Major power cut-off problem with Bafang BPM 48V500w

[nukezero]

So my new ebike that I bought has a Bafang BPM 48V500watt. It is not a kit but a whole bike but the electronics are probably 100% similar to all other kits out there.

Anyhow, I was riding today on a full charge when all of a sudden the power cut off. Twisting the half twist throttle didn't work. Restarting the power at the battery and throttle switch didn't work. Then occasionally, the power will come back on but then shut off after 3 seconds.

When I got off the bike and lifted the rear wheel, throttle up and no problem! But once I got on the bike, throttle up, within 3 seconds, the throttle cuts out again! Again, I get off and sometimes I can spin the rear wheel up in the air with throttle. But as soon as I jump back on the bike the throttle will come on and off very badly.

I checked both e-brake switches and they are connected. I even disconnected both ebrake switch on both handles and lifted the rear wheel up and throttled up, and no problem. So the controller doesn't care if the ebrakes are connected. It will still spin the motor.

The problem seems to occur when I put a load on the bike like I'm sitting on it. Is this a clutch issue? The motor is not hot at all, in fact it is cold. I can only get about 20 feet before the throttle cuts me off again. As I'm twisting the throttle a hundred times it becomes scary because I don't know when the motor will come back on again. When it did come back on intermittently, I'm jolted as I'm caught off guard.

Now if you remember last week, I mentioned a strange clicking noise which I thought was the spokes. The noise occurred only when I'm riding the bike(applying a load/weight). I'm still thinking it is the spokes but now I'm wondering if it could be related to the motor.

 

[wannesd]

sounds to me like your bms is cutting out. If the bat was fully charged, perhaps one cell is acting up, getting so sagged that the bms goes to lvc.

 

[nukezero]

sounds to me like your bms is cutting out. If the bat was fully charged, perhaps one cell is acting up, getting so sagged that the bms goes to lvc.

Why would the BMS cut out? I didn't gain any weight the past 3 weeks I had the bike. (150 lbs). No modifications to the bike.

 

[wannesd]

If one cell (or row of cells for that matter) is weaker, it could sag to beneath lvc under load, causing bms to cut power.

 

[Russell]

Is your warranty still in effect?


-R

 

[nukezero]

Is your warranty still in effect?


-R

Yeup! Just got the bike 3-4 weeks ago. I got a 2-year warranty on everything, frame, motor, battery, etc. Man, I thought these Bafang motors/controllers were reliable. I only put about 160 miles on it. Took out the controller and nothing looks out of the ordinary. Will take it to the bike shop dealer tomorrow and let them figure it out. That's what I paid them for right? lol

 

[Russell]

I would tend to agree with wannesd who said it was likely your BMS causing the power to cut out on you. If it were some kit you bought from China then you'd want to troubleshoot it yourself but since it's under warranty let the Dealer fix it.

I've owned two 250W Bafangs and a BPM over the past few years. I did have a noise issue with my BPM but after reading your other post it appears the symptoms are different. My BPM would make a clacking noise when cruising along on level ground with the motor lightly loaded and it got especially noisy when passing through the top speed, around 26 MPH. I bought a new clutch assembly for it but the motor/wheel is not currently on a bike so I haven't tried it out yet.

-R

 

[nukezero]

I would tend to agree with wannesd who said it was likely your BMS causing the power to cut out on you. If it were some kit you bought from China then you'd want to troubleshoot it yourself but since it's under warranty let the Dealer fix it.

I've owned two 250W Bafangs and a BPM over the past few years. I did have a noise issue with my BPM but after reading your other post it appears the symptoms are different. My BPM would make a clacking noise when cruising along on level ground with the motor lightly loaded and it got especially noisy when passing through the top speed, around 26 MPH. I bought a new clutch assembly for it but the motor/wheel is not currently on a bike so I haven't tried it out yet.

-R

I also do have a clicking noise when the wheel spins and it is definitely only occurring when it is loaded.

I just disconnected the motor hall wires (cylindrical) which has other power wires to the motor. Then I reconnected it tightly. I was able to bike smoothly for about 10 whole minutes. Then suddenly, same thing again, it cut power. It's so strange I really thought it was just a loose connection/wire.

When I put my hand on the cable connection, it feels very, very warm. Not super hot, but definitely warm. Today is not that hot at all and I've ridden it harder on 90F days before. I am really at a loss what could be happening because now it seems like it will take a while before the symptoms occur again.

What I have to do to get it to work again is to jump up and down my bike (load and unload) to get it work. It really sounds like a loose connection or really poor contact or something.

