Bicycles

Battery-free ebike relies on quick-boosting supercapacitor power

Battery-free ebike relies on quick-boosting supercapacitor power
Pi-Pop's third-generation supercap ebike is in production now
Pi-Pop's third-generation supercap ebike is in production now
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Pi-Pop's third-generation supercap ebike is in production now
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Pi-Pop's third-generation supercap ebike is in production now
Unlike a battery that drains after a certain distance, Pi-Pop's supercapacitor keeps charging and discharging throughout the ride
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Unlike a battery that drains after a certain distance, Pi-Pop's supercapacitor keeps charging and discharging throughout the ride
Pi-Pop runs wires from the supercapacitors internally through the frame
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Pi-Pop runs wires from the supercapacitors internally through the frame
In the cockpit of the gen-3 Pi-Pop ebike
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In the cockpit of the gen-3 Pi-Pop ebike
The Pi-Pop bike comes with a large, colorful computer
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The Pi-Pop bike comes with a large, colorful computer
The supercapacitor boxes don't appear much lighter or more compact than an ebike battery, but they do offer other advantages
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The supercapacitor boxes don't appear much lighter or more compact than an ebike battery, but they do offer other advantages
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The French-designed Pi-Pop ebike doesn't look like a hotbed of innovation at first glance. In fact, it looks more like a very basic urban ebike-sharing platform. Those looks are deceiving, however, as the step-through e-wheeler houses a unique electric-assist system that trades out the battery pack found on virtually every other ebike in favor of a more active supercapacitor-boosted system that collects energy on the flats and downhills, delivering it back by way of pedal-assist power during uphill slogs.

Pi-Pop has long looked for a different path to clean, sustainable urban bicycle commuting. Along with releasing three generations of battery-free supercap ebike over the past two years, it's dabbled in the design of a compact chain-free ebike system. Its gen-3 supercapacitor ebike went into production in mid 2023, incorporating evolutionary improvements over the second-generation version that include the addition of a torque sensor, suspension fork and updated component set.

Instead of using a battery pack that charges via hookup to the grid, Pi-Pop's electric bike stores and dispenses power more rapidly through the ups and downs of the ride. Its hardware siphons off energy from rider pedaling and regenerative braking, converts it into electricity and sends it to the supercapacitors stored in the long boxes that flank the rear rack. The impact on flat sections is designed to be minimal so as not to penalize the rider with noticeably difficult pedaling, and energy generation increases during downhill coasting and maxes out when the rider is actively braking.

Unlike a battery that drains after a certain distance, Pi-Pop's supercapacitor keeps charging and discharging throughout the ride
Unlike a battery that drains after a certain distance, Pi-Pop's supercapacitor keeps charging and discharging throughout the ride

The stored electricity is automatically and immediately discharged when the rider starts pedaling uphill, providing up to 250 watts of electric pedal assistance to ease the climb. The whole charge/discharge process happens automatically through the ups, downs and flats, managed via sensors.

The first potential advantage that comes to mind when eliminating the battery from an ebike design is less weight and bulk, but Pi-Pop makes no mention of weight savings and the 48-lb (21.7-kg) bike definitely doesn't win any "world's lightest" awards. The long supercapacitor boxes don't look any sleeker than a modern battery pack, either.

The supercapacitor boxes don't appear much lighter or more compact than an ebike battery, but they do offer other advantages
The supercapacitor boxes don't appear much lighter or more compact than an ebike battery, but they do offer other advantages

Instead, Pi-Pop emphasizes other advantages, saying that the supercaps don't require the sensitive materials involved in lithium battery production, relying instead on basic materials like aluminum, carbon, cellulose and polymer. It also says the supercaps last longer than batteries, providing an estimated lifecycle of 10 to 15 years. Much of the material is also readily recyclable at the end of that lifespan.

Not having a battery to charge also means the Pi-Pop bike is always ready to ride and never tethered to the grid. Hop on and let the bike charge up its own motor power and continue doing so throughout the ride. The supercapacitors will drain over time if left unused, and Pi-Pop estimates they could go from full to zero charge in about two months, so the first ride of the season might require a pre-charging lap or two if you intend to face an uphill out of the gate.

The Pi-Pop bike comes with a large, colorful computer
The Pi-Pop bike comes with a large, colorful computer

Pi-Pop does make clear that its system has a few limitations. Since the supercapacitors can only store small amounts of energy, the system will run out of juice on anything longer and/or steeper than a 10% grade over 1,640 feet (500 m) or so of distance. Around that point, the bike power will gradually reduce to nothing, leaving the rider pedaling (or walking) a heavy, non-electric bike up the remainder of the hill. The company, therefore, markets the bike at urban riders who will encounter modest hills while commuting around the city, not at buyers looking to cross the French Alps or otherwise tackle long, steep climbs.

According to a recent feature in Euronews, Pi-Pop assembles roughly 100 bikes per month at its Orléans, France headquarters. It is planning a tenfold production increase for 2024 and a greater European expansion thereafter. The third-generation Pi-Pop supercap ebike retails for €2,450 (approx. US$2,675), including VAT.

Source: Pi-Pop via Euronews

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8 comments
8 comments
Fairly Reasoner
So, just when you'd need it most ...
MCG
Would love to see an added mini-battery pack, disguised as a water bottle? Hidden in the down-tube? So as to create a hybrid. Yes, a bit more weight, but seems like the overall positive would outweigh the negative, filling in each other's weakness to create a more stabile result?
Ric
These prices…
paul314
This seems targeted for people who are already well-conditioned cyclists and can deal with losing a gear or so worth of ease on the flats. Almost the opposite of battery-powered ebikes, where one of the big attractions is that you don't have to be in great shape to ride well.
Trylon
Hills aren't the only things casual riders dread. Just as worse if not worse are headwinds. With the small amount of energy in this supercapacitor, you'd be struggling against headwinds long before you get home.
EVUK
Supercaps - especially the latest generation of (now near-taboo) energy-dense supercaps - belong in electric cars, electric race cars and e-motorbikes - not in bicycles/ebikes. We cyclists love to free-wheel downhill and along the flat too much to tolerate the energy-sapping drag exerted by all forms of energy-capture/re-use/regen technologies. Just as we don't want rub-on-the-tyre dynamo lights any more. And even if energy-dense supercaps for regen are ever fitted to consumer EVs drivers must have the option to have regen kick in only when the brakes are activated.
Paul G
lon4
I was the design engineer for the original Pi Mobility in Sausalito, California, more than ten years ago. No longer in business. We considered this approach and disregarded. Reason? "Normal human metabolism produces heat at a basal metabolic rate of around 80 watts. During a bicycle race, an elite cyclist can produce close to 400 watts of mechanical power over an hour and in short bursts over double that—1000 to 1100 watts; modern racing bicycles have greater than 95% mechanical efficiency." Wiki. If you pedal at a high cadence and you charge the Cap, you won't have sufficient stored energy, since a large portion of energy used in pedaling goes to moving the bike and rider. We did testing and found the best we could get out of regenerative braking was about 10% of all energy used on a ride. It comes down to time. You take much more time on the flat and going uphill. Downhill much less of the time.
Gordien
I like MCGs hybrid idea - I thought that right away.
I drew up a plan for a take-off assistance device years ago that used a wind-up spring built into the front wheel. It has bounced around in my mind for a long time. It's a great idea and advances the state of the art - wish I knew more about super capacitors.