Project: ghEttoBIKE

[danielrlee]

Times are hard.

Hi everybody. I am a new member of this forum (it has been such a great resource to me so far) and have been lurking for a few weeks while deciding what I was going to do regarding an e-bike purchase. Sick of the ever increasing cost of motoring and dreading the upcoming Olympic traffic jams, I have made the decision to switch to cycling where possible, although I haven’t owned a bike for over 13 years (now 32). Cutting to the chase, with a fairly low budget, I have failed to find anything that floated my boat.

I love a DIY project. That is why I now find myself the recent owner of the following:

One brushless hub motor – 'Two Knives DX-3000' (24v, complete rear wheel w/ 6spd Shimano freewheel);
24v controller;
Twenty (yes, 20) nearly-new 12v 7ah SLA batteries;
A choice of serviceable free bikes.

So far, I have spent less than 40 quid Let's hope it's not money wasted....

A couple of things about me. I love technology, electronics, car maintenance, DIY and just generally getting my hands dirty. I own a decent car mechanics tool kit. I know what a soldering iron is and I'm not afraid to use it. The idea of the ghEttoBIKE doesn't scare me. The only thing I seem to be lacking is the e-bike specific knowledge......

That's where you guys come in (hopefully). I just want to say thanks in advance for any assistance you may be able to provide. I'm very much looking forward to getting this project started and sharing the experience with you.

I will take some photos shortly and then will get back to you guys with a plan of attack.

Dan

 

[banbury frank]

Hi Dan

And welcome to the forum please let us know approx where you are so local members can try and help you

I Think you have the basics of a serviceable E bike

Frank

 

[danielrlee]

Hmmm.... 15 minutes in and there's a snag already. The 3-phase power cable for the electric hub had practically been severed at where it enters the axle. I tried to resolder it (such a bitch of a place to go - poor design IMO) but even if I do a GREAT job, it's unlikely to last. Here's some photos:





The only way to do this properly is to replace the cable in its entirety. I removed the freewheel and popped open the hub motor. It appears that this is an 8fun motor (see photo below) - a name I have come across before, rather than a nasty Chinese jobbie.



Assuming I'm able to fix it, is this motor any good?

Can anyone suggest the best way to go about doing this? There is an e-clip where the axle enters the hub and a hole just above this:



I'm not sure if this hole contains some sort of grub screw, since it's filled with a black sealent, which I assume is for waterproofing duties. How would I go about removing the axle from the hub motor, so that the wire is easier to tackle? I thought I'd ask before diving in and most likely breaking something.

 

[danielrlee]

Hi Frank. Thank you for the warm welcome. I'm from Buckhurst Hill in Essex (just updated my profile).

As far as I can see, I'm only missing a throttle, pedlec sensor and maybe a battery meter and motor cut-out (if I'm feeling really flush ).

 

[danielrlee]

It's just occurred to me.... Is 8fun an ebay cheepie brand? I'm new to this e-bike malarkey

 

[neptune]

Those photos, although excellent are no substitute for seeing the motor in the flesh. I t may not be necessary to remove the axle, and I would guess that you can not remove the axle without first removing the wiring. Here is what I would do. First cut the wires where they emerge from the insulating sleeve inside the hub. I would guess that the only thing then preventing you pulling the wires out of the axle is the sealant . If necessary, try warming the axle gently with a blow lamp, but not hot enough to destroy the temper of the metal. Pull out the wires from the axle. Try from the outer end, but if necessary , from the inner end. Push new wires through the axle and join by soldering and sleeving . After cutting , you may need to gain a bit of slack by extracting an inch of wiring from the string lacing of the winding, unless varnishing or epoxy encapsulation prevents this . I would guess there is no grub screw, and that axle removal is by removing the circlip in the photo. You may get better info from someone who has done the job.

 

[wurly]

The Bafang hub is chinese as are most hubs. It's a good motor. I would also assume it's geared with a freewheel. Your initial problem is to rewire the stator, which shouldn't be difficult. The problem is getting hold of the correct wire with teflon insulation. You should be able to pull the original wires out of the motor shaft, so it shouldn't need dismantling any further.

