heater does not get hot

<div class='quotetop'>QUOTE(jayman\";p=\"59837)</div>

You have a choice of several options:
-get electric seat heaters (available from Toyota)
-get a 12V aux electric heater plugged into lighter socket (up to 150W)
-get a 12V aux electric heater hoooked up directly to 12V line for more power (300W)

Since 12V for accessories is not drawn from the small 35Ah battery rather than being supplied from the voltage converter from the main battery you could, in theory, have as much power as the 12V fuse lets you consume.

Let me also tell you a story:

A friend of mine was working a few months in Minsk where it also get very cold (I believe it was averaging -35C in winter). He was given a Lada to drive to work to. After freezing his knuckles off for a few days he asked one of the natives how they survive the commute to work every day. 'Didn't you turn the heater on' was the question - 'I did, I did but it didn't work'. So someone went to his car to check the heater. He sat in and pushed the button on a box attached to the dashboard (that my friend didn't know what was). Hot air started to fill the overfrozen Lada immediately.

It was a petroleum heater.

Boris

 

Prius car heater is not great, but still surprisingly good for the
engine size. Only cars I've owned with good heaters were all
V8's, and most of my cars have been cold once temperatures
got below around 5 degrees F.

So what are people doing to fix the problem?

1 Anyone tried to get and install the Prius block heater made
by Defa?
I can't seem to find a US dealer on their web site. They
do list both a Prius block heater and a cabin heater to
preheat the cabin. They also list tools needed to install
the unit. (http://www.defa.com) Doesn't look easy, so
maybe some Toyota dealers here could be talked into
making these available!

2 I plan to put an electric preheater in my cabin to
warm that up at least before I start out on really
cold days. Anyone tried this? I have used one in
my old car and 800-1000 watts is plenty to warm up
fast before starting out. I got a marine plug to install
so the wires don't have to go through the door seals.

3 I once saw a block heater for cars that ran on propane.
That might work for people not near power outlets.

4 The 300 watt 12 volt heaters might be all that is needed
if you installed 2 of them. I would wire these direct from
the battery probably with a relay so they would be
disabled with power off. Each would need to be fused
at 25 amps or so, more than I would want to had just
to the fuse block.

The biggest problems I see would be finding safe places
to locate the heaters so as not to risk a fire. The Defa
type made for the cabin would be nice as it is a ptc device
so should be somewhat self limiting on heat output. and
therefore safer.

 

<div class='quotetop'>QUOTE(jayman\";p=\"59818)</div>

If you have to sit in your car, you are much better off driving. It will warm faster. I go out to the car, start it, pull far enough out of the garage that the exhaust is going out, and then I lock the car and come back inside for 5 minutes. When I then go back out to the car, there is heat coming out of the vents and some of the bite has been taken out of the interior cold. Maybe I'll try 10 minutes one of these cold days.

 

<div class='quotetop'>QUOTE(BorisSlo\";p=\"59948)</div>

Sort of like the LP heater the old VW Bug used to have??

Hmmmmm ... hot air immediately you say .....

Two please!

 

Just occurred to me that the built in Prius electric heaters might help! The computer probably disables them soon as the engine warms a bit, to save on fuel.

For really cold weather there should be an override switch so they can be left on too! Just need a sw upgrade with another button on the climate control.

Or a relay and switch could be used to bypass the software.

 

Just a warning, there are only 2 fuses to the ACC output from the power control. One is 15A to the console outlet (this is why it is not easy to change it to full time 12V), and a 7.5A fuse for everything else.

"But Dan, too many things are running in ACC to be supported by 7.5A"

Yes, this is true, if all the power was coming from that 7.5A fuse. Truth is, ACC is only a control signal for most devices. They then take their main power from the B line which supplies full time power. Works much like an amp would.

If adding an electric heater, be sure to convert watts to amps by dividing by 12. There is a 100A fuse to the converter, but be conservative and limit total power consumption to 80A, including what comes with the car.

Radiator cooling fans run continuously with AC compressor running, and normally the HVAC will run it even in heat in order to de-humidify. Might be nice if it were possible to reverse the AC and get cabin heat from it, would use less power than pure resistive heating, much as a home heatpump would.

 

I wonder how many watts the electric A/C compressor takes? It's probably at least 1.5 tons cooling capacity. So at least 1,500 watts?

Since the ICE runs a lot more in colder temps anyway, it would be nice if the HV battery pack could be used to power a SERIOUS electric heater, say 1,000 - 1,500 watts.

