Mini experiments: 300w vs. 800w block heater warm up time

[christofoo]

I agree with Daox on economics. Mine consumes about .75 kWh in 2 hours to give me a 50-60 degree F delta, or $0.06 per use at $0.075/kWh. The benefits include several stops and EOC's for me, since without the block heater I need the engine on all the time to prevent frost, so I would throw out 25 mpg vs 40 mpg for the first mile as a guestimate (probably not too far off), which works out to .015 gallons, or about $0.06. There might be some additional savings for a few miles after that, but not much (for me). EDIT: suppose it's 18 mpg without the heater, a number I think I've seen the Civic's SGII report for that first mile with the engine on, then it's 0.031 gallons or $0.11 in gas per plugin.

EDIT: not including wear-and-tear, my ROI would be 800 plugins for a $40 install, or about 10 years if I assume 5 days a week and the season is 1/3 of the year. For a $140 install that would be 2800 plugins or 35 years. Then again, it's really difficult to calculate something like this with much confidence.

For me the primary benefit is smog emissions, but it also should be expected to reduce wear-and-tear. My heater is only 400 W (360-380W in real life), so it doesn't actually get the engine warm enough to heat the cab right away, although I get warmth in about 5 miles vs about 10 without.

I think that hood insulation has some similar benefits at a lower cost, depending on daytime highs and driving patterns. I'm still putting this one off though, for no reason.

Originally Posted by pete c

that 3 mpg increase is quite good. i suspect you have a fairly short commute. i can't imagine it being that much if you have a longer drive.

how difficult is the install on a typical vehicle?

I wrote a tutorial for my old Corolla, although I believe several cars are similar. http://ecomodder.com/forum/showthrea...9-a-23864.html

EDIT: Here's a thread featuring a recirculating engine block heater: http://ecomodder.com/forum/showthrea...6-a-24259.html Here's another freeze-plug version, in a Civic but almost the same as my installation I think: http://ecomodder.com/forum/showthrea...stall-765.html

[slownugly]

I did a quick ROI equation. If a car isn't driven much then it's going to take a long time to recoup the money spent on the heater. The more you use it the faster you will make the money back. I drove 1941 miles last 4 tanks with the heater every chance I could get. Without it I would have used 3.5 gallons more. 3.5 gallons times 3.53( price of gas now) is a little over 12 dollars. My 75 dollar investment divided by the 12.35 I saved would mean I would have to drive that 1941 miles 6.07 times to break even. That comes to 11700 miles in winter weather averaging 48.5 mpg. Let's round it up to 12000 since I didn't include the electrical cost of the house yet. (1.2 dollars a month)

I drive 3500 miles a month so 12000 divided by 3500 would be 3.42 being more conservative I'll round that up to 3.5 months. So I can expect to pay my investment off in 3.5-4 months of winter driving.

[jray3]

Been thinking of a radiant panel on the garage floor to warm my EV battery pack, and it seems the same approach could help an engine. Radiant panel(s) should provide more uniform heat distribution while also taking away the need to manually plug in, and allow heating of the transmission. (Yes, plugless connections are heresy for an EV advocate, but why plug in if you can do better without!) Your parking spot would need to be narrow enough to prevent tires from hitting the panel, but the panel could also be activated by either blocking a light beam, or completing the circuit with a pressure plate.
Of course, there are smart-phone enabled remote switches that could also handle the morning warmup schedule now. Lastly, it keeps things simpler onboard the vehicle, WRT extra wiring, weight, and potential for leaks.

[oil pan 4]

If you want a fast block heater try something like my little 220v powered 3500w heater.
http://ecomodder.com/forum/showthrea...mer-23893.html

[Ryland]

Originally Posted by jray3

Been thinking of a radiant panel on the garage floor to warm my EV battery pack.

Most people put small heating pads under the cells of the battery pack allowing for as small as 300 watts of heating pad to heat a pack in just a few hours, as little as half an inch of foam is then used to insulate the batteries allowing them to stay warm for many hours due to their great mass.
For EV battery heating, this type of heating can increase your watt hours per mile even after counting the energy used in heating the batteries, I doubt that a heater that is just under the batteries would give the same kind of gain over unheated batteries.

