Batteries, part two or Better living through sewer pipe

Nearly a year ago, I discussed Cleverchimp’s battery packs. I say “Cleverchimp’s” instead of “Stokemonkey’s” because I conceive of the batteries as a commodity rather than part of Stokemonkey. Stokemonkey users shouldn’t have to use Cleverchimp’s batteries any more than drivers of Ford cars should have to buy Ford gasoline. We sell batteries solely because nobody else is offering them with suitable performance and physical characteristics at a reasonable price. That’s a little ridiculous, because there’s nothing exotic about these requirements. Anybody operating an electric bicycle, scooter, or similar has certain broadly similar desiderata. Meanwhile, we spend an inordinate amount of time sourcing, testing, rejecting, re-sourcing, and assembling batteries. We’d love to be able to refer our customers to any of several more specialized battery providers instead.

This post is a plea for other companies–battery pack makers and ultralight electric vehicle (ULEV) companies–to consider adopting the battery format we’ve worked out for Stokemonkey, because we think it will work well for others too. It’s in everybody’s interests for standard formats to emerge, especially in an industry composed of many small players. Standards are essential to achieving economies of scale, and scale is required to speed adaptation of the numerous promising new battery technologies on the horizon to ULEVs.

batteryspaceIt boils down to packaging. Lots of companies are selling batteries that only robot squid could love, resembling shrink-wrapped bricks with half a dozen or more wires sticking out of them (three chargers for one pack?). Others offer a huge variety of different shapes, presumably to fit a huge variety of enclosures. But where are the enclosures? Selling battery packs without enclosures is like selling hamburgers without buns, utensils, or even napkins. Heavy battery packs composed of 20-40 cells desperately require enclosures for physical protection, because vehicles suffer a lot of shock and vibration, occasional spills, and weather.

rabbittool pack with bracketRabbit Tool makes many packs with enclosures; they are costly because built to order in any of dozens of configurations, again defeating economies of scale. We bought several packs from them during Stokemonkey’s development. They performed well, but all failed ultimately from physical abuse, as they are designed to be fixed to the vehicle with pricey clamps specific to a given tubing diameter, and we carried them loose in the Xtracycle slings instead.

The enclosures need to be easy to carry on the vehicle, and easy to carry off the vehicle, with no sharp edges or special mounting hardware. They need to be able to take a hit, because it happens. They need to let the battery shed heat (no padded bags, please). They need robust, locking connectors with a high cycle life for charge and discharge functions, with strain relief for any exposed wires, because wires get pulled in the real world. They need fuses for safety. And because batteries necessarily come in many different sizes, the enclosures need to be manufacturable in low volumes at low cost. One offset is that the cost of shipping packs goes down with enclosures, because smaller boxes with less packing material are required to assure that the packs arrive safe.

With these criteria in mind and loose cells in hand, a trip to the hardware store quickly revealed that standard 4″ ABS sewer pipe has the perfect inside diameter to accommodate 3 cells across, with just enough void to accommodate chassis-mount connector bodies or switches, fuses, a small circuit board, etc. The snug fit means no shimming or padding is required to prevent jiggling. It was an epiphany, and we’re sharing. Just cut the pipe to length and you have enclosures for a wide variety of packs based on standard D and F-size cells:
packs

If you’re not asleep yet, here’s full detail about how we assemble our packs. Please rip off anything you like; if you rip off enough, we just might send you a little business, or a lot.

54 thoughts on “Batteries, part two or Better living through sewer pipe”

  • fred

    After reading this post and the links within the text, especially the “how-you-do-it” link, I can’t see how someone could
    improve on your methods, Todd. There’s very little wasted space, but enough room for cooling airflow. PVC pipe is pretty
    impact resistant too, as enclosures go. I’m not about to lift a battery assembly by the connector, but it speaks volumes to
    know that it’s strong enough.

    Reply
  • Todd

    ABS, fred! PVC shatters more easily, and vinyl is high on many environmentally-minded people’s no-good list.

