[LrBen]

I have been lurking on here for quite a while. Mostly in the car section. I have plans for an MG F conversion using a leaf motor in the future. However currently I am working on converting a 1987 Yamaha Big Bear 350.

As you can see in the photos I got it in quite a state. It was an impulse buy on Ebay and wasn't my wisest purchase. I bought it last August and have spent most of my time since then restoring every single piece on the bike. I have built my own electrolysis tank for removing rust and an electro-plating setup for plating nuts and bolts.

I am currently at the stage where I can actually work on the conversion part of the build. I have a 48v 4KW chinesium BLDC motor. The plan is to hook into the transfer gear via a belt drive to the motor. This way I can change the ratios if my initial maths was wrong.
I'm planning to use gel lead acid batteries, but might swap these out for something else if I can find something reasonable.

More posts to follow with a little more detail on installing the motor.

 

[LrBen]

I have a rough idea of where the motor will go. The plan is to fabricate brackets that will attached to the rear of the frame and hold the motor in line with the transfer gear.

The first step is to fabricate a bracket to hold the transfer gear in the position it would have originally been when it was attached to the ICE engine.

I am currently designing this part now, as you can see I have printed out a rough prototype just to verify my measurements. I am in the process of printing out a 2nd prototype with adjustments. The CAD model of this 2nd prototype is attached. The final bracket will need to have a cap on it, as originally this transfer gear would have been immersed in engine oil at the geared connection.

 

[Duncan]

Hi
Forget Lead Acid - waste of time and money

You need some battery modules from an EV - Nissan Leaf, Chevy Volt, Tesla

 

[LrBen]

Hi
Forget Lead Acid - waste of time and money

You need some battery modules from an EV - Nissan Leaf, Chevy Volt, Tesla

I'm still pretty open on the battery front. For this quad I do need weight, so heavy batteries are less of an issue. Range is also less important.

I have been pricing up Leaf cells, you can get them for around £60 a cell in the UK at the moment. It works out more expensive up front, but I know I'll get way more usable KwHs from the pack.

I also thought about making up 18650 packs, but that seems to be quickly going out of fashion.

I heard that Ecocharger experimented with swapping out the lead acids in their quad bikes with lithium ion packs, but the loss of weight really affected their towing ability.

 

[LrBen]

Change of plan in the Battery department. After having second thoughts on Lead Acids due to all the down sides to them I found some LG Chem E48 pouch cells going for a reasonable price on Ebay.

Going to be using them in a 13s2p setup for around 4.6Kwh storage. Much happier with the results these should give. It might actually give the bike a reasonable range, not that it is currently going to be road worthy.

 

[LrBen]

Making some progress with the battery construction. I have decided to split the battery up into two sections to make it easier to mount. One 6s2p and one 7s2p. Just finished up making the smaller pack now as you can see from the photos.
I printed off the white holders in PETG, used aluminium busbars for most of the connections and copper for the first and last connection. The casing is 3mm acrylic. I didn't really design a very clever way to open and shut the pack so for now the top is just held on with duct tape.

I think for the larger pack I will place the holes for the cable glands a little more in line with the cells.

Also got the motor mounts back from the fabricator and those are installed now. The last thing left there is to get a sleeve made up for the transfer gear so I can attach a taper lock pulley.

 

[LrBen]

Got the motor mounted today! First had to shorten the transfer gear a little.

I have tons more space that I thought I would have. Planning to place the bigger battery pack in front of the motor now.

I have also been playing with the idea of moving the motor lower down. Hopefully I could then place the 2nd battery pack above the motor and keep everything in the engine bay. Given that it will be chain driven(too close to use belt pulleys) the distance from the motor to the transfer gear doesn't matter as long as they are in the same plane.

 

[tylerwatts]

Hi LrBen
Have you made further progress on your build?

Cheers
Tyler

 

[LrBen]

It's been slow progress so far. I managed to fit both the batteries in front of the motor which is fairly neat, pic attached. Spent most of my time in the last couple months fabricating a decent basket to hold the batteries in place.
Decided to also fibre glass the battery cases as they were a little susceptible to shock damage.

I had to rewire the main power wires after a minor miscalculation at the start of my project meant the wires were about 3 times too small to carry the maximum potential amps. Currently just finishing this part off now, it has meant having to make some small modifications to the lids so the larger wires fit through.

Planning to get the controller, motor and batteries wired up on the desk before the end of the year. Then it should just be a case of throwing it back in the bike and away we go.

