Temperature and efficiency

[snoltor]

Temperature dropping, efficiency too. 39 this morning, below 40 the next couple of mornings (*I grew up in the Northeast so I know that 40 degrees is not really cold). I got my EV in May this year and I’m waiting to see how much the weather will impact efficiency. For comparison, here’s the MPG efficiency for the Prius I drove over 3 years before getting my Rav4 EV. The graph shows MPG readings for every tank of gas I put into the Prius from Aug ’09 till May ’13 when I got my EV. The red line is the overly optimistic estimate the Prius calculates, the blue line actual MPG. Main point: a lot of variability, especially in the beginning, but you see the seasonal impact on MPG: good MPG in warm weather, worst MPG in December and January during cold*, rainy, windy weather in California’s Central Valley winter. My highest MPG rating for a tank of gas was 58.9, lowest 46.5: for a 21% decrease over peak efficiency. To account for potential tank filling error / variability I averaged MPG for each month; best month = 58.5, worst month 48.2 MPG: an 18% difference between best and worst months.

The past week it’s been colder, some rainy and windy days and I’m seeing a 15% decrease in the miles per kWh reading you see on the instrument cluster when you shut down the car.…. and I’m not even running the heat yet. I’ll report back at the end of winter with more data.

One interesting difference I noticed in daily driving between the Prius and the EV: My commute is over mostly flat terrain with one ‘hill’ crossing a bridge over the Sacramento river. Coming down off the bridge the road has a slight downgrade for about 2 miles and in the Prius I get a 50 to 100% increase on the instantaneous MPG efficiency from baseline 50 MPG up to between 75 – 100 MPG. I was surprised at first when I didn’t see the same increased efficiency in the EV on that downgrade. But I realized that in the Prius I’m seeing the benefit of driving downhill plus the benefit of electric drive efficiency: the Prius electric motor is nearly strong enough to provide most of the propulsion on that downgrade. In the EV I’ve already got that electric drive efficiency working for me so all’s I get is the slight increased efficiency of driving down that slight grade.

 

[mark_rivers19]

Don't use the GOM. ( guess o meter).
Use your actual trip A/B

Personally, i would start with an 85 on Normal Charge with these cold temp.
At the end of the drive, 75-80 miles on trip A with 19-25 left on the GOM.

 

[snoltor]

I don't use the GOM. I use the Energy Monitor on the main display that gives you the minute by minute MPkWh feedback, and the efficiency monitor on the right hand cluster for instantaneous MPkWh feedback, and then take note of the efficiency report that pops up on the right cluster when you shut down the car.

Don't use the GOM. ( guess o meter).

 

[Bassman]

I think it may be related to the battery heater having to warm the batteries during driving to keep them at the optimum temp. I'm seeing about a 10 to 15% drop in efficiency also.

 

[snoltor]

I think it may be related to the battery heater

I agree. This morning it was 38 degrees up here in Davis and efficiency was very low for about 10 minutes, less than 2MPkWh, even when coasting to a stop. But then approached normal levels after the battery had apparently been warmed up to a good operating temp.

 

[EVBill]

I believe it's the battery heater as well. Ever since the mornings got colder I've seen about a 10% drop in efficiency from my morning commute. It's also seen in an immediate drop in the GOM range immediately when you turn on the car (with nothing on such as the air).

 

[mhkp]

I've also seen a drastic drop on my GOM. I used to get 100 on extended charge a week ago and now its 87. The only things that changed was I got my 5000 mile check and updated firmwear (Toyota was not able to tell me what update they made) and it got a bit cooler (low 50's in my garage at night) so i used the seat heater a bit.

Do any of these items explain the sudden GOM drop?

 

[eplantz]

Another observation point:

here in Chicago, temps have been from 9F to low 30s. In the summer months, my GoM reading would normally be 135 (as high as 138). Now it is about 100 consistently. No firmware updates for me (Toyota doesn't like us out-of-CA people).

Gene

 

[mark_rivers19]

I've also seen a drastic drop on my GOM. I used to get 100 on extended charge a week ago and now its 87. The only things that changed was I got my 5000 mile check and updated firmwear (Toyota was not able to tell me what update they made) and it got a bit cooler (low 50's in my garage at night) so i used the seat heater a bit.

Do any of these items explain the sudden GOM drop?

The problem with the GOM is that, it's based on your last driving.
if you were not efficient at all.. ex 2miles/kwh then the GOM will be extremely low.
it's really the trip meters ( A and B) that can tell you how many miles your traction battery provided.

 

[snoltor]

Yeah. If you're like me and drive the same route day in and day out, and if you drive the same way each day, as I do, then you can look at your efficiency feedback as you are driving, and when you shut down the car, as indicated in the original post, and see right away how different factors impact efficiency from strong winds to low or high temperature. Don't rely on the Entunes report on your phone for most recent drive... that number is all over the place. It's too bad the car doesn't keep track of how many kWh go in during charging, or at least report this data, because then we'd all be able to do simple calculation based on miles driven.

ex 2miles/kwh then the GOM will be extremely low.

