Author Topic: Do you believe in perpetual motion? Zehus electric hub claims no recharge needed  (Read 1873 times)

Andre Jute

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My eye was caught by some details in promotion for Klaxon bikes, with a new electric hub called Zehus, selling at Velorution in London for 2195 for an otherwise barebones bike that will require another thousand pounds spent on accessories to make it a 1200 bike. (Looks like two grand is the price of being a beta-tester on a trendy brand. Thanks for offering but I'm fully occupied recalling my sins.)

This is what the hub looks like:


And this is Velorution's description, with my bolding:

Quote
We first saw the Zehus hub at Eurobike this year and were blown away by the technology. Brushless motor, batteries, electronics and sensors. Everything stays within 180 mm diameter and 120 mm width. It has a battery capacity of 160 Wh and a weight of just 3 kg. Bluetooth connectivity allows you to connect your smartphone (iOS and android supported) to your BIKE+ all in one to select your favourite power mode, manage your trip data and even lock the bike. Your smartphone acts also as a gateway through the Zehus community, allowing you to access to services such as online diagnosis, bike-oriented navigation, mobility stats and other social functions (e.g. find a stolen bike).

BIKE+ technology represents the 3rd generation of e-bikes.

With a Zehus powered bike, you have the first e-bike that does not need to be recharged! Helping when you need it and recharging the battery by coasting and back pedalling. The Klaxon chat at 2195 is our first Zehus bike and features our favourite Gates carbon belt drive system

If it is reliable, this motor could take off for short flat commutes and city utility riding; the excessive price, currently justified by the novelty of the motor and the Gates Drive on the particular bike offered, will eventually fall.

However, I doubt experienced bicyclists will take to it. My comments are from a personal perspective, neither necessarily fair to makers with a different target-customer in mind, nor all of universal application:

1. All-in-one solutions are attractive from an aesthetic, clean-design viewpoint but in service one part failing can cause trashing of the whole.

2. The battery is currently the most expensive part of an electric motor installation: the battery costs several multiples of the motor itself, the electronic and electro-mechanical controls together cost a bit more than the motor, and the motor itself is cheap compared to its casework and peripherals. The battery in an electric motor normally has a recharge-cycle life of 500-800 cycles, or in practice about three years in the hands of a conscientious maintainer.

3. Thus the mean time between rebuilds or replacement of this motor is 3 years.

4. Does look clean though.

5. Control is via an app on your iPhone. That tells you immediately who this motor is aimed at. I need my iPhone for phone service, for respiration control, for map reading. It could get very busy on a no-mechanical speed bike where the entire "gearing" is in the electric hub. It's bad enough on my simple Bafang midmotor installation controlling everything with three hardware buttons if you're wearing gloves, as I invariably do (and mine in summer are skintight leather, not cyclist's thick winter clumsies as I sometimes wear in winter). On an iPhone any motor control change could happen a block or two too late, and cyclists could become a menace precisely like mobile-phoning drivers are now as, eyes down, they scroll madly between the various pages to find the Zehus command page, and then have to press several times to get connected through the foulweather protection baggie. Maybe there will be Siri voice commands to control the motor, though how they will work in the noise of traffic is another question.

6. The battery is described as 160 Watt-hours to hide the fact that it is small. A small battery does not just limit range at any speed, it limits the torque of the motor by offering a lower rate of current-discharge than a bigger battery. (This notorious C factor of batteries, immensely important in the usability of vehicle batteries, is analogous to the force of a stream of water: the bigger the overhead tank, the more forceful the stream.) I don't see a spec for the operating voltage, but if it is 36V, which most practical motors are now, that's a 4Ah battery, very small indeed. If the motor is a limp 24V item, the battery will be 6.7Ah, which these days is middling, but the small motor will in any event be shut down by its electronics for thermal protection before you can apply much torque for even a short period. In either case, this is a motor without any pretentions to hill-climbing. It's a flatlands short-commute or utility bike motor.

7. I'd like to see the Zehus rider recharging the battery by coasting and back pedalling. 160 Watt hours? Plus inefficiencies that will consume at least 50% of his power? I wonder whether the sort of riders who will buy these bikes (with app-controlled hubs) even put out 240W, never mind have it spare for recharging the battery. Lance Armstrong, come back, all is forgiven, you can live in my bike shed and charge up my Zehus battery by backpedalling.

8. I wouldn't mind having some of the Zehus programming on my bike though. For instance, an n'lock (which locks the bicycle's steering, for those who don't know), currently seen as an affordable luxury by retired jocks with fused vertebrae who don't want to bend over the bike more than they have to, could suddenly start looking expensive if you can get an electronic bottom bracket lock on your mid motor, a feature already available on the Zehus rear motor. And the anti-theft features that the iPhone makes so accessible are very attractive too. But would I buy a Zehus just for them? No, I don't think so: that all-in-one construction is simply not practical for me.

9. Actually, the fact that the Zehus is a rear motor rules it out for me. I have really been taken by my balanced mid-motor, which lets me keep my Rohloff hub. (Yeah, I know, overkill, in effect 14x9 gears, but my excuse is that just because I have it I don't abuse it.)
« Last Edit: October 08, 2015, 03:32:44 PM by Andre Jute »