 

[flecc]

You're lucky that it's not an 8 wire Hall sensor motor, it should be possible to replace the three phase wires ok. There's usually some silicone rubber holding the wires within the spindle, but you should be able to pull them out once you've cut them internally. The fiddly bit is the cable lacing on the stator, patience being the best tool.

 

[danielrlee]

Thank you to everyone for your suggestions so far. Hopefully this'll be the biggest snag of the whole project (I'm an eternal optimist).

I'm just about to have a late dinner and then might tackle this after. I'll get back to you at the first opportunity.

Another hurdle to overcome is identifying the controller and deciphering the wire functions (which I've got no doubt that you guys'll be able to tell me in a heartbeat). A couple of photos:





1 - Motor
2
3
4
5
6
7 - Battery

I, like any fool, can tell 1 & 7, but what about the rest?

 

[danielrlee]

I cant believe I was being such a wimp. A snip and a tug and the wire came out without any issue.

I haven't got any wire of the correct colour (anal I know, but I like doing a proper job and I'd rather not have to struggle identifying the wires at a later date), so cannot complete this right now. I'll find something suitable tomorrow.

Just a thought, how many amps is this motor likely to draw? The controller says 'rated current 7A', but maths tell me that the motor produces more, assuming 250W.

 

[shemozzle999]

I cant believe I was being such a wimp. A snip and a tug and the wire came out without any issue.

I haven't got any wire of the correct colour (anal I know, but I like doing a proper job and I'd rather not have to struggle identifying the wires at a later date), so cannot complete this right now. I'll find something suitable tomorrow.

Just a thought, how many amps is this motor likely to draw? The controller says 'rated current 7A', but maths tell me that the motor produces more, assuming 250W.

I have a few replacement 3pin and 9pin motor cables available to members, complete with the advantage of an in-line weatherpoof plug and socket so your can disconnect it should you need to remove the wheel for repairs and the ability to slid all the nuts and washers over the connector as it is only 10mm diameter.
Seach the classified section for Replacement motor cable for details.
PM me if interested

 

[banbury frank]

Hi

The controller you have looks like it is for a motor with hall sensors and it is 24 volts

You need a 36 volt sensor less controller
I am sure another member will come up with where to get one

As for the throttle ? battery Gauge and pedal sensor I can Help If you send me your address to frank@xipi.co.uk I will send you them Free

To get you Going

Frank

 

[neptune]

The amount of current a motor draws will vary according to how hard it is working at the time. Cruising along on the flat at 15 mph , I would expect it to draw about 6 amps. when you hit a headwind, or a hill climb, then the motor will slow down and draw more amps.The worst case scenario is hill climbing below 8mph. To prevent the motor overheating in these circumstances, the controller has an inbuilt current limiter. On most controllers this can not be adjusted, and is preset. The actual value will depend on the controller, and can be typically 12 to 20 amps. As pointed out previously, the controller must match the motor .That would be a 36 volt brushless type. Other members can tell you a suitable current limit for this motor/, probably around 18 amps.

 

[amigafan2003]

1st piece of advice - ditch the lead acid batteries - they have no place on an ebike.

 

[neptune]

@Amigafan2003. You are obviously not a fan of lead acid batteries. Whilst having the greatest of respect for your opinion, I do not share it. For local pottering about they are in my opinion the best choice. The guy is building a project on a shoe string , and already has these batteries. They will do to get him started, and who knows, he may well develop a taste for more exotic stuff later. They certainly have a place on my ebike, firmly enclosed inside the battery box!

 

[danielrlee]

Hi guys. Ahhh, finally home after a 12 hour day. I've had no time to source some suitable cabling with which to repair the hub motor, so that's going to have to wait until next week sometime - I've got a weekend camping trip planned with the boys and then my girlfriend is here for the week. I can't see the repair being too difficult now I have stripped out most of the old cable.

@Amigafan2003 I am aware of the pros and cons of various battery technologies and their suitability on an electric bike. Neptune pretty much summed up the reality of the situation for me - it's largely about the bottom line. The plus side is that I weigh a paltry 9 stone, so this should offset my biggest problem with the humble lead acid battery - its mass.

