Question about efficiency

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Jetronic

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I'm really in the dark on this but I think some members know. What is the energy efficiency of charging an EV? for every kW coming out of the wall, how many watts can you get out of the battery?

And, what is the efficiency for the energy recuperation (recharging the battery while coasting)? Just wondering if someone was not paying attention to road conditions if there's a range penalty.
 
Jetronic said:
I'm really in the dark on this but I think some members know. What is the energy efficiency of charging an EV? for every kW coming out of the wall, how many watts can you get out of the battery?

And, what is the efficiency for the energy recuperation (recharging the battery while coasting)? Just wondering if someone was not paying attention to road conditions if there's a range penalty.
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Charging efficiency varies greatly depending on whether its AC or DC, and battery state.

Bjorn Nyland does charge efficiency testing but Id have to go dig it out.
 
They aren’t all the same, the onboard chargers are different, and the electric motors are different. The regen is also different because the motors are all different. On the Weber auto tear down videos he makes remarks at the improved Toyota electric motors they have been honing for twenty years. Stators, magnets, rotors, all kinds of things can be tweaked by engineering.
With ev’s they have a charge rate and time, and you know how much was used so the difference is the efficiency loss. Efficiency during driving is extremely dependent on the driver, just like a gas car. Just like a gas car, they are not all the same. There is a huge ev range penalty by being aggressive etc, or bad conditions. I think with ev the delicacy of driver input is even more telling than with gas in the range. Just my opinion from use of a plug in which was used almost entirely on electric. It got so I changed routes just to avoid an extra stop sign or a hill, not to burn battery.
In other words I spent most of my time thinking about the car and not other things. It was sort of ridiculous actually. I bought another one anyway 😀.
 
I was hoping someone would have figures for some particular car, or ballpark figures anyway.

I'm thinking coasting is better than recuperation is better than braking. It makes sense from a conservation of energy point.
 
Not sure if pulse and glide is as beneficial on EV as it is for ICE--the ICE is more efficient at high loading. EV likely has sweet spots too, conversion of electricity into mechanical energy is likely not a fixed number but varies with power level, but it's probably much flatter than ICE. I suspect energy spent moving the car, for an EV, is probably nearly the same, between constant speed and a P&G that has the same average speed--might be worse, actually, due to air drag being worse at higher speeds, air drag going up proportional to the square of speed.

But not having convert energy types, sure, less loss. If one could coast to a stop rather than brake, I would think that would hold the edge.
 
Yes, I would say. Works well in conventional cars that lack regenerative braking, cannot see why it would fail here. Same premise really, not converting energy into waste heat.
 
Jetronic said:
I was hoping someone would have figures for some particular car, or ballpark figures anyway.

I'm thinking coasting is better than recuperation is better than braking. It makes sense from a conservation of energy point.
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The epa mpge figure is there to look at, it shows differences of quite a lot. Coasting regenerates slower is all, over a longer time. Most of ev braking is regen. Even on an older Prius in my family, at 106k the brakes are still not down far enough to replace. On my Volt at 41k the brake pads looked new. I don’t think they would ever need replacing.
 
The literature suggests that lithium battery efficiency itself is very high, in the neighborhood of 99% of the energy input is returned for use. For comparison, lead acid is only about 90%. Other systems like the charging and inverter have higher losses.

The motor efficiency varies depending on design, loading, speed, etc. The link below gives a breakdown of typical EV losses and the gains from regen braking.

https://www.fueleconomy.gov/feg/atv-ev.shtml#:~:text=EVs are 60% to 73,77% to 100% efficient.
 
Direct and accurate answer:

EV's convert 59% to 61% of grid power to wheel power.

Claims of higher efficiency include regenerative braking. Something that hybrids can also do. You'll note the narrow range of a couple percent. That's because charger efficiency, battery charge efficiency, battery discharge efficiency, controller efficiency and motor efficiency, and transmission/drivetrain losses don't vary much.

The numbers can be worse in extreme cold weather (battery must be heated) and cabin heat must be operated more. However, most EV owners park in a garage that is not -10F. The fact that EV's lose 40% range in extreme cold weather is only very slightly due to lower efficiency. The battery also has lower performance when very cold. (note the difference, performance vs. efficiency)

Tesla's can "precondition" the battery in extreme cold (heat it) and that too uses substantial energy from the grid.

Despite some wild internet claims of 40%, 50% or even 60% winter range loss, a real world range loss of 30% around freezing is normal. The energy use may not change all that much and you could drive without heat, but battery capacity is reduced when cold.
 
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Gyro Gearloose said:
The literature suggests that lithium battery efficiency itself is very high, in the neighborhood of 99% of the energy input is returned for use. For comparison, lead acid is only about 90%. Other systems like the charging and inverter have higher losses.
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This is true in theory. Nearly 100% of what you can get into a Lithium battery, you can get out! HOWEVER, battery packs do produce heat, especially under hard use, and there are heat losses in the battery conductors. Also preconditioning a battery, such as in cold weather is wasted power. Your meter will spin faster.
 
Jetronic said:
I'm thinking coasting is better than recuperation is better than braking. It makes sense from a conservation of energy point.
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That depends on speed. Aerodynamic loads can still slow a fast and sleek vehicle rather rapidly. Regenerative braking is efficient enough to recapture the distances lost to aerodynamics, if used to slow a driver like me.....
 
To add to Cujet's point, heat = loss. [Or more precisely, heat = energy.] If you have to cool something then there is loss, a flow of energy that has to get out (or leak out). The energy to make the heat came from somewhere.

Ergo, if you have to cool a battery... it must not be doing something quite perfect. Even if it's just copper loss, if the copper is inside the battery it's still "loss" inside the battery.
 
Cujet said:
That depends on speed. Aerodynamic loads can still slow a fast and sleek vehicle rather rapidly. Regenerative braking is efficient enough to recapture the distances lost to aerodynamics, if used to slow a driver like me.....
Click to expand...

Yes I have considered that, but once speeds drop below 50 ish mph aerodynamic losses don't seem that much anymore.
 
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