I want to make a slight change to how the motor is mounted, but that should be a simple matter of a couple holes and some bracer bars.

The last major hurdle to get the bike moving is to fabricate an adaptor to fit a taperlock pulley the transfer gear. The trouble is that the splines are JIS, and not many people around here are able to fabricate internal teeth, let alone to JIS dimensions.

 

[LrBen]

Progress!!!

The battery BMS is now wired up and working, managed to put in a few hours of charge over the weekend. Charging will take a while at the moment, I just have a 4 amp charger for the 94AH battery pack.
With the battery pack fibre glassed all that is left to do now on the battery side is to figure out how to reseal the tops now that the larger wire lugs get in the way of putting the lids back on.

The attached photo gives a fairly good view of the electrical side. The BMS and 12v fuse box is in the old air box, the 48v-12v converter is sitting on the rear where the original voltage regulator sat. The motor controller is mounted inside the fuel tank. The contactor is mounted just above where the motor will sit using a combination of angle iron, Mechano and 3d printed parts. Yes that is allot of chocolate box wiring connectors, once I get the wiring finalised I will change these to DTM or some other fancy automotive connectors.

The last hurdle was also overcome in the last week. The main shaft coming out of the transfer gear was machined down so that I can attach a standard taperlock sprocket. I am planning to have the motor back in next week and a test fit of the chain drive. If all goes well I should have a moving electric quad bike by next weekend.

Still allot left to do after that. But that is mostly aesthetic in nature. Top tip, don't let brake fluid drip on your nicely painted handle bars.

 

[tylerwatts]

Loving your fab work and tucking things into existing places. Any pics of your battery boxes?

Sent from my moto g(7) plus using Tapatalk

 

[LrBen]

Loving your fab work and tucking things into existing places. Any pics of your battery boxes?

Thanks. It kind of made sense for most of it. Although I do like the idea of reusing as much of the old bike as possible. I am planning to use the rear brake light switch in order to activate the regen braking. In this model they didn't have rear brake lights but the mount for the switch is still there. Should activate well before the mechanical brake has to do any work.

The battery boxes turned into a bit of a mess once I did the fibre glassing. I made up the basket before I fibre glassed them. So once that was on the basket was a tiny bit too narrow. Had to cut off a little bit to make it fit.
The top of the battery boxes is now also an issue. I had them all sorted nice and neatly before I had to change the main power wires to a much thicker gauge. Now the cable lugs are too large and hit the lids.
For the moment I am just leaving them off. I want the bike moving under its own power first. Then I'll go back and polish/redo things/not use any Mechano.

 

[LrBen]

It moves! Got the transfer gear all put back together this weekend and back into the bike. Chain is half a link too long, but that's a quick fix once a half link turns up.

Wired up the reverse switch as well. So I can go forward and backwards. Found that the mounts don't quite hold the motor stiff enough when the torque starts to increase, so the motor turns slightly and pushes against the transfer gear sprocket which then causes it all to jam up and the controller anti stall kicks in. You can see in the photo that the motor has already pushed up against the transfer gear sprocket a tiny bit.

I will add a threaded bar on the other side of the motor attached to the frame. Then I can finely tune the angle at which the motor is held.

This is the major building stage complete, it's just polish now.

 

[tylerwatts]

Excellent progress, well done. What happened to the transfer gear to need putting back together? Will you put a guard of sorts over the chain to keep it cleanish and grease/lube off your legs? 3d printing candidate!

I'd consider a better mount for the motor that is a rigid connection between transfer case and motor, might make chain mounting difficult. And I'd have a small tensioner on the chain, a sprung or adjustable sprocket maybe, to keep a bit of slack in the chain but no slap etc. Easiest seems a slotted hole in the motor plate to slide a tension sprocket up/down. Needs to stay in position as on regen it will be under some load.

This quad has huge potential, really impressed! Also, I didn't realise it was 4wd before, double bonus. It'll be unstoppable.

Cheers
Tyler

 

[tylerwatts]

Just wondering, and sorry for crashing your build, but would the motor fit other way round with the sensor lug between the transverse frame bars where the old mounts are (maybe removed) and then you can have a single solid plate mounting both transfer case and motor in 1 with easy access to the chain? Perhaps move the motor further off center line with a longer chain?

Cheers
Tyler

 

[LrBen]

Excellent progress, well done. What happened to the transfer gear to need putting back together? Will you put a guard of sorts over the chain to keep it cleanish and grease/lube off your legs? 3d printing candidate!

