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Thread: motorcycle vs battery form factor issues

              
   
   
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    motorcycle vs battery form factor issues

    Bear with me here, I'm new to this. But I just finished reading Toll's "DIY Lithium Batteries" book (which seemed well worth the purchase price) and I've spent some hours here and at the other two big ev forums reading about batteries/projects and I've got a couple of questions for which I've not seen answers.

    Motorcycles lean, and they need ground clearance when they do that. A lot of potential "vehicle quality" battery choices don't look very good for fitting into a leaning vehicle.

    There seem to be two main choices on e-moto batteries -- prismatic/boxy units like the Leaf/Volt/Bolt/BMW I3 etc automotive batteries and the cylindrical batteries (18650, 38120. 40152).

    The Leaf looks attractive on performance/ruggedness/availability/price but it and the other's like it are roughly a foot square on height and width which means they've got to be raised higher off the ground to stay in the ground clearance/lean boundaries I want to use (50 degrees at full suspension compression). I've not seen anything comparable that might be closer to 4-6" square allowing more of them to be packed into a not-rectangular space. The Samsung cell in the BMW is smaller at about 5" x 7" but it seems to only be offered commercially in DIY quantities at a very high price. The Tesla packs appear to need liquid cooling and I want to avoid that.

    Cylindrical batteries give a lot more options for fitting into the required vehicle shape than the large automotive batteries. The 18650 cylinders are probably ruled out because the ones I've seen being used need connectors spot welded to them, as well as needing around a thousand or more of the small cells.

    I've read several threads on builds with the Headway 38120/40152 type of cylinder batteries (e.g. frodus and SplinterOz). The screw terminals and larger capacity (for fewer cells) than the 18650 seems attractive, though possibly needing around 400 @ $6K to get in the 13-15 kWh range is pretty daunting. At least they can be purchased new instead of having to come out of salvaged vehicles.

    However, the Headways seem to be a design dating back around 10 years and battery technology has no doubt progressed since then. I did see at least one comment about them being dated technology. Are there versions of the 38120/40152 or other suitable models that have updated chemistry/technology in them or does the convenience of the size and connection (and apparently reliability/longevity) end up being something you take in exchange for somewhat dated performance?

    Are there other manufacturers making cylindrical batteries like the Headway that would offer better performance for similar levels of reliability/longevity? Is there a good option for a small height/width prismatic battery that might be an easier fit than the Leaf style?

    I won't be buying batteries soon, but as this won't be a conversion but rather a fairly clean-sheet design a battery spec needs to be established reasonably early in the design process. I'd like to have a kWh capacity in the range of 13-15, something similar to a Zero with Power Tank. I don't want an ev with a real world 40-60 mile range, but I'm also not going to sacrifice having a reasonable level of handling for range.

    thanks,
    Michael

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    Empulse R #24 frodus's Avatar
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    14-15kWh is going to be a tall order fitting into a chassis unless it's designed from ground up. The chassis of an existing motorcycle likely isn't made to fit the motor/controller and batteries of an EV. Even zero, who manufactures a bike to fit their batteries and custom makes the pack, has trouble getting into that range.

    What range DO you want?

    What is this going into?

    Headway was OK, 8 years ago when I used them in my first bike, but after time, they rusted. Their IR wasn't super great, and they weren't exceptionally inexpensive.

    Lifepo4 isn't exceptionally energy dense. LiIon is better, but to get something small form factor that is easy to assemble, and can fit into something like the Kingston bike, might be hard.

    There's also Pouch cells, but they require a lot of manual assembly like the small cylindricals.

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    Quote Originally Posted by frodus View Post
    14-15kWh is going to be a tall order fitting into a chassis unless it's designed from ground up.
    As I said, "a fairly clean-sheet design", not a conversion. I now have only one "built in a factory" motorcycle and that is getting modified. I don't anticipate owning another bike designed by someone else, the Zero from Stuart is strictly a component donor, and he gets to recycle the suspension/wheels instead of me paying to have them shipped because I have no need nor desire for those parts.

    As to range, 120-140 miles freeway seems reasonable, enough to ride from San Francisco to the south bay or Marin/Sonoma and back without needing a recharge, just as I'd expect to ride my Honda there and back without refueling. I'll be addressing aerodynamics in the design somewhat along the lines of the Alan Smith's Vetterized EX250 "low boy" streamliner.

    I'll probably want the largest individual cells that have a good form/price/performance in order to reduce the amount of wiring needed. I'm not looking for a "let's build batteries" hobby, I want to build a motorcycle that has e-power. I'll do what electrical stuff I have to do, but doing wiring/wrangling electrons is not my goal.

    cheers,
    Michael

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    Empulse R #24 frodus's Avatar
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    Just saying that you might not meet those requirements for range and kWh, unless the vehicle is large enough to house the batteries. I think they'll take up more than you think.

    Do you have a picture of what you're thinking the vehicle is going to be like? I still haven't been able to picture what you're doing yet.

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    Senior Member T Rush's Avatar
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    I still want to see someone do something with Chevy Bolt modules http://elmoto.net/showthread.php?t=4642
    ...they are narrow(stood on end) and about as light and energy dense as 18650 packs

    but my Honda Blackbird, Suzuki GSXR, and BMW boxer bikes aren't really all that skinny...and you are talking about a big heavy bike to have any long range battery in it, so its likely not also going to be quick and nimble
    Last edited by T Rush; 3 Weeks Ago at 2053.

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    Picture this BMW C Evolution with hub center steering bolted to the front of the battery case/chassis, and the top of the battery case being a bit lower with possibly some additional battery space on top behind a solo rider, and you'll have an idea. Oh, and the bottom corners of the battery case shaved to allow 50 degrees of lean at full bump, and 17" wheels with a FF (Feet Forwards) riding position too. I'm not averse to moderately long wheelbase, my Honda CTX700 is plenty nimble at 60" so 66" or so if needed wouldn't bother me.

    https://www.bimmerarchiv.de/images/resize.php?img=4512

    The front wheel is mostly done:

    http://www.eurospares.com/graphics/c...R6HCS0128a.jpg

    cheers,
    Michael

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    Empulse R #24 frodus's Avatar
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    OK, now I see what you're doing.

    I'll take a look, but there's not much for large format lithium cylindrical out there that a DIY person can easily get.

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    That's the impression I've been having. I could use prismatic if they are small enough in two dimensions. The bottom of the truncated lean angle triangle is about 3" wide so 4-5" could fit fairly far down into that and then maybe two above that and then double horizontally towards the back. But 9-12" square raises the battery mass and also starts to impinge into the seating area.

    The attached screen capture should make my concerns more obvious as you can see Leaf modules inside the ghosted chassis/box. The green spars are the base for the footbox at the front, the ME1507 plunked in the back. A central low Leaf battery is almost OK but cabling on the top might raise the top of the cover higher than I want. A couple of 100v Leaf assemblies end to end in parallel might work but the calculated length has the back one trying to occupy the same space as the motor.

    cheers,
    Michael
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    Senior Member Stevo's Avatar
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    It's a challenge, isn't it? IDK how you are going to get that kind of range without adding side paniers or some other kind of bolt on range extender.. battery tech just isn't there yet for us.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: http://elmoto.net/showthread.php?t=4354

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