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jstept's picture

The Rezistor - still works...

Rode the Rezistor to work yesterday and today. I haven't been able to find any electrical outlets on the outside of the (very old) building I work in, so I had to improvise.


Not that this is absolutely necessary: my commute is 6 miles round trip, which is well within the Rezistor's range. I just wanted to see what I would have to do if I really needed to charge up at work for some reason.

I just started taking voltage readings before and after riding and charging. Right after a charge, the batteries read at 42V. After sitting overnight in the garage it drops to around 37V - might I have a slow charge leak somewhere in the system? Then after I ride it 3 miles to work it reads 36V. I'll continue to take readings, and I should really start to check the individual cell voltages to see how well Yesa's BMS is keeping the cells balanced. The BMS on one of the packs is rather inaccessible, unfortunately, so I'll have to take readings from one of them and assume they're both behaving the same way.

I've been swamped on a deadline at work, so I haven't had time to get the turn signals working or to build license plate illumination and reverse lights. I ordered some LED replacement bulbs for the rear signals (about $6 for the pair on ebay) and some blue electroluminescent wire that I plan to wrap around the motor power cables for ornamentation.

I've also started some research on what to do about the bodywork. If I go with the bare-metal look, there's a product called Gibbs penetrant/protectant that will prevent and supposedly even reverse corrosion. I found some pictures of a roadster restoration that was left in the bare-metal state using this product. I suspect you have to reapply it at regular intervals. There are some local powder-coating companies that will apparently do the sandblasting for you as well as the powder-coating; I might be able to get this done for less than $300. I plan to ask about the possibility of clear powder-coating, but I might just go for the brightest color I can find for safety reasons.

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The Rezistor - World's Quietest Vespa

This weekend I rode the Rezistor to Spring Scoot, a scooter rally held annually each year here in Portland. It basically served as the initial test run and range tests. I started with a 6.6 mile ride on Friday night and rode progressively longer distances Saturday and Sunday. I finished with a 14.5 mile ride Sunday evening, much of it at full throttle. There seemed to be juice left when I got home, although my headlight (and presumably the rest of my accessories) seems to have given out a few blocks earlier. The controller, motor, and power cables were only a little warm.

I've been recharging right after every ride back up to full capacity. There's a little LED on each charger that changes from red to green when each pack is fully charged. After an 11 mile ride on Sunday it took roughly 4 hours to fully recharge the two 36V 20Ah LiFEPO4 battery packs from YESA.

The motor and controller are working well. I noticed sometimes that when I twist the throttle from a dead stop, a brief rattling noise comes from the motor and acceleration is delayed momentarily. If I give the bike a tiny push forward with my feet, then ease on the accelerator very slowly, this seems not to happen. I'm theorizing that the controller gets "confused" when the motor is at a dead stop, not knowing exactly what the rotor position is, and the rattling sound is caused by the rotor flipping back and forth. When I give it a little push, the controller seems to realize that the motor is spinning forward and it engages smoothly.

I also noticed some differences in acceleration, probably due from the presence or absence of the 10-second temporary current boost to 250 amps from the controller. Without the boost, acceleration is pretty slow, even slightly less than I would expect from a 50cc ICE scooter, but it's pretty decent if I get the boost. I find that, when stopped at a signal, I can get the boost pretty reliably if I put the forward/reverse switch into neutral while I wait, switching to forward when the light turns green (and then pushing the bike forward - I almost never get the boost if I hear the rattling noise). I don't know how often the controller allows the 10-second current boost to happen, whether it's a function of the fwd/rev switch, some amount of time between boosts, or something else.

I can feel the motor drag when I coast; I presume this is the regen activating. I'm learning to use the brake levers as little as possible to maximize my efficiency. I'm also riding hunched over a lot when at speed, since the Vespa's aerodynamics are bad enough without the addition of my torso as a sail.

Sunday I clocked 35 mph with my GPS, which seems to be about my maximum on flat road. I'm assuming I'm getting 100 amps at full throttle. At some point I may send the controller back to Team Delta to increase the continuous voltage, maybe to 150 or 175 amps. The motor is rated for 100 amps continuously, but it's getting plenty of ventilation, and with the way I'm riding it's not really a continuous demand.