    Reply
  • Joshua Goldberg

    We have one already, almost finished testing it and doing the mounting hardware and no Crystalyte is not involved.
    The enclosure is PVC and can be painted to any color you wish–even with flames. Price at the moment is around $50.00 CAD and they will house 24V-36V-48V (not sure about going higher since finding a 72V charger will
    be most interesting. Have Pics too, Wink Wink, Nudge Nudge

    Reply
  • NickF

    well its easy when you know how. I’ll try this out tomorrow morning. someone’s going to have to wait an extra 1/2 hour before they get their new bathroom suite installed.

    What a great contribution.

    Any ideas on how to make a permanent fixing to bike frame?

    Reply
  • Todd

    How do I get a clubhouse pass, Joshua? :^) Will the party selling the enclosures be selling them stuffed with good packs?

    Nick, “permanent fixing” makes it tough to charge batteries where the vehicle won’t go, swap among many packs, keep the packs at good temperatures, remove quickly for theft protection, etc. For that reason it was a non-priority in the design. I think the best way to carry weight on a bike is on racks designed for such, whether an Xtracycle or a traditional rack/pannier system. For Xtracycles in particular I think putting heavy things in the front triangle is not a hot idea, because the front end of the bike is already more heavily loaded than ideal with the rear wheelbase extension.

    Reply
  • Jess Austin

    the front end of the bike is already more heavily loaded than ideal with the rear wheelbase extension

    An epiphany! Thanks Todd, I’ll be dialing up the front fork in about 5 minutes.

    Reply
  • Spence

    I’m working on a nylon harness that fits both batteries right now. The XtraCycle bags don’t work as well as I’d like. Actually considering mounting (via Nylon Bag) the batteries below the bags… clearance will still be around 3 inches and it will keep the center of gravity low.

    Another addition I’m thinking of is a triangle of diamond plate aluminium that goes between the snapdeck and the seatpost, tightening up the wobble felt due to the two low attachment points at the rear dropouts and the bottom bracket. That was a run-on sentence, but I’ve had a glass of wine so it’s OK. The stabilizer triangle will have a rubber mounted bracket to hold the StokeMonkey control box, making a more stable platform for the electronics and will allow the removal of the bag.

    If I blow up, I’ll let you know.

    Reply
  • Todd

    Jess, dialing up, as in raising the front end will slacken the effective head tube angle, exacerbating the floppy steering feel that I think the weight-forward distribution produces. Lowering the front end will lighten the steering, but at the expense of dropping the bottom bracket (grounding pedal risk) and steepening the seat angle (pitching you forward onto your hands more.) So you see, it’s complicated.

    Spence, I’m loving the process here. I tried mounting the batteries way low, suspending them from stubby wideloaders. They have to be a ways out not to interfere with the kickstand and/or derailleur. The handling was surprisingly atrocious. As for removal of the controller, note that the small connectors there won’t put up with lots of cycles, so beware.

    Reply
  • Jess Austin

    Todd, the main thing I’ve noticed so far has not been floppy steering — I can still coast, pedal, and lean-turn around obtuse angles hands-free. I was thinking of a phenomenon I’ve noticed where when I really start pumping (and perhaps rise from the saddle), the front shocks really start bouncing. I thought perhaps that decreasing the sag would reduce that bouncing, although if I leave the FreeRad on long enough I’ll probably modulate my cadence to reduce it unconsciously. I’ll try it for a bit and see what happens. As you say, it’s complicated.

    Reply
  • Todd

    I hope you’ll forgive me for slipping into sales mode, Jess, but this out-of-the-saddle hard pumping thing doesn’t have to happen with a Stokemonkey-equipped Xtracycle; it lets you smoothly spin your way through most anything, at least as long as you’ve got juice. I think this increases the effective carrying capacity even if you don’t mind out-of-the-saddle effort, because the bike can get scary noodly with really big loads and thrashy pedaling.

    Reply
  • Spence

    Right.

    I tried the lower weight sling with a sleeping bag cover and a few tie-downs and it really made the handling weird. You’re right. So maybe the sling needs to ride inside the pouch higher up, leaving room for veggies from the farmers market below them.

    As to the controller: I was actually thinking of just leaving the controller in place with all connectors connected.

    Reply
  • Todd

    Sigh. Spence, the problem with the batteries is that they’re too dam4 big and heavy, or else if they aren’t, they don’t perform well, or they tend to blow up and be really expensive (lithium). But it’s changing. This post discloses essentially that I want to limit Cleverchimp’s investment in any particular battery technology. Really fabulous totally custom carriers would tend to tie us to one-and-only. It was probably Stokemonkey’s biggest single birthing pain to stop sweating the inevitability of change in the battery world, and to just go with today’s good-enough NiMH and package it in a good-enough manner, cheap, until a horizontal market for better batteries develops to take over the problem.

