Volt range estimator equations

[DonC]

Is one of the ingredients battery temp.?

Battery temperature is certainly a factor but even in your hypothetical probably not much of a factor. The Volt battery is very well insulated so the drop in ambient temperature would probably not have much of an impact on cell temperatures. Also, the battery activity is exothermic so you'd expect it to heat up. Finally you'd be into ERDLT so there wouldn't be an immediate impact.

Temperatures when charging might have a larger impact. My Leaf takes much more of a charge when it's cooler. That keeps the range about the same regardless of the temperature during charging.

On temperatures it seems that for every 8F or 10F you're looking at a 1-2% change in range due to the need for increased energy due to colder temps. A drop in temperature from 70F to 20F would thus cut your range by 2-3 miles. My guess is the Volt range estimation would drop by a few more miles than this, which may because when it's colder it's usually more windy, and the estimate would take that into account.

Keep in mind that the Volt and the Leaf are using large format cells which are designed for electric cars. The 18650 cells used in the Tesla are designed for consumer electronics so they might respond more strongly to colder temps.

[tboult]

Good one Steverino.

Is one of the ingredients battery temp.?

Lets say you came home on a 70 degree day and charged up the Volt and you live in South Dakota. Then, during the night, a huge cold front came down from Canada and the overnight low went to 10 degrees F. After you charged the Volt let's say the estimated range showing was 38 miles.

What would the range show as the next morning? Assume the car was not plugged in overnight. and it was parked outside.

Well I'm not going to imaging living in South Dakota.. but in Colorado we can get pretty big temp swings. As I mentioned above

I disagree about the temps, I've had it drop 4 miles of EER just sitting in the cold over the weekend. (70F sat am, 30F monday), and I think we only drove it 5 miles on sunday and all at low speeds, so not enough to be the cause.

Though I ment to say we drove it 5miles on sat (and we recharged sat). It was unplugged as I plugged in the electric mower. The car then sat all day sunday unplugged in the cold. By monday morning I was down to 37EER while it had been 41 on saturday.

So I've seen drop in estimated (and real) range with overnight temp drop. While I don't normally precondition, on mondays when I'll have more than 34 miles of travel, I do now, so I don't look the extra range. (And FYI, its not just the estimate range, its the actual range I loose a bit of). Even when I leave it plugged in for the weekend it scommon for monday to have only 96-98% full charge and the usable milage to be lower (if I don't pre-condition to get it warm and recharged).

This was back in Nov, before I had much OBDII monitoring.
I cannot guess if its ambient or battery temp, I'd guess it was sitting long enough that both would be low.
30F is cold enough that the battery heater will turn on as soon as you start the car. So it might not even be estimating base on battery chemistry as much as based on the fact it will use the heater to warm the battery.

I can also say that for me at least, the speed at which I deplete the cold battery (about 30min) vs its rise in temp (even with the heater) is probably not a huge change in capacity. It wil start at 30F, and when the ICE comed on will only be up to 60F or so.

Here is another piece of info. Day before yesterday it was mid 50s. Yesterday AM I had 40miles of estimate range, Temps during the day yesterday fell to 19F. (drove 36, but 4 were ERDTLT, 2miles showing when I parked. charged it last night when I got home. It shows 32miles of range. (SO maybe yesterday's ERDTLT impacted it as well).

[George S. Bower]

Though I ment to say we drove it 5miles on sat (and we recharged sat). It was unplugged as I plugged in the electric mower. The car then sat all day sunday unplugged in the cold. By monday morning I was down to 37EER while it had been 41 on saturday.

So I've seen drop in estimated (and real) range with overnight temp drop. While I don't normally precondition, on mondays when I'll have more than 34 miles of travel, I do now, so I don't look the extra range. (And FYI, its not just the estimate range, its the actual range I loose a bit of). Even when I leave it plugged in for the weekend it scommon for monday to have only 96-98% full charge and the usable milage to be lower (if I don't pre-condition to get it warm and recharged).

This was back in Nov, before I had much OBDII monitoring.

).

Thx tboult. That's the answer I was looking for. Can you monitor battery temp? If I remember you are not running Dashdaq. It would be interesting to get more data.

Speaking of which:

If we had one of them EfiLive thingy's maybe we could pull the maps and find out how it really works.

or....

maybe we could buy a group EFi Live and figure out how to get Hold mode into our cars as a group effort. I'm pretty good at understanding the maps but not that great at the computer side as you (and others are).

