Rear Brakes Locked Up Or Motor?

[JohnGault]

Hello, I'm new here.
This is a copy and pasted post I put on a different forum that seems like it doesn't much activity on it.
I'm not very bright when it comes to mechanical issues so, I'm probably overlooking the obvious? That being, the motor sized up, not my brakes? But, I'm not really sure? I'm leaning toward a hub motor issue, now that I've been trying to make sense out of this for the last 3 hours. I could be wrong though?

"I have a MotoTec Knockout 1000w/48v Fat Tire Electric Scooter. Today while riding, out of nowhere my rear brakes fully engaged and the scooter came to a hard skidding stop. I thought they froze up? But after getting off the scooter to try and figure out what was going on they seemed to disengage on their own, about 30 seconds after? I rode home slower than usual because I was concerned that it might happen again, and... it did, one other time. I can't understand what would cause this? Does anyone have any ideas? It has hydraulic disk brakes. I'm wondering if it wasn't the brakes that locked up but was the motor because the motor is located in the rear wheel? The scooter is equipped with an automatic safety switch that automatically turns the scooter off due to over heating or other issues and can be reset with a button located on the battery compartment. The scooter automatic safety switch did not engage when this happened.
Also, I got new batteries back in October (4 - 12v Lead Acid Batteries) and the charge does not last very long, at all. I can go about 3 miles and the battery indicator will drop to zero when I turn the throttle, then shoot back up to 100% when I let off the throttle. The scooter will still operate but goes about 6MPH slower when the batteries fail like this. (The max speed of this scooter is only about 18MPH when fully charged and operating normally, and normal range is about 10 miles when fully charged.) I noticed that if I go somewhere 2 miles away, then come back right away.. the batteries perform better. But, if I go 2 miles away, park it for 1-1.5 hours, then ride it the 2 miles back, the batteries seem to drain to zero when I'm halfway home. Not sure what's going on? Did I get ripped off on my new batteries? The batteries that came with the scooter when I bought it lasted about 2 years before they started to fail, like these batteries are failing. I'm wondering if it could be some kind of electrical component that could be causing this battery performance issue?"

Now after thinking about it. Hydraulic brakes wouldn't lock up like that, would they? Cheap, Made In China Hub Motors would though. Anyway, I just wanted to put this up on here to see what people would have to say. If it is the hub motor, is it worth going through the trouble of ordering a new one online? Maybe I should just sell the thing but let people know that it needs a new motor and let them deal with it? Either way, it sucks that my scooter is failing. I really enjoyed having it.

 

[amberwolf]

Any brake that can lockup the wheel could sieze, but would need to be engaged first.

But most likely it is an electric system malfunction.

If your system has regen ebraking that is powerful enough to lockup the wheel, then whichever lever or button is used to engage this system (usually a switch inside the brake lever(s)) could have malfunctioned, if it got wet for instance, or was impacted in a crash or the scooter falling over, etc. Similarly, a wiring or connector fault in the wires from that switch to the controller could cause it.

It could also be damage to the wiring from controller to motor, such as a short between phases where the cable comes out of the motor axle for a hubmotor, can make a motor feel locked up when it suddenly happens while riding at speed.

However, this type of problem often damages the controller FETs, so it won't operate correctly at all after this happens.

Similarly, overheating of a motor can short it's windings to each other or to the stator laminations...but this is also a permanent failure that doesn't reset.

I'd recommend closely examining all the wiring that is exposed anywhere, especially coming out of the motor, or the brake levers, in direct sunlight, for any kind of damage or surface markings, scratches, dents, etc. Wire damage that allows a short (permanent or temporary) in a cable isnt' necessarily visible from outside, but is usually found at a point where external marks or damage *is* visible.

If you find any damage, you can post good clear pics of it and we can try to suggest testing you can do.


Regarding battery life with SLA, it's not uncommon for batteries to sit on a shelf a long time, and not be kept charged. If SLA is not kept full, it sulfates, which damages the internals "permanently", decreasing both capacity and ability to deliver current. It only takes one of your four batteries being damaged or old to cause the system to behave as you see, but it's common enough for everything to be in the same condition if it was all from the same place at the same time.

Addtionally, there are several kinds of SLA batteries, and only some of them are really any good for EV use. Many are intended for "standby use", like in a UPS or emergency lighting, and have thin plates not meant for high current, for instance, and also don't usually work well when deeply discharged like an EV is going to do. Deep-cycle batteries, and ones designed for sustained higher currents are what you want to find. Mobility-scooter batteries are generally intended for this (I think the last ones I used, over a decade ago before I switched to lithium, were MKPower?).

Leaving the batteries only partly charged also degrades them faster, and the longer the cumulative time they are left not full, the further degraded they will be. So if it's possible for you to do so, I'd recommend bringing your charger with you and plugging in to charge at your destination every time you go anywhere, to make your batteries last longer, and then also recharge as soon as you get back home as well.

(this is the opposite of lithium batteries, which degrade faster the longer they are left full)


Optionally, you can replace the SLA pack with a lithium pack and it's own new charger to go with it, but I strongly recommend not going for any of the "cheap" ones, as they are not generally built well or of good cells and probalby wont' work any better than the SLA (and be more of a potential fire hazard). If you decide to go this route, post a link to anything you are considering buying so we can help you make sure it is not a "junk" battery before you spend money on it.

