[pauldon]

It seems to come up quite a bit so I thought I'd measure it to see what it is. Luckily the heated seats have their own fuse which makes it easy to tap the circuit and measure the current.

The answer is about 3.25A per seat when the seat is heating. I sat in the car about 45 minutes playing around with the different H-M-L settings to see what was going on and here is what I saw:

Starting on Low I saw approx 3.25A for about 30 seconds then no draw (ok, 100mA or so) for about 1 minute, then repeat.

On Med I saw 1 minute at 3.25A and 40 seconds with no draw. On High I saw 3.25A constant and after 10 minute gave up watching for it to cycle. I got up and got out of the car and came back about 3 minutes later and it was pulling no current. About 15 seconds after I sat down it pulled 3.25A again.

This does not APPEAR to be a fixed cycle on any of these settings and here is why I say that. When I went from Med back down to Low it took over 5 minutes before it drew power again. This leads me to believe that the seat was warm enough that it didn't need to apply any current. Once it got into it's cycle it was again about 30 seconds on and 1 minute off.

So an approximation of average load per seat, which may well depend a bit on your ambient temp (mine was 50), using 13.8V for nominal voltage would be:

Low: 15 Watts
Med: 30 Watts
High: 45 Watts

Which means if my HV battery is a loaf of bread the heated seats are the crumbs in the bottom of the bag. I'm driving to work on High tommorow.

It just occured to me I measured with climate on Eco and there is a possibility, though it seems unlikely, that 'comfort' might yield different results. I'll check that and follow up perhaps this weekend when I have the time.

 

[jsmay311]

GREAT post! There's nothin' better than good ol' fashion measurements and data. Thanks!

I was actually rather amazed that the power draw could be so low, so I did a quick search online for seat heaters that plug into the 12v "cigarette lighter" and came across one with a rating of 45w. So 39w would seem to be right in the same ballpark.

This is definitely useful info for people trying to maximize their cold-weather electric range.

 

[pauldon]

GREAT post! There's nothin' better than good ol' fashion measurements and data. Thanks!

I was actually rather amazed that the power draw could be so low, so I did a quick search online for seat heaters that plug into the 12v "cigarette lighter" and came across one with a rating of 45w. So 39w would seem to be right in the same ballpark.

This is definitely useful info for people trying to maximize their cold-weather electric range.

I realized after your post that I (lazily) just used 12V for the calcuation when in fact, on and operating the APM targets about 13.8V which is what I had at the time. I fixed my post redoing the wattage calculations and 3.25A * 13.8V = (you guessed it) 45 Watts.

 

[Lee Willis]

This is good stuff.

It has become clear to me that any possible use I can make of the seat heaters uses less power than running the heater in comfort mode when it is cold outside. The seat heaters really do not seem to materially affect range, at least not if I use just a brief burst of full (until I feel the heat) and then back off to low.

 

[tboult]

This is good stuff.

It has become clear to me that any possible use I can make of the seat heaters uses less power than running the heater in comfort mode when it is cold outside. The seat heaters really do not seem to materially affect range, at least not if I use just a brief burst of full (until I feel the heat) and then back off to low.

Give Pauldon's measurements, lets say its even 50watts, and given a cold volt get say 30m range on its 10kw charge (I'm rounding very conservatively to make math simple), or about 3m per kwr, running the seat heaters on full for an hour would take < 1/6 of a mile off your range. Probably don't need to do much pluse and glide on the seat heaters.

 

[scottf200]

Which means if my HV battery is a loaf of bread the heated seats are the crumbs in the bottom of the bag. I'm driving to work on High tommorow.

Outstanding post/thread. Crumbs indeed. I'm using heated seats more regularly now. And thinking about turning on the precond CONFIG option to warm the seats!

Low: 15 Watts - 33% duty cycle (30SecOn/(30+60))
Med: 30 Watts - 60% duty cycle (60SecOn/(60+40))
High: 45 Watts - ??% duty cycle

 

[DonC]

Heated seats are great. Never realized how little power they took. Just as a comparison data point, my Leaf draws 1.5 kW when running the heater and the heater completely sucks. It simply would not work in cold weather.

I actually prefer heated seats because unlike the heater they don't dry out the air so much. You get the same feeling that you experience when you're siting out in the sun on a cold day -- it's cold but the radiant heat from the sun is keeping you nice and toasty.

 

[Codyozz]

Give Pauldon's measurements, lets say its even 50watts, and given a cold volt get say 30m range on its 10kw charge (I'm rounding very conservatively to make math simple), or about 3m per kwr, running the seat heaters on full for an hour would take < 1/6 of a mile off your range. Probably don't need to do much pluse and glide on the seat heaters.

Tboult Your humor is humorous! Thanks for the friday funny!

 

[pauldon]

Low: 15 Watts - 33% duty cycle (30SecOn/(30+60))
Med: 30 Watts - 40% duty cycle (40SecOn/(40+60))
High: 45 Watts - ??% duty cycle

I'm not one so usually split hairs but since it's math it was bugging me. On med I measured 60 on, 40 off so duty cycle would be 60% for medium. I do think it's thermostatically controlled though but I'll bet with an average human on the seat there is probably a pretty consistent cycle.

 

[voltcrazy]

This is great info!

 

[DCFusor]

Yup, I second the praise for good old real measurements. I run a sci/tech forum and I make my members shut up and measure regularly, else the baloney flies far too thickly.

(OT but here's the link, more Volt stuff there under alt energy:
http://www.coultersmithing.com/forums/index.php)

In my Volt, the battery seems to be held at 14.92 volts FWIW, which is a problem with the inverter I put on there for emergency AC power - it shuts itself off with an overvolt warning periodically!

Nice to know the seats aren't going to affect the range much. Now if they'd just do the steering wheel (those numb fingertips) it'd be pure gold.

 

[pauldon]

And the elegant tool for measuring this stuff in the Volt is this. I think I paid $15 or so. Pull the fuse, put fuse in the side of this thing and plug it into the fuse block. I have one that is a loop to so you can just clamp it.

For the heated seats I had to pull the fuse for the parking brake next to it to get it to clear. I now know the indicator for a blown parking brake fuse is the little yellow brake icon with a wrench next to it on the instrument cluster.

 

[scottf200]

I'm not one so usually split hairs but since it's math it was bugging me. On med I measured 60 on, 40 off so duty cycle would be 60% for medium. I do think it's thermostatically controlled though but I'll bet with an average human on the seat there is probably a pretty consistent cycle.

No worries. That is why I put the math in. I wrote the numbers down wrong. I corrected my post.

Re: thermostatically controlled
If that is true then I would think that it would vary in the first couple minutes and then be pretty steady.

 

[scottf200]

Now if they'd just do the steering wheel (those numb fingertips) it'd be pure gold.

100% agree. I need to start thread on that and buy one until I get my Gen II and give my wife the Gen I. She wears gloves and drives a much shorter distance.

 

[Robinpdx]

Thanks for the timely post. I was about to ask this very question because I noticed on my Volt I am now only getting about 25 miles with the heater and lights on going to/from work ( vs 35-38 with no heat, no AC and no lights) However today I preheated the car while plugged in ( need to remember to put on comfort the night before for best results) and set the heat at 65 and had the seat heater on, and I got 32 miles - with the lights on!

So now my question is how much power do the lights take ?

 

[pauldon]

So now my question is how much power do the lights take ?

I got the meter out and confirmed that in fact each headlight pulls 55W like GM says.