Regenerative braking
- Thread starter Jonah
- Start date
Something I wrote on another thread:
I think that any talk of regenerative braking is just a waste of breath. Bicycle riders hate to use the brakes, because any energy you burn off with the brakes must be replaced with the legs. Check how many seconds of braking you do in a half-hour ride. Not many. Normal (non-regen) bike motors have a free-wheel between motor and wheel, so when you get off the gas going downhill, the motor (almost) stops and the wheel keeps spinning. The only drag in the system is the drag in the freewheel - not much different to the drag in a pushbike's derailleur when you stop pedalling. But in a regen system, wheel and motor are locked together, so any time you are going downhill and get off the gas, the magnetic drag on the motor will slow the bike. You can check the effect of magnetic drag by turning your drive wheel backwards. Kinetic energy is lost and it will have to be replaced before you tackle the next uphill section. Admittedly, the regen system will try to store energy it collects in the battery, but you pay a conversion fee. When you take kinetic energy, convert it into electrical energy, then convert it again into chemical energy stored in the battery, then reverse the process so you have kinetic energy available for the hill, you pay a conversion fee of about 30%. Much better to preserve the kinetic energy and avoid the fee.
Things are different in the car world. A car weighs much more than a bike and rider. Around town, a car spends a much bigger percentage of its time on the brakes, so it's worth collecting and storing energy that would otherwise be burned off by the brakepads. But when a car is cruising city to city, it spends a very small percentage of time on the brakes and regenerative systems take more than they give.
I think that any talk of regenerative braking is just a waste of breath. Bicycle riders hate to use the brakes, because any energy you burn off with the brakes must be replaced with the legs. Check how many seconds of braking you do in a half-hour ride. Not many. Normal (non-regen) bike motors have a free-wheel between motor and wheel, so when you get off the gas going downhill, the motor (almost) stops and the wheel keeps spinning. The only drag in the system is the drag in the freewheel - not much different to the drag in a pushbike's derailleur when you stop pedalling. But in a regen system, wheel and motor are locked together, so any time you are going downhill and get off the gas, the magnetic drag on the motor will slow the bike. You can check the effect of magnetic drag by turning your drive wheel backwards. Kinetic energy is lost and it will have to be replaced before you tackle the next uphill section. Admittedly, the regen system will try to store energy it collects in the battery, but you pay a conversion fee. When you take kinetic energy, convert it into electrical energy, then convert it again into chemical energy stored in the battery, then reverse the process so you have kinetic energy available for the hill, you pay a conversion fee of about 30%. Much better to preserve the kinetic energy and avoid the fee.
Things are different in the car world. A car weighs much more than a bike and rider. Around town, a car spends a much bigger percentage of its time on the brakes, so it's worth collecting and storing energy that would otherwise be burned off by the brakepads. But when a car is cruising city to city, it spends a very small percentage of time on the brakes and regenerative systems take more than they give.
J.R.
Well-Known Member
- Region
- USA
- City
- Piedmont Highlands
Well stated, Herb.
I've read accounts that stated it would take about 200 miles on the best systems, as long as there was no further use of the battery. I have no first hand experience to back that up.For entertainment purposes someone should put their bike on a treadmill and set it to regen and report how long it took to charge battery full
stevenast
Well-Known Member
For entertainment purposes someone should put their bike on a treadmill and set it to regen and report how long it took to charge battery full
So if you have regen, in case your charger breaks, have a treadmill standing by?
pxpaulx
Well-Known Member
For entertainment purposes someone should put their bike on a treadmill and set it to regen and report how long it took to charge battery full
As long as you put a watt hour meter between the treadmill and the wall socket! Guessing it would be slightly less efficient than say charging the battery directly
Trevor Tucker
New Member
Just read the review for the Easy Motion Nitro Cross. (500 watt geared hub motor)
In the summary it says, this bike has motor inhibiting brake levers. So does this imply regen brakes are charging the motor?
In the pros section it says the Tekro Dorado levers have motor cut off switches built in.
To encourage me to buy this bike l have told this bike has regen brakes. True or false?
In the summary it says, this bike has motor inhibiting brake levers. So does this imply regen brakes are charging the motor?
In the pros section it says the Tekro Dorado levers have motor cut off switches built in.
To encourage me to buy this bike l have told this bike has regen brakes. True or false?
Ravi Kempaiah
Well-Known Member
- Region
- Canada
- City
- Halifax
Wrong. Easy Motion bikes don't have regen.
Motor inhibition means simply that, cut off and it doesn't convert the motor into a generator.
Last edited:
Trevor Tucker
New Member
Thanks Ravi, l will inform the salesman he should get his facts straight before talking rubbish
Jonah
Member
I spoke to the Easy Motion rep and asked about this. The manual is written to cover all possible e-bikes, including those with gearless motors - hence, the regenerative braking icon on the control pad and the inclusion in the manual. I think they should invest more effort in the manuals - one manual for the Evo line, for example?
Ravi Kempaiah
Well-Known Member
- Region
- Canada
- City
- Halifax
The gearless motor was phased out back in 2012
They switched to Bafang BPM and finally to Dapu.
Trevor Tucker
New Member
Thanks for the info, you guys have helped me a lot.
You guys with any kind of manual should stop whinging. When I unpacked my neo volt sport, there was some safety advice, but no manual and nothing on how to operate the machine. It took me two days to unfold the bike and another two days to activate the electric systems. This forum and some kind words from Crazy Larry was the only advice I got. If I hadn't found the forum, my $2,800 bike would still be a wall decoration.
NYC Rider
Member
However, I spoke to a local e-bike expert and he pointed out that if I roll my geared hub motor backwards, and then pull the brake enough to activate the motor cutoff switch, I would feel resistance to rolling backward. I thought he was mis-informed, but I tried it anyway and its true! Next time I'm at the top of a mountain in the Rockies with a dead battery, I can just roll backwards to base for a few hours holding the brake. I don't miss regen capability, though I am on the brake a lot as I like to/need to stop at many intersections.
Ravi Kempaiah
Well-Known Member
- Region
- Canada
- City
- Halifax
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