KR-E ...lectric

[MENTAL490]

Have finally got my electric conversion of a KR-1 going, still some tweaking and testing required but happy with the progress. One design constraint I had was to make it look good, none of this square battery poking through frame/fairing BS, and I think I've achieved that

anyone can talk to me bout having a go on it too

WOW looking at these pic's brings back memories, I must admit my kr1 was my fav 2 stoker, not sure how much you have ridden it so a little heads up, put a better stand on it, the wind used to blow mine over till i got sick of repairing the fairings and mode'd the stand.

Great project tho

[bogan]

All them batteries significantly lowered the center of gravity, not much chance of the wind blowing it over! (especially not now since the batteries flogged out and it resides in the back of a shed)

[Wired1]

I'm currently scheming to build an electric motorbike and stumbled across this thread. Are then any updates on this bike on any other electric bike conversions?
Battery technology had progressed a lot in the last ten years and hub motors are getting more powerful.

[bogan]

I'm currently scheming to build an electric motorbike and stumbled across this thread. Are then any updates on this bike on any other electric bike conversions?
Battery technology had progressed a lot in the last ten years and hub motors are getting more powerful.

Nothing yet, am vaguely looking into battery options still; imports of any lithium stuff is pretty much by sea only now (due to overzealous pencil pushers), which means larger order sizes and longer to wait.
Not a big fan of hub motors due to their increase in unsprung weight (yes I know I put my motor in at about 30% unsprung).

I've heard of a few conversions being done down your way, have you got a donor bike lined up?

[Wired1]

Nothing specific yet.

It needs to be 72v minimum to get me to the 100kph range and 96v would be nice but that is 8 x 12v batteries and that is a large frame area. The full-fairing bikes look like an easy way to hide the batteries and if you use AGM deep cycle batteries they are smaller and lighter so you could do a smaller frame but with the motor in the frame too you are looking for a 650cc plus bike to fit it all in. I like the look of the bigger jap 750-four frames so I will keep an eye out for a suitable donor bike in the south island. I only want to spend $1000 to $1500 for the donor so I will wait for one close to home.

I like the cylindrical LiFePO4 cells and at 3.2v per cell you only need 24 of them to get 72 volts (or 30 to get 96v). They are still a bit pricey if you want the higher capacity cells like 70aH plus so might need to wait for them too. And they are hard to ship as you pointed out above. AGM lead-acid batteries are a good affordable option and have high capacity for the size and weight so I might do that but they are harder to fit in than the cylindrical cells.

The pros for the hub motors are the space saving in the frame and less losses in the transmission of power through the chain/sprocket etc.
It is hard to get a hub motor big enough (I reckon 10kW is the go) and then hard to find one that will take a proper back tyre size so it might be either wait for the technology to catch up in another year or go with the 6" motor behind the swing-arm pivot many e-bike builders follow.

For motors in general I think the less parts the better so brushless DC (basically a 3 phase induction motor) is the best way to go and I think it was this thread that convinced me to go for regenerative braking. The latest hub motors are just this and sop are some of the ETEK type motors. The control is a bit tricky but you can buy all the bits as kits.

I still have another bike in the queue before this project so it is early days yet but I am impressed with the speed and range the commercial e-bikes are achieving now. Not sure how far you have to travel to buy a Zero but it's probably Aussie.

[Honest Andy]

Casual musings...
When you stack your batteries in like bricks do you need to worry about heat build up?
If you use a hub motor will the extra weight affect suspension response?

(I probably should be thinking about my OWN projects... )

[Wired1]

Casual musings...
When you stack your batteries in like bricks do you need to worry about heat build up?
If you use a hub motor will the extra weight affect suspension response?

(I probably should be thinking about my OWN projects... )

The hub motor weight would have to change the way the swing arm moves and alter your sprung weight too so I guess moving the motor onto the wheel would mean you should use lighter shocks. Then again the batteries are bloody heavy so maybe not.
I'd like to keep the batteries as low as possible and a number of bikes you see on YouTube racing around race tracks at 200kph have very tall stacks of batteries in them - not so sure they would handle all that well. But you gotta put them somewhere. Maybe the traditional frame shape isn't the best way to build an electric motorbike - then again, I do want it to look like a motor bike.
It looks like the heat build up is an issue from looking at overseas builds and the spacers some of them are putting in their stacks. Stacking them up to face the wind where your cylinder jugs used to go has to be the best option for air cooling.

[jonbuoy]

Is there a reason no one is using 18650 cells that Tesla use?

[Wired1]

Is there a reason no one is using 18650 cells that Tesla use?

The sheer number of cells? The 18650 cells are 3.2v so for 72v you need about 23 of them per battery.
Then to get 50Ah (the 18650 are about 2.8ah each) you would need to multiply that by 18 so 18 x 23 = 414 cells.
They are cheap at about $2 per cell so under $900 for a battery.
And they would fill every nook and cranny you wanted to pack them into, might have to look into them.
I wonder how hot they get?

I like the look of the 60280 cells 3.2v 65Ah cylinder but at around $85 each that is about $2000 for a battery.

[bogan]

AGM are pretty rubbish for longeivity, that is what I used initially and they just didn't have the grunt, and quickly lost capacity; might be different if you overspec by a large margin though. Yeh 3phase motor kit with regen would be the way to go if I were doing another one.

18650 and 26650 cells are used a bit, you can get off the shelf cell spacers and weld tabs etc. So it's not that hard to build a large pack, BMS is a little trickier though as it necessitates a lot of cells in parallel.

For any cell, make sure to look at the C-rate, otherwise some packs will have the total kwhrs you need but not the kws.

[jonbuoy]

The sheer number of cells? The 18650 cells are 3.2v so for 72v you need about 23 of them per battery.
Then to get 50Ah (the 18650 are about 2.8ah each) you would need to multiply that by 18 so 18 x 23 = 414 cells.
They are cheap at about $2 per cell so under $900 for a battery.
And they would fill every nook and cranny you wanted to pack them into, might have to look into them.
I wonder how hot they get?

I like the look of the 60280 cells 3.2v 65Ah cylinder but at around $85 each that is about $2000 for a battery.

Using Panasonic ones in a few projects the capacity is a bit over exaggerated in a lot of the cheaper knock offs. I believe Tesla surround the cells with some kind of fire retardant coolant fluid. Might be possible to air cool them - plenty of gaps between the cells. Not sure about moisture causing issues?

A decent battery pack will make a huge difference to useability.

[jonbuoy]

You could probably use high voltage transformer oil, pump and radiator.