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Found something interesting out about my block heater over the weekend. Here's the back ground. My daughter was asleep in the Prius, and I really needed to let her sleep. So :o with AC set to a chilly 79ºF while it was a toasty 93ºF outside, I let the car idle while I worked about 5 feet away in the garage :o.

So once I committed to this terrible act I started wondering, how can I hypermile a dead stop idle? The solution... my trusty EBH. So two bars on the battery Engine temp at 75ºC, I hook up the block heater. The battery is at two bars, so the ICE is cycling on for about 1 minute out of every 10. When my work was done (about 30 minutes later, I unplugged the block heater and headed out. To my shock, the engine temp was still at 73ºC. The engine had only run about 3 minute out of the last half hour, and had 25 minutes to cool, and in effect it didn't cool one bit.

So even though the block heater may only bring a cold block up to 50ºC or so, apparently it can keep a hot block hot for hours. I'm beginning to wonder if I could keep my block over 70ºC all night long and get a 20ºC jump on start-up temp in the morning simply by leaving my block heating all night.

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Interesting....Here's my though. In the winter I keep my Prius housed in the garage...temps in there are usually above freezing even when it's cold out, but battery temps can be darn low...30-40F. Leaving the car in Ready + EBH with the heater on at a lowly 65F could keep the battery temp up nicely.

Better yet, at work I park outside so the battery usually drops to ambient temp. Keeping the car in Ready there at 65f would offer huge advantages in the extreme cold. Hard to know what the trade-off point would be for time, FE advantage, CO2, etc.

Yeah I thought about leaving it in READY, but it seems to draw too many amps. I think just leaving it plugged in might yield surprising results. I've actually moved away from the leave-the-car-running camp. With the EV button, warm-up doesn't hit me as much. I also found that the thermo's do a good job of keeping the system hot over the short term. What I really need is a way to heat the collant in the thermos since it always seems to get colder than my pre-heated block

I'll give it a shot tonight.

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Dan, for what it is worth I've been plugging my car in as soon as I pull it into the garage. Most mornings during the summer if the temps are about 70 the engine is literally already completely warmed up (if I'm to believe the temp gauge on the dash -- never checked the SG). If the temp is lower it is still anywhere from 1/2 to 2/3 warmed up.

What I really need is a way to heat the collant in the thermos since it always seems to get colder than my pre-heated block

You'll have to talk to Hobbit for the details, but he mentioned that the coolant dump from the thermos is actually delayed and speculated that the temp drop that you observe upon start up is due more to circulation of the oil in the ICE. I always find it hard to disagree with Hobbit, but it has been my sense that the temp drop was from cooler coolant circulating into the system including that from the thermos.

I'm still very much interested in a system to attach a 'hair dryer'-like heater that would blow warm air through the battery ventilation ducts to keep it from getting so cold. I think that even a little 200W heater would be adequate to maintain temp though probably not adequate to warm up an already cold battery.

Allright, initial numbers in.

6:34pm = 77ºC
6:54pm = 80ºC
9:13pm = 76ºC
11:30pm = 76ºC

seems to be stabilizing at 76ºC. This is going to give me a S4 startup ;)

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Hi Dan:

___Now its time to do the power cost and emission calc’s … Sure looks like some great coolant temps well after shutting her down though!

___Good Luck

___Wayne

Allright, initial numbers in.

6:34pm = 77ºC
6:54pm = 80ºC
9:13pm = 76ºC
11:30pm = 76ºC

seems to be stabilizing at 76ºC. This is going to give me a S4 startup ;)

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My brain doesn't convert to C very easily
76 degrees Celsius = 168.8 degrees Fahrenheit
That's a little higher than I usually see. Sometimes I'll see 170F after prolonged plug-in in hot weather. In the winter months it usually peaks around 130F (54C) when the car is outside. On average I'd say it ends up around 145F (63C) after ~3 hours charger time. It may climb a couple degrees after that 3 hour plug in time, but not enough to justify leaving it plugged in that long.

Already done... For a Prius in Houston, break even is between 45-60 minutes. Anything over that and you'd have to have a 100mpg commute. Problem is that you can usually hit some good numbers without it, so those have to be compared to the "with numbers". I found that the most I could hope to save with a block heater was 5 oz of gas.

