Ah, so this is what a frozen battery feels like

[Bob64]

Originally Posted by JimboK

I find myself actually approaching red lights rather quickly to allow time to stop for the S4 idle routine; normally I time them to avoid stopping.

Yeah, except with my commute, its trying to find a huge buildup of traffic on the highway to permit a 7 second stop.

If I don't go into stage 4 before I hit the highway, I'm usually screwed in terms of "record-breaking" mpg. Plus daylight savings time also dents my mpg because of battery drain (from headlights). I hate winter :/

Personally I don't care much if the ICE starts easier, it's the idling at speeds below 35 that really annoys me. Theres got to be a way to tell the prius that I'm traveling at 0mph while rolling along traffic at 20mph.

For those of us that try not to use the battery, the "lack" of battery output isn't much of a concern too. It's the lack of regeneration - but that can be mitigated by doubling my normal brake distance and halving my brake pedal pressure.

Also gotta worry about all the stuff on the roads... sand, and the possibility of black ice has me curbing my normal "kamakaze" 90degree turns to a mild 16mph instead of a death-defying 30mph.

Can't wait till the summer. I think I'll try to stuff some insulation under my hood like what hobbit has done....

[Mjolinor]

Originally Posted by Bob64

I think an O2 sensor only reports oxygen content.... otherwise it'll be called a temperature sensor.

I guess I'm going to have to start using the heat more often then. No point in wasting it by letting it radiate away.

Anyone know what temp the radiator fan start turning on?

A lot of O2 sensors report basic temperature as in "warm enough" or " not warm enough" as they do not work until they are warm.

[Rokeby]

FWIW, you may be able to get "catalyzer" temps on a Scangauge.

These are reported as being untested, and I don't know the difference
between the two. Here are the codes:

Temp1
TXD 07E0013C
RXF 0441053C0000
RXD 2810
MTH 0001000AFFD8
Name Ct1

Temp2
TXD 07E0013E
RXF 0441053E0000
RXD 2810
MTH 0001000AFFD8
Name Ct2

I think I got these over at CleanMPG.com, but now I can't find them there.

[dogfriend]

Originally Posted by Bob64

Anyone know what temp the radiator fan start turning on?

I have a copy of the 2004 manual that indicates that the fan(s) should turn on at approx 100°C and turn off again at approx 98°C. I don't know (but I doubt) that it is different for later models. That section is missing from my 07 manual.

I have never seen a temp above 93°C on the Scangauge and I have never heard the fans turn on on my car. I don't do any grille blocking.

[efusco]

Originally Posted by Mike Dimmick

Turn the blower on yourself, and you should get the assistance of the electric heaters in the heater core and footwell, if the engine coolant temperature is below 55 celsius (and your car has them - apparently only fitted in 'cold regions'). There are a pair of PTC HTR relays in the centre relay box in the engine compartment, and corresponding 30A fuses in the right-hand-side (as you stand in front of the car) fuse/relay box which control the two heaters in the heater core, and a PS HTR relay next to the PTC HTR relays and a 50A fuse that control the footwell heater.

There's no point freezing to death in the car - turn the heating on and it will warm up the HV battery at the same time it warms you up. Battery chemistry is subject to temperature.

This chart comes from Panasonic EV Energy's webpage:



At a comfortable 20 degrees Celsius, the specific power is more than twice that at freezing temperatures (0 Celsius) and four times that at -10 degrees C (14F).

Much like the catalytic converter pre-heating, it's a trade-off between consuming more fuel immediately after starting up for better economy later on.

Can't believe this is the first time I've seen that graph...and it's exactly on target with my experience. The times my car's sat out in the cold long enough for the battery to drop to a below freezing temp the response was terrible....almost non-existant....and it takes forever to warm back up b/c of the thermal properties.

Keeping the battery over 40-50F, even if the ambient temp is much colder, has a huge improvement on performance and fuel economy.

[Shawn Clark]

In a recent discussion about battery performance in cold weather in a regeneration thread these graphs were posted. What I gathered in discussion with Ken is that the batteries will have to warm from being charged/discharged. And there won't be much discharge because you can't draw many amps from the cold battery...so that means that charging seems to be serving as the battery heater. It's a pretty large efficiency loss until the battery heats to a reasonable operating temp.

I suppose this explains the characteristic of the ICE merrily charging the battery well into the green even with the grill mostly blocked.

[JimboK]

Another observation that relates to this thread:

I was out of town on business last week. The car sat for several days in the parking lot before I headed home, so it had a good cold-soak. I hit the road Friday morning, straight onto the highway, with HV battery temperature at 32F. I had a passenger, so I ran the cabin heat. She had a coat on and I had an insulated vest on, so I didn't have to run it too hard to keep us comfortable -- thermostat temps in the low 70s. That's still considerably warmer than I normally keep it. After about 20-30 minutes on the road the HV battery temperature was still 32F.

This demonstrates how ineffective a warm cabin is in warming the battery. I really didn't see any appreciable warming until a little later in the drive when I had the opportunity for regeneration and lower-speed pedal-feathered EV mode.

[orange4boy]

I have two things to say: Block heater and battery heater.

Block heaters make a big difference in warm up time and they are easy to install on the Prius.

Battery heater could be a heating pad under the battery or around it. They make these for lead acid batteries and two of them would cover two sides of a Prius battery. Under would be better but harder to install. Then to keep the heat in, insulation. Just take it out in the warmer months. Foam is best. Light and easy to cut.

Even with the Prius as good as it is there is still lots of room for improvement.

[JimboK]

Originally Posted by orange4boy

I have two things to say: Block heater and battery heater.

Block heaters make a big difference in warm up time and they are easy to install on the Prius.

Battery heater could be a heating pad under the battery or around it. They make these for lead acid batteries and two of them would cover two sides of a Prius battery. Under would be better but harder to install. Then to keep the heat in, insulation. Just take it out in the warmer months. Foam is best. Light and easy to cut.

Even with the Prius as good as it is there is still lots of room for improvement.

I (and others in this thread) have a block heater. It does nothing to warm the battery.

Others have discussed a battery heater of some sort. Between the unanswered questions (see my quote embedded within the OP of that thread) and the rarity (for me) of driving conditions like those described in this thread, it's not worth it. On a more typical winter day the battery behaves fine and there would be no benefit to preheating. On such days the fuel economy hit caused by cold car parts is mostly from a cold ICE.

[Philosophe]

Originally Posted by orange4boy

I have two things to say: Block heater and battery heater.

Block heaters make a big difference in warm up time and they are easy to install on the Prius.

Battery heater could be a heating pad under the battery or around it. They make these for lead acid batteries and two of them would cover two sides of a Prius battery. Under would be better but harder to install. Then to keep the heat in, insulation. Just take it out in the warmer months. Foam is best. Light and easy to cut.

Even with the Prius as good as it is there is still lots of room for improvement.

It would be interesting to see some empirical evidence that there is a business case to add a battery heater (additional cost in electricity vs reduced cost in gas).

Note: Depending on your grid power source (hydro, nuclear, coal/petrol), you could decide if you still want to heat the battery even if it costs more in $$$ (to globally save on non renewable energy sources).

I tend to think that the ICE block heater does more than a battery heater would…