    Reply
  • Jess Austin

    Todd, please slip into sales mode whenever you like! I appreciate that the sale of Stokemonkeys is one of goals of this blog, and if I weren’t genuinely interested in the technology I wouldn’t hang around. I don’t plan any out-of-the-saddle stuff with big loads; I can already tell that the swing weight of the bike has increased considerably with an empty FreeRad. I can definitely imagine swinging the bike completely over, and I don’t think passengers would appreciate the out-of-saddle experience either.

    Reply
  • Spence

    Actually,… I’m finding that the small battery is absolutely perfect for my

    Reply
  • Spence

    Weird… I used a bracket instead of “sub-20mile” and it thought I was using HTML… dratted code monkeys! -s

    Actually,… I’m finding that the small battery is absolutely perfect for my sub-20 mile runs around the peninsula. We’ve got a ton of hills (well, actually just one big one that all roads go up and down) and I’m not using my car anymore. The only thing is,… I wish the xtraCycle could carry about 100 more pounds, cause with the monkey, I sure can… looking into beefy wheels next.

    Reply
  • uroburro

    I’m using a single black ‘bungie’ cord as a forward sling for the large battery. The inner bag on my freeloader is pretty torn up from repeated insertion/removal cycles. I attach one end of the bungie around the top of the free radical. The bungie gets wrapped around the battery and then attaches to itself. It works quite well, removing most of the strain of the battery on a pretty weak bag. The back of the battery is still inserted into the inner bag of the freeloader. (IMO, YMMV, BYO, YADAYADAYADA)

    Reply
  • Eric

    Have you ever tried to simply make PVC pipe sets with a single thread of
    batteries in series? For example, D Batteries are about 1.3″ in diameter
    and it looks like they might fit into a 1.5″ PVC pipe. If you took 10
    1.2 Volt D batteries and put them together you get a 12 Volt battery.
    Is it even necessary to solder/weld them together? If they are pressed
    together tightly with a spring (like a flashlight) it should be easy.
    Add connector plates on the end and “presto” you have a battery.

    Ever tried such a simple idea?

    Reply
  • Todd

    Eric, it is necessary to spot-weld the cells together for highest performance (low resistance). Your plan would result in a lot of extra bulk and weight, with less ventilation, than what I’m doing; then there is the matter of clean, strain-reliefed connections.

    Reply
  • Eric

    “…it is necessary to spot-weld the cells together for highest performance (low resistance)” Is there a source from which this fact is derived? In other words do you have some sort of supporting data that says that batteries pressed end to end have really high levels of resistance? I was figuring that considerable pressure would be applied either by a spring or simply with a screw to keep the batteries tight. After all, flashlights have been doing this for ages. Are flashlights poorly designed then? As for weight, PVC pipe weighs next to nothing and since the pipe has only one battery per cross section the thermodynamics should be good as long as you leave airspace between the pipes when you install it. If you really want to go overboard you could simply use aluminum pipes instead of PVC. It seems like an idea solution because you could simply pop the old batteries out and replace them when needed. (and replacing a bad battery would be a snap!)

    Reply
  • Todd

    Eric, flashlights aren’t discharged at as high an amperage as vehicle batteries. Even small-gauge wire and friction-type connectors will get hot from resistance in a typical vehicle application. It is a fact that a welded join will have less resistance than simply 2 cells touching.

    Compactness, weight, and ventilation of your design might be good enough for some applications, but as it is my scheme is bulkier, heavier, and hotter than I’d really like, and your design is a step in the other direction. I tested several packs composed of cells packed in close-fitting aluminum tubes as you suggest. All have been destroyed from the thin-wall aluminum taking dings and forcing the welds apart, and from the soldered wires at the ends joining the columns cracking from vibration. I should have suspected they weren’t too tough when as few as 4 10lb packs required shipping in wooden crates….

