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New battery for the Radon Swoop

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Svara

So, after having used the current 20s5p molicel pack for a couple of years it decided to give up during a ride in the snow a few weeks ago. It suddenly lost voltage and would not recharge and when I took it apart two cell groups were sitting at 0V. As I had taken a shortcut bypassing the 60A chinesium BMS to get the power output I wanted from the battery I guess this was bound to happen. The BMS at least prevented me from charging the battery when any cell group were at a bad voltage, so that’s good.

I took the pack apart and put all the 18650s through a thorough testing program and capacity measurement. All cells in the 18 cell groups that were at an OK voltage were good but the cells in the bad groups were at very low capacities if they took charge at all.

Before this ride I’ve had the bike sitting untouched for several months so I guess it’s gotten slowly discharged during this time and when I took it out for a ride pulling 100-ish amps from cells already low at charge it eventually killed them. (This is just me guessing at what happened).

As the battery box I was using was a bit cumbersome to build and mount due to me trying to make a quick-change battery at the time I decided to design a new pack from scratch.

Fitting 100 cells in the swoop frame is tight fit, so I had to make some prototypes before finding the best shape to get an as-decent-as-possible battery layout that’d actually fit (and be able to mount) in the frame. To make it as sturdy as possible I could not fit the side covers before putting the pack in the frame so it’s tight.. 🙂

Since I’ve upgraded to the BAC2000, pulling A LOT more current from the battery (this might also be part of the reason for the failure of the old pack) I built the new pack as a copper/nickel sandwich that should be capable of providing all the amps I need. To save some money I only replaced the bad cells with cells I already had at home. Doing this it’s important to make sure the “old” cells aren’t mixed with new cells as the drain profiles might differ causing individual 18650s to see more load than the average cell which could lead to failure.
To give the pack the best chance to survive I installed an ANT BMS capable of 120A cont and 300A peak. This allowed me to route the power through the BMS even for the consumer and letting the BMS kill the power to the bike if any cell group goes low. The BMS can be monitored via bluetooth so I can keep track of the health of the battery too which is a nice feature to have.
The pack looks nice and being a fair bit wider than the old pack doesn’t matter. As it sits it’s not in the way of anything when riding. The pack gives a good punch when slamming the throttle and the bike wants to lift the front wheel all the time which is awesome.

Hopefully this pack’ll last a couple of more years before needing a rebuild again.

Final assembly and test ride

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Svara

So, it’s been a while since I last posted and it’s been a lot going on. I have had to rebuild the battery for my Radon Swoop which has taken quite some time with measuring all cells and cleaning everything up for re-use but there’s been a bit of progress on the RunBike project too.

So, this kind of is where we left things off last time.
To be able to fit the brakes on the 203mm discs I had to make some adapters. The first version I 3D-printed, until I got it all right and then I made it from aluminium.
I have come up with a way to mount the battery pack which is a bit cumbersome to get in and out of the frame – but once it’s in there it really doesn’t have to come out..
The cockpit of the bike is super clean, with just the tiny eggrider cluttering things up. There’s the domino full twist throttle on the right clustered with the front brake and eggrider display. On the left there’s the rear brake, a thumb-throttle mounted the wrong way around for regen braking and an emergency cutout which kills the controller. On the upper triple clamp I also added an ignition key which acts as the master on/off switch for the entire toy.
The controller fits super nice in the frame box. Mounted in the top of the box it’s protected from any water that makes its way inside. I’ve welded all the holes in the box but water always finds its way, so I’ll be adding a drainage to the box at the lowest part too.
The BAC2000 and BAC4000 are super easy to wire, and both use the same harness so upgrading the bikes will be super easy in the future. 🙂

Drilled a 24mm hole, sealed and added the charge connector for the battery.

The battery has 4 pieces of EC5 connectors spreading the load equally over the pack cells, so the controller needs matching 4 connectors to draw current from.
When all is connected this is what it looks like. Just the signal wires needed but those will be the last connectors I install as they’re in the way of the battery.
I printed and added grommets to all cables going into the box. Partially for sealing the holes but also to protect the wires. All grommets are printed from TPU.
The battery is finally installed and the battery box is ready to be closed. Everything will have to come out again for painting later on but first we have to test the bike out to see what modifications we have to make before paint.
So, finally it’s time for the long awaited test ride..

The bike runs super smooth with tons of acceleration and a seemingly high top speed. The spedometer isn’t calibrated yet so I have no idea how fast I’m going and the roads are covered with ice, but it feels nice! The torque makes the motor pull the rear wheel forwards though so I’ll need to add a chain tensioner to secure it in place. I also need to add brake fluid to the rear brake, which is good to have even though the regen braking is awesome! Also, footpegs will be nice to have to be able to ride standing up!

After a bit of riding I had to test the charge inlet out. Everything works as it should and I get a good bluetooth connection to the BMS inside the box.

To be continued with more awesomeness..