Saturday morning at Spring Scoot 14. Breakfast was at Mickey Finn's in southeast Portland. Behind all the scooters on the street, you can just make out the Rezistor parked way in the back on the sidewalk, next to a door through which I ran my extension cord inside.

Charging up at breakfast on Sunday.

Twist'n'Play Scooter Club awarded me the rally trophy for Best Rat Bike. It's sitting on the floorboard and yes, it has a big rubber rat on top. The other rallygoers had many questions, many of which I really couldn't answer completely because I wasn't done testing it yet. It was especially fun to demonstrate reverse gear.

In general, I consider this weekend to be a success. I built the thing mainly as a commuter vehicle, and Sunday I rode almost three times the distance of my round-trip commute on a single charge. I have yet to find out what my ultimate range is, but I suspect it's not much further than 16 miles.


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The Rezistor - preparing for road tests

The replacement controller from Team Delta arrived on Wednesday. Fantastic service from Dan, considering I just explained the problem to him on Sunday. I installed it and, at first, got the same "MOSFET short circuit" error message from the controller as before. I wondered if the contactor might be faulty, so I took that out, fiddled with it as much as I could (which wasn't much) then reinstalled it. But then it occured to me that the 12V converter might be faulty, so I left that disconnected. That must have been it, because the scooter worked after that. Changing the controller setup from "speed" control to "torque" control did the trick.

But without the converter, I had no lights or horn. So on Thursday night I pulled out the converter and tested it. It was bad...somehow I had blown it out and it was creating a short-circuit between the negative battery terminal and the B+ connection on the Sevcon controller - hence the MOSFET short error message. So Sevcon has been vindicated; the controller was not bad after all.

Good thing I had the foresight to buy two converters - I installed the second one, this time with a fuse on the + input wire. Lights and horn were restored.

Thursday night I also installed the turn signals I made (LEDs, acrylic, and 5-minute epoxy) and a couple of mirrors. Turn signals aren't working, though...I think the LED's aren't creating enough of a current draw to activate the flasher, or maybe I have something wired wrong.

I made a little "REZISTOR" sign to fit in the horncast strip, and got my wife to paint the logo on the legshield. I was hoping to have it ready to ride on Friday night, where I could debut the scooter at the annual Spring Scoot scooter rally in Portland, put on by Twist'n'Play scooter club. The rally would basically serve as the initial road tests.

Results to follow shortly...

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The Rezistor - Final Assembly and Testing

Well, it's been an exciting week. I spent much of last Saturday getting the brakes working, installing the levers, cables, and switches. The brakelight switches install in-line in the brake cables within the headset, so I had to figure out where to cut the cable housings to get them in the right spot.

Then I finished wiring the headset, making the connections to the switches, horn, headlight, brakelight, turn signal flasher, and reverse light. I also finished the controller wiring and put new leads on the keyswitch, the wires of which kept breaking off. I installed the horncast and the taillight and completed the wiring connections for those.

Last Sunday I started off by putting in one of the battery packs under the cowl. The BMS is just an exposed circuit board, so I wrapped it with a plastic bag and some tape to give it some nominal protection and weatherproofing. It's wedged in a small space on top of the battery so it's pretty well protected anyway. Getting the battery in was a tight fit.

I ziptied the two battery chargers into the underside of the seat. I plugged each one into an orange extension cord and then stuffed all the cords in there as well.

I bolted in the controller and by Sunday afternoon I was ready for a power check, using only one of the battery packs. I put the motor next to the scooter, connected the power cables, turned it on. I hear a click as the contactor engages, and my LED headlamp lights up, so that's a good sign. But I get the flashing LED on the controller indicating some error...oh, look, the control wires aren't connected to the motor. Plug it in and it works!

So then I had to move the thing off the back deck of my condo and into the garage for final assembly and a test run. Pushing it down the hallway and down a flight of stairs was a chore.

On Sunday evening I put in the second battery pack, hooked up the motor, plugged in the battery leads, and was ready to test. I turned the key, engaged the forward switch, and slowly twisted the throttle. I could hear the motor and chain moving, but there was no forward motion. I looked down and could see the chain spinning around the sprocket, but the welds between the sprocket and main axle had broken.