    Reply
  • Eric

    “All have been destroyed from the thin-wall aluminum taking dings and forcing the welds apart, and from the soldered wires at the ends joining the columns cracking from vibration.” These problems all occur because the batteries are welded… and therefore are now brittle and breakable. If the batteries are allowed to “bounce” with the bike (which is what they do) then they should never have to deal with vibration related issues that you’ve named. The only real issue I see is the potentially high levels of resistance jumping the current across a non-welded interface. One wonders if some sort of special highly conductive gel could be applied to the battery connectors where they meet each other. Any ideas? Or are you so dead set about your present solution that you don’t want to return to thinking about alternatives? Free floating batteries, if perfected, would expand the ease of use by a large margin. (make my life easier that’s for sure)

    Reply
  • Eric

    Something like this: http://www.siliconesolutions.com/prod/SS-24.php

    Reply
  • Eric

    I’ll bet this isn’t cheap, silver is the primary ingredient, but look at the resistance numbers:

    Typical Properties
    Viscosity, cps 600,000
    Specific Gravity 3.06 Consistency : thixotropic paste
    Working time, mins. @ R.T.: 15
    Tack Free Time, mins. @ R.T.: 30
    Cure time 24 Hrs. @ R.T.
    Durometer, Shore A 70

    Tensile Strength, PSI 280

    Elongation, % 165
    Volume resistivity, Ohms/cm 0.005
    Conductive filler silver

    Reply
  • Todd

    Eric, the cells aren’t directly welded together. Nickel tabs are welded to the cells, and the tabs are then welded to each other. This is pretty much standard industry practice for high-discharge-rate battery packs; it’s not “my solution,” and I’m not re-examing it. I’m re-examining the notion that packs can be sold to end-users (“consumers” if you insist) without enclosures or connectors. You may have called me on some BS about the inter-cell welds breaking; all I know is that the aluminum tubes are dinged up enough to have failed in their protective role, and that the soldered wires joining columns of cells into series are cracked

    Reply
  • Eric

    “…the cells arenââ?¬â?¢t directly welded together. Nickel tabs are welded to the cells, and the tabs are then welded to each other” I have been studying how it is currently being done and know about the tabs and the spot welds. That’s why I’m investigating other ideas like using a silicone gel to achieve the higher electrical conductivity required. (better to think hard before you begin rather than get into it and realize afterwards) Without some sort of conductive gel I can see how raw metal simply touching raw metal would not work very well. Do you see my point here? The only thing stopping the use of free floating batteries is the electrical conductivity problem. Fix that and the pack building nightmares go away. Let me also say that the gearing you are doing on your bikes is the same kind of “advanced” thinking that I want to apply to the batteries. There’s almost always a better way to do things if you think long and hard enough about it.

    Reply
  • Eric

    Another product. Dow Corning is a more recognized name: http://www.dowcorning.com/applications/Product_Finder/PF_details.asp?l1=009&prod=02785935&type=PROD&pg=00000032

    Reply
  • Eric

    A quote from a link: “Silicones have long been recognized an attractive materials for use in electronic applications due to their unique combination of properties. Now, technology which couples high electrical conductivity with silicone performance characteristics has been developed. The new silver filled silicone adhesives are processed and cured similar to conventional heat cured silicone compositions. Resultant cured products were both highly flexible and highly conductive, exhibiting volume resistivities down to 2 × 10 (-4) ohm-cm. Both flexibility and electrical conductivity were retained after extended periods at elevated temperature. The electrical performance obtained while the new adhesives were under stain, induced either mechanically or thermally, was attributed to changes in the spatial packing of the silver.”

    Any chance you might buy some of this gel and try it first? I haven’t finalized what I’m going to do yet and would love to get this idea tested. (if you beat me to it you get the credit!)

    Reply
  • Eric

    Todd, I have another question. How do you charge your battery packs? Is your charger using all the latest “tricks” to get the batteries charged without destroying them? (a real problem it seems) What about this problem of “rogue cells” that can go bad and bring the entire pack down? When you realize all the potential things that can go wrong the NiMH option is looking difficult to pull off.

    Reply
  • Todd

    Eric, we carry 2 common NiMH “smart” chargers. They look for the voltage to reach a certain peak and then drop a bit, which indicates that the charge is complete. Because this cue is subtle and can be missed, there’s a redundant temperature sensor and cutoff (this also prevents a charge cycle from initiating on a too-warm pack). Finally there’s a temperature fuse on the charge lead in case the preceding measures fail to terminate the charge current appropriately.

