Swedish Kona DH Cromotor 10kW Kelly *Water cooling?*

[Peter Sternersson]

Since there isn´t any real suiting swedish forum for electric bicycles, I thought that I would present my ongoing build here instead, for the best support and knowledge, cause this is a goldmine of awesome builds and sweet caracters.

Mind you, I do not write in english every day, so spelling mishaps will occur.

After completing a commuter build last year with a KTM bike, 16S LiFe 15Ah, 1000W hubmotor, and riding it to and from work last fall, I decided that I wanted something more powerful, and something able to climb rocks and trails in the nearby woods.

I got my hands on a used Kona Stab Deluxe 2003(?) from the swedish equivalent to Craigs list.
It came with a Marzocchi Bomber Monster 03 front fork, and some Hayes Nine hydraulic disc brakes with 203mm discs.

It looked something like this (not my bike in the picture, but looks the same apart from the color of the rims).

A short summary of the build is as follows:

Frame: Kona stab deluxe

Tyres: Maxxis Hookworm 26" 2" wide

Motor: Cromotor ver 2

Controller: Lyen 24FET with some beefed up traces for 110-120Amps

Batteries: Haiyen LiPos 20S4P = 74Vnom and 20Ah. They are hardcase 4S so the mounting should be very compact and tough

BMS: Signalab 20S 30A (I will only run charging and the "on" voltage to the controller through the BMS so the 30A limit is not the limit of the system)

Charger: Bulk charging with a 600W BMS-battery alloy charger. Might go ahead and buy a Mastech 100V 10A power supply later on


A very nice feature on the Kona Stab is that the dropouts are removable, so I went ahead and drawn up some new dropouts with good clamping ability around the axle.

I got some help with CNC machining from a friend, and it fits in the frame like a glove!

It also fits really snug around the axle. Almost no need to clamp it actually.

I want the possibility for a powerful regen to save brakes, so I beefed up the rear swing arm with some 3mm stainless steel.
Also welded a 3mm piece of steel for the brake caliper.

I had some problems with the chain on my new BMX freewheel, it would come of when power to the pedals was applied. I was convinced it had something to do with the Shimano chain tensioner that I had modified for the wider chain. So I machined out a new arm and a guide wheel.
Turned out that the chain tensioner had nothing to do with my problem, and the real culprit was the cheap chineese freewheel that had very sharp edges on the teeth so the chain climbed. Some grinding later and it was smooth as a babys bottom.

This is more or less how it stands today. With some luck I´m getting the 20pcs of Lipo from Haiyen today. That would mean that I have the entire easter holiday to build a batterybox, somewhere on the bike
The controller is so large that I´m thinking of putting it on the luggage carrier on the back. You can see the cardboard mock up on the picture. The 24FET is a monster!

 

[Rodney64]

Peter your builds coming along very well and well done on your documentation so far.

 

[Peter Sternersson]

Thank you Rodney. I like sharing my progress and misstakes, since I have learned SO much from reading about other peoples misstakes throughout the years...

However, I must have confused easter with christmas, because this was waiting for me when I got home today

1480Wh of LiPo-power!

Now I just have to wait for them all to warm up, then measure for DOA-cells, discharge them with some 12V lightbulbs or something, measure again, then charge them and measure again. How many cycles of testing should I put them through before mounting them on the bike?

With my 20Ah and max of 120A I will just pull 6C out of these 20C-cells, I hope that makes for long lifetime...

 

[pchen92]

My 24 fets is pulling 130A (beefed up traces but no shunt mod)
I wonder how many Amp it can handle with a shunt mod.

 

[Peter Sternersson]

That sounds like serious fun

I just asked Lyen if you could modify the controller somehow to handle more current, he said that for a couple of bucks he could solder up the traces, and ha claimed a 10-20% current increase.

As of now I dont think I will be pushing so many amps, maybe take it up in steps like 3kW, 4,5kW, 6kW and full power (8,5-9kW). I am in no way used to handle this much power between my legs :lol: so for my own sake I think I should just ramp it up slowly...

All cells are now measured. One cell was "bad" with 0,1V difference between the highest and lowest cell. I have to keep an eye on that one. The other ones had between 0,001 and 0,06V difference between cells. Seems like the "Matched cells"-sticker might really have something behind it besides sales argument.

Of course I couldnt resist ducttaping some cells together on the frame. This is 10 of the 20 cells. I think I can squeeze the rest of the cells in the area of the triagle of the frame, if I can place the cells 3 in width as I have now...

How bid of a no-no is it to connect all the cells in series of 5 first, and then in parallell of 4?
I know Drbass recommends his Makita 18650 to be joined in parallell first, and then series, but it is so much easier the other way around :wink:

 

[pucksterpete]

Nice looking build I wish you luck with your 600w BMS charger, I didn't have much luck with my 900w from them. So I went with a Mastech 100V 10A, its been a dream.

