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Car Forum / Toyota / Toyota Cars / January 2007More on Prius "EV" mode
To help inform future discussion, I have done another test of my Prius' "EV" mode. Some values here are guesses (reasonable ones, I hope) or are "roughly" where I could not obtain readings. * The car is a 2005 UK-spec "T4" model Prius, unmodified in ways liable to affect performance. (Eg, it has floor mats.) Seems to be in good condition. This model has "EV" (Electric Vehicle) mode. When engaged, by pressing a button, dashboard icon lights and car tries not to use petrol engine (limited by battery state and effort/speed being asked of car). * Weather: 7C (44.6F), overcast + enough drizzle to warrant the wipers on "slow intermittent". Good visibility. * Wind: Rain drops were falling at an angle to the vertical of 20-25deg. Assuming 25deg (for worst case) and that drops were moving sideways at same speed as wind and that terminal speed was 20mph, wind speed would be 20 * sin(25), or about 8.5mph -- not fast enough to worry about here. * The Course: A local road, more or less level but with gentle curves and local undulations (worst gradients 1:100). Reasonable surface but not truly "flat", except for last 100yards. Lack of other traffic allowed car to run without halting. * Battery: At start, main battery showed 6/8 charge. I do not know whether this was "barely 6/8" or "almost 7/8". (Datum: main battery never seems to reach 8/8 -- display turns green where 7/8 might become 8/8.) * The Method: I drove the car, from cold, some two miles to the Course. Pulled over and switched off all electrical loads except wipers. Reset trip meter (which measures in 1/10 mile). Pressed "EV" button: dashboard icon lit. Moved off gently and speeded up to 17-20mph, never exceeding displayed 20mph. After car had gone 1.0 miles, charge was 2/8. EV icon began blinking and dashboard sounded some "pips"; then car cancelled EV mode and switched back to normal mode. * FWIW: within a further 6 miles of unstressed steady driving at 50-55mph the battery was back to 6/8. HTH.  SignatureAndrew Stephenson So you got 1.0 mile at ~ 20mph between 6/8 and 2/8 charge. That's less than my prediction of 2 kilometers! I notice that the battery discharges a great deal overnight. Perhaps turning off the keyless entry system would save energy. Are there any other ways to preserve battery charge while parked? Too bad the battery pack is 288V instead of 220V, which would make it easier to charge from utility current with inverter. BTW, I found a Prius manual far superior to Toyota's Owner Guide. http://john1701a.com/prius/documents/Prius_User-Guide.pdf Like the Toyota manual, this says not to use B (brake/battery) mode because it lowers fuel economy. But then it says B mode is great for slowing down around corners when roads are icy. It also says that B mode has no advantage for energy recovery over braking. However I suspect B mode recovers more energy than coasting... The manual talks briefly about "glide" but says nothing about using N (neutral) mode instead of pedal-feathering. > ... > * Battery: At start, main battery showed 6/8 charge. I do not > know whether this was "barely 6/8" or "almost 7/8". (Datum: main > battery never seems to reach 8/8 -- display turns green where 7/8 > might become 8/8.) Our battery indicator turns from green to blue when 6/8 becomes 7/8. Are you saying yours doesn't turn green until almost 8/8? > * The Method: I drove the car, from cold, some two miles to the > Course. Pulled over and switched off all electrical loads except [quoted text clipped - 4 lines] > sounded some "pips"; then car cancelled EV mode and switched back > to normal mode. How much energy do you think the wipers use? > * FWIW: within a further 6 miles of unstressed steady driving at > 50-55mph the battery was back to 6/8. That's quicker than I would have expected, indicating more energy input from the gasoline engine than I thought. > So you got 1.0 mile at ~ 20mph between 6/8 and 2/8 charge. > That's less than my prediction of 2 kilometers! It would depend on so many factors. Also, bear in mind what I said, about not knowing exactly how full the "6th 8th" was. And how accurate are your predictions, usually? ;-) > Perhaps turning off the keyless entry system would save energy. Does one have the option? > Are there any other ways to