JD's BMC V3 Build - in progress

[oatnet]

I weighed the cell, and my kitchen scale reported 404g instead of the 401g manufacturer claims. Maybe my scale is inaccurate, maybe they intended some of the tabs to be trimmed off. Here are some dimensional reports:

The 16ah cell is listed as being 150mm/5.91" wide. This is fairly accurate, including the folded edges. The edges on the sides of the cell are folded back 3 times at the factory. In my application, one of these sides will be facing down. Hopefully, a lot of load will be carried by compression and that will minimize flexing of this edge.

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The 16ah cell is listed as being 211mm/8.70" long. However, the main body of the packet is precisely 8.25", and the tabes extend the length to 9 5/16. I suspect that folding the tab over once will give the factory cell length of 8.7", but maybe they intend for it to be trimmed to that length. It is interesting to note that the actual material of the cell starts 9/16" from the the top of the pouch, and 3/16 from the bottom of the pouch.

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Here is a slightly better shot of the cell next to the side of a AAA battery to give you an idea of how thin this is! You can also see how the edge is folded over 3 times from the factory. Notice that the foil edge on the bottom of the cell is against one of the flat sides of the cell. On the top of the cell, the tabs come out of the exact middle between the flat sides.

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[disndat]

Hey JD where in Socal are you?I'm in santa monica right on the beach.If you are close maybe we could compare bmc bikes.PM me if you want.

Chris

[voicecoils]

You may want to photochop the barcodes off that second photo.

[johnrobholmes]

Dang, looks like a sweet ride! I may have to try the fork mounted pack on a build. I know I like how the bike handles with the packs up front on the top tube, so putting them on the fork would be similar I bet. Plus it would be decently easy to mount.

[oatnet]

I bought (4) WenTeq clamps that are used to mount lead weights on race cars. The inner diameter is 1.25" (32mm), perfect for the upper stanchions on Boxxer forks (<2010), with mounting holes for 1/2" bolts. Overkill for what I need, larger than I would like, but the only ones I found that were up to the task. I test mounted them on a set of forks, pictures below. It looks like I will have some interference with the downtube on extreme turn angles, more extreme than I could use while actually moving, but worthy of a rubber stop.

I am going to lay the cells flat instead of on edge, which will make the box a little bigger. The 14lb pack will be 7"x 10" x 4.5", will I'm going to have an aluminum box built a 7" x 7" x10" ID. This leaves me the ability to carry a few things in the box, or expand the battery to 72v/21lbs if I end up scrapping the V3. The green towel on the front of the bike is about 7" tall and 18" wide, so picture a diamond-plate box about the same height but 4" shorter on either end.

-JD

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[oatnet]

Hey JD where in Socal are you?I'm in santa monica right on the beach.If you are close maybe we could compare bmc bikes.PM me if you want.

Chris

Hey Chris, sorry I missed this post. When I get enough time to get this bike fully roadworthy, lets give it a shot!

-JD

[cell_man]

Hi John,

good to see some progress on the pack. The termination method you showed on the other thread looks interesting and very straightforward. Be interested to see how it works out. What are you using for a BMS?

[oatnet]

Hi John,

good to see some progress on the pack. The termination method you showed on the other thread looks interesting and very straightforward. Be interested to see how it works out. What are you using for a BMS?

Hi cell_man!

Please call me JD, the john is down the hall with the shower, tub, and sink.

I gave up on BMS's back in '07, and even today they seem like a high failure point in packs. I know the top dogs here are building reliable one's, but I lack the skills and time to assemble one , and I can buy a lot of replacement cells for the cost of a prebuilt one. I have been tempted to buy a few for LVC my VW Bus conversion, but haven't gotten there yet.

For charge balancing, I went to single-cell charging at the for balance. I have a bank of 2a Voltphreaks chargers for smaller cells, and use a bank of Vicor 20a DC-DC converters for my larger cells like the 80ah in my VW Bus. Several reputable folks have claimed that if you parallel-charge quality LiFePO4 cells prior to making a pack from them, they will stay in balance. I will test that theory with this pack, and accordingly I have kept the cells paralleled for a long time, with several charges. If it doesn't hold true, I'll bulk charge most of the time and run a balance charge every few weeks, using the 20a or 2a charger banks.

For discharge/LVC, I'll use a cycleanalyst. The first few runs I'll watch voltage closely and get a baseline of how many WH the pack actually supplies. Maybe it is simply from learning to scan from flying, but at any point in my ride, I'll know how many wh I have pulled from a pack, and what the general voltage is like. I count on a CA to be my gas gauge, and I have never run a cell down with it. Of course, it helps that I size my packs to the build's duty, such that routine rides are within 70% of the pack's rated capacity.

