4 ms·

Brakes in trucks are already using regenerative braking for about 20 years right now and its called retarder. Because conventional braking is too expansive.

exDM69 9y ago
I took an interest in this and looked up "retarder" on Wikipedia and it mentions engine braking (and exhaust braking), hydraulic retarders and electric retarders which are eddy current brakes more commonly used in the railways. Which one are you referring to? According to the article, most commonly these are not used for regenerative braking, the energy is wasted as heat instead. Eddy current brakes can be used for regenerative braking if there's an electric drive train (and high power electronics to handle it) but more typically the energy is just wasted as heat in a cooled resistor grid. Mechanical/hydraulic braking can be used to spool up a flywheel and this was used in Formula 1 in late 2000's (now they use electrical regenerative braking instead). Which of these techniques is commonly used in trucks? https://en.wikipedia.org/wiki/Retarder_(mechanical_engineering) https://en.wikipedia.org/wiki/Retarder_(mechanical_engineeri...
- PinguTS 9y ago
  Sorry, for not checking Wikipedia. Because I work in the industry as an electrical engineer defining standards, and owning a historic truck myself just for fun, because I can. Originally, it is right that retarders were introduced to just having a non-destructive brake by just wasting the energy. That was around the 1980s. This was just to save maintenance cost as brakes were a big part of that costs. The trucking industry is about costs and every little penny you can safe. So, years ago it started: Why do we waste that energy and do not re-charge the battery with that, because that reduces load from the generator and that will reduces fuel consumption? Retarders have a huge impact in costs when your are counting miles. Retarders are having the disadvantage you can't brake to full stop with them. That's why they never worked in cars, because they are always additional to conventional brakes. So they add complexity and weight, both of which you want to reduce in cars.
  - foobarbecue 9y ago
    My 2013 Mitsubishi Outlander Sport has regenerative braking. Seems to work ok but I'm not sure how much it actually helps.
  - Cshelton 9y ago
    Do note though that engine braking is banned in many population areas because it is so damn loud!
  - neltnerb 9y ago
    What fraction of the energy recovered by braking is actually stored? I would have thought the battery on a non-electric or non-hybrid truck would be far too small. Surely the battery gets topped off and then the extra power is dumped as heat right? Is the energy from braking really so small that it can't even fully charge the starter battery? Honest questions. I figured that since regenerative braking in cars seems to double fuel efficiency, that order of half the power used to accelerate was recovered and I would have thought that was a very large amount of power to store. Or is it because of the nature of long-haul trips? I know hybrids have much less advantage on the highway, maybe for long-haul trips the ratio of energy lost as air friction to energy lost in braking is vastly different.
    - arghwhat 9y ago
      There will always be situations where you can no longer recover energy, fully electric or hybrid. Your battery could be full, or overheating. At that point, you have to waste the energy. I believe the normal way to handle this scenario is to just fall back to mechanical braking.
      - averagewall 9y ago
        Why do most/all electric and hybrid cars have regenerative braking while ICE cars don't? It's because, as the GP said, the battery would be quickly topped up and extra energy wasted. Only electric vehicles doing frequent stops/downhills can make productive use of regenerative braking. Potential energy lost by a truck going 10 m (vertically) downhill: 40 000 kg * g * 10 m = 4e6 J. Capacity of car starter battery: 40 Ah * 12V = 400 Wh = 1e6 J. Let's guess a truck battery has 4 times the capacity of a car battery, so 4e6 J to full charge. That's just down one small hill and all subsequent braking energy for the entire trip is wasted.

exDM69 9y ago

I took an interest in this and looked up "retarder" on Wikipedia and it mentions engine braking (and exhaust braking), hydraulic retarders and electric retarders which are eddy current brakes more commonly used in the railways. Which one are you referring to? According to the article, most commonly these are not used for regenerative braking, the energy is wasted as heat instead. Eddy current brakes can be used for regenerative braking if there's an electric drive train (and high power electronics to handle it) but more typically the energy is just wasted as heat in a cooled resistor grid. Mechanical/hydraulic braking can be used to spool up a flywheel and this was used in Formula 1 in late 2000's (now they use electrical regenerative braking instead). Which of these techniques is commonly used in trucks? https://en.wikipedia.org/wiki/Retarder_(mechanical_engineering) https://en.wikipedia.org/wiki/Retarder_(mechanical_engineeri...

PinguTS 9y ago
Sorry, for not checking Wikipedia. Because I work in the industry as an electrical engineer defining standards, and owning a historic truck myself just for fun, because I can. Originally, it is right that retarders were introduced to just having a non-destructive brake by just wasting the energy. That was around the 1980s. This was just to save maintenance cost as brakes were a big part of that costs. The trucking industry is about costs and every little penny you can safe. So, years ago it started: Why do we waste that energy and do not re-charge the battery with that, because that reduces load from the generator and that will reduces fuel consumption? Retarders have a huge impact in costs when your are counting miles. Retarders are having the disadvantage you can't brake to full stop with them. That's why they never worked in cars, because they are always additional to conventional brakes. So they add complexity and weight, both of which you want to reduce in cars.
- foobarbecue 9y ago
  My 2013 Mitsubishi Outlander Sport has regenerative braking. Seems to work ok but I'm not sure how much it actually helps.
- Cshelton 9y ago
  Do note though that engine braking is banned in many population areas because it is so damn loud!
- neltnerb 9y ago
  What fraction of the energy recovered by braking is actually stored? I would have thought the battery on a non-electric or non-hybrid truck would be far too small. Surely the battery gets topped off and then the extra power is dumped as heat right? Is the energy from braking really so small that it can't even fully charge the starter battery? Honest questions. I figured that since regenerative braking in cars seems to double fuel efficiency, that order of half the power used to accelerate was recovered and I would have thought that was a very large amount of power to store. Or is it because of the nature of long-haul trips? I know hybrids have much less advantage on the highway, maybe for long-haul trips the ratio of energy lost as air friction to energy lost in braking is vastly different.
  - arghwhat 9y ago
    There will always be situations where you can no longer recover energy, fully electric or hybrid. Your battery could be full, or overheating. At that point, you have to waste the energy. I believe the normal way to handle this scenario is to just fall back to mechanical braking.
    - averagewall 9y ago
      Why do most/all electric and hybrid cars have regenerative braking while ICE cars don't? It's because, as the GP said, the battery would be quickly topped up and extra energy wasted. Only electric vehicles doing frequent stops/downhills can make productive use of regenerative braking. Potential energy lost by a truck going 10 m (vertically) downhill: 40 000 kg * g * 10 m = 4e6 J. Capacity of car starter battery: 40 Ah * 12V = 400 Wh = 1e6 J. Let's guess a truck battery has 4 times the capacity of a car battery, so 4e6 J to full charge. That's just down one small hill and all subsequent braking energy for the entire trip is wasted.