 

[nukezero]

holy crap you guys are right. I think it may be the battery. My bike has one of those 3-stage LED on the half twist throttle showing full battery, half battery, and low battery. I know the battery is fully charged, so when you are at full throttle, it will drop to orange led half power. But after 5 minutes riding in the night, i'm able to see what exactly is happening. When I apply full throttle, all of a sudden, I see the battery meter go down to empty (red). Then the power cuts out a few seconds later. The LED is then showing only half power (orange), and then 5 seconds later, the green LED will slowly rise and lit up. That's really strange. It sounds like a huge voltage sag or cell is depleting.

It's definitely intermittent, and the controller is definitely cutting out the throttle due to LVC.

just went out for a quick ride again with the rear brakes detached. Nope, not a dragging brake problem. The pads are far away and not dragging the rotor so it's gotta be the battery.

 

[TheBeastie]

Yeah its got dodgey battery written all over it. When you apply a 'load' you are significantly draining the battery more so it cuts out past its LVC much quicker.

You got to get the battery fixed. You can hook up a watt meter between the battery and the controller is where I have mine.
http://hobbyking.com/hobbyking/store/__10080__Turnigy_130A_Watt_Meter_and_Power_Analyzer.html
This watt meter shows total Ah used on the battery, so if you got a 10Ah battery you should see it at least get close to 10Ah before it runs out of power.

I got a Bafang 500w too, in enthusiast circles its sometimes considered a more weak motor but really it can happily handle a fair amount of power especially if you got large controller along with it. You might consider building a Lipo battery but only after you have watched a few Lipo danger elimination saftey test videos.
http://www.youtube.com/watch?v=zQheOtdCTjs
http://youtu.be/tatq8KcaGY0

 

[nukezero]

Yeah its got dodgey battery written all over it. When you apply a 'load' you are significantly draining the battery more so it cuts out past its LVC much quicker.

You got to get the battery fixed.
I got a Bafang 500w too, in enthusiast circles its sometimes considered a more weak motor but really it can happily handle a fair amount of power especially if you got large controller along with it. You might consider building a Lipo battery but only after you have watched a few Lipo danger elimination saftey test videos.
http://www.youtube.com/watch?v=zQheOtdCTjs
http://youtu.be/tatq8KcaGY0

Yikes, I'm not building my own LiPoly's. The battery is a Polymer NCM according to the manufacturer and the label on the battery. I can't help but think, I only got about 25-30 cycles out of it in the full 3 weeks I've owned it and most of that were not even deep discharge/charges. They were also slow charged at 2A on the 10Ah capacity.

I've never thought that owning an e-bike was 5X more troublesome than a regular bike. Now I understand why this market will take a while to take off. Battery technologies just haven't matured well enough and there is so many things with the bike that can go wrong. Regular bikes can be ridden the ground with barely any maintenance these days and e-bikes really require more TLC.

 

[d8veh]

You've got one minor problem in your battery, which can probably easily be fixed if you know how. It would be best to ask your retailer to change the battery for one that works, otherwise you have to open up the battery to do some measurements inside to find the problem. What battery is it? You need at least 20Ah at 36v and 15Ah at 48v for the 500W BPM.

 

[nukezero]

You've got one minor problem in your battery, which can probably easily be fixed if you know how. It would be best to ask your retailer to change the battery for one that works, otherwise you have to open up the battery to do some measurements inside to find the problem. What battery is it? You need at least 20Ah at 36v and 15Ah at 48v for the 500W BPM.

The battery is a 48V 10Ah LI-Ion NCM, polymer pouched based. I'm guessing it is only capable of 2C or 20Amp discharge maximum at best. Maybe only 1.5C. I did test it's range capabilities and while doing full throttle for 14.6miles, the battery still had a good charge. The advertised range is 18-20 miles on 10Ah. I did 14.6 miles one day and still felt I could do another 3-4 miles easily. This is on flat road with no hills full throttle 25mph. If I open this battery up, I would most likely void the warranty (see below). Although I would love to have opened it up and fixed it myself when it runs out of warranty.

I'm actually a comp/EE engineer so I have some knowledge of EE stuff. But anyhow, last night when i charged it up, the charger was showing me that it was fully charged so I unplugged it. This morning, when I measured the battery, it showed me 50V instead of the 54V full. So it lost 4 volts overnight for no reason. Unless of course the charger was lying to me.

I took it to the shop this morning and they were very helpful and they pushed the manufacturer to give me a new/replacement battery because this one seemed kind of fishy. We got on the phone with the owner of the company and he told us it sounded like the BMS card. (At first I thought the BMS was in the controller, but its integrated into the battery). They've agreed to replace the battery for me. They didn't verify my claims. I only told them the symptoms when I was riding on a fully charged battery that it would cut out on me after 1-5 minutes, only when I'm on the bike.

