Most go by a guesstimate value since they don't have any way of actually testing for total Kwh. I can see what you are pointing at though and for more reasonable accurate measurements I guess people can just go by their output. However, it is not written in stone for anyone to have exact measurements as to how much they actually have total for power.

I can say for those who want to be more accurate can state the total voltage and amphours of the batteries for others to toss around fthemselves.
Unless Robert wants to make a simple calculator in the column where the total watt hours (power rating) is posted to which a person types in all their values of volts and amp hours, controller amps, minus loses, etc that will give a more accurate answer more easily. Which, is not a bad idea, but then it takes time to do such.

 

Can we have an official policy on this?

Steve, I know this type of power rating is widely "fudged" with a lot of converters. Many choose to quote the max theoretical based on pack nominal and controller output amps max rating.

Perhaps we should ask Robert if he can add a field for methods by which the power was measured or guestimated. Not everyone is planning to measure motor volts and amps, and most tend to measure only battery volts and amps. If we could get a datalogger to measure controller/motor watts, that'd be far closer to accurate than the simple V*A = kW number.

 

Steve, I know this type of power rating is widely "fudged" with a lot of converters. Many choose to quote the max theoretical based on pack nominal and controller output amps max rating.

Exactly. I have a 230.4 V "nominal" pack, and a 1000 A controller. Does that mean I have a 230 kW system? Hell no. I limit my battery current to 650 A. Does that mean I have a 150 kW system? Certainly not, because at 650 Amps my battery pack sags down to 144 V.

The only real way to measure the output of the car is to dyno test it, and if you want you could try and extrapolate powertrain losses. I don't really see much of a problem with how the ratings are right now though.

You're right, the true output of the car can be measured on a dyno. That would be the "best" measurement, but is impractical for many of the people on this forum. The point is to compare apples with apples, and to do it with numbers that are relatively easy to obtain. I don't think it's unreasonable for people to quote max measured (battery amps x battery volts), since you really should be measuring those anyway.

 

The only real way to measure the output of the car is to dyno test it, and if you want you could try and extrapolate powertrain losses. I don't really see much of a problem with how the ratings are right now though.

 

I guess thats not out of line since all it takes is some basic math to get the better picture and the cars should already have the amp and volt gages.

 

Like the old saying, take with a grain of salt what they claim for Kw, mpg and sex life.....

 

I've got a 72KW sex life.

 

Even if #1 is pure "fantasy land", it's still a ballpark way to compare vehicle performance and it's very easy to calculate. If I see someone has a max power of 72KW and mine is 48KW, I know his vehicle is substantially more powerful than mine. Good comparison, not absolute number.

In addition to range, how bout "power to maintain XX speed". It's pretty easy for people to see the power their car needs to maintain 30 mph or 55 mph, and it is a good indication of the vehicle's efficiency/aerodynamics.

 

In addition to range, how bout "power to maintain XX speed". It's pretty easy for people to see the power their car needs to maintain 30 mph or 55 mph, and it is a good indication of the vehicle's efficiency/aerodynamics.

I like that a lot actually

 

Steve, if you don't mind my asking, is your range estimate tested or based on calculation? I'd love to know how those LiFePO4 batteries are performing.