No battery level and motor assist

[Cargo_Bike_Bristol]

Hi

So I've come back to an ebike project I got quite frustrated with back along and just left for a bit! Basically a MXUS XF08 motor 48v battery on a Yuba Mundo v3 cargo bike. It worked for a while but the hall sensors kept blowing (3x) which I had to pay someone to fix each time. Eventually I just opted for an external speed sensor which appears to be working fine but now there is no level indicated in a fully charged battery and no drive to the motor with assist or throttle, but only when I manually call for it on the LCD (S866)..... Checked all the wiring and can't find anything loose. Any ideas what this could be?

Brainpower controller SL-QX041KZ

P1 - 3
P2 - 1
P3 - 48
P4 -10
P5 - 0
P6 - 26
P7 - 1
P8 - 18
P9 - 0
P10 - 2
P11 - 24
P12 - 5
P13 - 6
P14 - 20
P15 - 39
P16 - 35
P17 - 0
P18 - 100
P19 - 1
P20 - 0
P21 - 1
P99 - 0

 

[Woosh]

XF08 is too small, underpowered for use at 48v on a cargo bike. The small motors will overheat on long hills. You should upgrade the motor wheel to something like my DWG22C or SWX02 or Aikema 128.

 

[saneagle]

Hi

So I've come back to an ebike project I got quite frustrated with back along and just left for a bit! Basically a MXUS XF08 motor 48v battery on a Yuba Mundo v3 cargo bike. It worked for a while but the hall sensors kept blowing (3x) which I had to pay someone to fix each time. Eventually I just opted for an external speed sensor which appears to be working fine but now there is no level indicated in a fully charged battery and no drive to the motor with assist or throttle, but only when I manually call for it on the LCD (S866)..... Checked all the wiring and can't find anything loose. Any ideas what this could be?

Brainpower controller SL-QX041KZ

P1 - 3
P2 - 1
P3 - 48
P4 -10
P5 - 0
P6 - 26
P7 - 1
P8 - 18
P9 - 0
P10 - 2
P11 - 24
P12 - 5
P13 - 6
P14 - 20
P15 - 39
P16 - 35
P17 - 0
P18 - 100
P19 - 1
P20 - 0
P21 - 1
P99 - 0

What you're saying doesn't add up with what my knowledge and experience tells me. That controller is only 13A so your motor should be OK at 48v, but it depends how fast you go. If you go too slow with maximum power, things can get hot, but it's normally the controller that goes first, not the motor halls. Can you gtell us a bit more about how those problems happened. Were you just riding along at 12mph and it stopped, or did each problem come after you repeatedly fell off the canal path into the river? Changing a speed sensor should have no effect on the hall sensors.

 

[Cargo_Bike_Bristol]

XF08 is too small, underpowered for use at 48v on a cargo bike. The small motors will overheat on long hills. You should upgrade the motor wheel to something like my DWG22C or SWX02 or Aikema 128.

Ok crap well that will explain a lot. The hall sensors always blew when I had my kids on the back and where we live it's hilly. It was fine when I test rode it after repair but that was on the flat with just me. I wish I knew that from the start, would have saved me throwing good money after bad! Although at least I can focus on what next. When you say it's too small, are you talking form factor? I have a Rad Runner plus which is '250w' 48v motor but is it basically just a larger motor de-rated?

 

[Cargo_Bike_Bristol]

What you're saying doesn't add up with what my knowledge and experience tells me. That controller is only 13A so your motor should be OK at 48v, but it depends how fast you go. If you go too slow with maximum power, things can get hot, but it's normally the controller that goes first, not the motor halls. Can you gtell us a bit more about how those problems happened. Were you just riding along at 12mph and it stopped, or did each problem come after you repeatedly fell off the canal path into the river? Changing a speed sensor should have no effect on the hall sensors.

So now you mention I do remember that the controller was replaced when the hall sensors blew the first time. Do you think it's possible this controller is damaged as well after over heating? I was definitely always going slow up hills with the kids on the back, the hall sensors always blew on the hilly school commute. I was told by the guy who replaced the hall sensors previously to fit an external speed sensor so I could get a mph read out.

