The Supermoto / Zero S and DS Elecrtic Motorcycle

After launching its first street-legal bike last summer – the Electric Supermoto, or Zero S – California-based Zero Motorcycles has introduced the 2010 Zero DS, a road-worthy dual-sport sibling and latest stablemate to a growing line of on- and off-road machines.

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Zero Motorcycles

The S continues as a 2010 model with minor updates, and the two bikes are nearly identical except the DS comes with a few changes to suit it for light trail duty.

Both of these electric motorcycles perform similarly to a “150cc to 250cc” 4-stroke gasoline-powered bike, according to CEO Gene Banman.

To make the DS, Banman says Zero replaced the S model’s street-oriented 16-inch front and rear rims with a beefier 17-inch front and 16-inch rear, and swapped tires to on/off-road knobbies.

The rebound and compression-adjustable fork now provides 9 inches of travel, instead of 8, and different graphics set the bikes apart.

Voila, instant dual-sport!

Both the S and DS are rolling showcases of proprietary technology, including a unique lithium-ion manganese (Li-On) battery, an 18-pound (without shock) alloy perimeter frame, specially-designed brake rotor carriers that augment self-cooling, and a passive/active (airflow plus fan) cooling system for the motor dubbed “Z-Force Air Induction.”

Of these innovations, Zero’s people are undoubtedly most proud of their battery, which was designed and is hand-assembled at the company’s Scotts Valley, Calif., facility.

Unlike some other Li-On batteries, Zero’s salt-based innards are highly resistant to getting hot or potentially catching fire from thermal overload. The 58-volt at 70 amp-hour (4 kWh) battery is also low-voltage enough for someone to touch both poles with wetted fingers and not receive a harmful shock.

Because it contains none of the toxic metals some other Li-On batteries do, it is landfill approved, although Zero’s VP of Worldwide Sales, John Lloyd, strongly suggests that worn out batteries be sent back for recycling.

As with all electric vehicles, the battery represents both the enabling and limiting factor in the state of the art.

In Zero’s case, its Li-On battery is enabling because it delivers four times more power per unit weight than a conventional lead acid battery, and that’s enough to create a reasonably light and powerful bike. But it’s also limiting because gasoline yields about four times more power per unit weight than a Li-On battery, so Zero’s battery needs to be the bulkiest component on the bike.

The Zero Motorcycle Engine

The curb weight for the S is 273 pounds; the DS is 277 pounds. This is about 100 lbs more than the MX, Zero’s heaviest off-road bike. The streetbikes’ battery assembly is therefore twice the weight and output. Unlike Zero’s dirtbike batteries, it is not set up for quick swap-outs, and including ancillary electronics and on-board charger, it weighs 95 lbs – about 34% of the total weight of the S/DS.

This notwithstanding, Zero reps say they have created the best electric bike battery on the planet. They predict significant and continual improvements in its storage capacity-to-weight ratio.

Lloyd says all Zero’s batteries are good for 1,000 full re-charge cycles, and as is typical for Li-On technology, Zero’s battery can be stored on its smart charger for months.

If an owner subjects it to irregular charging, it doesn’t develop a “memory,” and recharging as-needed is actually recommended, says Lloyd, adding that small recharging top-offs do not count toward the total.

Depending on how drained it is, the battery can be replenished in four hours or less by plugging into a 110 or 220 volt outlet. In all, based on conditions the bike is subjected to, the battery is estimated to last from four to six years.

The expense of replacing a battery – which Zero considers “worn out” when its capacity drops to 80% – would likely be the highest cost of long-term ownership. Because they are so new, and would be under warranty for two years, the batteries have no price set as of yet. In a couple of years Banman says a replacement battery could sell for $3,500 or so, but this might not be as bad as it sounds because Zero predicts they should have more capacity by then – possibly as much as 30% more.

Because of a commitment to advancing its technology, all Zeros are modular, and will accommodate improved batteries as they become available. It is possible therefore that a replaced battery could make a Zero perform better than when it was new by increasing speed, range or both.

And unlike a gas-powered bike, motor work might be relatively paltry. Zero’s motor is estimated to last five to 10 years, but thus far none have worn out through normal use because the company only began producing bikes about three years ago. Banman says hypothetical rebuilds would not require the motor’s removal. Instead it would be a 25-minute job involving removal of an end cover to replace the brushes. He estimated the cost for such an overhaul based on a $75/hour shop rate plus parts at about $150-250.

Speaking of motors, Zero’s battery provides motivation for the S and DS via a single brushed-type permanent rare-earth magnet motor.

Lloyd says he has seen this motor dyno’d at about 30 hp and 65 ft-lbs of torque, but its power delivery is completely different than that of an internal combustion engine.

Zero’s 95-lb battery assembly sits low in the frame. Note the recharging cable which accepts the same semi-triangular 3-prong connection that many home computer power cables have.
The Z-Force Air Induction System allows passive airflow to cool off the hot-running motor, and it supplements cooling airflow as needed with a fan. This was deemed necessary for the street Zeros to increase the higher output motor’s power and longevity.
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