Dynamo...

[JamesW]

Wondering about a dynamo on my ebike 3 reasons:
1) sort of a backup for if the battery runs out or is not fitted
2) means I don't mess with the electrics of my conversion kit while it is still in warrantee.
3) the fun of tinkering?

should make it electrically more simple I think in the Lighting dept, could even have a switch to flick between battery and dynamo powered lights.
Would also like to be able to charge my phone so I can leave the backlight on and run maps without draining the battery.

I have a front hub motor and was wondering what people know about dynamos out there on the market!

I am aware that there are front hub dynamos, but these will not suit.
Do rear hub dynamos exist or something more powerful than the really ancient style of rim rubber?

What sort of Voltage and power do people think I might be able to get out of a dynamo?

Again I am aware a dynamo on an ebike is silly in terms of total power user to generate the electrical power to drive the lights as the battery has to work harder to push the dynamo - but this only holds until the battery is exhausted!

Thanks for suggestions

James

Update - have had a little look at some bottle dynamos and found that they seem to produce 6V, wondering if I mount 1 on the left and 1 on the right of the front wheel If I can generate the 12V to drive my lights and other stuff by connecting them in series??? (Or will I kill both dynamos do you guys think?)

 

[grldtnr]

Wondering about a dynamo on my ebike 3 reasons:
1) sort of a backup for if the battery runs out or is not fitted
2) means I don't mess with the electrics of my conversion kit while it is still in warrantee.
3) the fun of tinkering?

should make it electrically more simple I think in the Lighting dept, could even have a switch to flick between battery and dynamo powered lights.
Would also like to be able to charge my phone so I can leave the backlight on and run maps without draining the battery.

I have a front hub motor and was wondering what people know about dynamos out there on the market!

I am aware that there are front hub dynamos, but these will not suit.
Do rear hub dynamos exist or something more powerful than the really ancient style of rim rubber?

What sort of Voltage and power do people think I might be able to get out of a dynamo?

Again I am aware a dynamo on an ebike is silly in terms of total power user to generate the electrical power to drive the lights as the battery has to work harder to push the dynamo - but this only holds until the battery is exhausted!

Thanks for suggestions

James

Update - have had a little look at some bottle dynamos and found that they seem to produce 6V, wondering if I mount 1 on the left and 1 on the right of the front wheel If I can generate the 12V to drive my lights and other stuff by connecting them in series??? (Or will I kill both dynamos do you guys think?)

Eons ago,I used to run a Sanyo roller dyno, which mounted under the frame behind the bottom brkt, ran over the full tread of the tyre , generated a lot of power and needed a rectifier to control the volts ,I don't think they are made anymore, they were popular with the Randonee crowd, for long distance night rides.
Dont't think twin dynos mounted L& R will work as you need the drag of the tyre wall to pull the rotor onto the tyre, could mount one on the front and back, as to it killing dynos ran in series, I should not think so, but you should be able to control the volts with elec- trickery, i.e. store the current in a battery to power whatever you connect.

 

[JamesW]

... as to it killing dynos ran in series, I should not think so, but you should be able to control the volts with elec- trickery, i.e. store the current in a battery to power whatever you connect.

Ahh but I was trying to avoid another battery on the bike and the need to work out how to setup a BMS for it!!

 

[Deleted member 4366]

It doesn't make any sense to have a dynamo on an electric bike. Why would you want to use the bike's battery to turn a motor that turns a dynamo to provide electricity for a light, when you can get electricity from the battery directly?

If you want emergency lights, get some of those little Aldi or Tesco ones. They only cost a couple of quid and weigh a few grammes. They're more than bright enough, and probably as bright as any dynamo light, if not brighter.

 

[JamesW]

and there it comes!!!

I know it doesn't make sense - but my battery has a history of not working 100% of the time. In fact I have an electrical fault once a month due to the mounting style and connection, so I am trying to mitigate against that. Also I oftem find myself cycling at the very edge of my battery range, so I would rather just wack a dynamo on and be sure that my lights will be there!!!

Ignoring the sense/no sense... any recommendations Dave?

 

[Deleted member 4366]

Like I said, Aldi lights.

 

[JamesW]

I get the feeling that you are missing my point here Dave - I don't want to have to worry about whether or not my spare "aldi" lights have working batteries or the battieries have drained. I have plenty of USB powered rechargeable lights that I can put in my bags, but often when I get around to needing this sort of thing the battery is dead from lack of use!!

James

 

[flecc]

Most bottle dynamos have considerable drag James, and two would only exacerbate that. Though I've never tried them, it seems from reports that some of the expensive high end bottle dynamos are not so bad for drag, but two for what is really a back up system will be rather expensive.

Here's another idea for back up lights if the ebike battery runs out or isn't fitted, wind up bicycle lights, one wind giving 30 minutes.
.

 

[selrahc1992]

I get the feeling that you are missing my point here Dave - I don't want to have to worry about whether or not my spare "aldi" lights have working batteries or the battieries have drained. I have plenty of USB powered rechargeable lights that I can put in my bags, but often when I get around to needing this sort of thing the battery is dead from lack of use!!