preserve battery charge while > parked? Take your life in your hands by disconnecting the battery? When I parked it, last July, without special preparations other than a drive of about 30 miles, then went off to the US for four weeks, it showed 6/8 before and 6/8 after. Started w/o fuss. (Weather while I was away was reported _very_ hot for UK; and that should count as warm for anyone except maybe a Desert Arab on a camel.) > Too bad the battery pack is 288V instead of 220V, [...] I have good news for you. It's actually (nominally) 201.6v. Me, I wouldn't muck about with the onboard charger. (fizzbangouch) > BTW, I found a Prius manual far superior to Toyota's Owner Guide. > http://john1701a.com/prius/documents/Prius_User-Guide.pdf Ok, ta. (Must seek it out another time; it's my bedtimeZZZ...) > Our battery indicator turns from green to blue when 6/8 becomes > 7/8. Are you saying yours doesn't turn green until almost 8/8? I could be mis-remembering. That is my impression. > How much energy do you think the wipers use? No idea. Presumably they are standard, so someone else may know. > > * FWIW: within a further 6 miles of unstressed steady driving at > > 50-55mph the battery was back to 6/8. > > That's quicker than I would have expected, indicating more > energy input from the gasoline engine than I thought. There was only a slight indication that the battery was charging more than usual. Such recharges, IME, are not uncommon, so the system here handles them without fuss. Yours may be different. SignatureAndrew Stephenson >> Are there any other ways to preserve battery charge while >> parked? [quoted text clipped - 5 lines] > while I was away was reported _very_ hot for UK; and that should > count as warm for anyone except maybe a Desert Arab on a camel.) Um, yeah...there is a sequence of events you have to follow to disconnect the battery pack. If this sequence is not followed, the consequences can be dire. The tech at work knew what he was doing, but he always wore his gloves and if there was any question at all, he consulted the manual! Disconnecting the main battery pack connector can cause arcing, burns, electrocution, etc, etc... >> Perhaps turning off the keyless entry system would save energy. > > Does one have the option? Yes, on US models there's a switch under the steering wheel. The manual recommends turning off keyless entry when leaving the Prius parked for a long time. >> Too bad the battery pack is 288V instead of 220V, [...] > > I have good news for you. It's actually (nominally) 201.6v. Me, > I wouldn't muck about with the onboard charger. Aha, another poster said 288V. Newsgroup reader "SMS" just posted a link to some PDF file describing how to install "EV" mode on US models of the Prius. Doesn't sound worth it, from your experiments. Maybe if I lived in an apartment building with underground parking garage... >>> Perhaps turning off the keyless entry system would save energy. >> [quoted text clipped - 3 lines] >The manual recommends turning off keyless entry when leaving the >Prius parked for a long time. Ahh, I'll file that one away for reference - because you KNOW that some guy at a Car Wash is going to bump the switch and the Owner is going to freak that "It won't work, I keep hitting the button on the fob but I can't get the car to unlock!" First, pop the hidden key out of the fob. Second, open the car door with the key. Third, check that switch... >>> Too bad the battery pack is 288V instead of 220V, [...] >> >> I have good news for you. It's actually (nominally) 201.6v. Me, >> I wouldn't muck about with the onboard charger. > >Aha, another poster said 288V. Just like a car "12-volt" battery is 12V to 12.5V at rest and 13.8V to 16V while under charge. I'll bet you get 201V at rest when the engine is off, and the maximum system voltage while charging the battery string is 288V. One of the oddities of batteries. With the electronic motor drive controls, making 180VAC 3Ph to run the motors is a drop-dead easy task, basically an Off-the-shelf Variable Frequency Drive design. Making pseudo-Sine-wave output isn't that much more work, and then you can use regular industrial motors that are "VFD Rated" >Newsgroup reader "SMS" just posted a link to some PDF file >describing how to install "EV" mode on US models of the Prius. >Doesn't sound worth it, from your experiments. Maybe if I lived >in an apartment