Keep up the good work on your build :wink:

 

[Peter Sternersson]

I have three BMS alloy chargers in total.
One 400W working like a dream, doesn´t get warm or anything.

One 600W that is downtuned to 450W due to heat and some wierd buzzing sound when on full power. Works fine now with a 120mm fan blowing on the parts inside.

One 600W that made my whole house dark when I plugged it in. A short between one of the phases and ground. Lays in parts in a drawer waiting for a new isolation behind a FET.


It almosts seems as I should buy a Mastech now at once

 

[litespeed]

Very nice!

Tom

 

[Qwiksand]

Very nice work, love the detail you showed on the dropout mounts/reinforcement work. Will this be a primarily road-going vehicle or will it need to handle the dirt trails as well? If primarily road, I'd suggest you look at mounting your batteries in a fork mounted box- it would really clean up your build. If you need quick-turn maneuverability, however, this would not be an ideal solution.

P.S. Your written/typed english is better than most of us "native" speakers

 

[ecross]

.

 

[Peter Sternersson]

Very nice work, love the detail you showed on the dropout mounts/reinforcement work. Will this be a primarily road-going vehicle or will it need to handle the dirt trails as well? If primarily road, I'd suggest you look at mounting your batteries in a fork mounted box- it would really clean up your build. If you need quick-turn maneuverability, however, this would not be an ideal solution.

P.S. Your written/typed english is better than most of us "native" speakers

Thank you. And I think it will be something like 50/50 road and dirt trails. With the speed this thing will put out, I will probably get to work faster on this than taking the car
My first plan was actually to have the batteries in a box on the fork, I have even made drawings in the CAD and everything.
But when I saw how small the batteries are I changed my mind.
It will be much stelthier with the batteries in the frame then on the forks.

I was able to duct tape all the batteries in the frame yesterday, and took it out for a test ride. Even with the batteries 140mm wide, and perhaps 20mm extra width for cables, I dont think I will rub my legs very much against the battery box...

Working on a cardboard template for the box. Unfortunatly I only have 200mm wide strips of aluminium, but I can get started on many pieces of the box before I need the side plates. I have a serious cold right now, but I think I can manage to drag myself to the workshop/garage on sunday and start cutting, bending and welding some aluminum.

As you can see the box is a bit higher in the front. Here I mean to have the CA, a main power breaker, and some sort of key for on/off to the controller. Nice and visible, and easy access to the main breaker if something goes wrong.

Dear Peter,

I think also it is much better to parallel first and then in series.
With your 20pcs. 4S-5000mAh case packs is your setup:
-5Ah x 4 pcs is 20Ah
-and 5pcs from 4S is 20S

This is a lot of cabels and work. What charger do you prefer?
Do you order the 20pcs. Haiyin hard case packs from the EU-Warehouse and how many postage costs do you pay?

Best regards
ecross

My wish to make serial packs first, and then parallel, is beacuse then I can use the existing bullet connectors on the batteries and just hook them up to each other. It will be done in five minutes or so.
If I need to parallell first, then I must cut the bullet connectors off, and solder them together into a larger gauge wire, and put a bigger bullet connector on. I am totaly okey doing this, if it means that the pack will perform better and/or live longer.

However, me and a friend discussed this yesterday, and came to the conslusion that for example a 12S store bought battery, is essentially made with 3pcs of 4S cells in series.
Say that I was going to run 12S 4P for example, then it would be the exact same thing to connect a string of 3pcs 4S in series, and then connect them in parallel, as it would be connecting the larger 12S batteries in parallel to start with, right?
But I do understand that there will be a risk of current flowing in the balance cables if a cell in one of the packs are lower then the equivalent cell in the other packs.
I will connect the batteries in parallel first, but it is always nice to discuss and think about it a bit before doing something...


My plan is to bulk charge the battery with a BMS Alloy charger (as long as it holds), and then buy a Mastech power supply.
I will have a BMS board connected to the pack all the time so it will hopefully stay nice and balanced.

I ended up paying 50 Euros for the shipping from the European warehouse, I think the package was something like 12kg in weight. Delivery was made in a week and a half...

 

[Peter Sternersson]

Got the battery box all taped up now, looks good enough.

I think I will actually build the whole box on the frame, with just the one side removable.
There is plenty of space to place the batterys inside and to overlook the wiring. Only thing is that I need to seriously think about how the cells connect in parallel and series to eachother so the length of wires will be enough.
Other than that, I should be able to reach everything I need with just one side removable.

 

[Peter Sternersson]

Got the card board battery box converted to aluminium today... well, almost all of it, the Argon for the TIG welder decided to run out on me
I´m gonna get mor tomorrow, and hopefully complete the box tomorrow evening or the next day.

Pretty happy with the result so far, I will weld the one side shut, and figure out some sort of removable lid on the other side. Not really sure what to do yet. It doesn´t need to be water tight, the more the better of course, but there are gaps and holes here and there in the box anyway so really doesn´t matter.
I have left e gap in the lowest point of the box so water can escape at least.

