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Re: Another EV bike :)

Posted: Sat Jul 05, 2014 4:36 pm
by ChrisBarron
It was going so well.....

The woodruff key on the motor/front sprocket has sheared through. It goes to show how much torque is being generated, not surprised really, I'm not the lightest passenger in the world !

It probably should be a sign that I definitely ought to change the gearing to keep the torque lower, losing some top speed but having lower motor current when accelerating.

The motor is getting pretty hot at 80V, I'm going to see about dropping the voltage, maybe down to 64V, but then again the heat might well be building up because of the low gear ratio. I think that I'm going to have to see how it goes with better gearing first.

Re: Another EV bike :)

Posted: Mon Jul 28, 2014 5:50 pm
by ChrisBarron
The woodruff key has been replaced (humourously with one designed for a Lambretta scooter, it's a perfect fit !)

I've moved on with a few other things too. The LiFePO4 Headway pack is assembled, and a fuse is fitted to both battery packs at their positive terminals.

The potbox is behind the headstock, below which is the main contactor. I've added Anderson connectors for each battery pack.

All brakes are operational. The rear sprocket with 46 teeth has been swapped for a 60 tooth version, to bring the gearing to 60/13 = 4.6:1 from 3.6:1 and this has made a big difference int he way the bike takes off, and hopefully will help to prevent another broken woodruff key.

The rear wheel bearings have all been replaced.

I don't have much more to do in terms of fitting more parts, there's a shunt and ammeter/voltmeter on it's way and I've left room for that.

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Re: Another EV bike :)

Posted: Thu Jul 31, 2014 4:02 pm
by ChrisBarron
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

Re: Another EV bike :)

Posted: Wed Aug 06, 2014 7:53 pm
by ChrisBarron
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.


Re: Another EV bike :)

Posted: Sat Aug 09, 2014 11:34 am
by ChrisBarron
The latest speed test video is here ...

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 I hooked it up and it appears to work correctly !
£10 for emergency on board charging, not much weight and small in size :)

Re: Another EV bike :)

Posted: Wed Sep 03, 2014 1:29 pm
by ChrisBarron
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.


Re: Another EV bike :)

Posted: Wed Sep 03, 2014 7:18 pm
by ChrisBarron
I've been asked for the code of my cell tester.

I have popped the code here ... %20tester/

Re: Another EV bike :)

Posted: Thu Sep 04, 2014 12:11 pm
by Grumpy-b
Re the sprocket and key, use a taperlock hub/ sprocket, that grips the shaft so doesnt rely solely on the keyway for the transmission of the power.


Re: Another EV bike :)

Posted: Thu Sep 04, 2014 5:20 pm
by ChrisBarron
I would do that if the shaft was parallel, but the motor shaft is already tapered. (Hence why I had to get the motor sprocket specially made)

I fixed the slipping key problem just by fitting a new key and torquing the sprocket nut to a higher value than before.

Things are going well at the moment and I think a drop in gearing ratio won't mean the present key is destroyed. I'll use the current limit and acceleration control of the motor to keep it under control too.


Re: Another EV bike :)

Posted: Tue Sep 09, 2014 11:02 am
by ChrisBarron
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)

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