EVFR 2.0: Building the pack

It’s been a slow summer. I’ve been too busy this summer to get much done and David moved his shop. I haven’t posted lately, but I have been doing things on and off. I’ve also been riding my SV650 a bit. Really glad I got this to practice on while the bike is being finished. I’d rather learn on this than the eVFR. I wouldn’t want to drop either, but I’d rather drop the SV650 (Has frame sliders) than the eVFR with rare fiberglass fairings.

A few weeks ago I decided I wanted to bin my cells. I borrowed an IR meter from a friend. It’s an AC impedance meter and I realize it won’t accurately give me the DC impedance, but it will allow me to organize the cells into groups of similar IR values. I spent a few nights with my girlfriend testing the cells and writing their IR value on them (she’s awesome!). I got ~150 cells that measured between 5.0-5.9mOhm and like 30 between 6.0-6.9mOhm. One I thought was above 7, but was just the leads not attached correctly. I had some cells that were test-cells and some that were showing low voltage, so I set those aside for testing and further study/destruction.

Now that I had boxes of cells, I noticed some had a tiny number of rust specs on them. None of the rust was very bad, but I wanted to get a pack with as little or no rust on it as possible. Some of the ends where the epoxy is applied seems to have been contaminated, and in some cases appeared between the case and blue plastic covering. After organizing the cells, I have ~165 cells that are near 100% and are between 5.0 and 7.0mOhm. The rest are extras and will be used if I need to replace a cell. I plan on putting a small pack of 16 cells together in a 4s4p 1/2kwh arrangement as a test pack that I can also use with an inverter for portable power (could be used as a small emergency pack to charge the bike).

So after sorting the cells, I got the water-jet cut copper buss-bar de-burred and ready for assembly. I used groups of the same IR value to assembly each parallel group. This will ensure that all of the cells share the current as equally as possible. I think I need some longer Stainless Steel screws. The screws that came with the cells seem to be all over the place with regards to quality, and some of the threads were easily stripped. Despite 2 screw issues, the pack went together well and It measured 36.38V (~3.3V/cell). Here are some pictures of building the 11s5p smaller pack (located above the motor):

I’m going to David’s tomorrow and turning the pack over to him so we can start on the plastic holders/battery box.

I also re-started my Discharger project. I’ve gathered most of the pieces and put together a schematic. I’ve gotten help from a few friends Bob Simpson and John Muchow (designed the CC400 discharger I’ve got). I think we’ve addressed any issues that were lingering and figured an easier way to stop charging when an alarm is triggered. I’ve got a sort of Interlock right now. The Low-voltage alarm, Over-current alarm, Over-temperature alarm and Emergency Stop are all wired to a latching relay. If any of them trigger, the gate of the FET is pulled low, and the discharging stops. The contactors are only there to connect/disconnect the battery, and not to stop the test. Here’s a pic of the parts and of the schematic:

Anyway, that’s it for now. I’ve cut down on my social obligations and renewed my motivation for the discharger and eVFR. I’ll probably start building up the larger front pack this week if I’ve got time.

EVFR 2.0: Slow progress but new bike

I’m sorry it’s been a while since my last update. It’s been a very busy and unfortunate last couple of months. My Aunt passed away and then shortly after, my cousin got sick and succumbed. I went to My aunt’s funeral, and went to visit my cousin before he passed away. Mixed in with all of that, I had 2 family reunions to attend, one in Idaho and one in Montana, as well as a get-away mini vacation for my Girlfriend’s birthday. It hasn’t left me much time at all to work on the bike.

With respect to the battery pack, the plastic has not been milled due to my buddy moving his shop, so I need to shop around for a place that can do it for me. He did, fortunately, get the copper bussbars drawn, sent out and waterjet cut. They’re sitting in my garage right now and I can begin rough assembly of my pack. I want to match their IR in parallel groups as close as possible while I’m putting the pack together so the current is normalized between parallel cells. After that, I can do some bench testing of the entire electrical system while I work over the next couple months to get the plastic cut and a battery box fabricated. I’ll probably bring the bike back to my place.

