Can I add a hub dynamo ,to my GTECH scent. I've never seen or heard anyone using a dynamo. My next question is can I use one battery and charge the other.
Hub Dynamo
- Thread starter daveinlancashire
- Start date
D
Deleted member 4366
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Not a good idea, especially the bit about charging a battery. You can only get energy out of a dynamo by putting more into it, so the net result would be a bike that's harder to pedal than a non-electric one, which makes it pointless.
Your charger charges the battery at about 2 amps, which is 80 watts. That's the same as the energy you use to pedal a non electric bike, so to charge your battery, you'd have to pedal as hard as a normal bike plus you'd need to pedal as hard again to go anywhere at the same time, so you'd need to pedal twice as hard as a normal bike to go somewhere and charge your battery at the same time, but what's worse is that there's an efficiency loss too, so you'd have to pedal even harder.
A dynamo has absolutely no place on an electric bike. The idea with an electric bike is to use electricity to help you, not to help the bike to make electricity.
There's also a weight penalty too.
Your charger charges the battery at about 2 amps, which is 80 watts. That's the same as the energy you use to pedal a non electric bike, so to charge your battery, you'd have to pedal as hard as a normal bike plus you'd need to pedal as hard again to go anywhere at the same time, so you'd need to pedal twice as hard as a normal bike to go somewhere and charge your battery at the same time, but what's worse is that there's an efficiency loss too, so you'd have to pedal even harder.
A dynamo has absolutely no place on an electric bike. The idea with an electric bike is to use electricity to help you, not to help the bike to make electricity.
There's also a weight penalty too.
I hate to disagree with d8vh, but I have a different take on it. A hub dynamo is an excellent way of powering lamps on a bike . Very much a set and forget product. With leds there is nothing to wear out and there is reliable light forever. Of course he is correct there is a power loss probably 6w of which 5w approx. goes into light. They are marginally heavier than an additional battery might be 500 gram's? . And of course they cannot be used to recharge the main battery.
I’m surprised there’s been no type of regenerative power recovery systems used . I know it’s used to good effect in formula one surely it’s only a matter of time before it’s used in some form on ebikes at least as a range extender ? All that wasted energy used on heavy braking downhill trails could be used to assist on the climbs . Or have I got entirely wrong ? I can’t see the point of a hub dynamo modern LED light systems are pretty efficient and not particularly heavy a dynamo takes rather a lot of effort for not a lot of gain ?
Regen works in the Alps (and maybe the Pyrenees...). e-bike batteries don't charge like F1 batteries, they want 2A and 42v, F1 batteries want god knows what. Speed isn't comparable. List goes on...
Regenerative braking is commonplace on bikes using a direct drive motor. Energy recapture is usually minimal though and is a secondary benefit to saving on physical brake wear.
The internal freewheel featured in geared motors prevents using them for regenerative braking.
Thanks for the explanation, I’m new to ebikes but everyone I have shown mine has expressed surprise that there is no energy recovery ! I didn’t have an explanation as to why not so simply said ‘ maybe in the future ‘ !
D
Deleted member 4366
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On our 15 mph ebikes, there isn't enough energy to make recovery worthwhile. Also, theres a significant downside to regeneration bikes: You lose the ability to freewheel when you stop pedalling. Most people don't like that. Some bikes have EABS, which recovers energy mainy from braking, but you still need a direct drive motor, that won't freewheel like a geared one.
The maths are against it.. the energy in a moving thing is 0.5mass x speed^2.
Now a bike with s person on board, is 100kg max, the speed is say 30km.hr or 10 m .s . A car will be 20 times heavier and travelling at 3 times the speed, so stopping will give 180 times more energy. The biggest energy loss on a bike is wind resistance not braking... Size matters.
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