Now, correct me if I'm wrong, if it was a BMS problem, shouldn't it fail open and fail completely and not be intermittent? It still sounds like a battery cell issue because overnight the battery cells lost a whopping 4V. The battery it has is a pouched based polymer Li-Ion NCM.

Also, the instructions from the manufacturer says that I need to charge this battery up fully atleast after each use. Is this true? I'm not supposed to leave it at 30,40, or 50% charge capacity. That I must charge it after each use? I thought that keeping batteries like this fully charged up degrades the cell?

I did explain that if I run down the block to the sandwich shop (1 block), that I wouldn't need to charge it. They agreed but if I did that for 2-3 consecutive days, then I would need to charge it up/top it off.

The battery looks like this:

 

[nukezero]

Just got an update. The shop got me a brand new battery. It is brand spankin' new and all charged up. Took it out for a ride while everything (motor, controller, battery) is ice cold. BOOM, in 3 seconds, the power cuts out again. Occasionally, I'm able to throttle up for 5-6 seconds maximum, then it cuts out and it cuts out for a 10-20 seconds. The battery indicators do not sag anymore. I have to wait atleast 10 seconds before I can get the throttle to work.

So... I think we can conclude it ISN'T the battery. It can't be.

Next, I tried the same test again: 1. Lift the rear wheel and throttle up. No problems! Sometimes, however, when I hop off after the throttle doesn't work, then lifting the rear wheel and throttling up won't work. I have to reset the bike.

So what is the likely culprit?

1. Would a sticking clutch cause this problem?
2. Bad controller? Maybe a burned out mosfet inside?
3. Bad phase wire? Motor spins when not under load but when you ride the bike, it will cut out after a few seconds.

 

[jateureka]

sounds more like a bad connection between the battery and controller

 

[friendly1uk]

You have a very very warm connector, and if you disturb it the bike works for a bit.

 

[d8veh]

Your original battery was faulty. It should give about 54v hot off the charger, which shouldn't drop significantly by itself. There's lots of potential internal causes that would give those symptoms you had.

The controller has a low voltage control, so if it sees the battery voltage go below about 38.5v, it would cut off, but you'd also see your throttle LEDs go out. The battery BMS has over-current control and low cell voltage control, so it cuts if you use too much current, or if any cell goes below a minimum; however, the low cell voltage is not likely to climb back up, so it would tend to stay switched off after cut-out. So over-current is a possibility if say you had a BMS set to 20 amps and a controller set to 25 amps.

If you have a faulty connection between your battery and the controller, so that the power was interrupted for a short time, the controller would need to re-initialise, which means that the throttle won't work until you let it back to zero. If you have a LCD or LED panel, it would shut down, so you'd need to switch it back on.

None of the suggestions you made for the cause are likely. It's much more likely a faulty connection between the battery and controller. Also a prime candidate is the solder connections on the battery key-switch, which are often dry because of the heat needed to fuse the solder to the large metal plates on the switch. This fault gives exactly the symptoms you have. Do you have a key-switch on the battery?

You have to take the top off the battery to check the key-switch, which might affect your warranty, so it would be best to take your bike back to the shop and tell them to fix it whatever the cause is. You shouldn't have to do anything. If you'd bought the bike from China with no warranty, you'd have to get the tools out.

 

[nukezero]

Your original battery was faulty. It should give about 54v hot off the charger, which shouldn't drop significantly by itself. There's lots of potential internal causes that would give those symptoms you had.

The controller has a low voltage control, so if it sees the battery voltage go below about 38.5v, it would cut off, but you'd also see your throttle LEDs go out. The battery BMS has over-current control and low cell voltage control, so it cuts if you use too much current, or if any cell goes below a minimum; however, the low cell voltage is not likely to climb back up, so it would tend to stay switched off after cut-out. So over-current is a possibility if say you had a BMS set to 20 amps and a controller set to 25 amps.

If you have a faulty connection between your battery and the controller, so that the power was interrupted for a short time, the controller would need to re-initialise, which means that the throttle won't work until you let it back to zero. If you have a LCD or LED panel, it would shut down, so you'd need to switch it back on.

None of the suggestions you made for the cause are likely. It's much more likely a faulty connection between the battery and controller. Also a prime candidate is the solder connections on the battery key-switch, which are often dry because of the heat needed to fuse the solder to the large metal plates on the switch. This fault gives exactly the symptoms you have. Do you have a key-switch on the battery?

You have to take the top off the battery to check the key-switch, which might affect your warranty, so it would be best to take your bike back to the shop and tell them to fix it whatever the cause is. You shouldn't have to do anything. If you'd bought the bike from China with no warranty, you'd have to get the tools out.