 

[Woosh]

When you say it's too small, are you talking form factor? I have a Rad Runner plus which is '250w' 48v motor but is it basically just a larger motor de-rated?

yes, form factor, MXUS XF08C: case diameter: 128mm, DWG22C: 156mm.

 

[saneagle]

So now you mention I do remember that the controller was replaced when the hall sensors blew the first time. Do you think it's possible this controller is damaged as well after over heating? I was definitely always going slow up hills with the kids on the back, the hall sensors always blew on the hilly school commute. I was told by the guy who replaced the hall sensors previously to fit an external speed sensor so I could get a mph read out.

If you go too slowly up a hill with full power, the controller can overheat and blow the MOSFETs in it. The hall sensors are in the motor. They're fairly robust when it comes to heat Their specification is around 150 deg C, but they can go higher without damage. At that sort of temperature you're more likely to get other problems with the motor. Are you confusing MOSFETs wwith hall sensors? Do you know the maximum amps from your controller?

 

[Cargo_Bike_Bristol]

yes, form factor, MXUS XF08C: case diameter: 128mm, DWG22C: 156mm.

I see, sounds like I've made a fairly expensive mistake . Cheers for the help, going to look at a new kit minus the battery. Either that or I cut my losses and buy a Mycle cargo bike.

 

[Cargo_Bike_Bristol]

If you go too slowly up a hill with full power, the controller can overheat and blow the MOSFETs in it. The hall sensors are in the motor. They're fairly robust when it comes to heat Their specification is around 150 deg C, but they can go higher without damage. At that sort of temperature you're more likely to get other problems with the motor. Are you confusing MOSFETs wwith hall sensors? Do you know the maximum amps from your controller?

It's what I was told was blown when I first took it in for repair and it came out fixed so I didn't second guess what I was told. The controller is max 13amp so not crazy but burnout would explain a lot. At least I can move on from what I've got, I'm just fed up with not having a double seated cargo bike and the kids aren't getting smaller! Cheers for the help, need to figure out what is most cost effective/easy moving forward.

 

[Nealh]

The motor should be fine even though a wee tiny one, my Bafang G370 is weeny . It is smaller then my Alfine 8 by about 2mm and I run it with a dual voltage KT controller at 44v , it is a front motor and tows a 200lbs loaded trailer with out issues.
Going up steep inclines might be a different issue but mainly flat where I tow, bar a couple of 3% gradiants.

My advice is to use a KT 22a 9 mosfet controller at 48v , one can reduce the current in the adv menus to 50% if one wishes to. I don't bother because in lower PAS's 1 - 3 one gets a slightly little more current and even in PAS 4 one only gets 50% of the max current . PAS 5 is the only power level where one would get the full 22amps .

A 9 mosfet controller will not get as hot as the smaller 6 mosfet controllers, I use to get the same issue with KT 6 mosfet controllers . They would thermally cut out if riding slowly up hill so I went for a beefier controller and the KT 9 mosfet sine wave ones.

 

[saneagle]

It's what I was told was blown when I first took it in for repair and it came out fixed so I didn't second guess what I was told. The controller is max 13amp so not crazy but burnout would explain a lot. At least I can move on from what I've got, I'm just fed up with not having a double seated cargo bike and the kids aren't getting smaller! Cheers for the help, need to figure out what is most cost effective/easy moving forward.

13A is too low. Your motor would work much better with 17 or 18 amps. This sounds a bit weird, but what happens is the extra power will keep your motor spinning at a higher speed where it's more efficient and makes less heat and puts less strain on the MOSFETs in the controller.

As an example, my friend was a big guy. His bike had a big 500w Bafang BPM geared motor in it, powered by a 25 amp controller at 36v. He had done thousands of miles with it without any problems. I had my new two-speed Xiongda motor that works like a winch going up hills - very slow, but can pull you up anything. We were going up the famous Lincoln Hill bike climb. His bike had been up there many times. This time, he wanted to ride side by side with me. We didn't get far up the hill before his conked out. I had a look at his controller to see what was wrong to find that the motor phase wires were smoking and melted, and the controller was very hot. After a slight cool-down, I separated the wires with some pieces of card and told him to go full power to the top of the hill and wait for me there. When I caught up with him, he said he checked the controller and wires when he got there and they were barely warm.

