Guessometer and efficiency gauges question

According to the efficiency gauge, I generally average between 4.5 and 5.0 miles per kWh. Since the battery has a capacity of 24 kWh, I would expect that my range with a fully charged battery should be in the neighborhood of 108 to 120 miles. But, it generally is closer to 90 miles (once I've seen it at 100 miles). So, what's up? I know the guessometer calculates the range based on very recent driving which can make it fluctuate a lot, but it still *always* gives a lower range than what should be expected based on the efficiency gauge multiplied by 24 kWh in the battery pack.

Are they leaving a "reserve" capacity in their range calculation?

Yes they have a reserve, I think the number is 22.4kwhr that can be used or around there.

Also as you get down low you will reach a point where it will stop guessing, it will go from say 6 miles to --. They've obviously programmed in a safety net so you don't come back and complain "the car said I could make it 1 more mile and I could only go 0.8 and had to push"

I would assume they programed the safety window as a %. For example (just a guess since I noticed the numbers add up, maybe it's just a coincidence not presented as fact) if you're at 4.5 and can use 22.4 you should be able to go 100.8 but it's showing you the low of 90, or 89.3% of what you could go if you held 4.5. If you're at 5.0 you should be able to go 112 miles but it's showing you 100, also 89.3%. As you get down to 10 miles left at 5.0 and it calculates that as 8.9 and rounds it up to 9 no one really notices that but at full state of charge you notice it.

Yep, the EV industry is doing the same thing as hard drive makers.

Advertise: 1 TB*!

*Formatted capacity 850 GB...

24 kWh* battery!

*22 kWh usable, when new, between 65 and 80F only...

At least it's not as bad as the volt.... Here's a 17kwhr battery, you can use 10.

On the other hand mitsubishi lets you use all of the 16 in the iMiev. Not sure if there are enough of them out there and people actually willing to drive them long enough to get data on if that was a bad idea or not. Also mercedes advertises the usable capacity on the B ED, and I've heard that the Kia is 27 usable. There's nothing wrong with one or the other but it should be a standard set by the EPA.

minispeed said:

At least it's not as bad as the volt.... Here's a 17kwhr battery, you can use 10.

On the other hand mitsubishi lets you use all of the 16 in the iMiev. Not sure if there are enough of them out there and people actually willing to drive them long enough to get data on if that was a bad idea or not. Also mercedes advertises the usable capacity on the B ED, and I've heard that the Kia is 27 usable. There's nothing wrong with one or the other but it should be a standard set by the EPA.

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Not sure why the EPA needs to be involved. As long as the manufacturer states the available capacity I don't see a problem. In fact, the Volt could be considered more "truthful" since thanks to under-stressing the pack that available 10kWH will probably be true for a number of years after purchase.

Besides which, the "actual" battery capacity is a bit of an abstraction anyway. If you insist, the battery will keep on accepting charge -- right up until it bursts into flames. Who decides the cutoff voltage?

Nubo said:

minispeed said:

At least it's not as bad as the volt.... Here's a 17kwhr battery, you can use 10.

On the other hand mitsubishi lets you use all of the 16 in the iMiev. Not sure if there are enough of them out there and people actually willing to drive them long enough to get data on if that was a bad idea or not. Also mercedes advertises the usable capacity on the B ED, and I've heard that the Kia is 27 usable. There's nothing wrong with one or the other but it should be a standard set by the EPA.

Click to expand...

Not sure why the EPA needs to be involved. As long as the manufacturer states the available capacity I don't see a problem. In fact, the Volt could be considered more "truthful" since thanks to under-stressing the pack that available 10kWH will probably be true for a number of years after purchase.

Besides which, the "actual" battery capacity is a bit of an abstraction anyway. If you insist, the battery will keep on accepting charge -- right up until it bursts into flames. Who decides the cutoff voltage?

Click to expand...

Without someone to set a standard and hold people to it then evetually someone will see a marketing oportunity and turn it around. Yes all the makers of EVs now could agree to advertise only the usable capacity but what would stop say subaru from coming out with an EV in 5 years and decide to advertise full capacity. So it may not need to be the EPA, it could be the SAE as they did with horsepower ratings many years back. I think that's a pretty good example, under the old system.

"Before 1972, most American engines were rated under the methodology laid out in Society of American Engineers (SAE) standards J245 and J1995, which calculated the output of a ‘bare’ engine on a test stand with no accessories, free-flowing exhaust headers (no mufflers), and optimal ignition timing, with a correction factor for standard atmospheric conditions."
http://ateupwithmotor.com/terms-technology-definitions/gross-versus-net-horsepower/" onclick="window.open(this.href);return false;

Is it fair to advertise that the engine can put out 400hp if you then have to run it with oil/water pumps, an alternator, muffler and ignition timing that will work anywhere?

Yes the volt would be considered more truethul in the long run without capacity loss if they advertised at 10kwhr capacity but it's less truthful now than the leaf. From what I've read Chevy is keeping volt battery info very close and not releasing details. It could be possible that Pheonix first year volts can only hold 11kwhr now but no one would know but GM. If the second gen car has a similar ratio in the battery I would guess that there are a good amount of volts out there with reduced capacity. If the volt could use the same capacity % as the leaf I estimate that the current volt could get rated at 58 miles. I'm sure a lot of Leaf buyers would be in a volt if it got 58 miles. (I'd have one for sure)

Your last question about actual battery capactiy, the capacity isn't what you can put in but what can be contained. Run your tub for 24hrs and measure the volume of water it can contain. Please get back to me with your results on it's increased capacity.

Besides which, the "actual" battery capacity is a bit of an abstraction anyway. If you insist, the battery will keep on accepting charge -- right up until it bursts into flames. Who decides the cutoff voltage?

Click to expand...

The car manufacturer decides the cutoff both at the high and low end. As such, it is fairly disingenuous to report battery capacity that the on-board charging system will NEVER give you access to. I'd argue that the capacity should be listed as the total available power at the battery terminals from a 100% charge to turtle under the same normal conditions used to test MPG or MPGe. I'd argue that there also needs to be some standards around battery degradation, but that is a whole other discussion.

It would be like advertising a car as 350 HP, then having the on-board computer limit the throttle to 250 HP to allow you to put a cheaper transmission and differential on the car. It still is a 350 HP engine after all, but you only get access to 250 HP no matter how hard to stomp on the gas pedal.

minispeed said:

Nubo said:

Not sure why the EPA needs to be involved. As long as the manufacturer states the available capacity I don't see a problem. In fact, the Volt could be considered more "truthful" since thanks to under-stressing the pack that available 10kWH will probably be true for a number of years after purchase.

Besides which, the "actual" battery capacity is a bit of an abstraction anyway. If you insist, the battery will keep on accepting charge -- right up until it bursts into flames. Who decides the cutoff voltage?

Click to expand...

Without someone to set a standard and hold people to it then evetually someone will see a marketing oportunity and turn it around. Yes all the makers of EVs now could agree to advertise only the usable capacity but what would stop say subaru from coming out with an EV in 5 years and decide to advertise full capacity. So it may not need to be the EPA, it could be the SAE as they did with horsepower ratings many years back. I think that's a pretty good example, under the old system....

Click to expand...

Ah, I think I misunderstood you. I originally thought you were saying there should be a common standard for automakers to make a specific percent of total capacity available to the user. I think we're in agreement that the energy available to the user should be stated clearly.