First Post and query about dual Bafang setup

[tasflyer]

et aOk, have been lurking and reading for a while, time to post !

Ok, first the saga of how I ended up here

Few months ago a bought an Electric bike for my wife. The requirement was for a bike that would allow here to allow her to ride with me and my 12 year old daughter on our mountain bikes allong bike tracks and the odd dirt road. Here in Aus we have the 200 W limit thing so I ended up getting a ladies step through bike fitted with a rear wheel Bafang and 36 v Lithium-ion for Green E-wheels in Melbourne. Have to give them a plug as they have been very patient dealing with me and the ensuing problems. I am actually in Tasmanaia so evrything had to be freighted. Anyway, first few rides were fine. The motor allows my wife to wind the thing up to ~ 30 Kph which is about what me and my non motorised daughter can keep up with pedalling. Needless to say the problem has come about on the hills. After a ride involving a ~ 3 k climb the bike failed on a steep pinch of the hill. After a bit of pushing and cursing we got the bike home. I have a bit of an electronics background so I did a bit of a diagnosis and concluded it was the controller on the basis of the 5v feed to the throttle and the Pedal Assist hall sensor was only ~ 2.5 v. Anyway, after posting the controller back, getting a replacement and fitting it the voltages measured the same. After a little more checking I determined the power supply to the hall sensors in the motor had gone short circut (and were pulling the 5v rail down) .. DOH ! Anyway, after explaining myself E-wheels posted me down another motor (laced into rim with cluster and everything). At this point I had done a bit of research and had found out about the reliability problems with Hall sensors. I then ordered a sensorless controller from Brett White. Guess what - it hasn't turned up (after three months). Anyway, fitted the wheel and all was good till a few rides later when the motor failed again on a similar hill. The problem in our case seems to be a combination of the string used to hold the cabling and the heat shrink tube used over the leads of the hall sensors. Obviously a bit of heat and the string causes the leads to get forced tohether and short. After reading this forum I was expecting to see some problems with the gears but they looked fine. I attribute this to the fact that my wife only ever uses Pedal Assist mode so the bike is always moving before the motor kicks in.

Anyway, apologies for the essay (ah thats off my chest). Now I can replace the hall sensor without much drama but want to get a bike together that will be reliable. What I am thinking is one of the following:-

1 Replacing the Hub motor with a higher pwer one. Basically, we're not after more speed just more torque for the hills. Ideally something like the BMC 600 w Torque version would be the go. This would be very expensive to get to Aus I imagine.
2 The other option I have been thinking of is adding a front Bafang motor to the bike and additional controller. It would be controlled by the existing throttle and PAS. A switch would allow it to be switched on when required. It would just freewheel the rest of the time. The other thing to note is the Bafang motor we have is "black" motor which is normally a front wheel config anyway ? I figure I can get some spare gears, etc which would be compatible across both mtors.

The idea is this would give a bit more power/speed on the hills and horfully reduce the heat generated. The other thing I was thinking that the the low voltage cutoff would save the motors if they are too heavily loaded bearing in mind its a 36v 10ah unit.

So has anyone tried a dual Bafang setup ?

 

[gogo]

Hi tasflyer and welcome to the ES forums.

Just to clarify, the hall sensor wires melted the heat shrink and shorted to each other? The phase wires were not involved?

 

[dogman dan]

I suspect the real source of the problems is my old buddy, Heat. It took me a few motors to get the hang of not melting them down, and even more before I finally got one that just plain wont. ( 5304 clyte)

Anyway, one of the first things you need is to put a temp sensor on the end of the hub axle, or if the wires fit, inside the motor near the halls. Then you can stop in time. On my fusin motor on a 13% hill torture test I reached danger tempreatures in about 2 miles in 15 minuites. If your hills are very steep that may be the main issue. Gearmotors shed heat slower, since there is essentially a motor spinning inside a 2nd case, adding a layer to the way it radiates it's heat. So you may be better off to get a big 5306 crystalyte, though it'll cost ya, especially if you go for high amp controllers and batteries. It just depends on the hills. If the hills are less steep, then lesser direct drive motors may work fine, like if the hills are under 5%, in which case the aotema with no halls has some appeal.