While this works for my experience level and the way my brain is wired, it may not work for others. Don't try this at home kiddies!

-JD

[Ypedal]

Ya know... i've tried.. and tried again with BMS's.. but they keep kicking my ass and costing me money.. i think you have to be a certified geek to use them darn things.. i'm only a nutcase so i don't yet quite qualify.

[cell_man]

Sounds good JD. I really like the idea of single cell chargers myself. I find the cells stay pretty well balanced as long as you don't discharge them very deeply and you might want to check the discharge on a cell level to see where the cells start going off the cliff as they say, but with single cell chargers it's never gonna get out of balance.

I've not had any problems with the BMSs I've been using but I'd like to rig something up to enable me bypass the Fets in a low current BMS and use a signal from the BMS to trip the brake signal or something. The 12S 30A constant BMS I was using handled 65A of controllers with 75A peaks shown on the CA just fine but I'm probably pushing my luck a bit.

[oatnet]

I was in the process of laying out the dimensions for my front battery box, to cut it out of diamond plate and weld it in TIG class. I noticed, right in front of me, one of the old ammo cans I bought at a swap meet, without logic or purpose. It was the ideal size for the a123 prisimatics, and figured I'd give it a go instead.

I had the choice of bolting the ammo can from the base, which would let me lay the cells flat but looked out-of-place, or bolting it from one side, which looked reasonable but rests the cells on their edge. I bought a couple of these ammo cans to get a quantity discount (did I mention the bit about "without logic or purpose"? ), so for now I drilled from the side and I may try another one the other way later.

Dropped $22 at ACE for a 9/16 metal drill bit, and a bit more for (4) 1/2"x1" hex bolts/plate washers/lock washers. After a suprisingly fast session on the drill press (140mm apart, 20mm and 145mm from the bottom, the ammo can was ready for mounting. I bolted the 32mm clamps onto the boxxer upper stanchions, and the box went right onto them with no fuss. The clamps are large, but happen to land right in gaps in the frame so there is no interference, and they add some agressive look to the forks. The upper crown does hit the top tube, but I put the bumpers cut from the stanchions no the top tube and they work great. Tight turns are not possible, but the rear end of this bike is easy to pick up and move.

The entire assembly (clamps/bolts/case) weights 5lb 6.4oz without the waterproof lid, and 7 11.5oz with it. This may sound like a lot, but is comperable to or lighter than a rear rack, a sturdy metal case, and hardshell packing on the cells etc. The lid is completely removable, and a whopping 2lb 5oz, I might replace it with something lighter, or I might live with it. This case could just as easily handle the 20ah a123 Prisimatics, just a little less padding.

Power switch and circuit breakers will be inside the case, I plan to open the lid to power on the battery. The lid interferes with the handlebars, so a bad human can't open it enough to pull out the battery. The stem comes off with a single bolt at the adjustable point so I can take the lid off easily enough if I need to.

I like the rough army green, but I will probably give it a few coats of gloss black rustoleum to match the theme. I still need to drill a pair of holes for grommets/8ga power leads, someplace discreet. The top handle rattles so it will come off, thinking about mounting a few cree LED lamps and a DC-DC converter to the the hard points it leaves behind.

This totally balances the bike! I think the size/dimensions are what someone might put on a regular bike to carry stuff around, so it doesn't stand out, adding to the overall stealth. I am tempted to put the black 18 fet methods controller on this, to drive a 5305 to see what 48v200a feels like on a 65lb ebike. Er, plus the extra weight of said controller/motor.

Now when I get around to terminating the a123 prisimatics they will have a place to go!

-JD

[oatnet]

I completed the battery for this build a ways back, but I am just finding time to compress the pictures and post them, so here they are. First up, the tab-to-tab terminations.

The two tabs are folded together over the balance wire, which is bent up into the fold to keep it from pulling out. This is the tricky part, because until the 2nd fold the tabs are not locked together and can slide around.

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Here is the 2nd fold, which locks the tabs together.

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The third fold. If I was careful, I could actually make 4 folds, but that left less room for the clip. Each fold holds the tabs tightly compressed against each other. Note that BOTH sides of each tab are in contact with each other, dramatically increasing the contact surface over a solution that merely compresses the tabs against each other.