Due to the unexpected family emergencies, summer vacations and relocation of my friend’s shop, I’ve had to put things off a little bit more. Oh well, my eye is still on the prize!

I’ve decided in the interim that it would be good to get some seat time, and I bought a 2000 Suzuki SV650. It’s sort of a street fighter with a nice tubular frame and naked look with circular headlight. I figure if I can go to/from work, I can at least get some practice in before my other bike is done. I’ve been itching to ride since I got my endorsement.

Anyway, that’s it for now. I expect I’ll be working on bussing the batteries for a couple weeks in between riding.


EVFR 2.0: Fiberglass fun!

Since Dave is working on the battery pack drawings, I figured I’d focus on other things like the fiberglass and headlights. When I first found the upper, it had no headlight holes in it. I decided to do a dual headlight conversion, but needed to fiberglass the lights into the fairing. I spent last night working a bit with Dave to cut out the headlight holes and make some tapered inserts to go around the headlights I’ve got. We also patched the gas tank filler hole. I’ll go back Friday to finish up the fiberglass and start sanding the fairings.

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I also got a race tail for the bike, but unfortunately it was damaged in shipment so it’s got to be repaired. I’m glad I’m still fiber-glassing stuff. Here’s a pic of it now, and what it should look like when its done (pic is from a gas bike of a guy I know).


So after all the fiberglass repair/filling/modification is done, I’ll get all the fairings mounted, drilled and sanded/bondo-ed so they’re ready for paint soon. It’s really starting to take shape.

I think I’ll keep it white, it’s a really clean look. I was thinking some Vinyl graphics, like a PCB design. I looked around one day and found the BMW Activee and it’s pretty much what I had in my mind. Simple silver shaded PCB traces on a white background. Nice and clean and unique. I’ll just have to get a hold of someone to do the vinyl. Here’s a pic of the Activee (courtesy of the e90post forum)



Back from a break

I moved in with the GF a couple weeks ago and unfortunately between packing and moving, I had to push the bike project aside for a bit. My buddy also had a huge project at work and couldn’t work on it either. Looks like it’s back to work this weekend and next to get things started up again.

I’d like to test my batteries a bit this next week on my spare time and do some IR matching/sorting. Also want to get some of the fiberglass drilled and sanded.

Starting to get more and more excited!

EVFR 2.0: Different pack design

With the previous pack design (trapezoidal), it was a nice simple shape, but the pack mounted inside the frame a little weird and made it difficult to fit in the controller and charger. I started thinking, maybe it would be more simple to have the batteries in a sort of L shape around the motor. Since there’s ~10″ between the frame posts, I figured we can  get 5 cells wide in a staggered configuration. The current would flow down one side, up the other and there would be 2 packs essentially. The lid would be simple and the mounting points for the pack would be near the corners/sides of the pack, which is great for strength.

I spent some of Weds with my buddy Travis (T2) kind of mocking it up and it looked like it fit. To make sure, I came back on Saturday and did a to-scale mockup of the pack with real dimensions. Just cardboard and tape this time (foam core was overcomplicated).

I fit it into the bike and it fit pretty well actually. It hits the tank right now on the sides, but there’s some extra space in the pack so I think it’ll fit perfect. The tank isn’t fitted with the front mount either, so it should raise a little off the frame. I think I want the pack to be just the batteries and leave the contactor and BMS outside. It’s just too hard to fit all that inside and make a nice lid for it. The controller fits right where the original radiator did, which is nice because it gets tons of airflow through the heat-sink Noah made. The charger can go right under the controller near the bottom of the pack. Even with the forks compressed, there’s about 5-6″ of horizontal clearance.

T2 and I decided that this will be the final pack style. Not only does it simplify mounting and increase structural strength, but it also makes it easier to fabricate the pack. It also leaves a ton of room under the seat for a box that contains the BMS, DC-DC and some other electrical components. We’ll be drafting the model in 3D this week and have the drawings to my buddy Dave for fabrication.