I testdrove a Prius recently (my second test). The demo car was parked outside and it was VERY hot that day. While waiting at a traffic light in town I attempted to engage EV mode. The computer just refused. Tried several times afterwards and still...nope! <_< Question...Under what conditions will EV mode NOT engage?
I got this from Darell's website, which has a translation from the Japanese manual... In the following conditions, the "EV" drive mode may not be turned on. In this case, the message appears on the multi-information display and a beep sounds. -The hybrid system gets hot. (after the vehicle is left in hot weather, after driving on the slopes or high speed driving etc.) -The hybrid system gets cold. (After the vehicle has long been left below 0 C (32 F).) -During gasoline engine warm up -The hybrid vehicle battery assembly charging level is 3 or lower. -The vehicle speed is about 45 km/h (28 mph) or over -The accelerator pedal is depressed strongly or on the slopes. -The defroster is in use
Usually once the battery gets to around 110 degrees F you'll start to encounter difficulty engaging EV...the increased draw EV mode would cause would make the battery temp go even higher risking potential damage. So, it won't let you engage.
You say it was an unusually hot day. I assume the AC was working hard on this test drive to get the temp down? When the AC works hard it is hard to get the PRIUS into EV mode for two reasons. One is that the battery (in the same compartment as you are) might be to "hot" (see efusco's post) so won't be used. Blasting the AC also drains the battery quickly which will start the ICE much sooner.
<div class='quotetop'>QUOTE(aaf709 @ Mar 14 2007, 08:00 PM) [snapback]405492[/snapback]</div> The most likely cause was that the hybrid system was hot. The car has been standing outside in 35C weather. I didn't have the aircon on, just the fan and the windows were slightly open. It's good to know that the Prius will NEVER allow any action, that has even the slightest potential to harm the battery. By the way the battery was almost full when I tried to engage EV. Funny thing is, if I did have the AC on and the cabin was say 18C, the battery would have been cooler. Maybe then it would have allowed me to use EV mode. Stupid me.... :blink:
<div class='quotetop'>QUOTE(Albertus @ Mar 14 2007, 11:39 AM) [snapback]405537[/snapback]</div> Apparently another time EV won't engage is if the SOC% is to high. If you've gone down a long hill and the bars are all green, and are going slow enough, etc. that EV should otherwise engage it won't. I'm not sure of the percentage, but I think it's about 67% or above that EV is prevented. That I don't understand. Dave M.
Dave, if the traction battery is all green, perhaps slightly overcharged, the Prius spins the ICE without gas or spark to simply dump the excess charge. This condition usually only occurs after a long down hill run where regenerative braking has completely turned the battery icon green. Sometimes it cycles the ICE on and off. It was very confusing to me the first time it happened. I thought, "Why is the ICE running when the battery is full?"
<div class='quotetop'>QUOTE(Bill Merchant @ Mar 14 2007, 10:53 PM) [snapback]405912[/snapback]</div> Bill, it still doesn't completely make sense to me. Why not just use the electric motors to dump the charge in driving the car? Dave M.
Probably because there's no AI in the car... yet. If there's a threshold above which the computer is not allowed to retain charge in the battery, then it will do whatever it can to get rid of it. It doesn't know whether you plan to continue braking, or save up *just a little more juice* for that long EV stretch, so it just takes a dump.
<div class='quotetop'>QUOTE(dmckinstry @ Mar 15 2007, 02:47 PM) [snapback]406028[/snapback]</div> It does, normally. But if you're not moving, or are decelerating, that's not an option. It'll hold off as long as it can, but when the charge has to go, it's gotta go.
<div class='quotetop'>QUOTE(dmckinstry @ Mar 14 2007, 10:19 PM) [snapback]405901[/snapback]</div> I'm not so sure the SOC being too high would prevent EV mode. I have gotten EV to engage at 80% SOC, but haven't tried for anything higher.
<div class='quotetop'>QUOTE(Presto @ Mar 15 2007, 11:08 AM) [snapback]406164[/snapback]</div> Hmm? Maybe it has to do with battery temperature. I'm just taking a shot in the dark. Dave M.
What is the internal resistance of a fully charged battery? Let's consider the following: A nearly full battery, when charged at a constant voltage, draws little current. High internal resistance. Right? If you then go and draw 100amp through that high internal resistance won't it dissipate more heat? That MAY answer why no EV when battery FULL. <_<
<div class='quotetop'>QUOTE(Albertus @ Mar 15 2007, 02:53 PM) [snapback]406321[/snapback]</div> That's just the going with the assumption that one of the EV operating parameters depends on the SOC being below a certain value, but there is still uncertainty if there is indeed a max SOC value that prevents EV from engaging, since EV can still be engaged at 80% SOC. Temperature (battery, inverter, etc...) is likely the issue.
<div class='quotetop'>QUOTE(Albertus @ Mar 15 2007, 02:53 PM) [snapback]406321[/snapback]</div> "Normal" batteries have lower internal resistance when fully charged. I don't know about nickel metal hydride though. On the other hand, if already heated up from charging, the internal resistance may be higher. I'll have to look at that specifically the next time I'm on a long downhill run. Dave M.
<div class='quotetop'>QUOTE(Presto @ Mar 15 2007, 01:08 PM) [snapback]406164[/snapback]</div> I have engnaged EV with all but the last green bar. Interestingly enough, I had a real hard time getting EV engaged on Saturday. It was mid-80s (F) and I had not been working the Prius that hard. I knew about the lower temperature limit but was unaware of the higher limit. Perhaps that was the culprit.
<div class='quotetop'>QUOTE(Albertus @ Mar 14 2007, 10:39 AM) [snapback]405537[/snapback]</div> Operating the air conditioner will help cool the battery, but it will take a while. Unless you took a very long test drive, I think it unlikely that the A/C would have cooled the battery enough to allow EV mode. <div class='quotetop'>QUOTE(Albertus @ Mar 15 2007, 01:53 PM) [snapback]406321[/snapback]</div> The current drops as the battery approaches fully-charged, not because of rising internal resistance, but because of declining voltage difference between the battery and the charger. As the battery approaches full, the voltage of the battery approaches that of the charger, and once there is no voltage difference, there is no current flow. I've only taken one trip through mountains since installing the CAN-View. But my experience was that, when the SOC was extremely high, it wanted to go into electric mode. I did not try to engage EV mode, but I saw long periods of so-called "super-stealth" (very poor term, in my opinion) where even driving uphill at constant speed over 42 mph the energy was all coming from the battery, and none from the ICE. Perhaps it will deny EV mode, but it should be extremely easy to go into electric mode without the use of the EV button.
It happened again today. No EV mode available, no triple beeps to indicate it would not/could not engage. Temps today were in the high 60s and it was misty. It would not work at lunch or after work today. Any more thoughts? SOC was displaying all but last green bar.