So I see 3 classes of hypermilers, environmentalists, conservationists, and competitor. There goals are to cut GHG emissions, reduce foreign oil consumption, and to get high score. So if your just a gammer, or a conservationists, this is for you. If your an environmentalists, perhaps not. Really more for gammers than anyone though.

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I really want to get a block heater - where can i pick up one for my 2006 scion xb and where can I have it installed?

___Now its time to do the power cost and emission calc’s … Sure looks like some great coolant temps well after shutting her down though!


Yeah, this I'd like to see... almost 4 amps of additional input to keep your engine warm, but does it lower total cost?

Final Results.

Prius Parked last night and hooked to block heater within 60 seconds of hitting the Park button. The temp when I hit the Park button was 77ºC (170ºF). Block heater ran for about 15 hours (over night) and the startup temp was 75ºC (167ºF). Once the ICE turned on for S1 transition, it dropped to 65ºC (149ºF) but made it back up to 75ºC (167ºF) by the time I pulsed up to my target velocity of 37kph (23mph).

Hit three light hard and dumped a lot of speed, so I only scored a 75 mpg this morning, but my opening 5 minute castle bar was pegged at 75 (usually 50 - 60).

So the 15 hours (4.5 kWh) didn't save any money, reduce emissions, or reduce consumption... but it might be a good way to keep the numbers up if your only motive is gamming. Now the idea of doing this over shorter periods starts to get interesting though.

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Not to discourage you from continuing your own experiments, but all this work has been done by others in the past. 2-3 hours gives you your best cost/energy/efficiency gain ratio.

Dan, good stuff. I'm starting to rely on you for all of my Prius experimentation needs. :)

This is OT, but probably not worthy of its own thread. Since you are hanging around here, I figured it would be a good place to catch you.

I find myself at times wanting to hop into the cleaners or somewhere else briefly, and I'd really like to lock the car and NOT SHUT HER DOWN to avoid the startup nastiness. I seem to recall you having a little trick to do just that. At least, I vaguely recall reading a thread that sounded like that.

At any rate, my searching for what I read is coming up empty, so I'm going directly to the horse's mouth. Do you have a way to lock the car without shutting her down? I can't seem to figure it out yet.

Maybe I'm just imagining what I read earlier.

FWIW I'm going to post the link to the original thread on the EBH at PriusChat...for reference if nothing else. It's a 16 page thread so the link will be to the middle of the thread where the discussion and measurements of EBH temps, energy requirements, CO2 production, etc. began.
http://priuschat.com/index.php?showtopic=11176&st=200#

Dan, good stuff. I'm starting to rely on you for all of my Prius experimentation needs. :)

This is OT, but probably not worthy of its own thread. Since you are hanging around here, I figured it would be a good place to catch you.

I find myself at times wanting to hop into the cleaners or somewhere else briefly, and I'd really like to lock the car and NOT SHUT HER DOWN to avoid the startup nastiness. I seem to recall you having a little trick to do just that. At least, I vaguely recall reading a thread that sounded like that.

At any rate, my searching for what I read is coming up empty, so I'm going directly to the horse's mouth. Do you have a way to lock the car without shutting her down? I can't seem to figure it out yet.

Maybe I'm just imagining what I read earlier.

Marc, perhaps you were remembering this (http://www.cleanmpg.com/forums/archive/index.php/t-3847.html) thread? Look for Hobbit's post...

Not to discourage you from continuing your own experiments, but all this work has been done by others in the past. 2-3 hours gives you your best cost/energy/efficiency gain ratio.No worries... I really just needed an excuse for a 15 hour soak to try to nail an 80 today. Dang lights dashed my hopes.

The differince in what I'm seeing is starting temp. Most start the block heater from ambient of 35ºC, then heat for 3 hours to get you to 55ºC - 65ºC. What I'm doing is applying heat to a hot block. I think if I could pull in off the highway at about 85ºC, plug in, block grills, and trow a nice warm blanket over the hood, I could probably hold 85ºC (or what ever the car stopped at) indefinitely.

