Block heater observations
 

So I thought I'd put a theory to the test, and that is that it's best to plug in around 3 hours before driving. This was done in my Toyota Avalon Hybrid that has the same engine as the Camry Hybrid. It has the OEM block heater from Toyota that is, I believe, 200W rated.

Most of the day was cloudy, snowing a little with no wind and around 30°F/-1°C the whole day. The engine was shut off all night and all day in the conditions until around 7:15PM. At 10:15PM the Scan Guage said the coolant temp was 64°F/18°C.

Then I drove it and warmed it up to 180°F/82°C and shut it off and plugged it in immediately. During the night it was plugged in for 7 hours (10:30PM to 5:30AM) in similar conditions (no wind, some snow) with the ambient temp dropping only to 27° or almost -3°C by 5:30AM. After those 7 hours were up at that time the Scan Gauge registered 76°F/24°C.

Conclusion:
At around freezing ambient temps:
3 hours plugged in cold engine = 34°F/19°C warmer engine
7 hours plugged in after running = 49°F/27C° warmer engine
Difference: 15°F/8°C warmer if plugged in longer and right after shutting off engine.

Can you check the power draw with an amp meter or kill a watt meter?

Good question, as I'd like to upgrade to a 1,500W block heater and compare the results. It would be good to know the power of this one to do a fair comparison. Also, does the power consumption change between cold and hot?

I made a graph showing how the warmup curve for a block heater for my Insight a while back. For that particular vehicle / heater, the sweet spot was around 2 hours.

When we lived in indiana I parked in an unheated garage, even at -20F outside it was easily 30 degrees warmer inside the garage. Even in more mild weather of +20F without a block heater it took several miles before the engine hit operating temperature. With the block heater it would reach operating temp before I even got to the edge of town (1 mile tops). I think I have it in a post/thread around here somewhere.

I had the stock 600w heater on a timer, would run about 5 hours each night. For me the fuel savings were icing, the cake was full heat much more quickly.

Yes more power.
Get that warm up time down to half hour or 1 hour.

The more powerful the heater the less waste you will have.

If you could pump in several kwh quickly, then you would avoid heat loss.


Too quickly can be a problem though. If it is too quick you can get uneven warming.

I have done some work on measuring precisely what the cost/benefit will be.

With my student we gathered all the data on the canbus for 20k km and we created a model of the car that mimicks its performance

For a given run, we are able to change the engine temp (by modifying the data) to have an output insicating what it would have been if the engine started warm. (Resolution of 1000 samples/outputs per second)

Could this be somewhat circumvented by circulating the coolant via a pump and heating the coolant, not the block?

I'm thinking about an electric pump circulating the small coolant cirquit and a heating element dumping a few kW of heat into it untill a sensor detects the coolant reaching near operating temperature.
If the engine is evenly heated by the coolant over a timeframe of roughly 10-20 minutes, uneven temperature distribution would be minimized and heat losses to the enviroment would be reasonably low.

In case of my car, I'd install the required systems inbetween frunk and firewall.
There would be sufficient space and I have access to the plumbing for the heater core.
Maybe running power to the cabin ventilation as well to heat up the cabin as well so it has a comfortable temperature as well as de-iced windows as soon as I get into the car.

Just an idea...

Rate of heat loss is determined by the temperature difference, and the amount of heat loss is that multiplied by time.

So circulatin the coolant is a good idea.