So on Monday night I unbolted the swingarm assembly from the body, removed the rear wheel and brake plate, and took the swingarm and motor over to my friend Arden, who was able to fix it with his TIG welder on Tuesday. Tuesday night I picked it up and reinstalled it into the scooter. Thanks again, Arden!

Late Tuesday evening I tried another test run. This time as I turned the throttle I felt a slight tug backward and heard a "tink", then heard the motor spin some more while feeling no motion. This time, when I looked down, the chain wasn't moving with the motor, so something else had failed. I felt around the engine case for a bit and pulled this out.

The 11-tooth front sprocket had broken in half. The notch cut for the keyway had really weakened the sprocket hub, and it broke right along the keyway and one of the set screw holes. Also, it turns out I had wired my forward/reverse switch backward, although I swear that I had checked the switch polarity beforehand...oh well, at least it's an easy fix.

I went to McGuire Bearing on Thursday to see if they had a sprocket with a thicker hub, but all of their 11-tooth ones were basically identical, and they didn't have one in stock with 12 or 13 teeth. I called around and found a place that had both, and picked them up on Thursday. Both of them have much thicker hubs than the 11-tooth.

Friday night I put on the 12-tooth sprocket, only to find that my chain was no longer quite long enough. I made a chain that was two more links longer (you have to have an even number of links, of course), but then it was too long, and the chain rubbed on the engine case. I switched to the 13-tooth to see if that would take up the slack, but it still wasn't enough. This is frustrating. At least I got an opportunity to reverse the leads on the forward/reverse switch.

This morning (Saturday) I took the swingarm off and took it apart. I was able to elongate the motor mount holes slightly, but just enough to shorten the distance between the motor axle and shaft so I could fit on my original length of chain. This was a relief, since I had feared I might have to make extensive modifications to the swingarm. I reassembled everything and decided it was time for another test.

This time it worked. Sort of. I got forward motion, but if I accelerated too much the power cut out, including the headlight. If I reset the system by turning the key off and on again, I could again get forward motion, but it didn't last. I could get up to maybe 20 mph if I go really, really slow on the throttle, but then the power cuts out. Interestingly, reverse seemed to work a little better (and felt really weird) but again, the power cut out as I gained speed. I looked at the controller after the power losses, and saw the LED indicator blink 9 times. Sevcon's manual says this is a "rotor position sensor fault".

I suspect that Yesa's battery BMS is set to limit the current draw, and that this is causing the shutdown. Decibel1, another member of this forum, described a similar issue with his Yesa battery packs a few months ago, and I had kind of been expecting that this would also be the case with my battery packs. So I took the batteries out and disconnected and resoldered the leads on the the BMS so that it would be bypassed on discharge. Decibel1 seemed to get decent results with this approach.

I tried a few more test runs, but the behavior was about the same. I still get power loss after initial acceleration. Then after a few more resets, it stopped working altogether. I turn the keyswitch and no power gets to the headlamp, and the LED on the controller blinks 3 times. The manual says this means "MOSFET short circuit".

I poked around the wiring with my multimeter for a while, checking various connections and looking for a short, then noticed that I was getting a 40V potential between the positive battery lead and the scooter body. This seems wrong (and somehow unsafe), so I figure out that the exposed charger connector on the battery under the cowl is coming into contact with the body. I insulate that with some electrical tape, and the potential goes away. But I'm still getting the 3-blink message when I turn the key, and no power. I'm hoping I don't have to send the controller back to Team Delta for diagnostic and reprogramming.

jstept's picture

The Rezistor build continues

I haven't blogged in a while, but it's not because I haven't been making progress. It's just that when I get free time, I'd rather spend it building than typing and uploading photos. Here's a summary of what I've been doing:

I had to reconfigure LiFeP04 battery pack 1 so it fit better in the space below the seat. This involved cutting the tape that held it together, cutting and resoldering some of the links between the cells, and extending some of the wires to the BMS.

I got some perforated angle, some hinges, and a bunch of nuts and bolts, and built a rack for battery pack 2 under the left cowl. Originally I was thinking this might have to be welded to the body, but I don't weld, so I ended up drilling some holes in the body. I don't think it looks too bad. It sticks out a bit underneath, but still looks better than an exhaust pipe.

