HVAC questions

So in my Grand Cherokee, the fan is pretty quiet on 1,2, and 3, but level 4 has to be 3 times as loud as level three. At 70mph, level 3 is under the road noise, level 4 is WAY over. Makes it hard to have a conversation.

How's the LEAF's blower noise?

Also how much delay is there for the heat? In an ICE, you have to wait 3-5 minutes (or more depending on your driving) for you to get heat. How long does the leaf take to get warm?

turbo2ltr said:

So in my Grand Cherokee, the fan is pretty quiet on 1,2, and 3, but level 4 has to be 3 times as loud as level three. At 70mph, level 3 is under the road noise, level 4 is WAY over. Makes it hard to have a conversation.

How's the LEAF's blower noise?

Also how much delay is there for the heat? In an ICE, you have to wait 3-5 minutes (or more depending on your driving) for you to get heat. How long does the leaf take to get warm?

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Owned now for 19 days, total miles 794. Drive it every day 40-60 miles 'cept Sun (so far).

The noise is proportional to the fan speed. Yes it gets pretty loud at the highest speed setting so I have turned it down on occasion because of that (or turned the music up )

The A/C works surprisingly well and the heater does not. I suspect the heater is simply small so as to leave more energy to prevent you from walking rather than keeping warm. The heater will take the edge off the cold but it takes about 7-10 minutes to do so, and again, it's only the edge... it's not a-blowin' like a raging fire like what you get with an ICE car but it does take the edge off. Actually it NEVER gets blowing very warm but beats not having one for sure (bring a jacket in the car with you for those times where in an ICE car you only need the heater). The A/C kicks butt and is spitting out the cold air in a minute or two. After seeing the heater performance I'm surprised the A/C works as well as it does. It looks like A/C uses less juice than the heater to do a comparable job.

Malcolm

The heater is like that because they are heating a coil that heats water that is then pumped to another core that has to heat up and then get blown on by the fan, all the while heat is absorbed into the lines. The heater is supposed to be quite large and I bet if the element were in the dash (heater core) and were the same kw load you would feel very high heat. I had the choice to put the LEAF heating system into my conversion and instead I put two heater elements where the air filter was, it was about 3kw max and worked quite well and was instant. No silly water tank, lines, coolant. pump, heat exchanger, etc.

For that reason among others, I still can't see why they didn't just use reverse cycle on the AC for heat: Simple, almost instant, and more energy efficient...

leafme said:

The A/C works surprisingly well and the heater does not. I suspect the heater is simply small so as to leave more energy to prevent you from walking rather than keeping warm. The heater will take the edge off the cold but it takes about 7-10 minutes to do so, and again, it's only the edge... it's not a-blowin' like a raging fire like what you get with an ICE car but it does take the edge off. Actually it NEVER gets blowing very warm but beats not having one for sure (bring a jacket in the car with you for those times where in an ICE car you only need the heater). The A/C kicks butt and is spitting out the cold air in a minute or two. After seeing the heater performance I'm surprised the A/C works as well as it does. It looks like A/C uses less juice than the heater to do a comparable job.

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mogur said:

For that reason among others, I still can't see why they didn't just use reverse cycle on the AC for heat: Simple, almost instant, and more energy efficient...

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How well does that work in below freezing temperatures?
I think both would have been better with the resistance heater to be only used in extreme cold. But then we should be preheating before we roll, yes?

Reverse cycle heat works down to an ambient temperature of about 40 degrees so, no, it would not be suitable for very cold climates.. As you suggest, a combination of both would be optimum, but more expensive, of course. Regardless, I still don't know why we don't just have direct hot air resistance heating and do away with all the other stuff...

smkettner said:

mogur said:

For that reason among others, I still can't see why they didn't just use reverse cycle on the AC for heat: Simple, almost instant, and more energy efficient...

Click to expand...

How well does that work in below freezing temperatures?
I think both would have been better with the resistance heater to be only used in extreme cold. But then we should be preheating before we roll, yes?

Click to expand...

I am thinking Nissan wants to avoid the high temperatures seen in a space heater.
The liquid heat system may well be lower cost due to space constraints.

Anyone know the BTU of the heating element vs. BTU of the air conditioner?

smkettner said:

I am thinking Nissan wants to avoid the high temperatures seen in a space heater.
The liquid heat system may well be lower cost due to space constraints.

Anyone know the BTU of the heating element vs. BTU of the air conditioner?

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It's not lower cost it is more complex, add up the many parts. The temperatures are not an issue, the ones I use mount directly to plastic with no problem. Water based EV heaters use:

Hoses
Fittings
Water tank
Overflow
Electric water pump
Submersible heat coil
Radiator
Valves
Coolant


Here is a description of one:

Offered EV heater is liquid heater type designed to be a heat source for existing heating system instead of an ICE. All vehicle's heat controls are retained and work the same way and apparent operation is the same. No under dash modification or taking the dash panel out is needed. The heater simply connects to the same heater core fittings at the firewall former engine hoses use to connect to, and on-off control switch is installed on the dash. The switch can be a regular toggle automotive type operated by hand, or linked to existing heat dial or lever.