 

[Cargo_Bike_Bristol]

The motor should be fine even though a wee tiny one, my Bafang G370 is weeny . It is smaller then my Alfine 8 by about 2mm and I run it with a dual voltage KT controller at 44v , it is a front motor and tows a 200lbs loaded trailer with out issues.
Going up steep inclines might be a different issue but mainly flat where I tow, bar a couple of 3% gradiants.

My advice is to use a KT 22a 9 mosfet controller at 48v , one can reduce the current in the adv menus to 50% if one wishes to. I don't bother because in lower PAS's 1 - 3 one gets a slightly little more current and even in PAS 4 one only gets 50% of the max current . PAS 5 is the only power level where one would get the full 22amps .

A 9 mosfet controller will not get as hot as the smaller 6 mosfet controllers, I use to get the same issue with KT 6 mosfet controllers . They would thermally cut out if riding slowly up hill so I went for a beefier controller and the KT 9 mosfet sine wave ones.

Ok cheers, that would be the cheapest option for me but I really am starting to think I started off down the wrong path and should have opted for a mid drive motor. I live on a steep hill and there is a steep hill on the school commute and it's already tricky enough on the geared Rad Runner Plus (rear hub motor) with one child so I think I need all the assistance I can get. I did also have quite an issue with the rear wheel being pulled out of alignment and have to rely on a small torque arm but I'm doubtful that I won't be constantly retightening it every so often so a mid drive would get rid of that issue. Looking at the Bafang 48v 250w BBS motor now as the possible next step.

 

[Cargo_Bike_Bristol]

13A is too low. Your motor would work much better with 17 or 18 amps. This sounds a bit weird, but what happens is the extra power will keep your motor spinning at a higher speed where it's more efficient and makes less heat and puts less strain on the MOSFETs in the controller.

As an example, my friend was a big guy. His bike had a big 500w Bafang BPM geared motor in it, powered by a 25 amp controller at 36v. He had done thousands of miles with it without any problems. I had my new two-speed Xiongda motor that works like a winch going up hills - very slow, but can pull you up anything. We were going up the famous Lincoln Hill bike climb. His bike had been up there many times. This time, he wanted to ride side by side with me. We didn't get far up the hill before his conked out. I had a look at his controller to see what was wrong to find that the motor phase wires were smoking and melted, and the controller was very hot. After a slight cool-down, I separated the wires with some pieces of card and told him to go full power to the top of the hill and wait for me there. When I caught up with him, he said he checked the controller and wires when he got there and they were barely warm.

That's so odd, I assumed it would be the opposite! The thing is I don't have much choice or desire other than slow riding with the kids on the back. The idea was it would be my commuter with the kids by for now I'm shuttle running it with the Rad which is ok but not ideal. Also I would like to get out on family bike rides. See my post above, thinking of a mid drive Bafang now.... I really don't want to throw in the towel just yet, as I literally built the bike from the frame up, sprayed it, made the decals and named it with the kids so we are emotionally and financially invested ha ha!

 

[Woosh]

That's so odd, I assumed it would be the opposite!

That's because your motor is not working in its sweetzone under 10mph, the yield drops, more battery turns into heat.
There is a tool on the ebikes.ca website to simulate your motor. XF08 is a tiny bit beefier than XF07, for simulation, just use the XF07 in their library:

https://ebikes.ca/tools/simulator.html?motor=MXUS_XF07&batt=B3614_GA&mass=150&hp=75&grade=5&cont=cust_15_70_0.03_V&axis=mph

Here is the comparison for a 5% gradient, 150kgs total weight, bike + rider +two kids, 15A controller. Look at the difference in efficiency (green plot) between your XF08 and a typical 48V kit like the DWG22C or a 48V crank drive at 10 mph on a 5% gradient

with a typical 48V kit:
https://ebikes.ca/tools/simulator.html?motor=cust_6_0.12_0.2_23_0.77_0.0185_0&batt=cust_48_0.2_12&mass=150&hp=75&grade=5&cont=C20&axis=mph

Bafang 48V BBS kit:
https://ebikes.ca/tools/simulator.html?motor=MBBS02&batt=cust_48_0.2_12&mass=150&hp=75&grade=5&cont=C20&axis=mph&mid=true

 

[saneagle]

When you choose a hub-motor, it's speed is very important. You should get one that spins with a naximum speed that's approximately 1.3 times your modal speed, so if you want to ride slowly, you choose a slow motor. Motors, like the XF08 are mainly a one size fits all. It spins to 20 mph at 36v and 26 mph at 48v, so is suitable for riders that want a modal speed of 15 mph at36v or 20 mph at 48v. If your riding deviates from that, you need a slower motor that you have to buy from a Chinese reseller.