I took apart the taillight and replaced the tiny bulb (it didn't have a brakelight) with some LEDs mounted in a piece of acrylic. It screws in very nicely to the existing taillight mount. I wired a couple of resistors in series with a bypass so it functions as a brakelight as well.

I figured out places to mount the main components. The main fuse holder, contactor, and 12V converter are screwed directly into holes I drilled in the body. I had a piece of angle left over from the B2 mounting, so I screwed that to the body where the fuel tank was, and I'll bolt the controller to that. B1 fits pretty well right in the space in front of that, and I don't think I'll need to build any special mount, maybe just a big rubber bungee to secure it to the angle.

The old horn runs on AC, so I bought a new DC horn from (interestingly they are in Boulder Creek, CA, where my mom lives) as well as a keyswitch. The Chinese horn was much less expensive than a DC Vespa horn. I cut some notches around the edge of the horn so I could secure it into the horncast with screws. The previous owner gave me a new horncast along with the old one, so in the photo you can see the old on the left and new on the right.

The brake parts I ordered from Ptown Scooters finally came in this week, so I was really glad to get those. I'm reusing the original front and rear drum brakes, so I needed new cables and rear shoes. As I mentioned before, this scooter never had a brakelight (or turnsignals, or speedo...) so Steve at Ptown found me me some brakelight switches that install in-line with the cables, and I think these will work out nicely. Thanks, Steve!

I got the missing bracket for the center stand, so I finally installed that. This makes work a little easier. I also got bolts for the seat attachment.

The old switchpanel was a mess, so I built a new one out of three layers of 1/8" black acrylic that I superglued together. The rectangular rocker switch on the left is for forward/reverse, the round rocker switch on the right is the turn signal, and the red button is the horn. The LED blinks red along with the turn signal. I bought the turn signal blinker at an auto parts store.

Most of the rest of the work is wiring. Today, using an unbent coat hanger, I pulled the rear brake cable through the wiring channel in the body, along with several wires for throttle control, forward/reverse, and lighting (including white LEDs for reverse, the housing for which I have yet to build). Pulling the wires was a total PITA; I'm really glad that's over.

Yes, still ugly. And the Vespa doesn't look so great, either. I've realized at this point that this is really going to be two projects: the conversion and the restoration. I've never done a scooter restoration before, so I'm not really sure how far I'm going to carry it. I suppose it depends somewhat on how much fun it is to ride when I'm done.

Oh, and I got married. Huge thanks to my lovely wife for her continued patience and support as I finish the project!

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The Rezistor - building the drivetrain

HUGE thanks to my friend Arden for helping me assemble the drivetrain. A fellow member of the Oregon Scooter Club, Arden has an amazing shop with machining and welding capabilities. He probably saved me over $100 in machine shop costs, as well as providing some of the raw materials.

First I had to cut the fat end off the axle (lots of pretty red sparks!). The fat end is normally where the gears go, but I have no need for it and it's in my way. Arden used his lathe to cut a 1" hole in the center of the sprocket so it could fit over the wider ends of the axle. We then machined a steel ring with a 17mm I.D. and 1" O.D. and then cut it in half; this allowed us to center the sprocket on the axle.


I had to cut a big slot in the V9A engine case near the left bearing to provide clearance for the 33-tooth sprocket and chain. Things were still pretty tight inside the swingarm, so putting the sprocket on the axle was a fairly convoluted procedure. We first had to position the sprocket, then slide the axle through the sprocket and bearing, then attach a split collar that clamps to the 17mm axle shaft with set screws, then fit in the split steel ring between the sprocket and the axle. I adjusted the location of the sprocket to center it in the swingarm slot, tightened the set screws on the collar, then Arden welded the sprocket to the collar and the collar to the axle.


The advantage of using an old engine case for a swingarm is that the front connection to the scooter frame, the rear connection to the shock, and the axle bearing are all exactly where I need them and perfectly aligned. The main disadvantage is that I now cannot remove the axle from the swingarm without cutting the welds on the sprocket (or maybe by removing the left bearing; I haven't tried this yet). Hopefully I picked the right gearing and won't need to change the sprocket. Arden almost talked me into abandoning the engine case and going back to my idea of building a swingarm from scratch (see my previous posts with photos of the wood 2x4 swingarm mockup). I still think this would have been more work, with a lot more welding and potential alignment difficulties. If it turns out that I weakened the engine case too much with all the cutting, I may have to start from scratch anyway.

