A series of electric assists

This is the first assisted bike I ever rode, a Surly Big Dummy with BionX.

I first tried a bike with an electric assist last March, just over six months ago, a BionX assisted Surly Big Dummy at Splendid Cycles in Portland. It made quite an impression. Later I tried a mid-drive assist at The New Wheel in San Francisco. Then I tried another mid-drive assist and a front hub motor.  Less than a year ago, I could not have identified the difference between these assists with schematic diagrams and prompts from their designers. I wish I knew then what I know now.

The electric assists I have tried:

  • A front hub motor operated by a throttle on the handlebar (eZee)
  • A mid-drive motor operated by a throttle on the handlebar (EcoSpeed)
  • A mid-drive pedal-assist motor (Panasonic)
  • A rear hub pedal-assist motor that responds to torque (BionX)

I have pretty strong feelings about what kind of assist I prefer after trying all of these (BionX, although it’s not perfect). Maybe you have no idea what I’m talking about, but wish you did because you’ve been hearing about this electric assist thing and it sounds kind of cool, but you couldn’t pick an electric assist bike out of a lineup. Read on, friend.

General thoughts

Electric assist bicycles are interesting because they are true car replacements for ordinary people. I have met lots of committed, fiercely strong riders who not only ride to work and for errands and on weekends, but also head for the steepest grades in the city to improve their hill-climbing chops. These guys (they are almost always men) are inspiring, but your average mom of two isn’t going to look at them and say: “Yeah! That could be me!” But put an electric assist on a cargo bike and you are looking at a transportation system that can haul the kids, handle a week’s worth of groceries, dodge traffic, and park right next to the front door of any destination in the city—at the same time. All of this for minimal operating and capital costs, plus enough exercise that you no longer get depressed about not making it to the gym since the kids were born. Many of the factors that make riding a bike seem intimidating—I can’t sweat because I need to look decent for work, no way can I make it up that hill, how am I going to carry the kids, I can’t handle the wind—disappear with an assist. All that’s left to worry about is wet weather. I personally got some waterproof outerwear and found out that I liked riding in the rain, but if I had hated it, heck, we could rent a car on every rainy day in San Francisco without coming close to the cost of owning a car. (In other climates people worry about snow, but from what I’ve read this involves getting some studded winter tires and a cover for the kids and then you’re good.)

Some people like throttle assists (operated by a grip on the handlebar, independent of pedaling) and some people like pedal assists (which multiply your effort as you pedal). My anecdotal impression is that people who come to electric bikes from bikes prefer a pedal assist because it feels like riding a bike. Whereas people I’ve met who ride both bicycles and mopeds, or bicycles and motorcycles, seem to prefer having a throttle. Everybody likes what’s familiar. I came to electric bikes from riding a bicycle as my kids’ weights edged up toward 100 lbs. I didn’t care for the throttle assists I tried.

None of the electric assist systems cost much to charge. Efforts I’ve seen to estimate power costs sort of peter out because they’re so trivial. NYCE Wheels, which sells a lot of assisted bikes and has some great articles on their website about the technology, estimated the cost per charge at maybe 18 cents in New York City, but of course prices depend on local rates. The better systems estimate that a charge can carry an assisted bike at the highest level of assist for 20-45 miles.

Currently there are three kinds of batteries that can power the motor on the market (that I know of): sealed lead acid (SLA), nickel-metal hydride (NiMH) or nickel cadmium (NiCd), and lithium-ion polymer (LiPo). The technology for batteries on electric assists is still considered somewhat experimental. Getting the longest possible warranty from a reputable manufacturer is a really good idea. Expect the battery to last only a little longer than the warranty and you won’t be disappointed. Battery replacement is the true cost of maintaining an assisted bike. Compared to the costs of maintaining a car, it’s still bupkis: with a good warranty, it will run $500-$900 every two years at the most.