building with underground parking garage... No, Stealth Mode is for leaving at odd hours when you know the next- door neighbor is sleeping behind the paper-thin wall 10 feet from your driveway parking spot. He'd reciprocate, but his car is a Dodge pickup with a Cummins. ;-P --<< Bruce >>-- > >Yes, on US models there's a switch under the steering wheel. > >The manual recommends turning off keyless entry when leaving the [quoted text clipped - 4 lines] > going to freak that "It won't work, I keep hitting the button on the > fob but I can't get the car to unlock!" Nice to know, but realize that this is ALSO covered by the owner's manual. No real need to file it away for future reference just from a mention here. > With the electronic motor drive controls, making 180VAC 3Ph to run > the motors is a drop-dead easy task, basically an Off-the-shelf > Variable Frequency Drive design. Making pseudo-Sine-wave output isn't > that much more work, and then you can use regular industrial motors > that are "VFD Rated" What's 3 Ph, three phase AC? If that's it, why do you mention it in the context of DC batteries? Just trying to understand. > No, Stealth Mode is for leaving at odd hours when you know the next- > door neighbor is sleeping behind the paper-thin wall 10 feet from your > driveway parking spot. > He'd reciprocate, but his car is a Dodge pickup with a Cummins. ;-P LOL. >> With the electronic motor drive controls, making 180VAC 3Ph to run >> the motors is a drop-dead easy task, basically an Off-the-shelf [quoted text clipped - 4 lines] >What's 3 Ph, three phase AC? If that's it, why do you mention it >in the context of DC batteries? Just trying to understand. The converter electronics in the engine compartment turn the DC battery power into 3-Phase AC power to run the big electric motors. Not sure whether it's chopper-style switched square-wave or pseudo-sine-wave, though PSW is a lot quieter. Just brought it up to point out it's nearly OTS industrial motor drive electronics. They just repackaged it for use in a car, and designed computer controls to make operation nearly seamless for the driver used to a conventional automobile - "Turn the key and go." --<< Bruce >>-- > >> Perhaps turning off the keyless entry system would save energy. > > [quoted text clipped - 3 lines] > The manual recommends turning off keyless entry when leaving the > Prius parked for a long time. I shall try to remember to look, next time I am under there. May be handy, one day. Could be T gave the USA that switch and EU/JP the EV as market research and are following these threads avidly. :-) OTOH, battery charge loss truly was not an issue, over those four weeks starting in July. SignatureAndrew Stephenson >>> Perhaps turning off the keyless entry system would save energy. >> Does one have the option? [quoted text clipped - 13 lines] > Doesn't sound worth it, from your experiments. Maybe if I lived > in an apartment building with underground parking garage... It probably isn't worth it, since the distance that the Prius can go on battery power is so limited, even with the deeper discharge. I read that the third generation Prius (2009) will use Li-Ion batteries, and hopefully they will offer an extended-range plug-in option with higher capacity batteries and a home charger. Geez, just 20 miles of range on electric would have a huge impact on gasoline consumption for most people, especially if businesses provided chargers, as some did for the Saturn EV-1. >>> Too bad the battery pack is 288V instead of 220V, [...] >> I have good news for you. It's actually (nominally) 201.6v. Aha, here is our answer. The original Prius had a 288V battery pack, while the second-generation (HSD) Prius has a 201.6V battery pack. http://john1701a.com/prius/documents/Prius_User-Guide.pdf (last page) > * Wind: Rain drops were falling at an angle to the vertical of > 20-25deg. Assuming 25deg (for worst case) and that drops were > moving sideways at same speed as wind and that terminal speed was > 20mph, wind speed would be 20 * sin(25), or about 8.5mph -- not > fast enough to worry about here. I think the formula should be "20 * tan(25)". The wind was a bit faster, about 9.3mph. IOW still slow enough to not be a problem, especially for a Prius with its drag coefficient of 0.26 approx. SignatureAndrew Stephenson |
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