Modern boardtrack-inspired cruiser build

Badass so far. You will love 20s RC lico.

I run mine naked, and find that if you don't deeply discharge them, they stay nicely balanced. Any that still won't balance get chucked before they can catch fire. The result is balancing at most every 25 cycles or so, and I do that quite quickly by either single cell charging or discharging. But battery medics would do it overnight of course.

Utility bikes can use the cheap crappy 20c packs, but a fun bike needs to have little or no voltage sag off the line. So get at least some lico that is 30 c or better.
For simplicity, I really like the 18s setups. Its still 74 volts charged up, and id only need 9 packs for 15Ah. Or 6 if i use the 8000mAh packs(kinda pricey).

Im still on the fence. I dont want to feel overwhelmed with a 20s3p setup. Thats 12 packs total....I need to iron out a good charging setup.
18s if you choose 6s packs for sure. 20s is natural if you get the 5s ones.
View attachment 3




Wheels came out really nice. The lower dropout in the rear is a bit too narrow for these wheels....oversight on my part.

I think i might heat the frame with a torch in the area that needs to be widened and then use a factory vw spare tire jack to spread the dropout.

Ill make it work one way or another.
Don't heat it. Just spread it.

spread it good.

i think ive decided to go with an 18s3p setup with a total of 6 of the above packs. From what ive read they stay pretty well balanced and can handle a boatload of current. They are only 110 bucks or so from hobby kings u.s. warehouse with their pop up discount. I can stick 3 in each of my pannier bags and wire them in parallel. Ill be sticking with an infineon 40 amp controller because of reliability.

From what I understand, as long as these batteries arent undercharged, they stay fairly balanced. Ill obviously check the voltage of each cell when i receive them, and do a few charge and discharge cycles to figure if i do have any weak cells. I might also pick up some low voltage alarms.

I do have a few questions though....
If im going to bulk charge these things at work and when i get home from work after each commute, ill have to carry my bulk charger in a backpack. Can anyone recommend a good bulk charger? Ive heard that bmsbatterys chargers are plagued with failures.

The other thing i need to figure out is how im going to balance charge these packs. I know ill need a power supply, and some type of balance charger. Ive seen other people do it a million different ways. Im assuming my best bet would be to do 3 packs at a time. Can anyone shed some light on this for me. Im going to keep hunting around in the meantime.

I was on the fence about lipo before, but I am comfortable with electronics and wiring and I want a high discharge pack without spending 1200 bucks, so lipo it is.

anyone use a hyperion eos1420?
looks like the 6s8000mAh packs are on ill have to go with (9) 6s5000mAh packs. Ive found a bulk charger i think will do the trick from evassemble-

is 600watts too much?(8 amps)... they also offer a 360 watt charger for about $40 less (5 amps).
I presume you are going to run 18s 15ah, In which case 8 amps is only just over .5c so it is definitely not too much, charge time from empty will be just about 2 hours, the 5 amp one would be 1/3c and 3 hour charge time.
i scratched the lipo idea entirely.

I went back and forth for a while...initial costs for lipo is pretty low for the dicharge rate, capacity, and voltage they pack....but when you factor in costs of wiring/connectors, failure rates, bulk charger/balance chargers, power supplies, cycle life, and overall risks if your not careful....its hard to justify going that route. Dont get me wrong, I think lipo is justifiable in certain cases, but not mine.

I really wanted to setup 72v in the frame triangle all along, but didnt think it was possible. After speaking with Paul from Em3EV i realized that with the samsung 20r cells he could configure a 72v 13Ah pack to fit my frame triangle. Ill be running a 40amp infineon controller so the discharge rate will suit the 20r cells just fine(i believe they are 5C). I sent him a deposit a few days ago and i was told the pack should be complete in 3 weeks or so. Best part is that he thinks the battery will fit the em3ev bags they sell too.

If the em3ev bag is too small ill have to come up with something. either way im going to beef up the bag with brown leather, so it matches the seat pretty well.

Also just ordered my infineon controller from grin cyclery. My order list is getting smaller and smaller and I hope to have this thing fully assembled and ready to ride by the end of april hopefully. Not too big of an issue though, because Ive worked up my endurance to ride back and forth to work on my old peugeot road bike a few times now. pretty exhausting though. Next bike on the list is a nice cannondale caad10 or something light i can ride when I want to put some serious pedal time in.
Can I ask where u got your seat post from? I totally screwed mine up, I dropped it in the seat tube frame and it is stuck, stuck stuck it's like atleast six inches down in it so I need to find a post that I can chop off a lil bit and use it.. I'm digging the laid back style of the one you got but I'm having a hard time finding it this one look like it might work for me what do u think?? I put sum pics up on my thread..
You can get that post out... I've made a variety of homebuilt slide hammers with a springy hook on the end the right size to pop into the top hole but jam on the way out. Had to use an actual toggle bolt on the end for one really stubborn one. Isn't it amazing how tight they wedge in there after only a foot or so drop?
Any updates on the bike brother?? I've been really excited to see it complete, also super curious of how the cellman battery comes out..

I finally got everything I need to put together my bike and should have it complete and ready to ride by the weekend :)
I have to weld up the drop arms and a caliper bracket, then put it all together. Got kind of busy with a couple of car projects, plus paul isnt quite finished with the battery. Picked up a very nice trek madone 2.1 with ultegra components, a carbon seatpost and fork, and bontrager rl wheels....never ridden for an absolute steal. Ive been getting pretty fast on a road bike. Just did a 25 mile ride for lung cancer on the seacoast and finished with the fastest riders.

But i plan on finishing this bike up as soon as possible. Ill have the frame welding finished up on saturday, then its bolting it together and getting the battery

just received my battery from em3ev- voltage tested out of the box at 76V!

right around 13Ah and fits in the bag nicely. it is a 21s7p composed of samsung 20R 18650 cells.
ill be running a 40A controller so it should do the job quite nicely. in comparison with lipo or headway Id say this battery is much better in terms of reliability and overall cell life, which in my opinion outweighs the cost. it cost me right around 1300 and change for the battery, with the 50A BMS, the charger, the bag, some extra cables, and shipping costs. This is the first 72v frame triangle battery that Paul and the folks at em3ev have made but plan on marketing it soon.

I have a few things left to sort out but I should be riding this thing this weekend, at the latest next week. :mrgreen: :mrgreen: :mrgreen:
That is awesome.. I noticed Paul put the 21s7p triangle battery up on the website the other day.. I'm curious how much room you still got in the bag with the battery. Could you take a pic with the battery bag open with the battery in it?? Great job by the way, that bike is gonna fly