  • SLA batteries are the least inexpensive electric assist battery. They’re incredibly heavy and take several hours to charge. Bikes with these batteries tend to have limited range (maybe 5 miles). When SLA batteries won’t hold a charge anymore, they have to be disposed as hazardous waste. These batteries are common on e-bikes in China. If you buy an e-bike at a big box store it will have an SLA battery, and it won’t last long. You’ll be replacing entire bikes more frequently than other people replace their bike’s batteries.
  • NiMH (more common) and NiCd (less common) batteries are somewhat more expensive, still heavy, and bikes with these batteries tend to have greater range (maybe 10 miles). They were considered an upgrade from SLA batteries at one time, but they have their little issues. One of these is charge memory; occasionally you have to drain the battery down or it will stop fully recharging, and you won’t be able to go as far. When they won’t hold a charge anymore, they will not win any awards for environmental stewardship. However in San Francisco, Sunset Scavenger will recycle them if they’re left taped up in plastic on top of a black can. It’s almost impossible to find these batteries on new bikes, as they’ve been supplanted by LiPo batteries.
  • LiPo batteries are the most expensive, most energy-dense, and lightest weight battery option. LiPo batteries largely dominate the market now. Bikes with these batteries tend to have greater range (20-90 miles). Using them with inappropriate chargers or puncturing them can make them explode (exciting!) They can be stored for long periods (1-2 months) without losing charge.

Front hub throttle assist

I tried the eZee front hub motor that comes standard on the Yuba elMundo. This is a 500 watt motor. You can tell there is a motor on the bike because the front wheel has an oversized hub. There are lots of other manufacturers that make front hub motors, and kits made in China, where electric bikes are fairly common, are often found on eBay. However eZee seems to be one of the more reputable manufacturers. On the elMundo there is also a battery attached to the frame, just behind the seat tube (that’s the part of the frame that attaches to the seat) and in front of the rear wheel; however the battery could be placed somewhere else on other bikes (a rear rack, a down tube, anyplace that would hold the weight). The suggested range for this assist system is 20 miles.

  • How it works: You activate the motor by twisting the right handlebar grip away from you. The more you twist, the more assistance you get. When the motor is on, your pedaling appears to add nothing. You can turn the motor on and off with a controller on the left side of the handlebars. The controller is pretty basic; just a switch with lights. The look screamed “high school science fair project” to me.
  • What it feels like: It feels like skitching. Skitching is when you are pulled along by something other than the bike, like when lunatic bike messengers grab onto a passing car. You’re hitching a ride. I have never skitched on a bike because that would be insane, but I have skied. Using a front-hub throttle motor feels a lot like being pulled on a rope tow while on skis (except obviously you’re on a bike).
  • Noise level: Medium. I definitely noticed the sound of the motor while I was riding. I wouldn’t call it noisy, but people walking along the sidewalk alongside noticed the sound, and it also muffles the noise of passing traffic somewhat.
  • Pros: You never have to work going uphill. The eZee motors work with many batteries. They are the Microsoft Windows of electric assists. The system is reasonably priced as electric assists go, although not so cheap that you wonder whether they’re a fly-by-night manufacturer.
  • Cons: A downside of using any of the throttle assist motors is that your power is limited to what the motor can pump out. Pedaling adds nothing. Unfortunately a 500 watt eZee front hub motor didn’t really have the kind of power needed to get two kids up steep hills in San Francisco. I saw one elMundo overheated and out of commission (two older kids on deck, bike on a hill) during our recent Kidical Mass/Critical Mass ride. I have heard other similar stories, although I haven’t personally witnessed them. There is also something weird going on with eZee right now; none of its products seem to be in stock. Using a throttle-operated assist doesn’t feel like riding a bike.
  • Battery type: LiPo. I’ve seen warranties on eZee batteries of either six months or a year.
  • Cost: around $1450 for this motor with a 36v battery.

Mid-drive throttle assist

This is the EcoSpeed Bullitt; the motor is not visible, but note the console above the handlebars.

I tried the EcoSpeed aftermarket mid-drive assist mounted on a Bullitt at Portland’s Splendid Cycles. This is either a 1000 watt or 1500 watt motor; the answer seems to depend on how you frame the question. Mid-drive motors are more efficient than hub motors, so comparing watts between systems isn’t helpful. Unlike many assist systems, the controller did not limit the maximum speed (many state laws limit the top speed on assisted bicycles to 20mph). This discovery led to the following entertaining conversation. Me: “Uh, is this system even legal in California?” Splendid: “Well… no. Maybe. It’s a gray area, legally speaking.”