A dual motor makes some sense though, since you can either run one while the other cools, or run both on seperate batteries, cutting the heating of each in half. Slowing down, using a lower gear, and watching the temps is crucial in hilly riding. In a lower gear, you can get up the hill using less throttle, and go a long way without overtemping. A sensor with a readout on the handlebars allows you to learn to ride cooler, which usually results in longer range too.

A guy near me in NM has been doing a lot of experimenting with dual motors to ride in the mountains. Rule one is don't run both motors on one batter at the same time.

The learning curve is steep with ebikes, since at first nobody selling you a motor tells you how easy you can melt one down.

 

[tostino]

Why not run both motors on the same battery?
If you go for two 15a controllers with two motors, you will be able to have the same peak power as one motor with a 30a controller. It should also take roughly the same amount of power cruising with both motors at once, as it takes to go the same speed with one motor. In fact, you may even get higher efficiency with two motors than one, because you are not using each motor at it's limit, and it is able to run in it's max efficiency zone for more of the time than one motor you are pushing past it's efficiency zone.

You could also make it so your throttle controls both motors at the same time, or with the flip of a switch you can have it only send the throttle feedback signal to one of the controllers so it is only using that one.

Just some ideas.

I have some experience with the Bafang. I live where it is completely flat, but I am pushing my motor to 35mph on 51v. It takes 1200w to keep me at that speed.

 

[OneWayTraffic]

I'd order a sensorless controller from JohnHolmes or ebikes.ca (check that the ebikes.ca one works with the Bafangs.) And just go to it.

It's now winter in Aus; I believe Tasmania sees roughly the same climate as the North Island of NZ. Of course northern Australia is always hot, but Tassie...

I don't think internal motor heat would be such an issue, at least not in the middle of the year. As long as you have good connections and no unexpected source of resistance anywhere, the motor should hold out.

you might consider a CA so you know what you're dealing with. http://www.ebikes.ca/drainbrain.shtml

 

[Rassy]

Hi tasflyer, welcome to the forum. In sort of an odd way, I am running two bafangs. Two major differences from what you would be doing: Smaller wheels, and one is on a trailer. The front wheel motor is laced into a 20" wheel and the trailer wheel is laced into a 16" wheel. Both were purchased from JohnRobHolmes. Even though the motors are identical, they each have their own throttle, because of the different wheel sizes. This setup was put together for slow and efficient multiday rides with other pedal only bikers.

Anyway, with the bike alone I can maintain about 8 MPH up a 15% grade. But with the trailer in tow (not much load) I can maintain about 13 MPH on the same hill. In order to keep the front Bafang from heating when using both motors, I use WOT on the trailer motor, and just enough throttle on the front motor to maintain the 13 MPH. I've had several other setups that used just one common throttle to run two or three matched motor/wheel combos, and those have all worked great.

So, bottom line, I think you would be happy with two Bafangs on the same bike with one throttle. And the idea of a toggle switch that cuts off one motor when not needed should work good to increase efficiency, but may not be needed. As stated by tostino, running both motors at the same time may be just as efficient as running one motor by itself, since you would be moving the same total weight at the same speed. Only some measured tests would tell for sure. Good luck with the project, whatever you decide to try.

 

[monster]

depend if you just want reliability or if you want power too?

if\> reliability
then\> get a brushed hub motor and a switch for a controller. something like the DB36. temperatrue sensor is a good idea too. this is cheap and has the advantage of not breaking the 200W law -maybe-

if\> power too
then\> go ahead and buy that X5 or X4 they are beautiful motors and very reliable

RMA that broken motor you bought and get your refund

 

[dogman dan]

Yeah, I suppose a lot of batteries could handle a 500 watt load, duuh. The case I was thinking of had two 35 amp controllers running on one battery, so that was harsh on the battery. Just stay under the comfy limits of your pack, whatever it may be. I like the idea of two throttles myself, because motor heating IS an issue here. With two throttles you could rest one motor and run the other if needed. I suppose you could simply unplug one motor too.

On my torture test of the fusin, that is similar to a bafang, on a 15 amp controller, I went from 90 F to 170 F in two miles. It just depends on how hard you are hammering it whether heat is an issue. One small part of that ride is 20% but the average slope of it was about 7%

 

[johnrobholmes]

I would probably get two motors and two sensorless controllers. I haven't tested the sensorless modules on the Shenzen controllers yet, I typically use RC controllers. One bit of testing to be done for sure...