    As for rogue cells (prone to polarity reversal), that’s what a warranty is for. Using the packs at only Stokemonkey’s “low” mode for a few complete charge/discharge cycles can help prevent cells from going bad prematurely — it’s too-high current, too soon after sitting idle after manufacture that pushes weak cells over the edge. One of the beauties of variable gearing such as Stokemonkey uses is that the motor needn’t ever operate at the very high current levels of other systems, meaning that one can use smaller, cheaper, lighter batteries to good advantage.

    ebikes.ca plans to sell NiMH packs that have been screened carefully during a preconditioning regimen to weed out the duds; you get a printout of each pack’s discharge curve. Of course, it costs money to set up and operate a computerized conditioning/testing facility; I hope they get the volume of sales necessary to support this. Enclosures would help I think…

    Some companies, such as Saft, make NiMH packs with elaborate management circuits to prevent common problems. While there’s a net reliability improvement with these, the added complexity of the management circuit is itself a liability, and certainly a major cost. Last time I checked, these packs cost several times what mine do wholesale, and they come in a shoebox-like format in need of… an enclosure.

    Reply
  • Eric

    If you are going to get serious about designing batteries, then this software based battery charger would be just the thing to use:

    “If you are already a battery expert you’ll be pleased to know that the UBA4 has enough features for even the most demanding battery test applications. With its graphical programming interface you can easily design a battery test to do exactly what you want. You can specify the charge method (constant current or constant voltage with peak, timed, or temperature termination) and the charge and discharge currents. You can even use conditional loops in the test. All voltage, current and temperature readings are stored in a standard results file.

    The UBA4′s power lies it its ability to leverage the power of your PC – it has neither display nor keyboard. We keep the UBA4 simple and put the intelligence into the S/W on your PC where it belongs. The UBA4 was designed by our president Marc A. Venis, a professional engineer with a Masters degree in Electrical Engineering and over 20 years of experience in the battery industry.”

    http://www.vencon.com/index.php?page=prod_uba4

    Reply
  • Todd

    Eric, the fact is that I don’t want “to get serious about designing batteries.” I don’t have the volume to succeed well in that endeavor. Business-wise, I want to devote my limited energies and inventory space to stuff I have a proprietary claim on, and where I think I can offer unique value. I’m in the battery business reluctantly, only because nobody else is (yet) offering a turnkey alternative suitable for non-hobbyists (read: no wiring, enclosure building required). Besides, I’m a Mac bigot.

    Reply
  • Eric

    After looking at the headaches (and cost) involved in getting into the NiMH/Lithium battery packs I’m actually looking to make my prototype using Lead Acid Batteries (for now). I’m going to use gears like you are (which is absolutely the correct thing to do) and not worry too much about the weight. With three 12V 28Ah Lead Acid Batteries the bike will weigh about 100 lbs, but with gearing and slick aerodynamics the top speed with a 750 watt motor should be about 47 mph (on the flat) and the range about 30 miles. As a percentage the weight diffeential is only about 12% from Lead Acid to NiMH. (from the overal bike perspective) It will be more motorcycle “road racer” (overgrown “pocket bike”?) than bicycle and will not have pedals. 24″ wheels nad a 50″ wheelbase. Your gearing article inspired me along these lines and you might look at this website for ideas:

    http://electricmotorsport.com/EGPR/egprPage.htm

    Reply
  • Eric

    Check this out:

    http://www.valence.com/ucharge.asp

    It’s designed like a “car battery”. Very cool!

    Reply
  • Tim R

    wow, those are pretty amazing looking, although the cells and packs look more suited to the stokemonkey.

    33% lighter, and twice the runtime as lead acid would be quite amazing, and quicker recharge times to boot.

    Reply
  • Eric

    $600 – U1-12RTL – 12.8V – 24 Ah
    $860 – U1-12RT – 12.8V – 40 Ah

    So it’s not cheap! (but very simple to use)

    Maybe with mass production the price will come down…

    Reply
  • Todd

    Note that you need 3 12V to run Stokemonkey, so how’s $1800 sound? For 3 large bricklike objects somehow to lash to your bike? No thanks. I’ve tested 3 different lithium battery systems. None have performed as advertised, all were very expensive, and the form-factor issue is still a governor at my low volumes.