To mount the right bearing, Arden had some 3/8" aluminum plate from which he cut two 2"x3" pieces, then used his lathe to bore a hole in one of them with the same O.D. as the bearing. I needed two plates because the axle stops just over 3/8" short of the motor mount plate. I fastened the plates to the motor mount plate with a screw in each corner, after aligning them using the engine case (which now includes the captured axle). Although I was careful to position the bearing plates such that they were clear of all the various internal bits of the swingarm, I didn't pay attention to where the screws fell relative to the motor, so I ended up only being able to install three of the four screws. Redundancy can be helpful sometimes.


The next step is attaching the 3-phase Etek motor to the motor mount plate using four 3/8" screws into the outer four holes provided in the motor. Positioning is fairly critical, so I first used my plywood template to locate the holes and make sure they were clear of the internal swingarm bits. I fit the chain around the sprockets to check the tension, and discovered I needed to locate the motor shaft a little further from the axle; this required that I cut more out of the engine case (fortunately it's aluminum). I also learned that the 11-tooth motor sprocket will need to sit really far out on the shaft to align with the axle sprocket, so I'll probably have to extend the motor shaft with some of 3/4" rod and a screw into the hole in the center of the axle.


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The Rezistor Headlight

The Vespa 50S Special originally had a 6V 15W headlamp. The old lens was partially obscured with overspray from past rattlecanning, but the previous owner gave me a brand new headlamp when I bought the scooter from him.

In any case, I wanted to switch to more efficient LED lighting and run it at 12V, so I bought five MR11 LED lights on eBay. I think these are intended to be replacments for the halogen spotlights commonly used in low-voltage lighting systems that you commonly see with exposed wires. Each of them is a cluster of 19 LEDs emitting "cool white" light, as opposed to the warmer yellowish light of halogen and sodium incandescents. I'm hoping the brighter white will produce a more distinctive effect and help make the scooter more noticable. Each MR11 is rated at about 0.78W, so the entire headlamp should draw less than four watts. I think this is a big improvement over incandescent.


First I spent a while rubbing the lens of the old headlamp with paint thinner to remove the spray paint. Then I sawed off the back end of the curved reflector and found a spider that had died inside. The five MR11 lamps just fit inside what remains of the reflector and the front lens. I cut a piece of black acrylic plate to about the size I needed to mount the lamps, then created a template to help me align the lamps on the acrylic. I drilled a hole for each of the lamp leads, used JB-weld to attach the lamps to the acrylic, then wired them all together in parallel. Then I epoxied the acrylic plate to the lens with some bits of plastic scavenged from an old wireless mouse transmitter.


I had originally planned to use the bottom three lamps as the low beam and the top two to be the high beam, but I abandoned this scheme to simplify both the alignment and the wiring. Also, I figured that for an urban vehicle, the primary function of headlamp is to make you more visible, with the illumination of the road in front of you being of secondary importance. Plus, I'm pretty sure that Oregon doesn't require a high beam on vehicles.

Interestingly, I didn't need to pay attention to the polarity of the leads for these lamps, which is not usually the case when working with LEDs. The internal wiring of the lamps seems to include a diode to allow current to flow in both directions.


Overall, I'm pleased with the results. Each of the lamps produces a fairly concentrated spot, and I did a fairly good job of aligning them all, but the lens spreads out the light somewhat. There is an adjustment screw in the bottom of the headset with which I can aim the light higher or lower. I think it will still be pretty visible and a big improvement over the old lamp.

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The Rezistor: figuring out drivetrain

I've mostly been working on figuring out what parts to use in the drivetrain. I've settled on #35 chain, which I believe is commonly used in go-karts. The guys at McGuire Bearing said this chain would be appropriate for the RPMs and torque of my application.

Here's where it got tricky: the Vespa axle is 17 mm at the location where I want to attach the driven sprocket, and the axle gets wider at both ends of the shaft - this means I have to use some sort of split sprocket. Apparently 17mm is an odd size, so I would have to have something specially machined. The bearing shop estimated 90 minutes of shop time at $1 per minute to modify a standard sprocket, so I decided to look for another option.