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Note the crude crimps, each indentation goes through all the layers, providing additional contact surface, and further locking the tabs together. The bonding from these indentations are what make the tabs difficult to separate. Also notice the slight bend along the length of the fold - this further compresses the layers together.

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This shows how I run the balance wire down the length of the tabs and back. If anyone tugs on the balance wires, this will give some play before it tears the tabs off. It also provides some strain relief were the wire comes out of the tabs. It also provides additional volume to lock the clip against the tab.

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I apply a gooey layer of adhesive heat-shrink. This stuff is not going anywhere, and the heat shrink glue seals the tabs against the elements and oxidation.

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The difficulty in sliding this clip over the heatshrinked tabs is a testament to how well it locks them together.

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A layer of fiber-reinforced tape will keep the clip from going anywhere. This is is sorta over-the-top, but whatever.

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3 sheets of newspaper go on top of the cell as a wear/insulation barrier, and on to the next tab. Note the newspaper covers the tabs I just finished, another flimsy yet over-the-top barrier but I'll take all the protection I can get. Note that both sides of the tabs are cleaned and polished before I put a new cell on, and note that I tape a loose bit of heat shrink over the tab I am not working on to prevent the possibility of a short.

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[oatnet]

While I have high confidence in the tab-to-tab connections, the power leads coming from the end of the packs cannot be bonded via the folding method. Instead, I run the 8 gauge wire into the folds, and wick some solder up into them.

I separate all the sub-bundles in the 8ga wire. There is more than I can fit, so some of them get clipped off.

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Here are the tire bundles folded into the tab.

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note the slight bend along the length of the tab, to hold compression

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As you can see from the flux, I was able to wick a suprising amount of solder up the tabs in a very short time. I had a WET sponge up against the tab where it goes into the cell while I soldered, but I never even heard it sizzle, and the tab was cool immediately after.

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I guess I missed taking a pic where I put heat shrink over the tab, but here is the clip in place. Notice that it extends far above the tab to provide strain relief for the power lead. I also used the smooth curved "end" of the clip on the power lead side. I put fiber tape on this too, but I guess I didn't photo that.

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[oatnet]

sadf

Here are the (2) 8s/24v packs in the box. I build them as separate packs so I could put the circuit breaker between them, limiting fault voltage to no more than 24v. Note the large bolts from the clamps protruding into the box, I need to protect the cells from them.

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I put an extra-thick layer of very high density foam over the bolts, and cut out holes for the bolt heads. Then I put a layer of phenolic plastic over the foam to distribute the load even over the bolt holes, and in the case of some extreme force that completely compresses the foam (like I am hit from behind by a car travelling 60mph faster than me) the phenolic should protect the cells from the bolt heads. I put a half layer of the same foam on the bottom and both sides. The front of the box doesn't see any load, so I used a simple sheet of thick plastic as a conductivity barrier.

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I ran 8ga power lines in through the back of the box, through rubber grommets. This wire is long enough to run through the top tube and reach the controller bolted on to the water-bottle bosses, hence the 8ga instead of the 10ga/12ga I would normally put on a 35a load.

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On the inside of the box, I cut 2 separate grooves in the thick foam to route the power leads. I then put the foam I cut out on top of the wire in the groove, and a layer of duct tape to hold it all in place. Note the holes for the bolt-heads cut into the foam

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I parralleled a pair of 50v/50a DC circuit breakers into little box to give me 100a/100v throughput for the pack, although they probably would supply a lot more before popping. Each breaker has its own 10ga wire, and they come together at the anderson connector.

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Here are the guts of the switch box. The red switch has 300ohm25w resistor around it so the controller can get charged up without a spike. All current is off until I turn the yellow switch on. The controller's capacitors charge up in 3-4 seconds, then I through the red switch which allows full power through. Main power connects to the batteries through the 8ga leads on either end. The two 12ga leads in the center are unswitched, and where I connect the charger. One of the 8ga leads coming through grommets in the back of the box is hard-wired to the switchbox, the other connects to one of the packs through andersons.

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Here is the whole thing assembled. Noted the switches on the far left side - all I need to to is lift the lid to flip the switches, and I have power. Note the layer of plastic between the packs; profiles of the breaker box and switch box are cut at the end, to keep the switch from settling down onto the breaker box and keeping the breaker buttons compressed. I later removed some of the foam on the switch side to make a place for the charging leads. The balancing wires are unterminated as yet, inserted into un-heatshrunk tubing for protection, and taped down in case I decide I need them one day. I am hoping this pack will stay balanced though. Also note the top layer of foam to the left has a groove cut in it to accomodate the layer of plastic between the packs.