House plans

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Svara
So, we’re planning on finishing the house project this summer. We’re going to extend the house a bit and add a lot of new windows and make the interior more open and spacious.
This is a quick sketch on how we’re going to build the extension. Hopefully we’ll get an OK from the authorities to do this. The footprint of the house will be the same but the roof’ll be a bit higher and steeper.
Since we’re always in need of more storage space we’re thinking of adding a shed on the back of the garage/workshop too. This’ll be insulated as the garage and we’ll use heat from the garage to keep this space at a few degrees C in the winter.

More updates will come as the project commences. This will be a huge project and the plan is to get the foundation and roof up this summer to be able to seal and insulate the house before winter.

Battery cell cleaning tool

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Svara

So, I’ve been repairing quite a lot of ebike batteries and to be able to re-use the old cells I need to get rid of all the nickel strips and spot welds that are on the cell poles. So for I’ve been using a side cutter to cut everything off to my best ability and then a dremel tool to grind off the remainder. The problem with this is that it’s quite messy and there’s a big risk of damaging the cells if grinding to much.

After wathing a youtuber make a servo-driven tool to cut the welds off 18650 cells I thought I’d give it a go, so I made a quick design in CAD.

It’s kind of a gilloutine with a cradle to support the battery cell and a grinded cutter (stump from a MGN-12 rail) that slides in a track.. I’d thought I’d see if a 3D-printed tool would suffice.

So, that’s what it looks like.

You slide the battery in as far as it goes, apply some pressure to keep it from sliding back and depress the handle.

And it cuts all the crap from the cell cap. It works fairly OK, I might need to re-grind the cutter to be more aggressive though.. but as for now I’m happy with the result. It’s on par with the grinding wheel without all the metal dust flying everywhere. Some welds and nickel strips take quite a lot of force to cut off though so we’ll see how long this tool’ll last.

Rear frame, shock- and motor mount

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Svara

So, it’s been a while since I updated the project but it’s been a slow progress.

Started by building a mockup for the subframe to test fitment and how it’d look on the frame.

I’m pretty happy with how the mockup looks and fits on the frame, and it seems to be sturdy enough and kind of not too heavy (this isn’t going to be a super light-weight bike anyhow) so, on we go.

After having upgraded the CNC plasma with a better Z-axis it’s good to cut steel sheet with pretty good precision, so I cut the brackets needed for making all the subframe parts from 2mm steel sheet.

The result is pretty awesome for a low-cost DIY contraption..

After a little bit of polishing with the grinder the final result is more than good enough.

Unfortunately the 20×20 square tube mounted on the side of the frame interfere with the rear shock, the way I were planning on mounting it so I needed to come up with a new bracket.

I milled the rear mount/cover for the motor from 13mm aluminium and secured it to the frame.
Then I made a bracket from 20mm aluminium to support the motor mounts and double as the lower mount for the rear shock.
Bolting it all together with M8 bolts, adding a bolt in the lower “ear mount” on the motor too, everything sits solidly in place.

So I cut a couple of “ears” from 3mm steel sheet and welded the upper shock mount onto the frame. Now the stance of the bike is decided and it feels pretty OK.

The motor/shock mount is easily removed from the bike with just 9 M8 bolts. This is great for service and painting later on. If I may say so myself it looks frekkin’ awesome! 😀

Making the subframe

I decided to make the subframe from 20×20 square tubing as it’s strong enough, not too heavy, cheap and easy to get.

I started with printing paper templates from the CAD drawing and cut tubing to size..
I drilled the holes for the mounting screws where needed in the subframe and now had enough parts for 2 complete setups.
Brackets and frame tubing for the 3 subframe sides needed on top of the mockup I’ve got on the bike already.

When this was done I just had to quickly weld everything together, drill and tap the mounting holes on the frame and make the joining parts for the subfrtame. The subframe goes under the bottom of the frame to be able to fit the footpegs.

Now I can fiddle with the bike “bicycle style”, putting it upside down on the workbench. This makes it a lot easier to fiddle with the motor mount and chain tensioner and so on. 🙂
It looks OK and feels OK to sit on too.

Battery and seat

So, that’s about where we are for now. What’s left is a few fairings, the seat, battery and electrics.. (And the brakes of course)

I made a quick CAD of a seat to see what it’d be like. I’m printing the seat core from PETG plastic and the seat cover from TPU. Experimenting a bit with getting the cover cushioning enough so we’ll see where we end up.

While the 3D-printer is making seat parts I’m finishing up the battery.

Since this battery will have to push north of 200A I’m building it as a copper/nickel sandwich. The configuration is 20s10p, ie 72V nominal. The cells I’m using are Samsung 30T, 3Ah capable of a continuous 35A. The BMS will be a 300A ANT BMS with bluetooth capability. In the picture you can see my new kWeld setup with kCap ultra capacitors. It works flawlessly and gives much more consistant welds than my car-battery setup did. Super happy with this.
To fit the pack in the box on the frame I’m making it fold, so at the moment I’m welding the outer sides and soldering the BMS wires to it. It’s going to be a tight fit but if it gets too wide I’ll just make new brackets and covers for the frame box, so that’s going to be alright.

Well, that’s all for now. To be continued.