    Reply
  • Eric

    I think the point here is that the manufacturer of the battery should design into it all the proper safety features so that a typical consumer has a sort of “plug and play” ability with the battery. Right now the battery business is a little bit like the early “wild west” days of computing… everyone was doing everything from scratch and you has all kinds of problems. Did you catch that they have a deal going with a european electric bike manufacturer to make long range electric bikes?

    Reply
  • Eric

    I was watching the Tour De France and realized (since I’ve been running the numbers every which way) that a properly configured electric bike could pretty easily with the race. Each leg is only about 100 miles long and they climb about 10,000 feet in total. (typically) I think it would be a “great race” to challenge all electric bikes to race in something similiar. Maybe even use the exact same course. People throw thousands into their bikes as it is, to spend $3000 to be able to outride the abilities of ordinary cyclists. Set the limit to 750 watts and let people use any battery technology they can devise.

    Reply
  • Eric

    Final note:

    Using a Valence 48V 48Ah pack (K-Charge Series 67lbs) I calculate a “full power” range of about 145 miles using a 750 Watt motor. For a 500 Watt the range is 185 miles.

    Reply
  • Joshua Goldberg

    will be testing a new Prismatic Ni-MH shortly that should blow every Ni-MH and Li-Po off the
    map, testing should take about 3 months b4 we know what we have.

    Reply
  • Martina

    The tour de france idea sounds like fun… I could see similar ideas going through Todd’s brain while watching the local Mt Tabor bike races. I know he was itching to show what the monkey can do!

    Reply
  • Todd

    I followed a pack of cat-1&2 racers for the penultimate lap of a Mt. Tabor race recently, on Xtravois with Stokemonkey, small battery, child seat, etc. And I kept up, barely. The gearing is too low to stay with racers downhill; I spun out, and caught up on the uphill. I didn’t dare draft the pack, as I wasn’t supposed to be on the course anyway, and plowing through a crash with a powered cargo bike, well, way bad publicity. After the one lap I was winded and legs were wobbly… but again I kept up, on an 80-lb bike, totally upright, small battery, and these guys were going balls out. It did get me thinking about mods necessary to win a race like this, but then… going stupid fast on a bike is not rocket science, really, and I don’t want people to associate Stokemonkey with daredevil stuff.

    Reply
  • Eric

    I’ve noticed that there is a “toy” level to the electric bike (pocket bikes) and the full fledged motorcycle that weighs in at 300 lbs or more, but very little in the “sweet spot” of about 120 lbs. The “electric bike” as a “scooter” is not built for speed, but for convenience. Seems to me that you need about 120 lbs to get some decent speed and range (given current SLA batteries) out of a bike. I’ve eliminated the true “bicycle” design because when you run the numbers the power of pedaling is pretty small compared to the electrical power. And in the end it’s aerodynamics that really wins the day. Aerodynamics is essentially “free power” and so if you could get into the “road racer” pose with a really tight fairing front and rear you save so much on power that all the pedaling becomes pointless. At 40 mph you spend all your energy “pushing wind”. By eliminating the “wind” you can then use a smaller motor to get the same speed. (recumbants are banned from the Tour De France because they are too aerodynamic… this ban went into effect 100 years ago) I would sum up my goal as:

    “Create the most efficient and economical electric bike possible that also has the highest performance given those constraints.” (in the “road racer” sense… make it fun to ride)

    Reply
  • Todd

    Eric, I’m chasing another vision with Stokemonkey that’s firmly rooted in true bicycle dynamics. I consider it essential for the vehicle to remain viable on human power alone, and not even to have a pure motor mode, in part to keep the user’s bicycle habits and fitness fully tuned for the likely majority of trips for which plain bikes are best suited. I’m not trying to improve upon a bicycle; I’m trying to offer a car alternative for avid bicyclists, for those errands that can’t really be enjoyed without motor help. Lots of bicyclists own cars that they use only a few times a month, for hauling stuff that Stokemonkey could make short work of. I agree with you that the smartest path to sustained speeds over 25mph is superior aerodynamics, and bents, especially faired bents/velomobiles, are a natural choice for this. If you know of any velomobiles with passenger and 6-bag grocery capacity that cost less than $4K or so, do let me know. But then with that kind of curb weight and high speeds together, well, safety demands more structure, more weight, more cost…. you re-invent the car, and human power becomes irrelevant.