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Here is the foam in place. I ended up taping the little piece of plastic on the right to the lid itself, so that it protects the battery leads but isn't flopping around loose.

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Here are the terminations on the controller side.

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[oatnet]

The fitment of the cells is extremely tight, it would take an extreme amount of force to move them from one side to another. The bottom foam is compressed a lot too, the cells are held compressed, although it seems like that compression is not as crucial as we once thought. I think this side compression takes some of the load off the downward-facing side of the cell. In addition, since the ammo box is angled along with the rake of the fork, much of road-vibration is directed to the flat side of the cells. This makes the battery and its connections to the breaker/switch all self-contained. I have decided to keep the waterproof lid in place, I open it to power on, and from that point on everything is sealed shut.

RIDING WITH THE WEIGHT UP FRONT IS AMAZING. Revolutionary. I will build ALL of my future ebikes with the battery pack mounted up front. The balance is amazing. Every other one of the dozens and dozens of ebike I have build has had a rear-weight bias.

In some cases - like my xtracycle with a rear x5 and 72va15ah Life mounted in over it - directional input from the front wheel is more of a suggestion than a directive. Turn the wheel too fast, and the back end doesn't comply. With this build, the bulk of the weight is right between my front hands. It is still easy to turn, but due to its mass, the rest of the bike follows like the tail of a kite. This makes this one 10x more maneuverable than any bike I have built to date. I expected I would be adjusting through turns to accomodate the weight up front, but instead it was completely intuitive. Heck, it even feels better than my Tidalforce/EMS bikes.

As a side bonus, the weight up front keeps the front suspension nicely compressed, so the ride is as smooth as silk, but the battery gets almost no road vibration whatsoever. Standing on the pdeals, I ran over some significant speed bumps with my weight on the handlebars, I never felt the bump on the handlebars but the rear end bounced around wildly, the contrast was stunning.


I tried a test ride to work, loved the handling, liked the visual stealth, and tolerated the BMC buzziness. Going up a short hill on the return trip I melted the phase wires. I think they may have been pre-melted by the Kelly Controller, and there was some light conduction, because the controller would shut down if I tried to launch too hard. At the end of the ride, the battery box was completely cool on the inside, so I don't have any cooling concerns for this pack.

A few days later I swapped in an x5 5305, which did not demonstrate the controller shutdown problem, but was unremarkable at 48v. I tried a 100a controller, which helped some; despite a 100a/6c load, the battery remained cool, as did the folded-tab terminations, which proved wrong some folks on the a123 termination thread who were skeptical. Sadly, the x5 also added so much heft in the back that the bike was merely balanced, not front heavy, and much of the handling magic went away. So the light weight motor is crucial to finding nice balance, and being able to run it at a mere 48v is Crucial to the overall gestalt. After I repair the BMC and install a CA connector on the BMC controller so I can limit to 35a, I'll put this combo through some serious tests.

I also bought another 28s of cell_mann's 16ah prisimatic a123 cells. I'll use them to make a 100v16ah pack capable of 250a, and will use them on another frame to power that x5 with some proper power. I bought a larger ammo box that can handle all 28s, maybe the additional 12s cells up front will help make the bike front-heavy again. I will will wick some solder up the folded tabs to make sure they can stand 250a discharge.

But here is the message I hope you take away from this thread:
MOUNTING THE BATTERY MASS TO THE FORKS DRAMATICALLY IMPROVES THE FEEL AND HANDLING OF AN EBIKE.
THIS IS A REVOLUTIONARY GAME-CHANGER.

-JD

[1000w]

Great work with the terminations JD, and those cells are looking very safe and comfortable in that ammo box.
The bike's balance is a really good result. I look forward to seeing the big 28s pack with the X5.
Cheers,
Matt.P.

[tritonwow]

I bought (4) WenTeq clamps that are used to mount lead weights on race cars. The inner diameter is 1.25" (32mm), perfect for the upper stanchions on Boxxer forks (<2010), with mounting holes for 1/2" bolts.

