Author Topic: Converting a bike to electric assist - a hair-tearing project!!!  (Read 4722 times)

The wife* (J) of one of my Rugby Regulars** had to give up cycling some time back due to health problems.   She has been tempted by the lure of electric assist but did not really want a clunky, lumbering electric bike, rather a conversion of a graceful and elegant bike.   

Keen to get her back in the saddle I was cajouled by the husband, (P), without much difficulty I hasten to say, to help convert the bicycle of her choice.

We paid a visit to CFC, a very worthy charity recommended by our own volunteer, Robgul, and bought one of these that they had in stock.   

I was also offered a secondhand front wheel conversion kit which came at a seemingly good price and have started the conversion.   I will detail progress in subsequent posts.

*  Also a friend

**  A pool of local cyclists with whom I ride out with on a frequent basis.

Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #1 on: 14 March, 2017, 07:04:50 pm »
There are a number of challenges in getting this kit installed and the bike working.

1:  The front wheel as supplied was a 700c, the bike has 26x1 3/8 (590) rims.   

2:  The bottom bracket as installed is not suitable for the sensor provided.

3:   The battery is a bottle mount version but step through is vital for J so the battery will have to be mounted elsewhere.

4:   We have had difficulty in getting the battery to fully charge.   

5:   As yet there is no sign of life in the kit.

Each one of these I will deal with separately in further posts.   

Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #2 on: 14 March, 2017, 07:13:26 pm »
The Front Wheel

It was decided by P and J that we should get a new rim for the bike and keep the existing front wheel intact as it could be put back into the bike and the bike sold in the future if necessary whilst retaining the electric gubbins.

SJS Cycles had two suitable rims in stock and the Ambrosio Benelux was chosen.   On arrival it was apparent that the rim was drilled for 13g or smaller spokes with the holes being too small for the larger nipples of 12g spokes used in these kits.   A Rolson reamer used with care has enabled me to spend less than an hour enlarging the 36 spoke holes in the rim which is now ready for spoking.

12g spokes are required for the build given the cavernous drillings in the hub flanges and Spocalc has indicated that 248mm 12g spokes are required.   I have found a place to order these spokes and hope to get them ordered in the morning.

The hub is slightly offset (248.1 offside, 248.4 nearside) but not enough to make a significant difference.

Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #3 on: 14 March, 2017, 07:22:26 pm »
The Bottom Bracket

Fitted to the bike was a crude but effective square taper cup and open bearings BB.   This was fitted with a notched lockring at the driveside and a hex profile on the nearside cup.   The pedal sensor is of a type which is entirely enclosed and fits between the crankarm and the bottom bracket cup held in place by splines which sit in the BB cup and the crankarm itself.   

When I locate the image of the sensor online I'll add it to the post.

In my vast box of bits I found a suitable UN53 square taper BB and did the transplant.   It was surprisingly easy - I had expected the bike to be odd size being cheap but no, it was a standard 68mm bottom bracket shell threaded as most are these days. 

Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #4 on: 14 March, 2017, 07:24:21 pm »
The Battery

The bike has extra braze ons at the dropouts for a rack as well as a crude extra plate near the top of the seatstays for a rack to be mounted.   I have a spare topeak rack which has a solid platform which is due to be drilled and modified to allow the battery to sit on said rack.

At first the supplied charger seemed not to be doing anything but finally, perhaps due to P not pushing the mains to charger wire fully home, life has been sparked into the battery.   There are two peculiarities though:

It's a 36v battery but reads 42v, and, no matter how long we leave it to charge it only goes green on three out of four indicator lights, the fourth remaining red.

We're hoping that this is not a significant issue.

Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #5 on: 14 March, 2017, 07:34:08 pm »
There's life Jim but not as we know it...

With everything plugged in the lcd screen flickers into life.  However,

1:   The screen does not register any life in the battery even though the battery shows 3 out of 4 green lights.

2:   Turning the pedals does not result in any activity at the motor.

3:   There is indicated on the screen some sort of indicator for the motor but nothing shows there.

Now, it could be that, as suggested by the vendor, that the controller unit is fubar'd and that once replaced life will be fully resorted.   The box is £40 if that is the problem so I think that we'll just have to bite the bullet and see.

Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #6 on: 14 March, 2017, 07:38:21 pm »
Fitting the kit

The kit includes replacement brake levers, a pedal sensor, a wheel magnet and sensor, a box of tricks, a trigger for extra boost, the motor, an lcd panel with a separate switch panel for on/off and assist level selection, the battery and the controller.   Most of this is now installed but it's not yet finished as I still have to build the wheel, secure the battery, fit the brake levers and tidy the wiring loom as well as potentially replace the controller. 

I will keep you updated on progress.

Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #7 on: 14 March, 2017, 08:40:02 pm »
There's life Jim but not as we know it...


2:   Turning the pedals does not result in any activity at the motor.



Are there sensors in the brakes, and are they adjusted correctly? At work I recently solved a problem with a electric assist bike by adjusting the brake sensors - they should have cut the motor out when brakes applied...
If it ain't broke, fix it 'til it is...

Kim

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Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #8 on: 14 March, 2017, 08:49:56 pm »
It's a 36v battery but reads 42v

This isn't unreasonable when fully charged.  36V is a nominal voltage.  (I assume it's some sort of Lithium-ion.)


Quote
and, no matter how long we leave it to charge it only goes green on three out of four indicator lights, the fourth remaining red.

Hmm...

Kim

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Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #9 on: 14 March, 2017, 08:54:45 pm »
There's life Jim but not as we know it...


2:   Turning the pedals does not result in any activity at the motor.



Are there sensors in the brakes, and are they adjusted correctly? At work I recently solved a problem with a electric assist bike by adjusting the brake sensors - they should have cut the motor out when brakes applied...

It *might* be interlocked against a moving bike (ie. the hub needs to be turning before power is applied).  Barakta's system won't apply power below some configurable threshold road speed, even with the pedals turning in the right direction[1].  But I don't think that's common.


[1] That's a point: You have installed the pedal sensor the right way round?  These things are directional, so the bike doesn't leap forwards when you backpedal.

Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #10 on: 14 March, 2017, 09:15:42 pm »
Not sure about the brake levers Wobbly - I have not yet dissected them in any detail but I cannot recall any obvious adjustment for the little micro switches.

Kim:  yes, I think that I will not know for sure until I put the built wheel in and give it a whirl.   The pedal sensor is definitely fitted correctly - I had to investigate this in detail last week but I managed to find it online and am certain that it's fitted correctly.

Kim

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Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #11 on: 14 March, 2017, 09:23:55 pm »
The brake switches will just be switches, so you can buzz them out with a multimeter to confirm they're working.

Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #12 on: 15 March, 2017, 06:47:10 am »
Brakes - They were reed switches on the one I worked on...
If it ain't broke, fix it 'til it is...

Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #13 on: 15 March, 2017, 07:22:02 am »
I have no idea what the switches are but they appear to be hidden in the lever housing and the lever presses against it when not braking.

Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #14 on: 15 March, 2017, 10:08:14 am »
Spokes ordered and a pending call with tech support.

Should be interesting.

We'll be putting the multimeter across all the sensors I'm guessing, the pedal sensor, the brake levers and the throttle.   

I am told that the throttle should operate independently of pedalling so it's a sign of something not being quite right that with everything being connected up nothing is happening.   

Kim

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Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #15 on: 15 March, 2017, 01:02:35 pm »
As it needs to determine direction, the pedal sensor is likely to be a hall-effect sensor with some electronics, rather than a simple switch like a cadence sensor.  I'd expect connections for power, ground and the output signal, and probing with a multimeter is unlikely to tell you much unless you provide power at the appropriate voltage at the same time.

At this point my spidey sense is saying "battery", though it could equally be a problem with the controller.

Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #16 on: 15 March, 2017, 03:00:25 pm »
Whenever you find that an electric bike is just not working, it is usually the controller. 
Loads of them are made which can't cope with the levels of current that they receive and they tend to blow.  When my wife had one, I used to carry a spare controller on our tours, wired with all the necessary connectors, so that I could swap it out in a few minutes.

Torslanda

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Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #17 on: 15 March, 2017, 08:10:10 pm »
Your dedication and determination screams for the proper recognition.

I'm sure the toys would have been well and truly hurled from the pram by now had it been me . . .
VELOMANCER

Well that's the more blunt way of putting it but as usual he's dead right.

Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #18 on: 15 March, 2017, 08:15:34 pm »
Whenever you find that an electric bike is just not working, it is usually the controller. 
Loads of them are made which can't cope with the levels of current that they receive and they tend to blow.  When my wife had one, I used to carry a spare controller on our tours, wired with all the necessary connectors, so that I could swap it out in a few minutes.

Interesting.   Have you ever taken a controller apart?   I'm wondering if there is anything in there that a skilled exponent of the soldering iron could perhaps replace.

If a new controller is required I think I'll get my friend Martin who is a bit of an electronics bod to have a play.   Unless, of course, Kim would like to? 

Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #19 on: 16 March, 2017, 02:10:23 am »
Whenever you find that an electric bike is just not working, it is usually the controller. 
Loads of them are made which can't cope with the levels of current that they receive and they tend to blow.  When my wife had one, I used to carry a spare controller on our tours, wired with all the necessary connectors, so that I could swap it out in a few minutes.

Interesting.   Have you ever taken a controller apart?   I'm wondering if there is anything in there that a skilled exponent of the soldering iron could perhaps replace.

If a new controller is required I think I'll get my friend Martin who is a bit of an electronics bod to have a play.   Unless, of course, Kim would like to?

No.  They always talk about mosfets though.  The controllers you want are ones that have had higher rated ones fitted.  There are (were) eBay sellers who did this sort of thing.  I don't know what a mosfet is.  Perhaps Kim will explain...

Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #20 on: 16 March, 2017, 07:29:06 am »
AFAIK mosfets are little black things with tails that get soldered onto pcb's in all sorts of electronic gubbins such as computer monitors and now ebike controllers.

I'll have to dismantle this one when it is replaced and get my friend to check it out.

Kim

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Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #21 on: 16 March, 2017, 01:17:40 pm »
Metal Oxide Semiconductor Field Effect Transistor:  A type of transistor that's suited to efficiently controlling large currents, hence commonly found on the business end of motor controllers, audio amplifiers, power supplies, etc.

MOSFETs are powered by magic smoke, and much of their specification pertains to the limits within which it won't escape.  With something like a motor controller, unless they've really cocked up the design, the big question is usually thermal - how much heat the MOSFET will produce, and how hot it can be allowed to get without damage.  How hot it gets for a given amount of power will depend on the physical design of the product it's installed in, and this is the bit that molishers of cheap Chinese kit will tend to take liberties with in order to keep costs down.  Overspeccing the MOSFETs, bigger boards, chunky heatsinks, fans, thermal cutouts, etc all cost money (and may add weight/bulk, and make waterproofing more difficult), and skimping on them when "it'll probably be okay if they don't thrash it" is good enough for a product that's being marketed primarily on price.

For added excitement, these sorts of components tend to fail so that they're stuck 'on' rather than 'off', opening up the possibility of further expensive failures as a result.  Fuses, of course, cost money and do nothing in normal operation...


Of course it might not be the MOSFETs.  A controller for this type of brushless motor needs some sort of feedback to know the exact position the rotor's in, so as to apply power to the right coils at the right time.  That may be done via Hall sensors inside the motor, which - along with the associated wiring - are relatively delicate and therefore another potential point of failure (think corrosion or mechanical damage).

And of course it's electronics, which means there's the usual power supply stuff to go wrong:  Cheap nasty smoothing capacitors (which might not take kindly to being baked by the output MOSFETs) etc.  If the power supply for the control logic goes out of spec, all bets are off.

Feanor

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Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #22 on: 16 March, 2017, 01:21:24 pm »
For added excitement, these sorts of components tend to fail so that they're stuck 'on' rather than 'off', opening up the possibility of further expensive failures as a result.  Fuses, of course, cost money and do nothing in normal operation...

The semiconductors are there to protect the fuses....

Kim

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Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #23 on: 16 March, 2017, 01:29:07 pm »
For added excitement, these sorts of components tend to fail so that they're stuck 'on' rather than 'off', opening up the possibility of further expensive failures as a result.  Fuses, of course, cost money and do nothing in normal operation...

The semiconductors are there to protect the fuses....

A truism.  The fuses might still get an opportunity to protect a motor winding or speaker coil, of course.

Re: Converting a bike to electric assist - a hair-tearing project!!!
« Reply #24 on: 17 March, 2017, 04:43:00 pm »
Spokes has arrived.   :thumbsup:

I'll probably not get to wheelbuilding though until we return from Scotland.    :(