Lets make it easy. look at that guy in Soundwave's video. He's pedalling hard. He's making about 130 watts output for about 200 watts of pedalling. it would take about 4 to 5 hours pedalling like that to charge up a 500Wh ebike battery.

 

That's without going anywhere. If you want your bike to move as well, you'd have to pedal with an extra 100w, which puts you up in the class of competition riders if you wanted to charge your battery in 5 hours.

 

The whole idea of an electric bike is to use stored electricity to help you to ride the bike so that you don't have to pedal so as hard as a non-electric one. What you're proposing is the other way round, i.e. to pedal harder than a normal bike to charge a battery. That doesn't make sense at all, unless, like in the video, you just pedal for exercise/training, and you don't want to go out on the dangerous roads.

... A fair question deserves a fair answer . The SAdynahub, and it's more recent successors are brilliant devices. They have very low mechanical friction... Certainly compared with the bottle dynamo. They were able to produce about 6 watts of electrical power when cycled at a very high speed. They produced at a voltage 6v at 0.18amp to drive the two special bulbs, at normal speeds This is a load of about 2watts. . All this energy came from the rotation of the wheel. If you were to spin the wheel by hand say 1 push, and did not have the bulb connected, the wheel would spin and after a length. of time slow down and stop. If you pushed the wheel with exactly the same push, with the bulb connected, it would take less time for the wheel to stop. The reason the wheel slows is due to friction between the bearings and cones, the air resistance of the spokes . When the bulb is connected there is also a slight extra load due to the magnetic field created when current flows in the bulb reacting against the magnets in the dynamo..

As a youngster, you were energetic and could put maybe 150watts if power into the bike .. maybe 200 watts when you were sprinting. The extra loss of a couple of watts when the lamp was on was not really measurable.Most of the energy lost was to air resistance ,wind.

An electric bike consumes around 200watts. The amount being consumed at any instant depends on the load.. higher consumption when going faster or uphill less on downhill. The EU law allows 250watts. Even if one were to take the energy from a dynahub, increase its voltage from 6 to 38 V, and feed it into the battery, it would only be giving about 2 watts of power or 1% of the consumption. There would only be a value in doing so when one would otherwise be braking e.g going down hill. If one were to use this energy to charge the battery while on the level, you would either need to pedel faster or use battery power.

You might consider using a much more powerful dynamo, but that merely makes the numbers bigger. Don't change the principle

Most people have no idea about how large or small a watt is. We talk about a 2kilowatt kettle or heater and 100 watt bulbs. If you lift a 1kg bag of sugar, from the floor to the table, and take 10 seconds to do so, you have worked at a rate of 1 watt. Assuming table is 1metre, and standard bag of sugar.

My new ebike came with a hub dynamo for the lighting. I think that this is a good idea .. if the battery packed up, i would still be legal after dark.

a great answer Dan, i should have listened to my Physics teacher more closely,

probably this bit here is key looking back on it "As a youngster, you were energetic and could put maybe 150watts if power into the bike .. maybe 200 watts when you were sprinting. The extra loss of a couple of watts when the lamp was on was not really measurable."

yeah, know what you mean SW, but i`m not after perpetual motion, only the possibility of adding a little time, say 15mins to the battery life over 100 miles or so

 

I like your bike tommie

.. if you were using a 12v and 2a your power would be 24w. and it would take about 25 hrs . Nice video

 

This video is pointing out to the "Young And The Restless"

Nobody,s mentioned solar power? Obviously not to enough to fully power an ebike? But suppose many have seen the YouTube clip about the lady doing long tour towing a solar panel the size of a decorators pasting table.

Nobody,s mentioned solar power? Obviously not to enough to fully power an ebike? But suppose many have seen the YouTube clip about the lady doing long tour towing a solar panel the size of a decorators pasting table.

 

Yes, there's been many attempts and a few actually used. Best in Australia of course, with California a good alternative. Not so good in an average UK year.