 

[JohnGault]

Damn! Thanks amberwolf. I'll take a close look at all the wires in the sunlight tomorrow, again. I've taken good care of this scooter. Never had it out in the rain or on wet roads. It has never crashed and never fell over. I cleaned the hell out of it yesterday too (the day before the lock up happened) and was checking all the external wires while cleaning it, didn't see anything abnormal. At first, I thought that I might have messed something up while cleaning the brake system and it caused the brakes to lock up but, I was just cleaning off dust and dirt build up with a rag and a can of compressed gas computer cleaner? Another thing I thought about. Back in December I rode it over a causeway near me that had a steep incline. It was the first time I took it over the causeway and the last because I was worried about the strain it was putting on the motor trying to get up to the top of the causeway. I went down the other side then had to go up the incline again to get back over the bridge. I wonder if that caused a problem? I got myself thinking that I fried the motor and maybe should try ordering a new hub motor? But, from what you're saying... I should probably hold off on that. I wish I knew more about this stuff. Maybe I could try replacing the control box first before messing with a new rear hub motor. I have to ride it to the post office and back tomorrow, about a 5.4 mile round trip. It'll be fully charged before I go too. It will be interesting to see if it locks up again. This will only be a short 5 minute stop though. No point in bringing the charger. But yeah, good idea for me to bring the charger the next time I go on an extended stay visit somewhere. I used to just keep the scooter plugged in at home all the time, to keep it fully charged. But, since I got the new batteries, I've been unplugging it after the charger light turns green. I always plug the scooter back in before taking it out too, and the light goes from red to green in like 10 seconds. I generally charge it daily and on average ride the scooter about 4 to 5 days a week on 4 - 5 mile round trips each time. The batteries only give me trouble when the turn around time is over an hour. About lithium batteries... I've seen too many videos of lithium batteries blowing up.

 

[JohnGault]

Any brake that can lockup the wheel could sieze, but would need to be engaged first.

But most likely it is an electric system malfunction.

If your system has regen ebraking that is powerful enough to lockup the wheel, then whichever lever or button is used to engage this system (usually a switch inside the brake lever(s)) could have malfunctioned, if it got wet for instance, or was impacted in a crash or the scooter falling over, etc. Similarly, a wiring or connector fault in the wires from that switch to the controller could cause it.

It could also be damage to the wiring from controller to motor, such as a short between phases where the cable comes out of the motor axle for a hubmotor, can make a motor feel locked up when it suddenly happens while riding at speed.

However, this type of problem often damages the controller FETs, so it won't operate correctly at all after this happens.

Similarly, overheating of a motor can short it's windings to each other or to the stator laminations...but this is also a permanent failure that doesn't reset.

I'd recommend closely examining all the wiring that is exposed anywhere, especially coming out of the motor, or the brake levers, in direct sunlight, for any kind of damage or surface markings, scratches, dents, etc. Wire damage that allows a short (permanent or temporary) in a cable isnt' necessarily visible from outside, but is usually found at a point where external marks or damage *is* visible.

If you find any damage, you can post good clear pics of it and we can try to suggest testing you can do.


Regarding battery life with SLA, it's not uncommon for batteries to sit on a shelf a long time, and not be kept charged. If SLA is not kept full, it sulfates, which damages the internals "permanently", decreasing both capacity and ability to deliver current. It only takes one of your four batteries being damaged or old to cause the system to behave as you see, but it's common enough for everything to be in the same condition if it was all from the same place at the same time.

Addtionally, there are several kinds of SLA batteries, and only some of them are really any good for EV use. Many are intended for "standby use", like in a UPS or emergency lighting, and have thin plates not meant for high current, for instance, and also don't usually work well when deeply discharged like an EV is going to do. Deep-cycle batteries, and ones designed for sustained higher currents are what you want to find. Mobility-scooter batteries are generally intended for this (I think the last ones I used, over a decade ago before I switched to lithium, were MKPower?).

Leaving the batteries only partly charged also degrades them faster, and the longer the cumulative time they are left not full, the further degraded they will be. So if it's possible for you to do so, I'd recommend bringing your charger with you and plugging in to charge at your destination every time you go anywhere, to make your batteries last longer, and then also recharge as soon as you get back home as well.

(this is the opposite of lithium batteries, which degrade faster the longer they are left full)


Optionally, you can replace the SLA pack with a lithium pack and it's own new charger to go with it, but I strongly recommend not going for any of the "cheap" ones, as they are not generally built well or of good cells and probalby wont' work any better than the SLA (and be more of a potential fire hazard). If you decide to go this route, post a link to anything you are considering buying so we can help you make sure it is not a "junk" battery before you spend money on it.

Hi amberwolf, I rode it to the post office and back yesterday, without incident. No rear tire lock-up and the batteries performed as expected. It must have been something somewhere that caused a short to make it lock up like that the other day, like you said. I inspected the wires again, didn't really find anything. I also opened the battery compartment and tried to rearrange some of the wires so they weren't so crammed up. I noticed that the hole in the battery compartment that the hub motor wire to goes through, didn't have a rubber grommet on it. I should probably get one for it.
Right before the rear wheel locked-up the other day, I rode it over a bumpier than expected grassy area at top speed for about 10 feet. That might have had something to do with the lock-up? I always only ride it on flat smooth surfaces, like sidewalks. Two people were walking on the sidewalk I was on, so I turned on to the street to get around them, then back on the sidewalk, over the bumpy grass, then it locked up.
This is the only mode of transportation I have. So, when something goes wrong with it I tend to panic a little.
Anyway. Thanks for your help.

 

[amberwolf]

Anything that happens when there is vibration but not when there isn't indicates a connection problem, or a wiring fault, in any part of the wiring that can physically move even the slightest amount (though the parts that can move more are more likely to be where the fault is).