 

[mhkp]

Thanks. I'll keep an eye on it, but I drive the same each day and environmental variables should not have had such a drastic impact. I'm very suspicious of Toyota service having 'adjusted' something and caused my car to be less efficient. My service dept in Simi was very unhelpful and lacked any EV information about my service.

 

[snoltor]

I'm very suspicious of Toyota service having 'adjusted' something

I'm at 7400 miles and haven't done my 5,000 mile check up for that reason... if it ain't broke don't fix it. I probably need a firmware update since I got my Rav4 EV in May 2013, but knock on wood haven't had any issues yet.

 

[mark_rivers19]

Yeah. If you're like me and drive the same route day in and day out, and if you drive the same way each day, as I do, then you can look at your efficiency feedback as you are driving, and when you shut down the car, as indicated in the original post, and see right away how different factors impact efficiency from strong winds to low or high temperature. Don't rely on the Entunes report on your phone for most recent drive... that number is all over the place. It's too bad the car doesn't keep track of how many kWh go in during charging, or at least report this data, because then we'd all be able to do simple calculation based on miles driven.

ex 2miles/kwh then the GOM will be extremely low.

Thanks! your method is better. =)

 

[fusiondynamics]

I've been driving a 80 mile round trip and always show about 20 miles left according to the GOM. With the cold temp I'm showing about 15 miles left with everything being the same. So it seems I'm loosing a little with the cold weather.

 

[mark_rivers19]

I've been driving a 80 mile round trip and always show about 20 miles left according to the GOM. With the cold temp I'm showing about 15 miles left with everything being the same. So it seems I'm loosing a little with the cold weather.

is this with a standard charge? OR an extended one?

 

[longrangeview]

I've been driving a 80 mile round trip and always show about 20 miles left according to the GOM. With the cold temp I'm showing about 15 miles left with everything being the same. So it seems I'm loosing a little with the cold weather.

Cold Snap in SF Bay Area today (OK, Canadians, U.S. Northerners, Easterners and Midwest folks, stop laughing!) gave me a temperature of 36 degrees as I drove to work this morn and a temp of 46 degrees as I drove home from work. Three days of cold is expected. (Stop giggling you guys, and please be helpful here. You guys know about COLD! Help us please.)

Regenerative braking was not available due to the cold outdoor temps.

Apparently, my battery can not charge to full capacity when the air around it is so cold. Is that normal? Usual fully charged range is 103 to 133 miles. Now I'm seeing 87 to 98 miles of range after charging.

Thanks to Tony and other forum members who posted 2012 info on regenerative braking not available when an EV first starts up and is "cold".

But I was surprised that regen still was not available after 20 minutes of driving. Apparently that's because the air is still cold and the battery was relatively cold. Right?

And when I set the climate control to 65 degrees AUTO. Nothing happens. It is cold in that car. I can get the seat warmer to work. That is it. What gives? The manual just says 'set Auto on'..

All constructive comments are welcome!

 

[TonyWilliams]

It's very common for the cabin heater to fail. Go to your dealer.

Also, the battery has a separate heater, which also may not be working.

 

[miimura]

And when I set the climate control to 65 degrees AUTO. Nothing happens. It is cold in that car. I can get the seat warmer to work. That is it. What gives? The manual just says 'set Auto on'..

All constructive comments are welcome!

If you really want to see if the heating is working, set it to Normal, A/C OFF, Recirc, 70 F, Vent Mode(Arrow pointed at the head of the figure). Within 2 minutes you should feel hot air coming out of the center vent. In Auto you may only feel the warm air coming from the side vent near the driver's window or the floor vents. If you really want to warm up the car, you have to set it like you mean it. Bump up that fan setting while you're at it.

Also, the reduced range on the instrument cluster (GOM) has nothing to do with how much charge the battery took. It has everything to do with the computer's guess at efficiency. Now, if you say that the car says "Charge Complete" and not all the fuel bars are showing, that's a different story.

 

[longrangeview]

It's very common for the cabin heater to fail. Go to your dealer.

Also, the battery has a separate heater, which also may not be working.

Oh My G! I will check with the Hayward, CA. Dealer ASAP! Thanks!

 

[longrangeview]

And when I set the climate control to 65 degrees AUTO. Nothing happens. It is cold in that car. I can get the seat warmer to work. That is it. What gives? The manual just says 'set Auto on'..

All constructive comments are welcome!

If you really want to see if the heating is working, set it to Normal, A/C OFF, Recirc, 70 F, Vent Mode(Arrow pointed at the head of the figure). Within 2 minutes you should feel hot air coming out of the center vent. In Auto you may only feel the warm air coming from the side vent near the driver's window or the floor vents. If you really want to warm up the car, you have to set it like you mean it. Bump up that fan setting while you're at it.

Also, the reduced range on the instrument cluster (GOM) has nothing to do with how much charge the battery took. It has everything to do with the computer's guess at efficiency. Now, if you say that the car says "Charge Complete" and not all the fuel bars are showing, that's a different story.

OK! I will try that tomorrow morning! Report imminent... 2 minutes to "warm" sounds great!