I already spend way too much money on my DashDAQ so I don't think I am willing to fork over the $ for all the hardware and software we would need but I wouldn't mind contributing some to the effort. Seems like you could make it worth your while just by charging guys to make the conversion. I think there is a lot of demand out there. My other problem is I have a lease car and I'm not sure I want to risk it but I might be persuaded.

I think guys would easily be willing to spend 300$ for hold mode.

I have approached Jesse about this but have not heard back. but I think he is not BS ing us. Perhaps he is busy trying to get beyond just the ICE maps and into the battery programing before he can say much more.

Send me a PM or answer here as to what you think.

GSB

[tboult]

Thx tboult. That's the answer I was looking for. Can you monitor battery temp? If I remember you are not running Dashdaq. It would be interesting to get more data.

Speaking of which:

If we had one of them EfiLive thingy's maybe we could pull the maps and find out how it really works.

or....

maybe we could buy a group EFi Live and figure out how to get Hold mode into our cars as a group effort. I'm pretty good at understanding the maps but not that great at the computer side as you (and others are).

I already spend way too much money on my DashDAQ so I don't think I am willing to fork over the $ for all the hardware and software we would need but I wouldn't mind contributing some to the effort. Seems like you could make it worth your while just by charging guys to make the conversion. I think there is a lot of demand out there. My other problem is I have a lease car and I'm not sure I want to risk it but I might be persuaded.

I think guys would easily be willing to spend 300$ for hold mode.

I have approached Jesse about this but have not heard back. but I think he is not BS ing us. Perhaps he is busy trying to get beyond just the ICE maps and into the battery programing before he can say much more.

Send me a PM or answer here as to what you think.

GSB

I can monitor bat temp and ambient temp (and electronics temp...) with my android/torque setup, though right now my students have that as I've no time for programming for fun so I started them working on the next phase of my project developing our own code OBDII monitoring for improve feedback. (Since torque cannot really do all I want). So I won't be able to monitor until i get that back.


I'll been meaning to dig into the EFFlive, just have to get a windows box to get the eval version.. I have some gearhead friends that might like to have that (or may own it), and maybe one of our local tuner's have it as well. I'd be happy to work a bit on the programming when I get time (but that does not look good for the new many weeks).

[George S. Bower]

just have to get a windows box to get the eval version.. .

Box?= like a windows PC??????

[tboult]

Box?= like a windows PC??????

Yea.. I'm a linux and mac guy.. don't own a windows PC. (though I have some at work/lab the are mostly used by students.. I just need to grab one for a few days of testing.. when I find a few days.

[jfkirk]

Mine sometimes is not used for a few days. I notice that when a cold front comes through the range does drop a few miles after 12 to 24 hours of colder temps in the shed. (Typically ambient dropping from 40's to 20's. ) . It lags ambient temperature and then when it is not plugged in. No reason to argue that avrage pack input isn't a variable, but my guess is it is looking at HV V... battery voltage which will be proportional to charge with a temp correction. There is a patent taken out by LG stating that SOH (capacity in Amp hours) uses this type of calculation using a temperature look up table.

Also no reason to have any opinion on small cell format unless you know the heat transfer coefficients for the entire system. My bet is they are quite close in order to shed heat at high C rates. The Volt has high surface area fins on flat cells while the Tesla is using a partial wrap on a much smaller cell ...probably works out to about the same transfer area. per unit capacity.

[DonC]

You wouldn't think that cell temperatures would have much impact on estimated range. Yes the lower the cell temp the lower the voltage, which suggests a lower SOC. However, if the car also knows the cell temp, then it should know what the SOC will be when the the cell temp is raised to the target. It would have to account for the energy needed to heat the cells but it shouldn't be very much. A hundred watts? Two tops?

[tboult]

You wouldn't think that cell temperatures would have much impact on estimated range. Yes the lower the cell temp the lower the voltage, which suggests a lower SOC. However, if the car also knows the cell temp, then it should know what the SOC will be when the the cell temp is raised to the target. It would have to account for the energy needed to heat the cells but it shouldn't be very much. A hundred watts? Two tops?

This is from memory of my last set of runs where I did watch battery temp and battery heater power draw.
outside temps were high 20s, car cold soaking outside, battery temp 30F. When the battery heater kicks in, its about 2kW of power, draw that for maybe 4-5 min until the battery is in the high 50s when it shuts it off.