The water (or regular antifreeze ethylene glycol solution for cold climates) temperature in the heater's tank is maintained at 70°C±2°C (158°F±3.6°F). Electric circuit consists of resistive element immersed in liquid and controlled by a FET switch, in turn controlled by a PIC micro controller. The firmware is sophisticated enough to provide safety check and emergency shutdown if any parameters exceed specified limits or electrical connections become loose. In case of emergency the heater is able to discharge vehicle controller input capacitors. Open collector output allows to monitor status of the heater. All inputs/outputs are galvanically isolated from the high voltage (traction battery) circuit.

Two models are offered: RM3 without water pump and RM4 with integrated pump. Each model has two versions with different working voltages: 100 VDC...250 VDC and 200 VDC...450 VDC, and both versions are made with 2 kW, 3 kW or 4 kW heater power. All versions still has the same set point temperature (70°C standard), and once it's reached, will consume THE SAME amount of power nesessary to maintain the temperature. It is only initial ramp up is quicker for 4kW model compared to 3kW or 2kW units.

16.5 mm, 18 mm or 20 mm diameter inlet and outlet fittings can be ordered. Standard size is 20mm. Manufactured by MES-DEA in Switzerland, one year warranty.

We'd be needing good heaters here on the east coast right now. It's been in the teens here in Philadelphia recently. And after living in the midwest for many years, I think Philadelphia weather is somewhat mild. "Take the edge off" will probably not cut it in colder climates. Hopefully Nissan will address this with the cold weather package, or maybe in MY 2012.

-11F as I rolled out of my garage here in NH today. At -40F I might consider staying home from work, but my (future) leaf needs to work down to that temp! I'm OK with range reduction though - my current communte is less than 20miles roundtrip.

The thermal mass of the coolant ("heat-ant") is probably a major reason Nissan decided to used the complex system rather than simple resistance heat, with or without a heat pump for use in higher ambient temperatures.

By preheating the system on grid power, you can sore the energy as heat, sparing expensive and heavy batteries.

I presume the heater is available immediately, without any war-up period, when you preheat the LEAF, correct?

Is there a way to turn the heating element off, but keep the fan and circulating pump on, to continue to draw down the stored heat?

Is this done automatically in low charge or "turtle" modes?

A good heater is a must. 3 degrees F this am when I left my house in Marshall VA at 5:05am


hopefully Nissan will address this with the cold spec pkg or at least by 2012 MY

Don't forget, folks, that we can pre-heat the car when it's in the garage.

In addition, the cold weather package is rumored to have heated seats and a battery warmer.

Here's a great paper on the effects of range and climate, BTW:
http://www.mynissanleaf.com/viewtopic.php?f=8&t=2464

This analysis shows that climate control loads can reduce CD [charge depleting] range up to 35%. However, cabin thermal preconditioning can increase CD range up to 19% when compared to no thermal preconditioning.

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So...no pre-conditioning and full-heat can eat up to 35% of range, while pre-heating only results in about a 16% range loss.

I do have to say this is disappointing to hear - regarding the performance of the heater system, as it definitely doesn't sound like it would cut the mustard, as things stand, for much of the northern states and midwest in the winter (as pre-heat only gets you for half of an out and back trip and temps are below freezing all the time). :-(

Definitely sounds like Nissan needs to do something about it (if this is really to be a car that people can drive nationwide throughout the year). It'll be interesting to see what the cold weather package consists of. Slapping seat warmers in there doesn't sound like it would be enough (your kids in the back would still get to freeze).

The lack of an effective heater provides fodder for naysayers looking for something to glom onto.

The lack of an effective heater provides fodder for naysayers looking for something to glom onto.

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Good point LTLFTcomposite, Nissan needs to get in front of this and have it fixed before next winter when they (should) be making significant deliveries to states with seriously colder climates, as the PR could be horrendously damaging otherwise (especially if Ford's car which will be rolling out about that time, doesn't have a similar problem).

My garage probably gets to around 40 in the winter. How long to preheat to around 70 degrees - or does it even get to 70 degrees?

I think it may be that the cold weather package includes a different type of heater all together than the current water/air unit

on the Japan website the cold weather pack desc includes a 5kw PTC heater

that is an electric element to air, totally different than the current system

in addtion to the heated front seat, HEATED REAR SEAT, and heated steering wheel (nice feature)

http://ev.nissan.co.jp/LEAF/OPTION/

kmp647 said:

I think it may be that the cold weather package includes a different type of heater all together than the current water/air unit

on the Japan website the cold weather pack desc includes a 5kw PTC heater

that is an electric element to air, totally different than the current system

in addtion to the heated front seat, HEATED REAR SEAT, and heated steering wheel (nice feature)

Click to expand...

Link? (I do trust Kevin, but I just want to see what else that site is saying now.)

Parking outside in quite cold conditions, sometimes with no "shore power" available, needs to be considered quite seriously. Damaged or depleted batteries are not an acceptable solution.

There should also be a low-temperature "pan warmer" type setting to just keep the EV "warm enough" when connected to power. No, it should not require a third type of socket. A simple connection to existing 120v pan-warmers should be designed in. Make it EASY, not DIFFICULT (like a special low-temp EVSE required for -40º operation) to use the EXISTING electrical infrastructure, Please.