I just had to press the transfer gear shaft out in order to get it machined. So had to press it back in. Planning to do some sort of guard. I was thinking about 3d printing something for it.

I'd consider a better mount for the motor that is a rigid connection between transfer case and motor, might make chain mounting difficult. And I'd have a small tensioner on the chain, a sprung or adjustable sprocket maybe, to keep a bit of slack in the chain but no slap etc. Easiest seems a slotted hole in the motor plate to slide a tension sprocket up/down. Needs to stay in position as on regen it will be under some load.

Yeah I am thinking of how I can make the mounts more rigid. There is a real weak point in how the motor mounts that I think can be remade. I kind of just bodged it on just to get the motor mounted. I'll see how the chain does once I shorten it, but I expect some sort of tensioner would be a good idea.

but would the motor fit other way round with the sensor lug between the transverse frame bars where the old mounts are (maybe removed) and then you can have a single solid plate mounting both transfer case and motor in 1 with easy access to the chain?

Unfortunatly that would mean cutting out some fairly major structural parts of the frame, or somehow extending the transfer gear shaft a long way.

The chain is actually fairly easy to remove and put back on at the moment. Where it goes over the transfer gear sprocket there is enough space to attach or detach the master link.

 

[LrBen]

Had some good progress on this in the last few weeks. I did remake the motor mounts into something more rigid which made a big improvement.
It is now driving pretty quietly and for now I am happy with the chain tension.

Currently looking into a voltage drop issue which is causing some issues. As my amps increase the voltage will drop quite significantly. Enough to trigger the BMS low voltage protection and cut the power. It also seems quite low on power. I can stall the motor very easily by standing in front of one of the wheels.

Initially I put this down to some dodgy connections, especially to the BMS and my use of copper grease in the lugs. However with these all changed I still experience the voltage drop.

The cells are rated to 150Amp continuous discharge (3C) and they are setup in a 13s2p configuration. So I should be able to pull 300Amps continuous from the cells. This happens to be the max power draw from the motor. So there is plenty of capacity in the batteries.

I have noticed in the BMS that cell 13 is consistently the lowest voltage cell. With no load, the rest of the cells will sit with in 0.001v of each other. But cell 13 will be around 0.006v lower.
Under load this gap will widen to 0.2v and it is usually this cell dipping below 3.2v that will cause the BMS low voltage protection to cut in. After talking to a friend it seems that the BMS low voltage setting for cells should be set to 2.5 rather than 3.2v. But that still doesn't explain the extend of the voltage drop.

I am planning to pull the battery pack out and double check the connections for each cell. Hopefully it is just a rubbish connection rather than a dead cell.

 

[LrBen]

Fixed the voltage drop issue! Luckily it was just a case of replacing the main battery positive connector.

There is now a bit of voltage drop, but nothing unexplained under load. The cells are all finely balanced and the voltages on all cells drop evenly.

I have decided to move the BMS screen from under the seat to the dash, as it does actually contain some useful information such as speed. So to that end I have decided to 3d print a custom dash. In there I can also re-purpose the original dash lights for reverse and power lights. Currently half way through printing the different components.

There does seem to be some issues with motor power still, and the motor gets very hot after not all that much use. Almost too hot to touch. It will also struggle to start moving when facing uphill with me on it.
I am going to look at the phase and hall wires, feels like maybe something isn't working quite right there.

Still lots to do on the bodywork, But I wanted to put some parts back on it to see how it would look.

 

[LrBen]

Fixed the power issue. I changed the sprockets to change the ratio between the motor and the transfer gear, from 0.9ish to 2.375. Drops the theoretical max speed from 30mph to 18mph or so. But the torque is now insane. Won't take very long to get to that top speed! I believe max torque at the wheel would be 653nm in theory.

That's the last engineering hurdle done. I am very happy with performance and the HV side is holding up very well.

The last things to do now are mostly smallish things. I need to add in some relays to make the 3d printed dash lights work, change the last few choc box electrical connectors to super seals, adjust the brakes and then restore the frames and plastic bodywork.

I'll try and get some decent videos in the next few weeks.

 

[tylerwatts]

Sounds great, well done! I look forward to the finished pics.

Can you tell us the motor specs? Seems something like a Golden Motor 10kw motor would give you the performance and some more speed to really make it fantastic. 30mph was about right to me.

Cheers
Tyler