JD,
I just stumbled onto this build (can't believe I haven't seen it before). DMR has some hindged clamps but they're 31.8mm but may still work http://www.wiggle.co.uk/p/cycle/7/DMR_Hinged_Clamps/5220000003/
I'm thinking this mounting style would work well with the TF frames. Mount 4x6s Zippy/Turnigys (two on each side of the fork tube, long axis parallel with the ground, and controller in front of the headtube; forming a U around the headtube). You might even be able to stack three on each side.
Triton
PS Very nice build BTW

[johnrobholmes]

While I mount my packs on the frame as close to the headtube as possible, I agree that mounting them forwards instead of on the rear of a bike is a "game changer". Suddenly the bike actually handles like a bike again, and stupid stunt riding is possible

[oatnet]

Matt, thanks for the kudos, Stay tuned

Triton, that is a great product. Apparently they are not readily available in the US for some reason, but I am thinking about importing a bunch. BTW, if anyone cares, I bought my "WenteQ lead weight clamps" from ebay seller "4raceparts" who offers them in 1.25" (32mm), 1.5" and and 1.75" flavors. http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=360266264657


John, I liked the idea of that location but my crude attempts were knee banging agony and awkwardness. With your skills, I am sure you crafted something much better.

OTOH, I like the feel of having the weight on the fork, the mass it acts as a steering damper. I expected to feel it exaggerating my motions, but it really just feels solid. I'd be unhappy if it felt like a basketful of loose groceries, I don't think I would like it if the mass could move around, and "bump steer". This just feels solid, like a nice german car. The pack gets the softest ride up there, plus I like to tell myself that with the stanchions taking the weight of the batts there is less pressure on the head tube (whether or not its true ).

The 15s3p a123 pack I originally built for this bike ended up on the back of a bike I built for my wife, which is featuring a rear Bafang you (John) built for me long ago. That motor left for Australia, never made it, and at long last ended up on this bike. Anyhow this bike is going to get the same treatment, using the smallest of the three ammo boxes below. I am also going to bolt the controller to her ammo box, and just run big phase wires and halls back to the motor. Everything else is local to the new controller location, throttle, CA, brake wires. I haven't figured out the best position for it though, it would be sweet if I could mount it between the box and the head tube but I don't think it will fit. I got a matched set of wheels using the DX-32 rim, 32 holes like, and put the front one on her bike. I had to get a centerlock Disk for it, 1st time on that hardware, I was glad to see it worked fit OK with my Avid BB-7 brakes.

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The middle ammo box is the same size as the one on the bike from this thread, and the large one is going to hold the (28s)100v/16ah pack of the a123 prisimatics. That one will have 6 clamps though.

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The front wheel on the BMC V3 bike is also a JohnRobHolmes creation. Hey John can you source that DX32 rim? I am thinking about getting another front wheel made...

[cell_man]

Good work JD and happy to see the pack is working out well for you. Lots of very innovative ideas going on with your build, very cool

[liveforphysics]

Nicely done Oatnet!

[johnrobholmes]

I still have one or two dx32's here actually.

Your bike looks very nice. Me likey.

[oatnet]

Thanks for the kind words Paul and Luke! John, I'll be chatting you up soon when I sort out where I want to be on the 100v/100a 5305 build.

-JD

[dbaker]

Nice job with the ammo cans! Super strong, waterproof, and cheap! What do they weigh? I may try a detachable front mount for my commuter bike.

[oatnet]

I have a new suspension bike on the way to me (allegedly) and I was going to buy a V2 motor from Ilia so I could run a generic controller on it. I already have one of the controllers in the pic above, and this new bike has a spot where I _might_ be able to conceal it very well. If it does fit when the bike gets here, I'll probably go with the V2 and put the V3 back on the IO frame. But if I have to conceal a regular controller, I realized I could just as well use my V3 instead...

It has been @ 5 months since I opened the V3 to replace the melted phase wires. I spent a bitch of an afternoon jamming new phase and hall wires through the )(*&#$%*(*)(@#$ too-small axle hole, and when I was done I was so frustrated by the process I let it sit.

I think what really constipated the process was trying to find the right high-temperature epoxy to hold the phase wires down, yet not so permanent that I couldn't chip it off if I melt the wires again. I eventually PM'd Dr. Bass, who said I should get a high-temp silicone instead... so I procured some high-temp gasket silicone from Ace hardware yesterday. Today I soldered the halls and phases back on, and applied the silicone. On top of that I put a layer of wax paper, and a circle of thick cardboard, and clamped down the motor cover down on top. Hopefully, the cardboard will press the wires clear of the motor cover while the silicone drys, and the wax paper will keep the silicone from sticking. In 24 hours I'll undo the clamps and see if the silicone cured despite the wax paper, and see if it spins up.

Next, I need to do Ilia's CA/throttle mod to the controller, so I don't have to replace the phase wires again:

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