 

i guess maybe that block heater option should be offered to people in US too

 

<div class='quotetop'>QUOTE(jayman\";p=\"60098)</div>

My point exactly!!!

 

We should offer to lend our cars for prototype heater testing, since we both live in cold climates. I've used 1,000 watt 120 VAC interior car warmers, and those babies keep the interior Tropical.

A 1,500 watt heater would be great for cold temps, but only if powered from the 200V battery pack. At 200V, you'd only need 7.5 A, a very small and manageable wire size. At 12V, you'd need 125 A, that's just not feasible in a car.

We're going to see more cars, even "conventional" ones, using higher voltages in the future. We've hit a brick wall with 12 V systems, due to the higher electricity usage in modern cars:

EFI, electric-assist power steering, power windows, electric rear window defrost, power seats, heated seats, etc etc. Some cars and pickup trucks need +130 amp alternators just to keep up.

 

1.5 tons? I doubt that. My house is only 3 tons for 1300 sq ft.
I haven't yet been able to find the max wattage consumed by the compressor, only that it runs on 200V, and is variable speed. Watts consumed is not heat moved. Those are two different things. Think of heat contained in a box, and you are using power to move the box. The power to move the box correlates with the weight of the box, but isn't the actual weight of the box.
AC moves heat, it doesn't create it, where resistive heat 'creates' heat.

 

Hi Dan:

Remember that 1 ton cooling = 12,000 btu. A rule of thumb is about 1,500 watts per ton of cooling, depending on A/C system. The A/C in my 2000 GMC was rated at 18,000 btu cooling, or around 1.5 tons. According to the shop manual, it needed a 2lb R-134a charge, which is about what you need for that capacity.

In contrast, my hobby farm has approx 2,200 sq ft living space. I have a Bryant Evolution 90i Plus variable speed gas furnace rated at 60,000 btu max heating (With variable fire gas burners) and a 2 ton Bryant Puron Plus two speed Scroll A/C.

On low-cool, according to my amp-clamp, it takes around 6 amps running. On high-cool, it takes around 14 amps running. So it appears running at low-cool is a lot more efficient than high cool.

Yes, I know we're not "creating" energy or heat, just moving it around. Despite what heat-pump makers tell gullable consumers. There is a fairly predictable relationship between energy consumed to heat (Btu's) transferred, whether in a central A/C or in a refrigerator. That doesn't violate the Laws of Thermodynamics. It takes "work" to move something.

Industrial uses (Chiller, flash-drier, etc) with +30 tons capacity, also have fairly predictable energy consumption curves. Rather than sized to maximum capacity - very wasteful - there are many energy saving trends. Many modern chillers and industrial A/C compressors are variable speed with Scroll compressors. So the capacity is much more closely matched to the need.

So if the onboard A/C compressor runs off 200 VDC from the NiMH battery pack, there is no reason why a 1,500 watt resistive element or ceramic substrate heater couldn't be run off the same NiMH battery pack. I am curious what the amp draw of the A/C compressor is.

At 200 VDC, a 1,500 watt heater only needs 7,5 amp wiring. That's the biggest advantage to higher voltages, much more manageable wiring size. The insulation on modern polyethylene jacketed wiring is good to at least 600 V.

Modern commercial and military aircraft use higher voltages as well, though at 400 Hz through the turbine generator. Although the primary heat source is bleed-air from the turbofan, supplemental windshield deice is always electric, usually +3,000 watts. Allied Signal and General Dynamics both make these systems.

Since my battery SOC is ALWAYS at the very top of the green in this cold weather, it would have been nice if Toyota had equipped the cabin with a "real" electric-auxiliary heater, not that 12 V thing.

It looks like I had better invest in the shop manual. I didn't know the A/C compressor was variable speed, though that makes perfect sense: maximise efficiency to match cooling demand. Are you sure the specs don't mention the maximum amp draw?

Well, here's hoping it warms up soon.

 

Hey Jayman,

Yes, I discovered the ton to BTU relationship when trying to find the running wattage of the compressor.
EER or SEER determines wattage/energy usage to BTUs moved.

I tried looking for the compressor current draw, as well as its cooling capacity, and I haven't found it. only that it is variable speed and uses 200V through inverter. Both New Car Info and repair manual states this.

Resistive cabin heat off the HV would be nice, if not using the AC system as a heat pump. At 1200W, battery would last maybe an hour, though that might limit acceleration.

For the repair manual, if time is not an issue, you can download all the PDFs from Techinfo, and assemble them using Acrobat or some other program that can edit PDFs. I would suggest keeping each section in a different folder, and prefixing the filenames with a sort order #, or you will go crazy trying to put them all in order.
Wiring diagram has also proved useful.