    Reply
  • Eric

    There will always be many categories. I’m seeking to answer a different question than most:

    “How can I (as a human) get from point A to point B with the minimal amount of energy, lowest cost and have fun while I do it?”

    Many of these Electric Vehicles weigh tons, like most regular cars do. This is a very inefficient way to use energy to transport your body even if you can “charge it” so that you can claim to be “green”. In the “big picture” of things, people like “sport” (thus the “Road Racer” styling, like the GP motorcycle) and they like not to spend much money. (look at WalMart) So I’m simply trying to create something that fits that niche of people who like to ride for pleasure, but who are also a little concerned about the idea of a pleasure ride that wastes gasoline. “Fun riding without guilt” might be the slogan.

    If someone wants exercise they can ride their bicycle.

    Unless it can be proven that pedaling increases efficiency of the overall system compared to “other options”, then it doesn’t contribute to the goal. I’ll add that my first sketches involved something that looked a lot like Stokemonkey in the drivetrain department, I was going to combine pedaling with the motor as you do. It STILL a great idea to use gears… that is completely missed even by the racing electric motorcycle crowd. Battery effeciency is closely tied to engine RPM (I’ve studied all the performance graphs) so you are 100% on track with that idea.

    Diversity is okay… :)

    Reply
  • Eric

    One solid advantage of keeping the pedals around is that you can run out of power and still get home. The inability to pedal means that you need to keep tabs on your trip. It makes the machine good for short “sport” rides, but not good if the distance is unknown. My idea is for someone that wants to take a quick ride through their favorite nearby backroad and then before the hour is up park it in the garage and do something else. It’s the “quick fun ride” idea, not the marathon. (of course with Lithium and a range of 150+ miles you could go plenty far enough)

    Reply
  • Todd

    Yes, diversity — I wasn’t trying to dump on your concept, just differentiate mine. Another advantage of driven pedals is simply to assure that the gears will be used more assiduously than without; use the human lizard brain instead of an automatic transmission. Also, even with variable gearing, certain moments will call for hard pedaling to avoid big amp spikes. You’d need a much more powerful/robust electric drive to make pedaling truly irrelevant; I’d argue that you get a big efficiency benefit right there, in not having to upsize the electric drive with associated weight gain. Also, yes pedaling is fun, or endorphins are, at least. I’d sure rather pedal than dance, or ski, or jog, or climb rocks, or swim, or all sorts of other physical activities that people undertake for pleasure.

    Reply
  • Eric

    Well, you can always downshift at the right moment to avoid those big spikes. It would be important to know how to ride the bike well because you could ride it in the wrong gear all the time and never know it. This is a very good point actually and one that I’ve discussed with the “other Todd”. (Todd Kollin at Electric Motorsports) One idea I had was to do like the Indy Car steering wheel LED lights for the RPM. If you look on those steering wheels they have three LED’s that light up when you go below the powerband and another three LED’s when you go above the powerband. Such a system could let you know when you are getting “peak” performance out of your electric motor. (you would know when to shift up and when to shift down)

    I was just working on the aerodynamic stuff and this is what I came up with…

    Aerodynamic drag can be calculated with this equation:

    Drag = 1/2 * (Air Density) * (Velocity) * (Velocity) * (Drag Coefficient) * (Frontal Area)

    There’s nothing you can do about “Velocity” because it’s the central factor and it’s squared too. The “Drag Coefficient” you can improve with fairings… but that shows diminishing returns. It’s the “Frontal Area” where a compact “Road Racer” could significantly out perform a pedaling bike. Compact the legs up into a “tuck” position like the motorcycle road racers do and you can cut the “Frontal Area” about in half. Look at the frontal view of a bicycle and half of the frontal area will be the legs. Legs that move also create all kinds of eddy currents… it’s an aerodynamic nightmare… and that means lost power… wasted battery energy.

