regenerative braking

Yes. It's not more efficient though.

 

Yeah, the most efficient method would be to actually accelerate slightly as you go down the hill (assuming that you decelerated going up the hill by using little gas, so that at the top you're somewhat under the speed limit).

 

i think people on here calculated it's 10% to 15% more efficient to use the regenerative function through braking, instead of just coasting. the gen III is probably a lot more efficient.

 

Coasting is generally more efficient, unless your speed gets excessive. With coasting all of the potential energy is converted into kinetic energy. With regenerative braking you lose a lot through conversion from mechanical to electrical to chemical and back.

Tom

 

Again, you'll get there more quickly by regenerative braking.

Are you trying for green bars? There's really no need for that or any value to be served. As we've stated, it's less efficient to use the brakes than it is to just let momentum go directly to work for you moving the car. My goal is to avoid the brakes or, for that matter, any regeneration at all, as the lack of regeneration icons on this from my morning commute shows:



But then I'm a little more obsessive with fuel economy than most.

 

You will charge more using regenerative braking. When coasting with no brake or throttle regeneration is at its' minimum (but non-zero).

What the above posters are trying to say, in an unclear manner, is if you regenerate power then use it later it's only -about- 50% efficient due to losses in the cycle of generation, storage, recovery, and reuse in the motor.
If you use that power (gravitational energy in this case) to push the car, then you get to use almost all the energy.

In your case, if you have to stop at the bottom of the hill, it's probably better to lightly brake all the way down.

 

Yep, the key here is that you SHOULDN'T be trying for green bars. It's most efficient to let the system decide when to charge the battery, and to brake as little as possible (in other words, brake only when necessary).

 

Ask a simple question and you get a pageant!

It's generally true that arriving at the bottom of the hill with maximum kinetic energy (faster) is better than charging the battery and getting there at a slower speed.

BUT

If the hill is long enough, and at two miles it may well be, you will probably reach an "equilibrium" speed before you get to the bottom. At that point, you are balancing the loss of potential energy with internal friction, aerodynamic braking, and battery charging. If you can brake for the upper part of the hill and then coast long enough to still reach the bottom going at the equilibrium speed, you're better off doing so. That way you will have more energy in the battery and still get to the bottom with the same kinetic energy.

Of course, if there's an unpredictable traffic light on the hill or at the bottom, it's a lot more tricky unless you can also time the light(s) using your GPS or other methods.

Richard

 

Earthman, are your asking this question as a quest for understanding, or are you satisfied with whatever gets you more MPG ?

If's it the latter, consider this: Fuel was not needed to get to the bottom of the hill and to recharge the battery along the way, so why spend it?

 

Assuming a depleted charge, yes I let the ICE recharge it as much as possible, but not through ICE-on coasting, if that's what you're asking. In fact, I avoid coasting, defined as foot off the pedals, altogether when possible. Instead, I glide when I can: feather the go-pedal just enough so that all arrows disappear on the Energy monitor. Do a good search of "pulse and glide" for more.

Best is to avoid the need to recharge. In other words, avoid using the battery. Instead, either let the ICE go to work directly moving the car or let available kinetic energy continue to move the car as much as possible with minimal impact on the battery by gliding.

I'm not sure whether you're asking 1) What's the most efficient way to decelerate? or 2) What's the most efficient way to charge the battery?

Assuming #1, here are the various methods of deceleration in descending order of efficiency:

1. No-arrows gliding
2. Pedal-free ICE-off coasting
3. Light (regenerative) braking
4. Hard (mechanical) braking
5. Hitting a large stationary object

Frankly, I'm not sure where ICE-on coasting would fall in this list, possibly somewhere between 3 & 4.

Assuming #2, I largely let the ICE charge it when the ICE is propelling the car, with whatever regeneration happens to come my way. Though I try to avoid regeneration, total avoidance is impossible and some regenerative recharging is inevitable.

 

If you're going down hill to a stop, yes, you'll capture more energy by using the brake.

If you're going down a slope while cruising, it's more efficient overall to let it coast.


It's all about using momentum. In the first situation, your momentum is energy you should capture. In the second, it's energy you should directly use to continue driving the vehicle forward. If you were to brake and slow the vehicle, you may have to expend energy to regain velocity lost.