Regarding the motor; I was under the impression that it is a 24v unit, because of a small sticker on the hub casing that reads '24v'. Since so many of you believe that it is a 36v motor, do I have this wrong? The motor and controller was purchased together in a single ebay auction. I have had no verification that these were originally supplied as a pair, or that they even work altogether for that fact. I am concentrating on these items first so I can verify that the motor is indeed operational - I don't have much of an electric bike without it! Below is a link to the original ebay auction:

ELETRIC BIKE 26" WHEELwith SHIMANO 6 GEAR+KENDA HIGH PERFORMANCE TYRE+CONTROLLER | eBay

Regarding controllers in general; Is there any standardisation of plugs and wire colours? I have already considered that this controller is more trouble than it's worth and I might be better off buying a new one, maybe together with the other necessary parts.

 

[danielrlee]

Hey guys. Right, I have repaired the motor wiring. Hopefully it's all good:



I havent terminated it yet (will most likely splice the original plug), but I've left a couple of feet of trailing cable.

I want to test the motor to see if it functions correctly. I would imagine that if could identify the throttle plug on the controller, I could short the throttle pins to get it running. Will this work? Can anyone tell me the correct plug as in the numbered photo in post #9? Even an educated guess from somebody would be better than me randomly stabbing at plugs

 

[neptune]

Looks like a first class repair job. The next thing you must do before worrying about a controller, is establish for sure what is the design voltage of the motor. Does the controller have a label on it with a voltage? Why not post all the numbers stamped on the hub, and someone may be able to tell from that. There is very little that can go wrong with this type of motor . If the bearings are OK , and the coils are not broken , burnt or earthing, that just leaves the gears and the clutch or free wheel. Do you have a multimeter? If so I can tell you how to test the windings.
There are no standard colours for wiring . If you post pictures of your controller, some one may be able to tell you . Do not short the throttle wires, or any wires until you have more info. On most controllers, you can simulate the throttle by using a 10K potentiometer [ aka Pot ,Variable resistor] . These cost about £ 2.
There is a fair chance that the motor wheel was working fine, when it came to grief by spinning the axle in the forks, and shearing the wiring. Need further info? Just ask .

 

[danielrlee]

Hi Neptune

Here are the photos of the controller label and connectors:





I have not yet been able to identify the connector for the throttle. Any help with this would be much appreciated.


Here is a photo of the only markings on the motor itself:



Up until recently, I was under the impression that this is a 24v motor (all evidence points to this), but a number of people on this forum have suggested that it is 36v. This has obviously cast a shadow of doubt in my mind. Unless somebody can give me conclusive proof that it is a 36v unit, I guess I'm going to have to trust the labelling.

I do own a multimeter and probably already have some 10k pots in my junk box. Thank you for your assistance neptune - your knowledge is absolutely invaluable to me.

 

[neptune]

OK . A quick look on the 8fun website shows that they do make some 24 volt motors. This probably is a 24 volt based on the sticker, and the fact that 8fun have some electric folders with 20 inch wheels which are 24 volt . Also the fact that the controller is 24 volt. In the absence of someone having the same controller, the best we can do is some intelligent guesswork . The heavy black and red wires [7] look like the battery connections . Do not connect a battery without a fuse [say 15 amp for tests. ] The three wires marked 1 look like the motor wires .5 and 6 are probably the brake cutouts. Problem is we do not at this stage know if they need to be shorted or open circuit to make the motor run .Often a throttle is a 3 wire device , so I would guess 4 . 2 and 3 are the problem . Possibilities are pedelec sensor, ignition switch, and battery level indicator . Someone out there knows the answer. This controller may be supplied by 8fun, and they may help .
WARNING. Before attempting to run motor , it must be firmly fitted in a bike frame, and the frame held firmly in a vice or similar , and free to rotate.

If all else fails, there are cheap brushless controllers on Ebay from Hong kong and china.
It is just possible that your existing controller is not compatible with your motor, because it may be designed for a brushless motor with Hall sensors. Your motor does not have hall sensors. so if you buy a controller, get one that is suitable for a brushless sensorless motor.