Dynamos and hub dynamos, Battery charging

[Rod Fuller]

I can remember both of these gadgets, for bicycle lighting; the most common rubbed against the tyre.
Has anyone increased the output of these to say 36V? which could be fed to the normal battery.

 

[Deleted member 4366]

Yes. If you put a direct drive hub motor in your other wheel, it will generate enough voltage to charge your battery, while you're going along. You will need a bridge rectifier to convert the AC from the motor to DC for charging.

 

[4bound]

You get nothing for free in this world - ie you can't make a perpetual drive machine. Whatever power you take off your dynamo will have to be input from either you or your motor. If its coming from you, then why bother carrying the weight of motor, battery around, just get an unpowered bike. If its coming from your motor, then you are burning up power faster than you generate it, so don't bother. The only other source of energy I can thinj of is the conversion of potential energy into Kinetic energy - ie going downhill - but how often, and for how long do you have spare power going down hill ( ie braking at present) - not long enough to put much power back into your battery I would say.

 

[Rod Fuller]

Yes. If you put a direct drive hub motor in your other wheel, it will generate enough voltage to charge your battery, while you're going along. You will need a bridge rectifier to convert the AC from the motor to DC for charging.

 

[Rod Fuller]

Thanks for that. I wonder what the police would make of a machine with ''two motors'' I assume that you do not approve of a bicycle dynamo with step up device with a rectifier.

 

[Deleted member 4366]

Bikes with dynamos make a bit of sense. Electric bikes with dynamos are only for either people that need their heads tested or the gullible that don't understand anything about electricity.

 

[Alan Quay]

Thanks for that. I wonder what the police would make of a machine with ''two motors'' I assume that you do not approve of a bicycle dynamo with step up device with a rectifier.

As far as I'm aware the police don't bother to prosecute those breaking the first law of thermodynamics.

 

[Rod Fuller]

Yes. If you put a direct drive hub motor in your other wheel, it will generate enough voltage to charge your battery, while you're going along. You will need a bridge rectifier to convert the AC from the motor to DC for charging.

Thank you RJF

 

[Rod Fuller]

Bikes with dynamos make a bit of sense. Electric bikes with dynamos are only for either people that need their heads tested or the gullible that don't understand anything about electricity.

Always direct, and sometimes d8veh is good for a laugh. RJF

 

[Rod Fuller]

As far as I'm aware the police don't bother to prosecute those breaking the first law of thermodynamics.

 

[Rod Fuller]

Mike, what if the additional hub wasnot only a dynamo, but could be used as an additional motor? R JF

 

[Rod Fuller]

You get nothing for free in this world - ie you can't make a perpetual drive machine. Whatever power you take off your dynamo will have to be input from either you or your motor. If its coming from you, then why bother carrying the weight of motor, battery around, just get an unpowered bike. If its coming from your motor, then you are burning up power faster than you generate it, so don't bother. The only other source of energy I can thinj of is the conversion of potential energy into Kinetic energy - ie going downhill - but how often, and for how long do you have spare power going down hill ( ie braking at present) - not long enough to put much power back into your battery I would say.

OK, understood, but F! and others with regenerative systems are not wasting their time. RJF

 

[Deleted member 4366]

F1 is different because they're braking all the time. The idea is to recover some of that energy and at the same time give the brakes an easier time, then use that energy to get a boost for acceleration. If you wanted to do that on a ebike, you would use the motor. Many controllers support EABS (electronically assisted braking system) and regeneration. It still wouldn't make sense to add another device when you have one that can already perform the same function.

 

[trex]

there may be a reasonably good argument for an optimally designed energy recovery system mounted on the non-motorized wheel. You can keep the gearbox on the hub motor, control and engage the energy recovery system when you want, not necessarily during braking. These are just two of the good reasons.

 

[JohnCade]

Yes, if you cycled predominately in a hilly area it might have some merit. You are going downhill as often as uphill then and the possibility of recouping some energy must exist. Whether it would be enough to make it worthwhile even then I don’t know. It would obviously have to disengage when you were pedalling though.

 

[Rod Fuller]

Yes, if you cycled predominately in a hilly area it might have some merit. You are going downhill as often as uphill then and the possibility of recouping some energy must exist. Whether it would be enough to make it worthwhile even then I don’t know. It would obviously have to disengage when you were pedalling though.

That is why I thought that a ''dynohub'' might work as it could be switched on and off,rather than a mechanically driven dynamo. As always dv8eh's response was good, see original reply. RJF

 

[Deleted member 4366]

there may be a reasonably good argument for an optimally designed energy recovery system mounted on the non-motorized wheel. You can keep the gearbox on the hub motor, control and engage the energy recovery system when you want, not necessarily during braking. These are just two of the good reasons.

All I can say is that I'm glad you're not the engineer designing my bikes! Wouldn't it be a bit easier to use the main motor to recover energy? Why would you want the expense and complexity of a separate motor for that?

 

[trex]

you are restricted to DD motors if you want to use the same motor to recover kinetic energy. The total weight of geared motor + dynamo can be less than that of a DD motor with similar output.
the voltage generated by a dynamo varies largely with the wheel speed, the output needs to be intelligently buffered and converted to 42V to charge the battery.

 

[Rod Fuller]

All I can say is that I'm glad you're not the engineer designing my bikes! Wouldn't it be a bit easier to use the main motor to recover energy? Why would you want the expense and complexity of a separate motor for that?

Because d8veh suggested it.

 

[Deleted member 4366]

you are restricted to DD motors if you want to use the same motor to recover kinetic energy. The total weight of geared motor + dynamo can be less than that of a DD motor with similar output.
the voltage generated by a dynamo varies largely with the wheel speed, the output needs to be intelligently buffered and converted to 42V to charge the battery.

A dynamo is a DD motor, so now you have a geared hub motor and DD motor. Wouldn't it be simpler to apply your intelligent system to just the DD motor, like what Giant and Kalkhoff do?