Well, I knew I’d leave too many loose ends explaining something before bed.
Not quite.
When you coast in a car with an internal combustion engine, you go further when you’re in neutral. Why? Engine braking. When you take your foot fully off the pedal, you restrict airflow to the engine and create a partial vacuum that the cylinders have to work against.
I’m not saying to coast in neutral for higher fuel efficiency. It’s quite the opposite with modern engines that cut off fuel injection when it’s not needed while in gear—and it can lead to increased wear and tear on the engine as well as your brakes fading on long descents. But now you have me covering my ass on every little point, ha. You could look up hypermiling and learn about more efficient driving techniques that way!
Now obviously hybrids have traditional internal combustion engines on board that behave the way we’ve just described. The engineers have also added a level of regenerative braking that is variably applied, even when the engine is not on, so that you scrub speed at a consistent pace. Without this, descending with the engine on or off would feel drastically different, and the car wouldn’t behave as expected at all times. It’s similar to how engineers for fully electric cars have added the “crawl” mode that makes a car idle forward when the brakes are off, even though there is no actual “idle” occurring. It makes the car handle the way you expect it to, and that makes you safer.
It is nice to recapture some energy that is used during the braking process. But only if you need to brake. Otherwise, you’re stealing energy you could be using right now and turning into less energy for later. The process of converting energy into various forms is inefficient, so you will always end up with less than you started, and the more conversions you do the more you lose. Potential gravitational energy to kinetic motion energy is more efficient than potential gravitational>potential chemical>kinetic motion, plus that last step is oversimplified because having the chemical energy turn a driveshaft is actually another kinetic energy conversion compared to gravity turning the wheels directly.
Thus e-bikes could benefit from regenerative braking if the system is efficient enough to overcome the loss of efficiency it introduces via weight and drag, but not from the constant low level capture of energy that would be better used now. Because you don’t get to fuel up an e-bike when the tank’s nearly empty—any toll you pay in inefficiency comes outta your legs and your lungs.
I am not an expert and I am sure I glossed over some nuances.
I’m not sure I get your point. What do you disagree with?
My point was hybrid regen is always on (unless accelerating), if it wasn’t, the car would basically coast in neutral. I’m pretty sure hybrid car designers did the math and examined use cases to discover its more beneficial to recover some energy and not coast as much vs coast as much as possible and ONLY regen when breaking. Lightly breaking applies more regen force. Or are you saying they do this for the feeling only and regen is a byproduct… if it even matters?
I’m not certain, but I’d say applying a little drag to regen on an ebike going downhill will be more beneficial than allowing the riders to go as fast as possible downhill. They could still turn it off, just like I can put a hybrid car in neutral and skip the drag, but why would I do that?
My point is exactly what I wrote! I know it’s a lot, I overcompensated.
Or are you saying they do this for the feeling only and regen is a byproduct
Yes. I said it’s designed this way to feel like a normal car. But it’s a very elegant solution! Far better to do it that way and re-capture some of the energy than let it leave the system, like heat from brake pads.
I’d say applying a little drag to regen on an ebike going downhill will be more beneficial than allowing the riders to go as fast as possible downhill
That “drag” is braking!
They could still turn it off
Like letting go of the brake lever! Far simpler than adding a new always-on brake that you have to manage separately.
but why would I do that?
Because sometimes you want to go full speed down a hill because it’s the most efficient way of moving forward! If you slow down, you have to pedal more later. If you slow down and save some of the energy, you still have to pedal more later, because you can’t save all of the energy from the hill, you can only save part of the energy.
There’s a maximum speed you feel comfortable going on steeper descents, and you manually brake to manage it. That’s the only time regen makes sense on a bike.
Also, because we’re not talking about drag that only exists on the hill. This system exists at all times in a hybrid, and if you implement it on a bike, you’ll be coasting less on flat ground too any time you stop pedaling! Why would we want that? Would you brake in a hybrid when you’re on flat ground to “save it for later”? No! Braking, and engine braking, slow you down.
