RegGuheert
Well-known member
One thing that should be mentioned is the likely possibility that accelerating at full throttle in the LEAF causes the battery to degrade faster than accelerating at lower throttle settings.
RegGuheert said:I meant what I said.johnqh said:I think you meant the heat loss in battery (and the whole electric system) is proportional to the square of current flow.
Many of the losses in the electrical system are NOT proportional to the square of current flow. Some are constant. Others increase linearly with drive current. There are likely other relationships, as well.
There is the inverter which drives the motor. This uses IBGT switches which have conduction losses which are fairly linear with current. These IGBTs also have switching losses, which are dissipated in the circuits which drive the IGBTs. This switching loss is largely a fixed amount of power, but it does change with battery voltage.johnqh said:What other form of energy loss is there in the electric system?
It may be commonly "known", but it isn't a fact. Rapid acceleration has only a minor impact to range - almost imperceptible compared to speed.Sven said:It is a commonly known fact that a heavy foot on the accelerator pedal will reduce range, but It would be nice to know the physics behind the fact.
In a very simplified point of view, the same amount of energy is required to bring a vehicle to a certain speed regardless of the acceleration. With this in mind, the rule does not make sense.
Can anyone with more knowledge explain this?
Ingineer said:This is really simple to imagine, even without taking into account all the complex math, systems losses, etc.
We all know that travelling at a faster average speed uses more power. So imagine you have a 1 mile "course". If you rapidly accelerate and your average MPH over that one mile is, say, 80MPH, it's going to take way more energy than if you accelerated very gradually and averaged 40MPH over that same 1 mile distance. Simple and intuitive to "get"!
-Phil
At last - sanity and something the masses can understand. :lol:EVDRIVER said:Well, with my front mounted fan generator I actually get more power to the pack when I go faster so I guess that kinda ends this debate. Look at the big picture folks :roll:
True. Noone is arguing that if you take more time to get there your efficiency won't improve. The bottom line is it all comes down to speed and acceleration has very little impact and even is beneficial for the (admittedly unrealistic) scenario of same average speed.Yogi62 said:That graph of efficiency vs motor speed and torque is cool data! Have to think about a bit...
I don't think it is given that if you accelerate slowly you then try to average the same speed. I am asserting that if you reach the same top speed, you will average a lower speed when accelerating slowly and cover less distance at lower efficiency high speeds.
RegGuheert said:One thing that should be mentioned is the likely possibility that accelerating at full throttle in the LEAF causes the battery to degrade faster than accelerating at lower throttle settings.
harryjpowell said:Wouldn't the actual test that pertains to the OP be like this:
Make two runs over the exact same distance
Complete the exact same distance over the exact same time
In one run use full acceleration to a defined speed
In the second use a slow acceleration to a different speed
Just end the test while at speed at the distance mark.
Obviously trying to eliminate all the other know variables like different avg speeds, regen etc. Just measure the efficiency difference between rapid acceleration and slow acceleration. To me you would have to lower the top end speed on the rapid test to eliminate a delta in the avg speed..
Someone should be able to math this out to a test...
TickTock said:harryjpowell said:Wouldn't the actual test that pertains to the OP be like this:
Make two runs over the exact same distance
Complete the exact same distance over the exact same time
In one run use full acceleration to a defined speed
In the second use a slow acceleration to a different speed
Just end the test while at speed at the distance mark.
Obviously trying to eliminate all the other know variables like different avg speeds, regen etc. Just measure the efficiency difference between rapid acceleration and slow acceleration. To me you would have to lower the top end speed on the rapid test to eliminate a delta in the avg speed..
Someone should be able to math this out to a test...
Definitely could be done. If you look at the green curve in the graph in the link below, it tells you what your top speed should be at the end of a 1 mile test for different acceleration profiles to keep a constant time to traverse the mile. Would have to put the Leaf into Eco mode (constant power acceleration profile) and figure out the mph/s --> kW conversion.
Faster acceleration vs slower acceleration
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