You can tell there is a mid-drive motor on the bike because there’s a bulbous protrusion near the chain wheel attached to a second chain. The motor drives the second chain and pulls the bike along. On the Bullitt, the batteries were mounted under the front box. You can fit a lot of batteries under the pallet of a long john, and mid-drive motors are pretty efficient; EcoSpeed claims their system can go 35-45 miles.

  • How it works: Twist the right handlebar grip and away you go. More twist, more speed. You can spin the pedals for fun but it’s not necessary, nor does it add any power or speed. The controller is a complicated-looking little computer on the handlebars that details the remaining battery power, speed, mileage, etc.
  • What it feels like: Hard to describe. It’s kind of like riding a train? I could feel that the motor was moving the bike underneath me, but it didn’t feel like I was being pulled; it wasn’t like a front hub motor.
  • Noise level: Unbelievably loud. It sounded like a moped.
  • Pros: This is an insanely powerful motor. It would be great for a construction company. Attach a trailer and you could haul, I don’t know, a load of concrete blocks up steep hills for miles on end. It would be overkill for hauling my kids around the city. Nonetheless, they thought it was wildly entertaining. They still ask about “the fast motor” sometimes.
  • Cons: It’s really noisy and really expensive. It may or may not be street-legal. The motor is so powerful that evidently it sometimes breaks chains on bikes. Using a throttle assisted bike doesn’t feel like riding a bike. To be honest the EcoSpeed scared me a little. I think this assist is best suited to someone who really understands the mechanics of electric assists. I am not that person.
  • Battery type: LiPo. The battery supplied by EcoSpeed has a two year warranty. There’s an option to supply your own battery.
  • Cost: $4,195 for the motor with battery, $150 for the computer.

Mid-drive pedal assist

Two types of bikes at The New Wheel: the Focus has a mid-drive pedal assist, the Ohm next to it has a BionX assist.

I tried a Panasonic mid-drive pedal assist on a purpose-built electric bike at The New Wheel in San Francisco, a BH Emotion Diamond Wave+. Some of the European assisted bikes have really weird and complicated names, I’m sorry to say. I’m going to refer to this bike as the Emotion because that was the name emblazoned on the down tube.

The Emotion has a 250 watt motor that’s built into the frame of the bike; you can tell it’s there because the chain guard looks really fat, like it’s been pumped up on steroids. Because the manufacturer built the system into the bike the torque/motion sensor is hidden inside the frame. There is also a battery mounted behind the seat tube and in front of the rear tire. Like many of the higher-end electric assist bikes, it comes with lights, fenders, chain guard and rack; this bike is designed to be used for transportation, not as a toy.

Mid-drive motors are so efficient that it would be a mistake to think that the comparatively low wattage means that you’re sacrificing power. On this bike I could easily scale hills that I’m fairly certain would have knocked out the eZee entirely. (The New Wheel is cleverly located near some of San Francisco’s more scorching hills. In my neighborhood the hills top out at a 25% grade; there are steeper hills near the shop.)  The BionX and EcoSpeed motors could handle the same hill; in fact I was riding with a friend who was on a BionXed bike (350 watt motor) at the time and he was just peachy. However the suggested range of the Emotion was 45 miles, whereas the suggested range of the BionX bike he was riding (an Ohm) was 35 miles.