Well, I knew I’d leave too many loose ends explaining something before bed.
Not quite.
When you coast in a car with an internal combustion engine, you go further when you’re in neutral. Why? Engine braking. When you take your foot fully off the pedal, you restrict airflow to the engine and create a partial vacuum that the cylinders have to work against.
I’m not saying to coast in neutral for higher fuel efficiency. It’s quite the opposite with modern engines that cut off fuel injection when it’s not needed while in gear—and it can lead to increased wear and tear on the engine as well as your brakes fading on long descents. But now you have me covering my ass on every little point, ha. You could look up hypermiling and learn about more efficient driving techniques that way!
Now obviously hybrids have traditional internal combustion engines on board that behave the way we’ve just described. The engineers have also added a level of regenerative braking that is variably applied, even when the engine is not on, so that you scrub speed at a consistent pace. Without this, descending with the engine on or off would feel drastically different, and the car wouldn’t behave as expected at all times. It’s similar to how engineers for fully electric cars have added the “crawl” mode that makes a car idle forward when the brakes are off, even though there is no actual “idle” occurring. It makes the car handle the way you expect it to, and that makes you safer.
It is nice to recapture some energy that is used during the braking process. But only if you need to brake. Otherwise, you’re stealing energy you could be using right now and turning into less energy for later. The process of converting energy into various forms is inefficient, so you will always end up with less than you started, and the more conversions you do the more you lose. Potential gravitational energy to kinetic motion energy is more efficient than potential gravitational>potential chemical>kinetic motion, plus that last step is oversimplified because having the chemical energy turn a driveshaft is actually another kinetic energy conversion compared to gravity turning the wheels directly.
Thus e-bikes could benefit from regenerative braking if the system is efficient enough to overcome the loss of efficiency it introduces via weight and drag, but not from the constant low level capture of energy that would be better used now. Because you don’t get to fuel up an e-bike when the tank’s nearly empty—any toll you pay in inefficiency comes outta your legs and your lungs.
I am not an expert and I am sure I glossed over some nuances.
I’m not sure I get your point. What do you disagree with?
My point was hybrid regen is always on (unless accelerating), if it wasn’t, the car would basically coast in neutral. I’m pretty sure hybrid car designers did the math and examined use cases to discover its more beneficial to recover some energy and not coast as much vs coast as much as possible and ONLY regen when breaking. Lightly breaking applies more regen force. Or are you saying they do this for the feeling only and regen is a byproduct… if it even matters?
I’m not certain, but I’d say applying a little drag to regen on an ebike going downhill will be more beneficial than allowing the riders to go as fast as possible downhill. They could still turn it off, just like I can put a hybrid car in neutral and skip the drag, but why would I do that?
My point is exactly what I wrote! I know it’s a lot, I overcompensated.
Yes. I said it’s designed this way to feel like a normal car. But it’s a very elegant solution! Far better to do it that way and re-capture some of the energy than let it leave the system, like heat from brake pads.
That “drag” is braking!
Like letting go of the brake lever! Far simpler than adding a new always-on brake that you have to manage separately.
Because sometimes you want to go full speed down a hill because it’s the most efficient way of moving forward! If you slow down, you have to pedal more later. If you slow down and save some of the energy, you still have to pedal more later, because you can’t save all of the energy from the hill, you can only save part of the energy.
There’s a maximum speed you feel comfortable going on steeper descents, and you manually brake to manage it. That’s the only time regen makes sense on a bike.
Also, because we’re not talking about drag that only exists on the hill. This system exists at all times in a hybrid, and if you implement it on a bike, you’ll be coasting less on flat ground too any time you stop pedaling! Why would we want that? Would you brake in a hybrid when you’re on flat ground to “save it for later”? No! Braking, and engine braking, slow you down.