    Reply
  • Eric

    Another subject is battery placement. Long, long ago I did a little “pit work” out at the old Laguna Seca Raceway for a guy racing in the Formula 2 (250cc two stroke) class. At the time there was a theory that placing the gas tank below the engine would lower the center of gravity of the bike. I was actually working on a test gas tank until one of the guys doing it already crashed badly and people realized that the theory was wrong. Apparently the way a bicycle/motorcycle steers is not as people theorized, the actual “pivot” point is up pretty high… about three quarters of the height of the wheel and basically the further from the “pivot point” you place any weight the worse the weight effect it produces. (it makes the weight “seem” heavier) These scooters that place the batteries very low are actually producing a very poor handling machine. The ideal location for batteries is hanging from the top tube of your bike. (or near there) This is a problem, however, because that’s exactly where your legs need room to pedal. So from a “performance” standpoint the batteries need to be between your legs in the middle of the bike. This is a bonus however when it comes to aerodynamics. Since the batteries are best placed high (near where the aerodynamic “pocket” exists) you are effectively “killing two birds with one stone”. You end up with the ideal handling and low aerodynamics. Placing the battery in the back in the “middle/forward position” is a good location since your body weight is forward to balance the battery.

    Reply
  • Eric

    And I’ll add that on the Stokemonkey the weight is low, but also in the rear. This is good. The problem positions is placing the battery low and forward. Imagine a “pivot” line stretching from the center of your rear wheel forward to the top of your front fork. As long as you stay near this “pivot” you are okay. Having the batteries straddle the rear wheel is correct. Above the rear wheel is too high. (many have the batteries placed like it were a bike rack)

    Reply
  • Eric

    The amount of batteries needed to have won todays difficult stage in the Tour De France?

    Using 2 of the Valence 12V 130Ah 41lb Lithium Batteries we get a calculated full power time of 6 hours and a distance on the flat of 250 miles using a 500 watt motor. On a 10% grade you get a maximum of 58 miles. So you get:

    (10% grade) sin(5) * 58 miles * 5280 ft/mile = 26,500 ft

    Which is about the amount of time, distance and climb that was needed for this stage. It’s definitely possible.

    For a typical 1.2V 10Ah Lithium Cell we would need to have:

    1.2V * 10 = 12V
    12V * 2 = 24V
    10Ah * 13 = 130Ah

    So we would need 10 * 2 * 13 = 260 Cells!

    At a typical price of $5 per cell we get $1300. (not bad)

    Reply
  • Eric

    Also, one other interesting “non-intuitive” fact about batteries and motor size is that while the range on the flat will go down with a larger motor because the bike will go faster (and thus push more wind) it actually has no effect on slow uphills. When you run the calculation for a 500 watt motor verses a 750 watt motor on the hills it produces the same range. Interesting huh? Within limits the motor size is not as important as one might think. (it’s okay to use a larger motor… but since you are tempted to push more wind it hurts the range, but it’s not due to losses that one couldn’t control if disciplined)

    Reply
  • Victor

    Hi Todd, congrats on your stokemonkey coming to fruition. The idea of making a battery connect and/or look like a water bottle seems like the best way to do it. (my epiphany, lol) I’ts good to see you have batteries for sale. Too bad you have to make them yourself. I really like your enclosures. And they look almost like water bottles! Of course I have no idea what the actual size of water bottles are for bicycles; I only know that my bike has screw holes for 2 bottles. And alsoI have bolted an aluminum frame to hold 18lbs of sla in there, attached only be 2 screws into the lower bottle mount. And duct tape to keep it steady. After many miles of wheelies and smashing road crevaces at 30mph, the battery mount ifs fine. (my spokes aren’t). When I get the appropiate lithium, I want to make a water bottle battery. Then this will fit just about any bike made? Do you think this is a viable route to take? If it is, then please (anyone) please steal my idea and make one, ’cause I’ll buy it. (It also must cost less than $300 per 5ah 36v bottle.)

    Reply
  • Todd

    Victor, I think 300 or so watt hours is the minimum worthwhile amount of battery to carry on a vehicle meant to complement plain bicycles, so I’d find the water bottle format too restrictive with today’s technology. Soon I’ll be evaluating a pack meant to mount to the water bottle bosses, though. Minimum nominal frame size for that mount point is 21″. I suppose I’ll just carry it in the cargo area instead of put that amount of weight in that part of the bike.

    Reply
Leave a Reply