  • How it works: There is a controller on the left side of the handlebars where you set an assist level of low, medium, or high (or off). Once it’s on it sends power as you pedal to multiply your effort. On low I wanted to gear down to make pedaling comfortable. On high, gearing down for the hill was optional.
  • What it feels like: Using the mid-drive pedal assist motor felt like riding a beach cruiser along the waterfront regardless of how steep a hill I attempted to scale. People do that kind of thing for fun on vacation. If you ride on a lot of hills already, the experience of using a mid-drive pedal assist is both intoxicating and a little spooky. If you always wanted to ride a bike but don’t because you live on a steep hill, this bike is a dream come true.
  • Noise level: The motor itself is silent. There was a slight rattling from the chain when the motor was running. It was fairly quiet but I noticed it, although someone walking on the sidewalk next to me wouldn’t have.
  • Pros: I like all of the pedal-assist systems because they feel like you’re riding a bike, but you don’t have to suffer (unless you want to). However this system is probably the most sophisticated I’ve ever used in that it doesn’t require you to think about how you’re riding: set the assist and forget it. The mid-drive motor works with internally geared hubs. The motor and battery are unobtrusive. There is a neat feature on most of the European assisted bikes, the “walking assist”, where you can push a button and the bike gives a trickle of power that makes it feel like you’re walking a bike that weighs 10 pounds instead of 50 pounds.
  • Cons: The biggest con is that these systems are currently only built into one-person commuter bikes (but see below for notes on the Stokemonkey). So although you could add a child seat to a bike like this, there isn’t any way to use the assist system to haul serious cargo or two kids, even though the motor is capable of handling those loads. Beyond that there’s only trivial stuff. If you’re using to riding a bike on hills, learning to use this kind of assist appropriately can be a little weird. The goal is to maintain a steady pedaling rhythm and not bear down on the hill, or even necessarily shift down (unless it would make it easier to maintain cadence). I had to remind myself not to *try* to climb the hill. It was like The Matrix: “There is no hill.” But if you haven’t been riding on hills a lot, this won’t be an issue. You’ll take to it immediately. Another minor issue is that people who like to tinker get frustrated that these are closed systems; you can’t mess around with the bike. However I have trouble believing that people like that would have the slightest interest in this kind of bike anyway.
  • Battery type: LiPo. The entire bike has a two-year warranty.
  • Cost: The entire bike, including the electric assist, costs $3,300 at the New Wheel; they offer 12-month 0% interest financing as well.

The Stokemonkey

Once upon a time, there was an aftermarket mid-drive pedal assist system specifically meant for cargo bikes , the Stokemonkey (designed and sold by Clever Cycles in Portland). Although the motor was created for longtail cargo bikes, Stokemonkeys have also been used on front loading box bikes (this is not recommended by the manufacturer, however).  I have, sadly, never ridden a bike with a Stokemonkey. However reports from people who have ridden them claim that the motor is silent, the assist is seamless, and that a stoked, fully-loaded cargo bike can easily climb any hill. The Stokemonkey was withdrawn from production when the cost of parts increased, but is apparently coming back at an unknown (to me, at least) future date and price. Yeehaw!

Rear hub assist that responds to torque

The BionX system can go on any bike with a rear derailleur, including this Yuba Mundo.

I have now ridden two different bikes with aftermarket BionX pedal assists, both in Portland: a Surly Big Dummy and a Bullitt. In both cases the motor was the PL-350 (350 watts), which is the model recommended for climbing steep hills. The BionX controller gives you the option of choosing between four levels of assist, which range from a 75% assist to 300% assist. There is also a thumb switch that acts as throttle, giving the bike a burst of power at the highest level. This is a handy feature when you’re crossing an intersection. The BionX system only provides an assist if you’re moving at least 2 mph, however, so the initial start has to be powered by the rider. This ensures that the bike won’t jerk forward if you accidentally brush a pedal while stopped.

The BionX is a rear hub motor. You can tell it’s there because the hub of the back wheel is much larger than normal. The (proprietary) battery comes in two versions. One is an odd and obtrusive tear-drop shape, which can be mounted in a couple of different places but usually goes on the down tube. The other is a less-obvious flat pack that mounts below a special rack. Although the rack mount is unquestionably more attractive, I have heard from more than one bike shop that the rack mount can be problematic, because that much weight placed high on the back of the bike can make it very tippy. Add kids to the rear deck and the problem is intensified.

The BionX system is an unusual pedal assist system for two reasons: first, it responds to torque, and second, it has regenerative braking.

The BionX provides more or less assist depending on how hard you press on the pedals. For this reason, riding with an assist feels the same as riding without the assist, except you’ve grown massively stronger: push down hard on the pedals and you rocket forward. For people who’ve been riding on hills for a while without an assist this is an intuitive system to use because it mirrors the way they already ride.