I'd always assumed that starting (EBH) cold or hot (given say 24 hours) would both end at the same place (ºC). What I'm finding is starting hot the EBH keeps it hot, no matter how hot it was. I'll have to try it with a really hot block, and might wreck a day homes commute to force charge or something to get the engine temp up.

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I find myself at times wanting to hop into the cleaners or somewhere else briefly, and I'd really like to lock the car and NOT SHUT HER DOWN to avoid the startup nastiness. I seem to recall you having a little trick to do just that. At least, I vaguely recall reading a thread that sounded like that.Two ways, both require the physical key ejected (look on the fob for how to do it, if you never have before).

1) step out of the car, insert physical key and rotate counter clockwise (towards front of car). This will lock all doors.

-OR-

2) Roll down drivers window, step out of the car WITH keys, reach in the drivers window and press the lock-all door control on door, then pull up the roll-up-window control, pull hand out of car while window rolls up automagicly. The window control will continue rolling up the window even after you take your hand off the control.

To get back in you just use the physical key.

Few tips.. to turn off the display press "DISPLAY" > "Screen Off". To turn it back on press "INFO" > "Trip Information". To get it to stop beeping at you, turn off smartkey (under left knee). Usually helpful to prevent broadcasting the fact that your car is on.

I find the break even point to be between 10-15 minutes.

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1) step out of the car, insert physical key and rotate counter clockwise (towards front of car). This will lock all doors.

To get back in you just use the physical key.
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In all these months I somehow never read/learned/was told that/asked if I actually have a physical key hidden away. Excellent! Thanks Dan. You have opened up a whole new world of 10 minute shopping for me. :)

Hi Marc:

___I have a feeling you will be spending some time with your Prius’ owners manual the next few days? It is a dry read but a good way to waste a few hours of your time either way. I did the same just yesterday in fact ;)

___Good Luck

___Wayne

In all these months I somehow never read/learned/was told that/asked if I actually have a physical key hidden away. Excellent! Thanks Dan. You have opened up a whole new world of 10 minute shopping for me. :)Just wait till you commit to a "quick" run in, and start your shopping with 5 bars SoC

Goes something like this for me.

-) Accel, accel, accel, glide, glide, glide, turn, glide, glide, turn, glide, glide, glide, turn, park
-) Check SOC (5) and start stopwatch to avoid over depleting battery
-) DISPLAY > Display Off (00:01.5)
-) Lock door with Fob (00:05.04)
-) RUN... RUN... RUN... (01:55:05) Potential parked 600 yards away :(
-) Get through shopping list (08:45.06)
-) Self Check-out, wait, wait, wait, wait, out-of-order (10:20.45)
-) Retry with chatty cashier, wait, wait, wait, done (12:45.00)
-) RUN... RUN... RUN... (14:56.08) Uphill remember... potental park.
-) Unlock door with Fob and dive into car. (14:56.58)
-) Check SOC (4.. uhh ohh), throw into N and open door for a little push (15:03.23)
-) Check coolant temp while rolling (68C... uhh ohh... EV override)
-) roll... roll... roll... turn... roll... roll... turn... roll.. roll... roll..
-) SoC drops to 3... @#&!#$@!!! roll.. roll.. roll...
-) Pulse up into traffic as those "impatient" ones scream and curse me.
-) Prepair for glide... hit EV... "beep-beep"
-) NOOOOOOO!!!!!!! throw it into "N" and patiently wait for coolant temp to get back to 70C so S4 will re-enable ICE-kill

But hey... "made great time" :D

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LOL!!!!!!!! :p

Hi Dan:

___I have got to see the movie of that ordeal :D

___Good Luck

___Wayne

Hey, better that you're paying attention to all that than yakkin'
on the phone while bombing around the parking lots!
.
_H*

LOL Dan! I know that routine all too well. :D

I'm not sure if this was made clear elsewhere but you can detach and re-attach the mechanical key from the fob while it's still plugged in. This way I always have at least the mechanical key with me (on my keychain) - no danger of somehow getting locked out, and it's always attached to the fob unless I'm making one of those 10-minute shopping runs.