I like the idea of a smart control for controlling when the heater comes on, something that taps in to the calender of your smart phone and heats it up before you have to go some place would be slick, but a simple timer also works great.
I haven't been able to get the plug out that my block heater threads in to, but when I do I would like to install an inlet with a cover either in my bumper or fender so I don't have a cord end hanging out, for a while I was waiting on new parts for my electric car and was plugging the charger right in to an extension cord instead of the inlet that is on the side of the car and it was annoying, much easier to plug and unplug from when one side is firmly mounted, it would also of course allow for a heater in the cabin to be triggered at the same time with the same cord.

[pete c]

I see some pretty wide variations in ROI calculations here. Obviously there are quite a few variables such route, temp and vehicle, but, I suspect the more conservative estimate (christofoo's) is probably most realistic.

Given that, I think a direct payback in fuel saved is questionable, but the other benefits of comfort, emissions, wear and tear make it worthwhile.

I think I will start by moding the wife's '09 Sonata. She could give two craps about the wear and tear/fuel/gas savings, but, the idea of being pretty much instantly warm will probably give her the incentive to have to reach down and unplug it in the morning. Won't do it to the rest of the fleet as they are older and less likely to be around in a few years.

[busypaws]

I installed 3 - 100Watt heaters, One on oil pan, one on transmission pan, one on a flat spot I found on the engine. Right now I plug them in when I get up so they only run 1/2 hour before I actually leave. I've noticed about a 10F difference in temp between air intake temp and coolant temp (Scan Guage) at startup. Before I ran the heaters the two temperatures were almost always the same. So 300watts at 1/2 hour gives you a 10degree rise. I have a timmer so I could set it to run for an hour or more but have not done that yet. Just my experience.

[Piwoslaw]

Originally Posted by slogfilet

To redo this experiment would require several nights with consistent outdoor temperature:

Day 1: run heater for 15 minutes, crank engine to mix coolant, check temp.
Day 2: run heater for 30 minutes, crank engine to mix coolant, check temp.
Day 3: run heater for 45 minutes, crank engine to mix coolant, check temp.
...
...
Day X: run heater for 15*X minutes, minutes, crank engine to mix coolant, check temp.

Done! Over the last two years I've been collecting data and I've finally crunched the numbers. I recorded the plug in duration, outdoor temperature and coolant temperature when it stabilizes 10-30 seconds after starting the engine. I did not record the data when something could have skewed it, for example if the car was parked in the sun, or if the engine had less than 12 hours to cool off.

As a reminder: I have a 550W coolant heater (no pump) and a 125W pad heater stuck to the oil pan. My lower grille is blocked year round, during the colder months so is the upper grille and then I have a piece of cardboard with aluminium foil insulating the engine from the top. Underneath is an OEM undertray. Coolant temp was from my ScanGauge, outdoor temp was always from the same digital thermometer.

I collected a total of 89 datasets, of which the first 9 where before I installed the pad oil pan heater. The graphs below show how much warmer (°C) the coolant was after how many minutes.

This surprised me: the oil pan heating pad helps much more than I expected. I thought that it would shorten warmup time after starting the engine, but it turns out to help with prewarming too

Also, I was was expecting the curve to flatten out much sooner. I usually plugged in for 1.5-2h assuming that longer time had diminishing effects, but the few times I've plugged in for up to 3h show that the engine is still keeping most of that heat

Notice how large the variation is between datasets with the same plugin time: 2 hours can increase the coolant temperature by anything between 22 and 33°C. I thought that this depends on the outdoor temperature (losing more heat when it's cold?), so I plotted the data in four outdoor temperature ranges: below -5°C, -5 to +5°C, +5 to +15°C, and above +15°C:

As you can see, this does not effect the wide temperature spread. There must have been other factors effecting how the coolant heats up, maybe wind?

Sometime in the future I plan to add some more insulation to the engine bay. When I do I'll start recording data again to see the effect on prewarming.

[Frank Lee]

2013 GM says no need to plug in more than 4 hours.
2013 Ford says no need to plug in more than 3 hours.

Don't know the engine or heater sizes. Might be moot; might be a blanket recommendation issued by each company.

[oil pan 4]

Originally Posted by Frank Lee

2013 Ford says no need to plug in more than 3 hours.

In '08-'10 ford was using at least an 800w heater maybe even 1000.