes.

Edit: Wes said it already.
 
Put a voltmeter on the battery wires. If the voltage drops when the motor stops, it's the battery. If it doesn't drop, it's the controller/motor.
 
Thanks everyone for the suggestions. I am going to add more cells to the battery pack in the next week or two when I get the additional 36 cells Samsung 25r's and I will test each cell to see if one of them is below the rest. I think I am also going to upgrade to a Kelly controller to see if that helps as well. But for now I am going to try d8veh suggestion and use a voltmeter to see if the voltage drops when the motor stops.

Also any suggestions on where I can get a quality Cycle Analyst?

Thanks
 
roflmao. Of course the voltage will drop when the motor stops. That's why the motor stops. That won't tell you a thing except if it's the bms tripping or the controller hitting lvc. Unplugging the battery pack resets the BMS cutoff, so if you get power back when you plug it back in, then the bms tripped. If it's the controller hitting lvc, voltage will go up after the motor stops as long as the battery pack is good.
 
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