Thanks, I will drop the bike off at the shop and let them figure this one out. I've done all I can on this side so far without voiding the warranty. The controller looks fine, all the wires, I tidy'd it up with zip ties, and wrap the connectors with electrical tape.

Yes I do have a key switch on there. You're saying the key switch part of the connection is probably wearing out?

Okay, here's the question. I read that it could be a bad phase wire or hall wire inside the motor that is giving out. But the symptoms occur generally only under load. Lets assume it was one of those phase wire or hall wire that fell off inside the motor, because I can hear clicking. Will it cause the controller to intermittently shut off like that, yet when not under load, it will keep working?

I remember I read a post a while back with a Mac that had similar problem. It turned out the green phase wire inside the MAC had a cold solder joint and it would cut out for him too. But I don't know if the motor can keep going under no load.

Thanks guys for your help, I will report back.

 

[d8veh]

I can almost guarantee that it's the key switch. I have personally fixed three like that, and have seen two others. The problem is the soldering of the power wires to the switch. The switch has two relatively large metal plates that the wires are soldered to. The high thermal mass of those plates sucks the heat away from the soldering so that you end up with a blob of solder on the wire that isn't fused to the plate. When you draw high current, the connection breaks down. Your problem could be caused by any bad connection, butI would put money on this one.

When you have a bad phase connection, younormally get fierce juddering that feels like your motor's broken.

 

[nukezero]

I can almost guarantee that it's the key switch. I have personally fixed three like that, and have seen two others. The problem is the soldering of the power wires to the switch. The switch has two relatively large metal plates that the wires are soldered to. The high thermal mass of those plates sucks the heat away from the soldering so that you end up with a blob of solder on the wire that isn't fused to the plate. When you draw high current, the connection breaks down. Your problem could

When you have a bad phase connection, younormally get fierce juddering that feels like your motor's broken.

D8veh - thanks for your help and suggestions. But i wish i had placed a bet with you now lol.

Anyhow, the verdict is in on the root cause this morning.

I went down to the lbs and we went through a process of elimination. The store had another bike so we were able to pull components off of it and tried one at a time.

1. We disconnected the brake cutoff sensor. Same problem.

2. We then swap the half twist throttle, same problem.

3. We then swap out the controller, and i would have money bet on this one, but now, same problem.

4. Finally we then pulled the other bike closer and using everything the other bike has (throttle, controller, wiring, battery, we just hooked up to the wires to my motor and lifted the rear wheel of my bike and still same problem!

5. Lastly we then hooked up my bike's entire electrical system to the other bike's motor and we can spin it!

The culprit is a bad motor!!

So you guys may remember how several weeks ago i was complaining about some kind of odd click noise coming from the motor. I believe these two issues are related.

I'm guessing a phase wire or hall sensor broke off inside and makes a click click noise and hitting the casing after each rotation. But the shop told me it's usually unlikely as that would create quite a bit of resistance in the motor.

Any how, the company is getting me a new motor and rim together as part of warranty.

Im quite happy because i don't think overseas companies like BMS battery would have given me a new motor for this trouble. But now it gives me an understanding of what to look out for the next time.

Again I only had the bike for three weeks and put about 130 miles on it on mostly flat land. Never jumped a curb or something like that. So the fact the the issue was intermittent just really sounded like a loose connection or component inside.

 

[friendly1uk]

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Is this not the round barrel you told us was broken days ago? The one you twiddled and bought the bike back to life for a bit? Then recently you plugged another bike on to this broken connector and of course the motor still wouldn't run?

 

[nukezero]

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Is this not the round barrel you told us was broken days ago? The one you twiddled and bought the bike back to life for a bit? Then recently you plugged another bike on to this broken connector and of course the motor still wouldn't run?

Yes, I have that round barrel connector, but no, it was not broken. I thought it was a loose connector but it is actually quite tight.

For now, the manufacturer has been very nice to me so far and went from replacing the battery first to now replacing the motor. But we finally solved the problem so to speak. They didn't charge me a dime and the turn-around time has been fast. I knew that choosing a ebike company locally would save me a lot of headache and time when problems arise.

 

[jateureka]

That round moulded connector is used on quite a few e-bikes, including FreeGo, Juicy bike and EmotoEV. It's nice for servicing the motor as it fits right through the motor axle.
Not sure how the cable attaches to your bike but on the FreeGo you need to be very careful when you remove/refit the rear motor wheel as the frame lugs that hold the cable have sharp adges and can easily damage the cable. I have filed the sharp edges off the cable lugs on my bike frame just to be safe.