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in theory, the sun gives us plenty more than needed to ride our bikes. The sun at altitude above the clouds, gives us about 1kw per square meter. On the ground, some is absorbed by the atmosphere but there is still plenty left from that 1kw/sqm. At the current rate of development, it won't be very long before solar cells can be made into fairings for your bike. When I got interested in solar energy, solar panel cost over $2/W. It's now less than 40c/W. £40 for a panel capable of recharging your bike while you are at work!

Do you want me to do a kickstarter project?

in theory, the sun gives us plenty more than needed to ride our bikes. The sun at altitude above the clouds, gives us about 1kw per square meter. On the ground, some is absorbed by the atmosphere but there is still plenty left from that 1kw/sqm. At the current rate of development, it won't be very long before solar cells can be made into fairings for your bike. When I got interested in solar energy, solar panel cost over $2/W. It's now less than 40c/W. £40 for a panel capable of recharging your bike while you are at work!

Do you want me to do a kickstarter project?

.. that would be nice as Mrs Brown says. To put numbers on it. The intensity is as you say about 1 KW per metres squared at top of atmosphere, and close to 800watt, peak value mid summer noon at our latitude. The efficiency of any commercial panel is touching 20% at present. So assume 160 watts at best. With inefficienices in power supply voltage regulator say 100w for the 4 hours bracketing noon. So it is feasible. The problem is if one is travelling , one has a big 1m2 panel catching the wind.

There are flexible film solar panels and these could be rolled up when traveling and extended during the off time. However these would not be as efficient I understand that 14% would be very good for that type.

The problem is if one is travelling , one has a big 1m2 panel catching the wind.

Most people only need about 100WH-200WH a day to use the bike for commuting.

I was thinking of molding the flexible panels into mudguards, chainguard, baskets, rack boxes, triangle bags etc. and connect then together in the controller box.

Ideally, the cost of adding solar charging should be less than £100 all in. Depending on the situation, you could offset some of the cost of solar panels by having a lower capacity (thus cheaper) battery.

But all those figures depend on sunshine, and some years that's a rare commodity in the UK, especially in some regions. All too often we wake up to dull overcast skies, day after day seemingly for weeks.

 

Also a major use for e-bikes is commuting, done at the beginning and end of the day. So far from ideal for gathering sunlight, low sun angles blocked by buildings, other vehicles and foliage etc.

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Edited April 3, 20179 yr by flecc

I see solar charging as more of a convenience than trying to go green.

The main drawback is the additional weight rather than cost.

Charging does not have to be limited to only while you ride. Your bike still has the battery, good for a couple of days commuting before recharging. Progress in solar cell will continue boost conversion yield and reduce weight for years to come. When I got interested in solar cells, you could only get about 100W/sqm at peak irradiance, now we get up to 20%-22% yield and in some situation, you can use mirror to concentrate the light onto a chip, with even better yield.

Most people only need about 100WH-200WH a day to use the bike for commuting.

I was thinking of molding the flexible panels into mudguards, chainguard, baskets, rack boxes, triangle bags etc. and connect then together in the controller box.

Ideally, the cost of adding solar charging should be less than £100 all in. Depending on the situation, you could offset some of the cost of solar panels by having a lower capacity (thus cheaper) battery.

... I don't think that the exposed area would be even in the ballpark. PV panels have a particular problem that segments in shade rob energy from the exposed areas. Moreover bikes are usually vertical and say the chain guard, or pannier , the only items with appreciable surface area be at the wrong angle. Might work on a long distance trekking bike if it includes a trailer.

I was thinking mainly about triangle bag and rack box, it may be possible to pull out 'solar sails' from them and hook the sails to the handlebars.

 

Something like this:

 

 

or like this:

 

I was thinking mainly about triangle bag and rack box, it may be possible to pull out 'solar sails' from them and hook the sails to the handlebars.

 

Something like this:

 

 

or like this:

 

.... These solutions would need a much more benign wind climate than I am used to!

Obviously direct sun light is best but maybe some benefit when cloudy? Have often wondered why electric cars, vans or even caravans don't have large solar panels attached their roles

Attached to there roofs......

Nice ICE trike Whoosh, used to have one in red myself at one time, from D Tek,s

Attached to there roofs......

 

their