On Tue, 4 Jan 2005 05:17:58 +1100, meb
<
[email protected]> wrote:
>
>[email protected] Wrote:
>> On Sun, 2 Jan 2005 15:18:18 +1100, meb
>> <[email protected]> wrote:
>>
>> [snip]
>>
>> >There are a few niches in which the regenerative braking benefits are
>> >there.
>> >Extreme stop and go urban commuting-no sense using the
>> >calipers/drums/discs all the time.
>> >Recumbents in hilly terrain-most recumbent bikes are weak in climbing
>> >yet strong on flats- imagine storing up that energy in advance of the
>> >climb.
>> >
>> >I don't think elimination of the chain is the way to go regarding the
>> >pedals (unless you're talking about mud/ice use)- much of the time
>> you
>> >need the efficient drive chain of the pedals. However, on a
>> commuter
>> >bike, eliminating the dirty chain might merrit an efficiency penalty.
>> >And on amphibious bikes, efficiency from driveline direction changes
>> >might be less of a penalty than gears/cables/paddlewheels.
>> >
>> >As for racing, imaging storing up that energy while in the pack for
>> >that extra burst at the finish.
>>
>> Dear Meb,
>>
>> Imagine an electric motor big enough to power a bicycle and
>> rider usefully, plus a set of batteries big enough to store
>> the necessary current--you have to haul it all up a big hill
>> to charge it, unless you're cheating by plugging it into an
>> outlet, in which case any motor scooter will run rings
>> around you with far less fuss.
>>
>> Imagine that the motor is about 80% efficient (a fantasy)
>> and that the charging is about 80% efficient (another
>> fantasy)--at least a third of the power is lost even in
>> fantasy.
>>
>> Imagine that you're going downhill in a race under steady
>> heavy braking that's busily charging your battery while
>> everyone else who climbed the hill a lot faster without the
>> heavy electrical equipment zooms even further out of sight
>> downhill--
>>
>> Oh, hell, let's imagine my basset hound's legs aren't four
>> inches long and enter him at the greyhound track.
>>
>> Notice that there are not even vague figures suggested for
>> either charging or engine efficiency, not even vague figures
>> for weight, and not terribly credible figures for how
>> heavily and slowly the rider would have to brake to achieve
>> any useful charging.
>>
>> How long does it take to charge an ordinary car battery with
>> a charger plugged into an outlet? And how far will a car
>> battery will push a bicycle and rider and electric engine up
>> a long climb?
>>
>> Carl Fogel
>
>Allright, lets consider the weight of some the current production
>regenerative braking systems.
>
>ZAP DX system 25 lbs with 288 W-H lead acid battery, 400W. Replace
>with 36W-H NiMH probably around 11 lbs.
>
>EPS System, 18 lbs with 72 W-H NiMH battery, 250W motor
>
>A couple of units not yet available, but nearing availability:
>Sanyo System, 18 lbs with 72 W-H 250 W motor
>Birkestrand, about 12 lbs with 72 W-H NiMH 500W motor
>
>There are a couple of Chinese systems under development that should put
>out around 300-400 W in the 10 lbs range with small NiMH battery packs.
>
>
>ZAP with its roller drive would certainly have a lower efficiency than
>the 64% round trip efficiency you propose. The others I’d expect a
>little better.
>
>Certainly viable today in many commuting environs. Would still need
>enhancements in weight and efficiency to make them practical for
>competition. You needn't go with large capacity batteries for a
>regenerative braking system.
>
>For touring, many folks have equipped their cycles with solar
>collectors for charging the batteries, so there is the additional
>practicality.
>
>I’d expect a car battery with 750-800 W-H capacity could propel a
>cyclist 30-45 miles at 15mph on the flats.
Dear Meb,
A much nicer reply than I deserved--thanks. There's no
excuse for my irritability, just an apology.
What's available is an 18-pound system.
Few riders are going to want to haul an extra 18 pounds
around. That's roughly the equivalent of a second bicycle.
Adding solar collector panels is going to add more weight
and wind drag.
The car battery estimate is intriguing, but I think that it
doesn't apply well because it speaks of the flats, while the
regenerative bicycle system relies on rolling very slowly
down hills under steady braking--it won't work in terrain
where 30-45 miles of flat riding is the norm.
Do you know of any tests of such battery-charging bicycle
systems that cut through all our attempts to calculate? That
is, something where the battery bicycle goes up and down
some real hills on a real ride and is compared to the same
rider on normal bicycle?
Carl Fogel