 

For all those suggesting a heated cushion or heated seat: I don't need to heat my bum. With longjohns and a winter jacket I don't care how cold the seat is. It's the air I want to get warm, so my fingers and toes don't freeze. Those are my vulnerable points. However, a heated steering wheel would be a boon!

 

Forgetting comfort for a moment. What does the Prius like?

I tried out John's discovery and used manual mode for the first
time with lower fan speeds. Can't tell if it helps yet since we
are having a heat wave here now with temperatures above 32
degrees!

But I noticed big differences from my usual "auto " mode. With the
car heat under manual I use recirc and high fan to get started warming.
I stop this if windows fog.

Then when I am getting warm I go to fresh air in but switch to the low
fan speeds.

At this point I am comfortable but what about the Prius?

Comparing with auto mode I consistantly pick lower fan speeds and
"auto" never seems to use recirc for heat.

So it occurs to me my manual mode is better for keeping the catalytic
converter warm and I notice the engine stops more! This is due to
brining in less fresh air so less engine heat gets used to keep the cabin
warm.

But the auto mode with higer fan speeds may force more warm air out
through the battery chute and warm it up faster.

So which is more important for economy? Warm up the battery as
much as possible first or minimize heat use from the engine to keep
it and the catalytic converter warmer? Cabin temperature can be
effectively the same either way till it gets really cold.

 

You CAN override the recirc and still maintain auto. I believe the idea is to bring in fresh air as much as practical for your health, than leave stale air in the cabin.

I also did an experiment. With ambient temps at 55 (please don't throw tomatoes!) I set the heat at 85. It took 30 minutes for fan speed to get down to medium. The center vents never came on, but the side ones did. I couldn't take any more of this after 40 minutes, and turned it off so it would naturally cool.
Also, with temp at 85, I was able to set EV. When EV is engaged at startup, no heat or blowers come up. Repeated after 1 mile of travel, EV still could engage, with whatever heat was retained in the coolant.

 

Hi Dan:

Even though it appears there is little I could actually do to service the car myself - asides from routine oil changes - maybe I should invest in the factory shop manuals. I already have Adobe Acrobat and don't mind working with pdf's.

I don't think an air-to-air heat pump would work very well in a cold climate, as those sort of heat pumps are notoriously inefficient in temps much below +20 F.

Unless I select Max Hot (Which isn't as Max as it should be) the ICE does shut down in traffic, though not as much as in more moderate temps. A small motor, combined with ICE shutdown, and you just don't get the heat you need at -30 C or colder.

I think I'll just resign myself to wearing a warm hat, nice mittens, and good boots. Thanks for the help though.

 

Hi Daniel:

At this point, I'm willing to try anything to keep warmer in city traffic. Maybe if I get my bum toasty warm, the rest of me will warm up? I've run out of options.

Since I spend +9 hours a day in a nice, usually overheated, office, I really can't try the longjohns. I'd just die with them on during the day.

The warm hat, good boots, and very warm mittens seem to work for now. Though with the mitties on, I have a very hard time getting the MFD to work.

Note that on the highway, just like you, after 15-20 minutes even at -35 C, I can take my jacket off and get really comfy. Since I spend 90% of the time in city driving, it's an entirely different story.

It should warm up soon. I'm guessing March.

Maybe April.

May at the latest. Though this year we had light snow in August. Hmmmm.

 

Hi Jayman,

I got the manuals downloaded to satisfy my curiosity, and it has allowed me to help others. I have always been one to take things apart, and I really have to resist doing that with my Prius. Well, it's not that big of an urge.

Yes, a small engine doesn't put out a whole lot of heat, especially when it doesn't run all the time. My tests were to answer the question about the dash vents not coming up in auto, and if EV is disengaged for heat.
I could not get heat to get to the point where the blowers automatically went to low, which is where the dash vents would probably go on.
Also from my tests, it seems in EV mode, heat is secondary. If there's no heat available, HVAC just doesn't come on to heat. If there is residual heat, it will come on, but EV will respond normally: EV off for acceleration, low battery or >34MPH.

 

Jayman: You must have a rest room where you work? If I have to, I go into the rest room to take my long johns off, and put them on again when it's time to go.

I don't drive with mittens, because I don't feel I am sufficiently in control. I use gloves. Oddly enough, while the medium gloves make it hard to operate the MFD, the heavy ones have stiff fingers which can poke the on-screen buttons quite nicely.

However, mittens would be much more cozy.

We had rain today! Nasty!