James

strictly for what its worth - I wouldn't consider a rim type dynamo, in my experience the noise and friction entirely destroy the je ne sais quoi that makes cycling such a transcendent experience - so, limiting myself to hub dynamos, I'd make an odd suggestion: an old sturmey archer four speed integrated rear gear hub/dynamo. I'm not very familiar with vintage stuff like this - but I think they're very cheap (under twenty pounds ebay), however, the output will likely be circa 1.5W, you'll have to build a wheel and there may be dropout issues.

 

[VictoryV]

Another consideration... I am certain most dynamos are alternating current (ac), usually 6 volt output. They were intended for resistive loads (lights) where the bulbs are not sensitive to ac or direct current (dc) supplies. However, most importantly, they also have to have specially matched bulbs to share the power correctly so that the front light is bright and the rear light is dimmer, get it wrong and all the power will go to one or other of the lights. Your existing dc battery fed lights will not have this design consideration. If you mix ac from the dynamo with dc from the battery you will most certainly have major problems. So not only will you need a dynamo, but rectifiers and voltage regulators, and possibly even isolating diodes... not a simple or sensible proposition considering all the prior good advice! Also, since they are ac devices running at their own independent phase relationship you cannot put two together to just add the voltages as you do with batteries, each dynamo would have to be correctly phased with each other all the time otherwise one dynamo could end up absorbing the power of the other if they were out of phase. So you would need to convert both to dc and then add them up. Finally you would have to make sure that one of them was totally insulated from "earth" and was wired with its own positive and negative wiring, otherwise you cannot "add up" their respective outputs when it was converted to dc.

 

[Aushiker]

I have three hub dynamos (in order of quality): a SON 28, Shutter Precision PD-8 and a Shimano Deore XT DH-T785. Now my primary use is touring and long distance riding so they get used to power electronics as well as lights.

Based on my experience I wouldn't buy anything less than the Shutter Precision for my use but given your comments a low cost Shimano hub dynamo might do the trick.

With my e-Bike conversion I haven't bothered with one as my front light is Bush & Mulluer e-bike light so not suitable to be powered by a dynamo. That said my tail light can be powered either way.

My emergency light is a reasonable Lezyene light but then I like to see as well as being seen.

Andrew

 

[oigoi]

I have done a lot of messing about with dynamos. They make 6v ac but you cam put the output through a bridge rectifier to make dc. Years ago I had a bottle dynamo that powered my walkman as I rode. The walkman had a pair of rechargeable batteries in it and it worked well with just the bottle dynamo and a bridge rectifier, having the rechargeable batteries there seems to keep control of the voltage. At the moment I am experimenting with two hub dyanmos in series in a wind turbine that are making 12v dc using a bridge rectifier.

 

[Deleted member 4366]

You might as well use your dynamo to charge your electric bike battery, while you're riding your bike. It's the same as using one to power the lights.

 

[tillson]

I really can not see any point in powering the lights on an electric bike with a dynamo. Particularly when, by definition, ebikes have a large electrical energy supply onboard in the form of a battery. The lighting power consumption by comparison to motor power consumption is negligible, so there is no issue regarding battery drain.

Why would you want to use a battery to create electricity to power a motor which drives a wheel against the planet, and then use another wheel to rub against the planet to turn a dynamo to create electricity?

 

[Alan Quay]

I might be wrong, but I thought that the EU had a rule that stated that lights have to be independently powered, not from the main battery?

I agree though, a dynamo makes little sense.

If I wanted to comply with that rule, I'd have some battery lights that charge from the main battery, but are good for a couple of hours independent use.

As it is, I do as D8veh suggests - power my main light from main battery, and carry some small, emergency lights with disposable batteries in 'em.

 

[RobF]

A dynamo on an ebike allows you to run a standard lighting set, which in turn makes obtaining spare bulbs easier.

 

[tillson]

I might be wrong, but I thought that the EU had a rule that stated that lights have to be independently powered, not from the main battery?

I'm not entirely sure whether this is the case and couldn't say for sure what the exact position is. When I bought my Kalkhoff back in 2008, for some reason they made a big play on the lighting claiming that it complied with certain European and German regulations. Those lights were powered by the bike's main battery with no back-up, so I suspect that it is ok to do this.

 

[RobF]

When I bought my Kalkhoff back in 2008, for some reason they made a big play on the lighting claiming that it complied with certain European and German regulations. Those lights were powered by the bike's main battery with no back-up, so I suspect that it is ok to do this.

In Germany, any bike designed to go on the road and weighing more than - I think - 12kg must be fitted with lights from the factory.

That's why all the German trekking bikes - powered or not - have lights.

The regulations conveniently allow drop bar road bikes and 'off road' mountain bikes to be sold naked.

 

[Deleted member 4366]

A dynamo on an ebike allows you to run a standard lighting set, which in turn makes obtaining spare bulbs easier.

Dinosaur alert! What's a bulb? Is it one of those things that kept blowing that they used to put in lights before they invented LEDs?

 

[Croxden]

My Grace MX came with a bottle dynamo, I thought quite antiquated but what a cracking light it had. Just like from a projector, rectangular with no light spill.

They claimed it was to comply with German law. Made hell of noise.