Milling and more prototyping

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Svara

So, since recovery from the fatigue syndrome is super slow so will updates on the project be. That’s just due to most of my afternoons being spent resting and trying to get the brain to recover. But some progress has been made lately, both recovery- and project wise.

I’ve iterated the motor mounting plate design a bunch of versions and am pretty happy with it. Time to make some proper parts.

After some CAM-work in Fusion360 I cut some sheet aluminium and got to milling.

The mill really makes a mess throwing shavings everywhere, but since I built the enclosure at least it doesn’t fill the entire workshop with metal shavings. 🙂

The result when milling aluminium is pretty amazing. This part looks even better IRL than in the pictures and being made from 13mm thick plate it’s super sturdy!

Bolting it down to the frame and mounting the motor everything fits super snugly and I’m starting to question the decision to make a mounting plate on the rear side of the motor too since the motor seems rock solid as it sits now. Buuut, it’s better to make it to tough so we’ll make one just for the fun of it.

Test fitting the chain again with the proper motor mount. I’ll have to make one last prototype of the rear sprocket adapter but now I get proper clearance to both the wheel and the frame so the next adapter is just to get the chainline straight. Right now I’ve got the largest sprocket I’ll use mounted to make sure the chain doesn’t strike the frame in the worst case scenario.

I’ve been getting parts for the second bike aswell. I’m going to build it up to use as a template for checking the geometry so as not to mess anything up when customizing the bike. It’s a chinese clone frame so the geometry probably isn’t perfect to begin with but it’s good to at least know what I’ve changed when re-designing it.

Winter is coming and right now the garage/workshop is a mess with all the projects and stuff that needs storing and protecting from the cold. It’s a bit annoying trying to get stuff done in there but it is what it is. I’ve got to move stuff out when using the plasma cutter that I need for the coming project of making a seat and upper shock mounts..

So, what’s next?

Since footpegs seem utterly expensive I’ve started mocking up custom footpegs for the bikes. I yet have not decided on how and where they should mount to the bike but I know I don’t want them sitting on the swing as the original pedals were mounted on the bomber frame.

The 21700 cells have arrived so I’m looking at making the batteries for the bikes. It’s going to be a 20s10p pack made from Samsung 30T cells at 3000mAh and 35A.

For the first time ever the build is not restricted by the available space in the frame as the bomber box would fit a HUGE pack if filling it up. I’ve decided to go with 200 cells per pack due to cost and weight. This pack is going to be around 14kg just in cells so it’s going to be heavy enough as it is.

72v nominal at 30Ah yields about 2,2kWh which should let us have fun for at least 100km at a time I hope, of course depending on how we ride. =)

I’m using the same method of building the packs as I do on regular bike packs but as with the avant battery this is going to be a CU sandwich type pack as to be able to deliver 300A of peak current..

Here I’m printing the cell frames, three at a time, on my “Stoorn v2”-printer. The next step in the battery process is making cell spacers, measuring the voltage on the cells and starting to put the cells into the pack before welding.

I’ve ordered a pair of ANT 300A BMSes as I’ve used them on all my avant packs and am super happy with the way they work. I’m looking at getting some 10A+ 72v battery chargers to charge the packs in a reasonable amount of time but we’ll see what we end up using.

This is where the CAD is currently at. I’ve printed the first iteration of the back plate and am going to fit that on the bike today as I’m milling the adapters for the rear wheel.

I’m trying to make shorter and more frequent updates but as  it is now the project stands still for huge amounts of time while I CAD and design and print stuff, and then I’m making progress that shows in a few days.. so I’m doing my best to keep everything updated.

Thanks for reading and if you’ve got questions or comments please post a comment on here or reach out on facebook, instagram or discord.

To be continued..

Mockup and motor mount

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Svara

Having done the mockup for the wheels and mounted the brake rotors and made a mockup for the rear sprocket adapter the next step is mounting the motor.

Since the frame is designed to fit a hub motor and we’re going to use mid-drive motors we need to figure out a good way to mount the motor on the frame. I’ve considered quite a few different positions for the motor but they all have drawbacks. I decided the best solution is to make a motor mount right in front of the rear wheel, making the shortest possible chain line while still keeping the motor as close to the pivot as possible as to limit the unsprung mass momentum of the bike. The tricky part is that this is where the rear shock sits.. So I started by mounting the 200mm shock I’ve got and made the bike sit in the fully extended position on the bench. I then removed the shock, cut the lower shock mounts off and did some measuring.. The CAD turned out like this.

There is going to be a bracket on the left side of the motor too but as of now I’m not sure wether to simply make a motor/shock bracket or to make a new custom endcap for the motor. The right bracket prototype is being printed right now and I’ll use that to check more clearances and get a better feel for the solution. In the CAD I’ve moved the shock all the way to the right to limit the forces on the M8 bolt that holds the shock but where it’s going to go is not yet decided. The upper mount might screw right into the frame or I’ll make it a part of the seat.

I’m going to try to make this modification without welding anything to the frame so it’ll be easier to reproduce if anyone else wants to build a similar “bike”.

TBC..