The box is welded around the frame, so it need to be cut if I´m going to remove it. I added four brackets that are fastened with pop rivets (not sure that´s what they are called)

I will dress the entire box with fake carbon fibre film, so I´m not so concerned with the surface at this point.

 

[MAGICPIE3FOCUSPOWER]

Well done for the battery compartment!

 

[Peter Sternersson]

Thank you, I am pretty pleased myself actually 8)

But GOD DAMN gas is expensive! Just got back from lunch and filled my 50L argon tube, and signed up a contract running on 5 years for a 20L gas tube for my MIG-welder.
It ended up something equivalent to 1150$. God knows it´s not cheap to have your own welder and supply gas for it...

I don´t think I´ll get the battery box finished tonight, I´m usually pretty tired the first day at work after the weekend.

 

[MAGICPIE3FOCUSPOWER]

Waauww $$$$$ o well at least the result will be good
You have to ride more on your bike then :lol:

 

[Peter Sternersson]

Got some work done on the battery box tonight.

Epic fail you might say

I didn´t have a big enough piece of aluminium to cover the whole side, so I made three smaller pieces and welded together.
Looked ok, and since I will cover the side with fake carbon fiber it didn´t matter.
So I grinded the welds smooth, and noticed that it had warped a bit. Took the hammer and gave it a whack.
All the grinded welds cracked!

Got them welded again, which was a nightmare because of all the crap that was burried in the aluminium from the grinding.
That, and the extra heat warped the side plate even worse.

Painted some satin black on it to see how much the carbon fibre film will cover, I think it will work, at least for now.

I need to come up with some other location for the main breaker, cause if I do a minor crash and comes to much forward, my balls will be history

I´ve tracked the package from Lyen containing the controller, CA and some other bits and pieces. It might arrive in the morning, but definetly before the weekend.
My birthday is tomorrow, so saturday will be spent with family, but sunday might have a first test ride coming :lol:

 

[Rodney64]

Starting to look good Peter will be good to see it all operational. Get someone to take a video the first rides always good to capture the EV grin.

 

[Bill Nye the science guy]

looks great! good choice of parts

 

[Peter Sternersson]

Got the controller yesterday. What a monster!

Also spent about 4h in the garage, welding some more on the battery box, and figuring out a mount for the CA. I might make a rectangular hole so the backside of the CA lies flat against the battery box, but this is how it sits for now.

I need to mount the main breaker somewere, and the only place I´ve found that is at least some what good, is in the upper front corner on the side. Not optimal in any way, but I think it´s the only place that it won´t interfear with something on the inside...

I need to figure out something smart in the way of making and mounting the removable sideplate. I will probably weld a piece of angle iron to the inside of the box, with tapped wholes in for fixing the side later on. Some sort of gasket in between and it should be good enough, the rest of the box is far from water proof and the bike will probably seldom se rain fall, but if I do find myself in a rain storm I want to be able to get home before the box floods and electrocutes my nuts


I also modified the luggage carrier with some flat pieces of alu, you can´t really tell by the picture, but there are tapped holes for mounting the controller.

 

[MAGICPIE3FOCUSPOWER]

Thanks for pictures update, keep going with good work!

 

[Elektryczne Motocykle]

It is going to be a monster. Congratulations.

 

[John in CR]

Nice. The batt box is turning out truly unique and those dropouts are great.

Re: the batteries, parallel only at the ends at first. Then a somewhat dud cell gets its effects spread over 19 others. Once the cells prove themselves good with 10 or 20 cycles and maintaining good balance, then do your parallel structure all the way down to the cell level. That makes balance charging or checking for balance a simple matter. Plus as they age cells that get weaker can be supported by their sibling cells in parallel. Paralleling only to the sub-pack level will never be a good idea, either all or none. ie at the ends of the 20s strings, or at the cell level. If you parallel at the sub-pack level and one cell goes bad, having it's effect spread over just 3 or 4 other cells in the pack while the packs in parallel force a voltage as if all cells are good is a recipe for disaster.

John

 

[dnmun]

yep, a lotta lipo and looks like have gasoline and solvents in the garage too. a smoke alarm might be a really valuable consideration early on.

 

[Peter Sternersson]

Don´t worry dnmun, the garage where I have done the welding and cutting is at a totally different location than where I have the lipos, and where I will store the bike later on.

And it is very well ventilated, haven´t had a problem the 10 years I have been having it anyway.

The bike will stay at home in the, at least, somewhat fireproof boiler room, plenty of smoke detectors since there is a 20kW wood pellet boiler down there. After seeing GCinDCs lipo fire I will have a fireproof blanket over the bike as well.
I have plans of building a shed out in the yard just for electric bicycle storage, but we will see...

John, I´m not totally sure I understand what you mean, could you possibly make a drawing or something? But all the cells will indeed be in parallell, but the subcells in the 4S packs will only parallel through the balance wires 0.5-0.75mm2 or something. Will this be enough?