Start up spike in energy consumption

Start up spike in energy consumption

Each time I "start" my car I have noticed energy consumption jumps to around 550-600 Wh/ mile for the first 3-5 miles then drops to a more reasonable level. Does anyone else get this? Has anyone recieved a good explaination for this phenomenon? I'm driving 20-30 MPH when it happens so I can't blame it on driving style. Also it corrects to 350 Wh/mile by the time I am at freeway speed (65-70 mph). Weird huh?

mkh1437 | January 6, 2013

Temperature? Are you in a cold climate? Perhaps the extra energy is going towards heating the battery.

DouglasR | January 6, 2013

I often lose a mile of rated range in the first six feet.

Sudre_ | January 6, 2013

Wow Doug you must really be in a hurry :-)

jat | January 6, 2013

When my car was delivered this morning, it was drawing a lot more current for the first 5 miles or so, and it had the yellow dashed line showing limited regen and a warning message about lower power available until the battery was warm. I assumed the extra power draw was warming up the battery (and the cabin), as it was about 40 degF.

Brant | January 6, 2013

Northern CA
It has been chilly lately (37 low)

July10Models | January 6, 2013

It makes sense. Until you start running up the miles in Wh/mi that number would be elevated because auxiliary power usage continues, especially to warm/cool the car.

Captain_Zap | January 6, 2013

I get the "Battery heating - performance will improve as you drive" message with the V4.1 software when starting cold, along with a couple extra kW of idle power on the energy meter. This causes high Wh/m and goes away after a couple miles. Interestingly, this has only happened when the car has sit idle for a couple days in an unheated garage. Normally I just get the dashed yellow line regen limit without warning message when starting cold after sitting overnight. This goes away in a couple miles as well.

With the battery heating message, there was no dashed yellow line for power limit, only regen. So I wonder what "performance" was actually being limited.

Here's a guess at how the cold temp behavior work based on my observations:

Cold (maybe <40F battery temp): "Battery heating" message, several kW routed to battery heat pump compressor and coolant pumps. Regen limited and perhaps power.

Moderately cold (40-45F): Both power and regen dashed yellow line limits, seems to be variable. Self heating probably warms up battery.

Cool (45-50F): Regen limit with dashed yellow line. Self heating probably warms up battery.

Brian H | January 6, 2013

Widely discussed by owners in cold climates, on TMC. Use a lower charging rate, e.g. by lowering amperage or using a 120V feed, so that the car is still charging when you come to get it. The battery will still be warm, on 'shore power', so you will get your full range and full regen.

DouglasR | January 6, 2013

I just went out to the garage to check on something (10:30 pm), and noticed that my car had finished charging, and I had 241 rated miles. I normally see only 230-235 in the morning. So I am losing 5-10 miles between the time the car finishes charging and the time I start driving in the morning. I can't wait for the app or other software enhancements that will let us charge on a pre-determined schedule. It will literally increase our range by that much.

Wayne3 | January 7, 2013

I have noticed energy consumption jumps to around 550-600 Wh/ mile for the first 3-5 miles then drops to a more reasonable level.

Well, this makes sense as you are accelerating up to speed. Watch the orange kW indicator in the right half of the speedometer. As you go from 0 mph to 25 mph, see whether it goes above 15 kW (likely it will -- perhaps it averages about 15 kW). Note the following calculation:

15 kW / 25 mph = 0.6 kWh per mile = 600 Wh per mile

Once you are up to a constant speed, note your orange kW indicator again and perform the calculation. For example:

10 kW / 25 mph = 400 Wh per mile
20 kW / 60 mph = 333 Wh per mile

Timo | January 9, 2013

You get 400+ mile range with 25mph. That's 85000Wh/400miles = 212Wh/mile or 5.3kW@25mph.

It could be rounding error from initial acceleration which can easily be 200kW/couple of feet.

lightly | January 9, 2013

What ever happened to the cars ability to be on a set schedule? Will this be on a future software update?
If so will that include preheating the battery while still connected to "shore power"?
That would certainly take care of this issue.

Captain_Zap | January 9, 2013

I heard second hand about a fimware update coming that allows you to tell the car what time you want charging completed. In theory, the car will be just topped off at that time and still warm and cozy. I'm got the impression that it may even use a lower charging rate if it knows that it has extra time to charge before your departure time. More pampering of the batteries is good as are fewer spikes in power usage on the grid. I did not get the impression that it would increase the charging rate if you were in a hurry.

mkh1437 | January 9, 2013

The scheduled charging has been a long-rumored feature of the forthcoming mobile app.

Timo | January 9, 2013

For that mobile app to work car itself must have some sort of scheduler that can actually do those things, if that exists you should be able to schedule it from the touchscreen before that app exists. Maybe even right now, if there just were a UI to do that.

Mark K | January 10, 2013

So why not enhance the scheduled charge app to include a scheduled pre-warm cycle?

After the battery is fully charged, you can still rely on house current to pre-heat the battery without depleting any charge at all.

This seems likely within a few months. A simple way to meaningfully extend range for drivers in cold climates.

Brian H | January 10, 2013

Yes, the MS is currently very inefficient in its use of "shore power". Cutting off all draw when full might make sense on a commercial outlet, but hardly at home. Same issue with cabin heating.

Timo | January 10, 2013

Inefficient isn't quite what it is, impractical is more like it.