I went to the McMaster Carr website (thanks for the link, Reikiman) and ordered a flat 30-tooth sprocket and a split collar with an 11/16" bore. The parts arrived the other day, and the collar fits nicely around the shaft and screws down tight. The hole in the sprocket will need to be increased to just over 1" to fit on the axle, then I plan to weld it to the collar. Fortunately, I have a very kind friend from my scooter club who has the requisite machining and welding equipment and skills and has offered to help me with the work.

We'll also be building a mount for the right axle bearing. Probably just 2 or 3 plates stacked up and bolted to the motor mount plate, with hole in the last plate machined out for the bearing to fit into.

I also got an 11-tooth sprocket from McMaster Carr. It comes right out of the box, slips onto the motor shaft, tightens with set screws and a 3/16" key, and Bob's your uncle. At least some parts of this project are simple.

I made a stack of the motor, the motor mounting plate, the swingarm (old engine case), and the sprockets to see how everything fits up. I discovered that the 30-tooth driven sprocket is too wide to fit in the engine case. Once I get the sprocket in the right place on the axle, I'll need to slice out a section of the case for the sprocket and chain to fit through. Hopefully this won't weaken the case too much, but I can probably get my friend to help me weld on some additional reinforcing around the slot.

Can anyone recommend how much lubrication my chain and sealed axle bearings will require?

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The Rezistor - a little progress

At this point I have all the major electrical components for the drivetrain: motor, controller, batteries, contactor, and throttle. I also have two 12V voltage converters for lights, horn, and other stuff, and four LED bulbs (replacements for low-voltage halogen bulbs, actually) that I'm going to put behind the old headlight lens. Not DOT-certified, to be sure, but should be the equivalent of at least 40W to 60W incandescent. I think the original bulb was only 15W anyway.

I pulled off the headset and disassembled it - it was filthy with grease and dirt. The last person who painted it didn't do a great job of cleaning beforehand, so some of the paint just flakes off, exposing a layer of greasy dirt. The moving parts of the headset for the throttle and gearshift I won't need, of course, so I'll have those welded fast after I clean everything. The throttle bar was just a little too big for the Magura throttle, so I had to saw off a piece of old mountain bike handlebar to make a new one, and that will need to be welded in place. I broke two screw extractors trying to get out one of the brake lever bolts, which was stuck in place with either rust, paint, or both, and ended up spending quite a bit of time drilling the thing out. I had to basically do the same with the footbrake assembly.

The big job of building the swingarm and motor mount is still ahead. I hadn't been able to find an old motor case yet, so I was expecting to have to build a swingarm from scratch. I went Ptown, the local scooter shop, and bought an old Vespa axle that fits my rear hub. They pointed me to McGuire Bearing, a local shop that was able to sell me some bearings that fit the axle. Then I built a mock-up of the swingarm using pieces of 2x4, to get an idea of where the axle would need to be and where the swingarm would attach to the rear shock and frame.

I propped up the motor in the location I think it will go, just to see what it will look like.

Then last week a guy from a scooter shop in Colorado calls in response to the ad I put in the classifieds. He said he has an old smallframe engine case he can sell me! I think this could possibly save me some work: the mounting locations for the hub and the attachment points to the shock and frame are already in place, so all I need to do is figure out how to attach the motor. That is, after I cut off all the bits related to the now-unneeded two-stroke engine.

So now I'm waiting for that to arrive, and building the swingarm is basically on hold until I can see how it fits with the parts I already have. Then I'll have to find some sprockets and a chain or belt and cogs that fit the motor and axle - I'll probably head back to the place that sold me the bearings and see what they have.

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The Rezistor - batteries are here

The two 36V 20Ah battery packs arrived yesterday. Pretty fast shipping, considering they shipped from China on Thursday. (sunglasses in the photo are for scale) Sam at YESA was able to have them configured two different ways so I can fit one (barely) where the gas tank was and the flatter one in the left cowl. I think I'll separate the BMS circuit boards and put them in the gas tank area where they're better shielded from the weather. The chargers (one for each pack) were a little bulkier than I had hoped, but they're light and I think I can fit them under the seat, where I'll also include the charging cord.

Thanks for the advice about checking the individual cells. The only real instrument I have right now is an analog multimeter; will I need more than this to check if the BMS is working properly?




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