Regenerative braking means that as you go downhill and brake, the battery recharges a little. This is a little bit of a gimmick, but not totally. For some reason, many people I talk to about electric assists to seem to think that pedaling the bike should provide all the charging they need for the assist system, as though an assisted bike were some kind of perpetual motion machine. I suppose this is technically possible, but only if you worked exactly as hard as you did on an unassisted bike, in which case, what would be the point of having an assist? Setting aside the expectation of a free lunch, however, regenerative braking has some advantages. The first advantage is that you can use the system to slow the bike while going downhill by setting the controller to a negative assist, turning it into a hub brake. On steep hills where brakes can overheat, which are all over San Francisco, this feature is outstanding. I am paranoid about brakes, so the news that BionX assists came with an independent second braking system had the same effect on me as a face mask full of nitrous oxide at the dentist. Whee! The second advantage is that regenerative braking can decrease range anxiety, because after going downhill you have a little bit more range.

  • How it works: There is a controller on the right handlebar that allows you to set an assist level; there are four levels of assist (and four levels of negative assist that act as a brake). There is also a thumb switch that acts like a throttle and gives a burst of power at the highest level of assist. The controller is also a computer that provides information on speed, distance traveled, and remaining battery life. It is a slick little machine, the iPhone of controllers. Once an assist level is set it sends power to multiply your effort. You can set an assist level and forget it, and just ride around faster than usual with no fear of hills.
  • What it feels like: They call this system BionX for a reason. When it’s on it makes you feel like you’ve suddenly developed super strength, but without the sordidness, health risks or expense of taking performance enhancing drugs. Because it responds to effort (torque), it really does feel just like riding an unassisted bike, except that the experience has become much, much easier. You still use the gears, but don’t ever slow down so much that you wobble on the hills.
  • Noise level: Completely silent.
  • Pros: This system feels more like riding a bike normally than any other assist I’ve used, and yet is powerful enough that I had no trouble hauling two kids up steep hills. In Portland, riding the BionXed Bullitt, I didn’t even need the highest level of assist to clear the local hills without difficulty on brutally hot days. On the hottest day we were in Portland (with a high of 105F), however, I did turn the assist to the highest level and it allowed us to go fast enough to catch a breeze even though I was putting in minimal effort because I feared I might pass out from the heat.
  • Cons: The BionX system currently only works on bikes with a rear derailleur and not with internally geared hubs (however BionX will be releasing a system with a 3-speed internally geared hub next year; this system will only be for purpose-built assisted bikes, however, as the torque sensor has to be built into the frame by the manufacturer). Having to get the speed up to 2mph before the assist kicks in can make starts on a heavily loaded bike very wobbly. There is no walking assist, which would be helpful. (If you make the mistake of trying to use the throttle button as a walking assist, as I once did, the bike will lurch ahead faster than you can follow it.) The BionX system is proprietary and does not allow the use of less expensive batteries from other manufacturers. This really ticks off people who like to tinker with their assists: BionX is the Apple of electric assists.
  • Battery type: LiPo. BionX offers a two year warranty.
  • Cost:  Ranges from $1200-$1800. The more expensive systems are better hill climbers and have greater range.

My conclusion

After riding all of these systems, the one that seemed best suited for our needs was the BionX (but how about a walking assist, BionX?) However, because the battery technology for all electric assists is still a little spotty, I wouldn’t get an assisted bike without the kind of gearing that would have a sporting chance of getting me up serious hills if the battery failed. Our new cargo bike has a wide range of gears.

Our needs are not everyone’s needs. I suspect a mid-drive pedal assist bike would be the best choice for an inexperienced rider facing steep hills. If I wanted to carry seriously heavy loads on a cargo bike, an EcoSpeed would be the better choice (or if it were available, a Stokemonkey). Personally, I didn’t really like being pulled along by a front hub motor, and the version I tried was underpowered for San Francisco hills. However many people like these motors better–I recently talked to one dad who wouldn’t consider any other kind of assist–and it’s possible to buy stronger assists for a front hub. Moreover there are some relatively inexpensive front hub systems available. Battery experience with these systems may vary.

No electric assist with any longevity is inexpensive, and some of them cost more than the bike itself. However I know many families in San Francisco who ride bikes but own a second car only to get the kids to school on top of a steep hill or because they can’t get a week’s worth of groceries home on a bike. Compared to car ownership, an electric assist is a bargain indeed.