A crank motor doesn't care about the bike's speed because you can make it whatever you want with gearing; however, it does care about your pedal speed. You should choose one with a max crank speed of 1.3 times your modal cadence for best efficiency and lowest heat.

 

[Cargo_Bike_Bristol]

That's because your motor is not working in its sweetzone under 10mph, the yield drops, more battery turns into heat.
There is a tool on the ebikes.ca website to simulate your motor. XF08 is a tiny bit beefier than XF07, for simulation, just use the XF07 in their library:

https://ebikes.ca/tools/simulator.html?motor=MXUS_XF07&batt=B3614_GA&mass=150&hp=75&grade=5&cont=cust_15_70_0.03_V&axis=mph

Here is the comparison for a 5% gradient, 150kgs total weight, bike + rider +two kids, 15A controller. Look at the difference in efficiency (green plot) between your XF08 and a typical 48V kit like the DWG22C or a 48V crank drive at 10 mph on a 5% gradient

with a typical 48V kit:
https://ebikes.ca/tools/simulator.html?motor=cust_6_0.12_0.2_23_0.77_0.0185_0&batt=cust_48_0.2_12&mass=150&hp=75&grade=5&cont=C20&axis=mph

Bafang 48V BBS kit:
https://ebikes.ca/tools/simulator.html?motor=MBBS02&batt=cust_48_0.2_12&mass=150&hp=75&grade=5&cont=C20&axis=mph&mid=true

Oh wow, yeah that really makes it clearer. If only I had asked some questions on this forum way back rather than taking the torque outputs at face value! Do you know if there any decent but cheaper alternatives to the Bafang, are Tongsheng recommended?

 

[Cargo_Bike_Bristol]

When you choose a hub-motor, it's speed is very important. You should get one that spins with a naximum speed that's approximately 1.3 times your modal speed, so if you want to ride slowly, you choose a slow motor. Motors, like the XF08 are mainly a one size fits all. It spins to 20 mph at 36v and 26 mph at 48v, so is suitable for riders that want a modal speed of 15 mph at36v or 20 mph at 48v. If your riding deviates from that, you need a slower motor that you have to buy from a Chinese reseller.

A crank motor doesn't care about the bike's speed because you can make it whatever you want with gearing; however, it does care about your pedal speed. You should choose one with a max crank speed of 1.3 times your modal cadence for best efficiency and lowest heat.

It definitely sounds like my riding style with this bike is more suited to a mid drive, I would never want to cycle with the kids at 20mph around little streets.

 

[saneagle]

It definitely sounds like my riding style with this bike is more suited to a mid drive, I would never want to cycle with the kids at 20mph around little streets.

Bafang BPM hub-motors go down to 180 rpm (code 16). One of those would be very suitable for your bike if you could find one.

 

[Woosh]

Oh wow, yeah that really makes it clearer. If only I had asked some questions on this forum way back rather than taking the torque outputs at face value! Do you know if there any decent but cheaper alternatives to the Bafang, are Tongsheng recommended?

do you mean cheaper than the Bafang BBSes? Nothing is much cheaper. The Tongsheng bb motors have torque sensor and cost about 5% less than their Bafang competitors. However, the Bafang have bigger motor compared to the Tongsheng. Tongsheng has just brought out their TSDZ2B Turbo with the same motor size and weight and costs the same as the Bafang.
If you like torque sensor, wait for the 48V TSDZ2B turbo, otherwise buy 48V Bafang.
The main issue with using bottom bracket motors for a cargo bike is chain wear. They eat through chains because of the heavy load you carry. Hub motors like the DWG22C don't wear chains.

 

[Cargo_Bike_Bristol]

Bafang BPM hub-motors go down to 180 rpm (code 16). One of those would be very suitable for your bike if you could find one.

Noted, thanks for the help