# The McElectric motorcycle



## fixitsan (Jul 9, 2014)

I've been building an electric motorbike for a while and have had some success recently.

powered by 840 18650 ex-laptop batteries and now at about 80V it goes so well that last week the motor woodruff key was sheared.

I'm going to change the gearing and limit motor current next.

in the meantime, the thread on the BVS has all the info, particularly covering the battery build in the earlier stages, here http://www.batteryvehiclesociety.org.uk/forums/viewtopic.php?f=34&t=3550&start=110

Chris Barron


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## fixitsan (Jul 9, 2014)

I've had time to make some changes, rebuilt the rear wheel, fitted the larger rear sprocket, added the Headway LiFePO4 pack and fitted appropriate Bussman fuses to both battery packs, and Anderson connectors for each pack.

It goes well !...

Not sure of the deal with posting puictures so try this link to my album on this site.... http://www.diyelectriccar.com/forums/album.php?albumid=322&pictureid=2554


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## fixitsan (Jul 9, 2014)

I just rigged up a datalogger and found a stretch of disused road to play on. Although the road was not long enough to allow me to run up to top speed, I was reaching 60kmh in under ten seconds and it felt like 70-80 was achievable because it had more to give. Still not getting my hopes up too much, but I think a sustained 45-50MPH is in sight


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## fixitsan (Jul 9, 2014)

Another test completed, this time with a current shunt in circuit to get some useful data.

Peak speed was 66kmh (I have a relay driver on it's way which will allow me to introduce a controller bypass. The controller only reaches between 90-95% pwm and has an output to drive a bypass controller. I'm hoping it will get me closer to the 50mph mark but I'm starting to wonder if I haven't undergeared it with the latest 60 tooth rear sprocket.

At peak acceleration the battery current is 225A and the voltage sags from 80V to 68V at that time.

The bike rolls along at about 25-30mph with a current of about 20A to 25A.

After a total distance of about 1 mile, made up of short bursts backwards and forwards at full current over about 80 yards, the voltage of the pack has dropped from 81.3V to 80V , equating to a cell voltage of 4.065V down to 4.0V. I have found that lithium ion cells drop quite quickly to about 3.9V and then the alloff slows down and is more linear over the discharge period to about 3.0V, so I find this encouraging. 

Chris


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## madma (Aug 7, 2014)

I bought one but the engine disintegrated after half a year


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## fixitsan (Jul 9, 2014)

You blew the engine or it expired itself ? They were favoured by track racers because of their abilities as a fast bike so when you come across them there's a good chance they've been abused.

In fact, mine came from a guy who had raced it, the circuit access pass was still secured under the seat. I did okay out of the sale of the engine, exhaust, radiator and ignition system though so am not complaining !


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## fixitsan (Jul 9, 2014)

The latest speed test video is here https://www.youtube.com/watch?v=LdhxEzJ7owk&feature=youtu.be 

As an added stroke of luck I was looking for acharger and saw an old Thundersky 80V (7A) charger on ebay, which was just managing to produce 2V and so was listed as faulty. The seller gave it to me for £10 incl postage because nobody else bid. I checked it over and sure enough there was very little output, but this is a smart charger and does not start charging until it detects a battery of the correct voltage has been connected.....so I hooked it up and it appears to work correctly !
£10 for emergency on board charging, not much weight and small in size


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## fixitsan (Jul 9, 2014)

I hope to have some more pictures and video showing all components of the bike soon.

Lately I've been playing with field weakening of the series would motor. My first test was with a short piece of very heavy (2 AWG ?) cable, but it produced too much arcing, although the speed increase was visible

The last test was using 2 metres of about 4 AWG multistrand cable and although I am getting more brush arcing than without it (it is still too much arcing though) I just clocked a top speed of 78kph , 48.5mph (that 0.5 mph is so important !), so I'm just about at 50mph on the flat and then I ran out of room so had to brake while still accelerating.

The brushes won't last long at this rate (they smoked during the first test !) so I can't implement field weakening. The brushes arc slightly without field weakening, probably because I/m using 80v and the motor's rating is for 36v. I don't want to tempt fate. 

To get more speed I think I'll drop down from 60 teeth at the rear sprocket to 54 teeth, and hope that the 10% gearing change gives me 10% speed change.

Chris


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## fixitsan (Jul 9, 2014)

I've acquired an ignition lock and barrel with key so have now got some security and the ability to switch all electronics off.

I have avoided putting pack voltage through the ignition switch by introducing a 12V supply. At first i was putting a hefty 12V lead acid battery in circuit, but then realised that I only need a battery which is strong enough to activate a 12V relay(with 40A rated contacts switching the 80V supply on) and hold it on until a 12V supply powers up when the relay makes contact. Then the output from the 12V supply holds the relay on and also recharges the 12V battery.

For the 12V battery I now have 3 ex-laptop cells in series, whcih are recharged through a diode and 33Ohm resistor from a non-isolated supply. I had to use a non-isolated supply because it is required for hte voltmeter/ammeter.

I have also collected a couple of 80V to 12V power converters by Powersolve, rated at 12V, 6.5A output. The circuit board which I removed the isolated supplies from also had a good quality line filter in circuit, designed for 100V input voltage so I've also cut that from the board and added it in circuit. Now all low voltage supplies receive filtered 80Vdc.

I've made up the brackets for the onboard charger too. I need to add isolation shields (plastic sheets) above the main terminals and below the charger (just in case) and add various other terminal shields.

The only mechanical thing needed now is the cladding for the main battery pack. Once that's in place I can consider running the bike down for an MOT test which I know it will fail, but which will give me an indication of what few things are needed (I know I need some fork oil seals and lighting but the rest is almost up to spec)


























https://www.flickr.com/photos/[email protected]/15001449907/in/photostream/


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## timk225 (Sep 19, 2014)

fixitsan said:


> The brushes won't last long at this rate (they smoked during the first test !) so I can't implement field weakening. The brushes arc slightly without field weakening, probably because I/m using 80v and the motor's rating is for 36v. I don't want to tempt fate.


You said the motor was designed for 36 VDC, exactly what make and model of motor is it?

You put it in this motorcycle with no modifications? And now are putting 80 VDC through it? From what I have read on these types of DC motors, advancing the timing on the brushes would be needed to improve performance and reduce the arcing, and in going from 36 volts to 80, I would guess an advance of about 8 to 10 degrees, have you tried that? Can a local motor rebuilding shop adjust it for you?

I am curious to see how much that helps.

Also, what are your motor rpms at top speed, and what rpms is the motor rated to redline at?


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## fixitsan (Jul 9, 2014)

I've run the motor up to 4000rpm and it held together well ! It is a GE type, I once decoded what was left of the original motor label and identified it as a 36/48V 2kW motor.

I know the brushes could be advanced. I tried to advance them but cannot do it with the motor in place so it will have to wait until I do the stripdown which I'll have to do in order to get the frame powder coated.

I've had a problem with the electronic volt/ammeter I was using and decided to put everything on hold while I build the electronics to monitor the battery pack. 

I'll try advancing the brushes when the time comes to take the motor out.

Cheers
Chris


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