How does electrical heating really work during a drive?

[Steepndeep]

Now we have had a couple of weeks with subfreezing temp in Sweden and I have been trying to avoid ICE start on short travels. Short being less than 30 kms. Using preheat is necessary and renders me a cozy car at start. I have then played with fan settings and temperature settings while observing the power consumed by the electrical heater during the drive. Not being totally scientific but my observation is that power consumption by the elctrical heater is totally independant on the fan setting. I.e. on lowest fan setting, when the airflow is not enough to heat the car, the powerconsumption is the same as on fan setting 4 or 5, which is necessary to keep the temperature in the car. This also seems to be confirmed by the guessometer as the fan setting does not effect predicted (guessed) EV distance.

As an example on fan setting 1 after driving for 15 minutes the ICE started as the brain noticed that temp difference between requested temp and actual temp was now more than 10-12 degrees. Obviously this has no effect unless I also increase fan setting, another Mitsu stupidity. On fan setting 4-5 the car maintains the internal temperature during the whole journey and no ICE start.

Do other people concur with this behaviour and maybe have an explanation for it? And if the fan setting does not effect powerconsumption by the electrical heater, where does the exess power dissapear when using low fan setting?

 

[maby]

Don't forget that it is not a fan heater blowing air over hot wires. It's an immersion heater in the engine cooling circuit. Admittedly, the water circulation pump is not running while the engine is stopped, but I assume that heat simply bleeds off into the rest of the cooling circuit.

 

[Fecn]

My understanding is that the pre-heat function ignores all of the climate control settings for desired temperature and fan speed and just pumps 4.3kw into the heater for the set amount of time.

 

[Steepndeep]

Thank's maby, no I did definetly not know that.

That explains a lot. That would mean that the electrical heater always heats the ICE cooling circuit and effectively the ICE. So running the fan at low speed simply wastes heat through the ICE and into the atmosphere. Interesting. Depending on where the elecrical heater is located, i.e. in the bottom of the cooling circuit or in the top, it would or would not cause some cooling water circulation. Would be nice to have a cooling water temperature meter to check.

A top tip at really cold temperatures (below -30 C) could be to run preheat and then leave to car standing still in ON mode, provided ICE does not start, with fan on lowest setting and temp setting at 15,5 C as that would the heat ICE before it starts.

 

[anko]

Thank's maby, no I did definetly not know that.

That explains a lot. That would mean that the electrical heater always heats the ICE cooling circuit and effectively the ICE.

This is not the case. There is a thermostatic valve between the ICE cooling circuit and the electrical heater circuit. It opens only once the coolant reaches 70 deg C, not before. At that time the heater will stop consuming electricity.

I am pretty sure the valve closes as soon as the ICE stops and not just when the coolant drops below 70 deg C, as I have seen the heater consuming electricity when the coolant was still more than 80 deg C. I think it would be better if the valve stayed open for as long as the coolant was above 70 deg C.

Back to the opening post: the power consumption may be as high, at lower fan speeds, but is it 'as prolonged'? I can imagine that, at a lower fan speed, it takes shorter bursts of power consumption to maintain the keep the heater water at a specific temperature level ....

 

[jaapv]

If the fan is on high the air circulation in the car will be more effective, causing the temperature sensor (behind the little grille in the dash) to be more accurate.

 

[Steepndeep]

@anko

Yes I agree it would be better if the valve stays open when ICE is warm, regardless of ICE is On or Off. Your statement would explain why the electrical heater goes on very quickly after I have being running ICE in Charge mode on highway to save electricity for city driving.

Now on my observation of how long the electrical heater stays on, depending on Fan setting. Your suggestion that it should run short bursts at low fan setting and longer bursts at higher fan setting makes sense. But that is not at all what I observe, admittedly only by looking at the heater indicator on the Screen. This is not scientific but shifting from Fan setting 1 to 5 or 6 has an enormous perceived effect on how much heated air is sent in the the passenger compartment and that same huge effect cannot be observed on the power consumption. I have been driving 10 minutes on fan setting 1, after that the ICE started because of dropped indoor temperature, and compared that to 10 minutes on fan setting 5. Huge indoor temp difference and no noticable power consumption change on the heater, nor on the guessometer.

 

[anko]

@anko

Yes I agree it would be better if the valve stays open when ICE is warm, regardless of ICE is On or Off. Your statement would explain why the electrical heater goes on very quickly after I have being running ICE in Charge mode on highway to save electricity for city driving.

Now on my observation of how long the electrical heater stays on, depending on Fan setting. Your suggestion that it should run short bursts at low fan setting and longer bursts at higher fan setting makes sense. But that is not at all what I observe, admittedly only by looking at the heater indicator on the Screen. This is not scientific but shifting from Fan setting 1 to 5 or 6 has an enormous perceived effect on how much heated air is sent in the the passenger compartment and that same huge effect cannot be observed on the power consumption. I have been driving 10 minutes on fan setting 1, after that the ICE started because of dropped indoor temperature, and compared that to 10 minutes on fan setting 5. Huge indoor temp difference and no noticable power consumption change on the heater, nor on the guessometer.

I kinda assumed more hot air would cost more energy. When you are correct (which I do not contest), it would mean a higher fan setting would be more economical. I am going to try that

 

[Steepndeep]

@anko

Yes please try, and if you have EvBatMon, which I don't, maybe that can give more scientific results.

Now if I am right it naturally begs the questions, where does the excess heat go on low fan setting. On explanation could be that the electrical heater package is poorly isolated so at motorway speed cool air circulates around the package and any "excess" heat is lost to the outside. If that is the case the proper way to heat the car is to run fairly low temp setting (16-17 C) and a fairly high fansetting (in my case 4-6 as more than 6 is really noisy). Worst scenario would be high tempsetting (20 and higher) and low fan setting.

So why would the heaterpackage not be isolated? Well, as there seems to be no real overheat protection maybe Mitsu took this simple route. M2C

 

[anko]

@anko

Yes please try, and if you have EvBatMon, which I don't, maybe that can give more scientific results.

That is kinda funny . Although the software, graphics, user interface, web upload function and what not of EvBatMon was developed by zzcoopej, I provided the OBD request / response parameters that form the basis of EvBatMon. I use my own tools for extracting the data from the car, using the same request / response parameters and more. So I pretty much have that covered