Two motors would give more pep at a small weight cost. Certainly less cost than getting a BMC.

 

[tasflyer]

Thanks for all the info/feedback guys. This site is undoubtedly the source for info. In summary:-

- It sounds like a couple of sensorless controllers a second front wheel Bafang and some metal/spare nylon gears I might actually get the reliable hill climbing bike for my wife that I wanted. I have already ordered/paid for one such controller from Brett White. I'll follow that up first up. I will add a temperature sensor as well.

- I had read here about the X5 series motors but that would be way overkill for this application. The bike is for my wife and I don't want to end up with something too heavy for her to handle. I have seen the the vidoes of the Stealth Bomber, etc bikes now and am tempted to build something for myself now !

- In the meantime I want to get my wifes bike back on the road while I wait for the other bits I need. I have included a photo of the hall sensors from the motor. As indicated the problem was the wires from the hall sensors were crossed and lashed tightly to the motor winding with string. The short circuit across the hall power supply went away when i prized the leads apart. I am going to re-secure the leads with cable ties and make sure the wires are suitable separated. There wasn't any discolouration of of the windings or anything so I expect the motor didn't even get that hot for this to happen. Cutting the hall sensor leads shorter and and soldering hookup wire to the shorter leads would also help.

Anway, unfortunately I pulled the leads off one of the hall sensors so I need a replacement. Do any of theother Aussies on this site know anywhere in Aus that you can get replacement Hall sesnors (e.g. Honeywell SS41 ? ). The two big Electronic retailers here (Dick Smith & Jaycar) both have a sensor which is the same form factor but is a linear device (ratiometric 3503) and would require some other logic to connect to the controller.


Also as the thing is pulled apart I was going to lube the gears. I usually use a lithium based grease for this sort of thing but I am wondering onthe effect on the Nylon gears ?

 

[marshy]

Anway, unfortunately I pulled the leads off one of the hall sensors so I need a replacement. Do any of theother Aussies on this site know anywhere in Aus that you can get replacement Hall sesnors (e.g. Honeywell SS41 ? ). The two big Electronic retailers here (Dick Smith & Jaycar) both have a sensor which is the same form factor but is a linear device (ratiometric 3503) and would require some other logic to connect to the controller.

Hi tasflyer - in the past I've found otherwise hard-to-get goodies at Farnell.com.au. However, they don't seem to have any SS41's at Farnell Australia. They may be able to send out from the US, or perhaps they have a suitable alternative locally.

 

[lesspedal]

Hi Tas,
From what i have read on forum, Best of luck with brett white.
If you have steep hills, i reckon chain drive systems are the only way.
Check out http://www.elationebikes.com.au , site also has lots of helpful info,watts required for % hills, graphs etc.
Trev.

 

[willywombat]

I read with interest as I too have a greenewheels 36v10ah lithium with Bafang 200w bought 4 months ago which has failed. Failed initially on steep hill (but only a short way - 200m or so up it) with a clicking sound from motor - like a non-engaging starter on a car. I immediately stopped and pushed! At top of hill motor seemed to work fine but after another 10 km or so has failed, initially intermittently - now completely. Problem is either with control box or (perhaps more likely) motor and Hall sensors. Greenewheels helpfully respond to emails and offer to sell more parts but say bike only had 3 months warranty and the implication is fault was mine (for pedalling up a hill! - and I only ever use with pedal assist). Annoying as have done only around 500km and have been very impressed til now!

Control box has normal input (42v) and output of 5v to all three phase wires (regardless of throttle ) and in and out of all three hall sensors (although didnt test with wheel rotating). voltage across the three phase wires is 0-10v yellow to green and blue to green but never above 0 blue to yellow as throttle opens.

I suspect a problem with one of the Hall sensors but am a bit relucatant to open the back wheel if unnecessary. Any ideas?

Greenewheels offer to sell me a new controller for $100 or anew motor/wheel/wires for $200 but are only around for five days in next five weeks so difficult to know which to buy (or both) as am keen to get teh bike back on the road. Or should I bite the bullet, open the motor and look into replacing the Halls? If so did anyone find a supplier in Australia yet? And.... if it looks like a need a new control box would I be better to upgrade to something more reliable? - if so any ideas what would be better and from where available.

All suggestions received with gratitude!