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Good point re: microeconomics between truck and trailer owners. The trailers could also charge off the alternator of the truck itself which could help to calm

by uoaei 3y ago

Good point re: microeconomics between truck and trailer owners. The trailers could also charge off the alternator of the truck itself which could help to calm concerns of long charging times at stationary sources. The percent gains would probably be in the single digits and would demand a bit more from the engine but maybe there's an optimal balance there.

nurple 3y ago
Interesting. At what point might it make sense for the tractor itself to evolve into a pure genset and steering unit, like a diesel-electric train? Might make sense as an interim step to carbon-free electrification.
talldatethrow 3y ago
An alternator is about 50% efficient. The engine turning the alternator is around 40% efficient. So charging a battery using your engine doesn't really pay off. If you optimize for a more efficient Regen using a proper purpose driven 'alternator', and only do it when the truck is slowing down, that would be much better. Aka, current hybrid tech.
- tablarasa 3y ago
  Good points. It would be a productive use of all of the time those trucks spend idling too, going into and out of ports and in freeway traffic. Seems like there are times and circumstances when directing excess diesel energy to the trailer battery could be reasonable.
  - talldatethrow 3y ago
    There is no such thing as excess diesel energy. If today an idling diesel engine uses n units of fuel per minute, if you try to put any power into a battery for use later, it will use more n+x fuel per minute. Now, if for some reason the engine was idling for no reason other than to keep a dome light on for an hour, then yes you could generate 100 watts as fast as possible and then turn the entire engine off, leaving the dome light lit for several hours off that 100watts you made. That is what a current hybrid does, again. But if the engine has to idle for other reasons, even laziness, making power while it idles is simply using extra fuel to make that power.
RecycledEle 3y ago
Alternators are suited to the electrical needs of the truck. Asking them for even another 1 KW is not practical. Charging a hybrid truck's lithium batter at 1 KW is nowhere near enough power to be useful. If you want to have the diesel engine charge the battery that means a total redesign if the truck, its engine, and its power train.
stetrain 3y ago
It probably isn’t worth charging the trailer from the truck. The truck would be capable of towing with an empty trailer battery anyway. Burning extra diesel to charge the battery is usually going to be less efficient than just using that diesel to go down the road. The trailer can charge next time you need to slow down or go down a hill and engage the regen braking.

by uoaei 3y ago

nurple 3y ago

Interesting. At what point might it make sense for the tractor itself to evolve into a pure genset and steering unit, like a diesel-electric train? Might make sense as an interim step to carbon-free electrification.

talldatethrow 3y ago

An alternator is about 50% efficient. The engine turning the alternator is around 40% efficient. So charging a battery using your engine doesn't really pay off. If you optimize for a more efficient Regen using a proper purpose driven 'alternator', and only do it when the truck is slowing down, that would be much better. Aka, current hybrid tech.

tablarasa 3y ago
Good points. It would be a productive use of all of the time those trucks spend idling too, going into and out of ports and in freeway traffic. Seems like there are times and circumstances when directing excess diesel energy to the trailer battery could be reasonable.
- talldatethrow 3y ago
  There is no such thing as excess diesel energy. If today an idling diesel engine uses n units of fuel per minute, if you try to put any power into a battery for use later, it will use more n+x fuel per minute. Now, if for some reason the engine was idling for no reason other than to keep a dome light on for an hour, then yes you could generate 100 watts as fast as possible and then turn the entire engine off, leaving the dome light lit for several hours off that 100watts you made. That is what a current hybrid does, again. But if the engine has to idle for other reasons, even laziness, making power while it idles is simply using extra fuel to make that power.

RecycledEle 3y ago

Alternators are suited to the electrical needs of the truck. Asking them for even another 1 KW is not practical. Charging a hybrid truck's lithium batter at 1 KW is nowhere near enough power to be useful. If you want to have the diesel engine charge the battery that means a total redesign if the truck, its engine, and its power train.

stetrain 3y ago

It probably isn’t worth charging the trailer from the truck. The truck would be capable of towing with an empty trailer battery anyway. Burning extra diesel to charge the battery is usually going to be less efficient than just using that diesel to go down the road. The trailer can charge next time you need to slow down or go down a hill and engage the regen braking.