Re: SRAM Sparc power assist
I have the more economical 400 W Currie electric systems myself, but glanced at SPARC a couple of years ago. I no longer see any US dealers advertising SPARC. Since you expressed range in km, I suspect you are in Europe and 25km is the new EU model top speed (EU regs effective May 9 established an EU wide limit in qualifying as a non-motorized vehicle). Old EU units (which are still current US units) had a 16-18 mph top speed (US Fed threshold is 20 mph, a few states have 25 mph thresholds and one state has a 30 mph threshold, Japan which has the largest electric bike market has a 20 km/hr threshold). SPARC was already below the new EU 250W limit (prior to May 9, there were higher and lower thresholds throughout the EU member countries).
In 2001 SPARC was one of the lightest systems (10 lb) on the market since it had a small 12Volt 7 Amp-Hour lead acid battery. It is intended for occasional propulsion for hill and starts. It’s a Pedelec so pedal operation from sensors is used to enable motor operation. (European and Japanese requirements to meet the electric bike legal exception qualifying as a non-motorized bike). It was one of the higher priced units in the US market at that time.
The reviews reported high torque outputs for hill climbs.
Dahon uses the SPARC system on their Roo El electric folder with a lightweight NiMH battery. Dahon mentions a microprocessor controller, so SPARC may have a brushless DC instead of brushed DC. As SRAM doesn’t mention a microprocessor, it is not apparent whether they used standard SPARC components, a special top end model which might not be available to non Dahon customers, or if Dahon second sourced an upgrade like they did on the battery. The unit is an SRAM Torpedo 5 internal gear hub with two 100 W motors added.
The 2 speeds with 2 motors use a control approach similar to the two brush motor Zap DX approach, high speed powering the motors in parallel, low speed powering the motors in series. Since SRAM put the motors are on the input side of the internal gear hub, there ought be more than just 2 speeds, in fact ought to be multiples of 5 since it’s a 5 speed drive.
If your looking for an internal gear hub, SPARC is probably a good way to go.
If your not looking for an internal gear hub on your pedal operation, you might want consider systems which use have a front wheel hub motor such a Heinzman (Heinzman has had some NiMH/NiCd systems as well as lead acid) or look at the new 5 lb Sanyo 250W kit with NiMH battery and regenerative braking (just coming to market). Heinzman uses brushless DC 24V motors. Sanyo has magnets in the motors and a throttle version as well as a Pedelec version so it probably is a brushless DC motor. Their US Technology transfer partner uses a 24V 500W AC motor. As compact as Sanyo’s battery pack is, I’d speculate its 24V rather than the new 36V trend.
Here are some reviews sites:
www.electric-bikes.com/others.htm#Betterbikeswww.electric-bikes.com
Electrics are a fun toy, and great for short radius transportation.
Great on hot days over 90F since you can get cooling air circulating with little effort. Also great for headwinds since you have the extra torque with no more wind resistance.
Helpful at starts, but when you are up to speed little assistance is given, though not a lot is needed. Most lead acid systems add around 25 lb to the bike. Therefore, more pedalling effort is needed for use at higher speeds-above that at which the electrics operate. The motor helps on slight upgrades, but for steep upgrades the weight reduces any advantage.