11 Comments

Filed under car-free, cargo, electric assist, family biking, San Francisco

11 responses to “A series of electric assists

  1. thanks for the great rundown on electric assists since I’m thinking of adding an electric assist to my front-loading cargo bike.

    I’m a little confused on the front-hub assist. You mention that pedaling doesn’t help when the assist is engaged, and I’m trying to imagine why. My first thought was that the front (assisted) and rear (rider powered) wheels should be cumulative (250W front assist +200W rider power=450 watts).

    If it isn’t cumulative as you suggest, then pedaling makes the assist automatically scale back?

    • I think it helps to think of the skitching analogy here. Say you got an “assist” for your bike by grabbing onto a passing moped. You could pedal or not pedal and it wouldn’t add anything to your speed, because the moped does not have any way of using the power of the bicycle it is towing. A front hub without some way of using your pedal power is much the same. (I imagine that there is some way to add a pedal sensor to a front hub motor, but there wasn’t one on the eZee hub I used.)

      Now, if the front hub motor began to overheat, there is a point at which it have so little power that your pedaling would be providing momentum, just like if the moped pulling you ran out of gas, you could push it forward by pedaling. But this is not how the system is supposed to work, nor would the experience be pleasant. As long as the motive power of the front hub exceeds the power of the rider, even by a fraction, the bike is only being towed by the motor.

      • Stochastic Sam

        I’m enjoying your blog but I have to comment. I’ve been commuting in San Francisco for more than a year on a front hub throttle bike (a Trek 7.2 with the eZee motor on the front, standard 24-speed on the rear). Twisting the throttle will get me about 15 MPH on a flat such as the panhandle. At that point, if I pedal in a tall gear the bike moves faster. Even then I can still get smoked by serious riders on road bikes. Perhaps my system is relatively underpowered; I can imagine that with a high-powered motor one couldn’t pedal hard enough to add speed, but that would take the serious sort of 25-30 MPH setup that enthusiasts prefer. Happy riding.

      • Interesting. Maybe my impression was based on being on a cargo bike? They’re so heavy that I might have gotten the wrong idea.

  2. Nicole

    Thanks so much for this absolutely timely review. We were talking about it for our Yuba, but nothing seems quite ideal…we want the pedal assist, but don’t want to give up hauling capacity. So…we’ll wait and see “what’s next” and settle for a little shorter range in the meantime.

    • I think that in the next year there will either be an updated Stokemonkey or a BionX able to handle heavier loads, or both. But it’s hard to wait I’m sure. I get the feeling that Yuba is concerned about the reports of eZee motor breakdowns in SF–the conditions are admittedly extreme, but the city is also pretty close to their headquarters. As an example, I was pleasantly surprised that the new eBoda Boda uses a BionX assist.

      • Nicole

        I was getting the impression that something is in the works too–especially with the change to Bionx on the Boda and the fact that the eZee kit is currently unavailable. I don’t anticipate that we’ll be doing much for long runs in the winter (Minneapolis) anyway, so we have the luxury of being able to wait and see.

  3. Nicole–same here. I would LOVE to see the StokeMonkey come back, as it seems to combine the best of both worlds for the Yuba in providing pedal-assist but retaining cargo capacity.

    I guess it’s ok on something like the Bullitt because the front wheel takes most of the weight? That’s something I’ve been wondering about. Regardless, many thanks to Dorie for putting together these thoughtful and well-researched posts!

    • In re: the Bullitt, Splendid Cycles said the same thing that you did; the weight is distributed between the two wheels rather than all perched over the rear wheel so the BionX doesn’t carry more than half of it. They recommend an EcoSpeed if you’re hauling extremely heavy loads on a trailer, though, because that would in fact challenge the BionX motor. However our trailer-bike and even a rear child seat on top of that would evidently not be an issue if we wanted to add them. The trailer-bike is no problem at all because (a) most of the load is on its own wheel and (b) the rider isn’t just dead weight.

  4. Peter

    Do you think it feasible to use an electric bike to commute 38miles
    twice daily?

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