what happens when the battery bar goes purple?

Nothing unusual Guz, lots of people here have reported the same thing when going over a mountain pass. The willingness of the battery/electrics to boost power pretty much varies continuously with state of charge (SOC). When you've got 7 or 8 (green) bars then it's really willing to add some boost because it actually wants to shed some charge. As the SOC declines it gets more miserly about handing out electrical power and so makes the engine rev harder and work harder instead. Don't worry, that's what it's supposed to do and it wont hurt anything, some people say they've gone to zero bars over a pass.

Also, some people say they don't notice it, but I can pretty easily feel the difference between how lively the Prius respondes with say 7 green versus 2 purple bars.

That one could be a problem. Many people have reported that when their inverter is overheating (hot but not hot enough to actually give the red triangle or any other warning lights) that one of the first symptoms is that they lose cruise control. Have you had the inverter coolant pump replaced yet?

 

The color-change for the battery display was to make it easier to notice the various levels. That's it.

The added color for gen-2. With so many people having the panic feeling after seeing that, it was discontinued for gen-3. You'd think with so many disregarding the actual low-fuel warning blink, a simple color change wouldn't be that big of a deal, especially knowing the battery is supplied with electricity from the engine. Oh well.

I am surprised myself though that you hadn't ever seen it before. My home is near the base of a valley. So driving across it with the engine off, then climbing up afterward will cause the drop to 2 bars from time to time. It's never been a problem, even with the hard-acceleration required at the turn right before reaching the top.
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The Rocky Mountains are littered with dead Prius. Drivers get half way up one of those big inclines, the battery drops to zero bars, and that's it - a dead and useless Prius, never to be driven again.

It's gotten so bad that the state of Colorado has put on an extra fleet of flat bed wreckers just to remove the dead Prius. Not only are they unsightly, but they present a road hazard, since many of the mountain roads have no shoulder or verge.



I shouldn't have to say this, but obviously I'm kidding. First and foremost, a Prius takes care of its battery. As pointed out above, if you run down the battery you will end up driving more slowly, but nothing bad happens. On steep mountain roads I like to stay in the right lane and use the slow and steady approach, which generally ends up being faster than blasting up part way, then creeping up the rest with a low battery.

Tom

 

Actually, you can run the traction battery down so far that the car stops using it. There have been a few reports of people doing exactly that when they drive too fast up a long grade. No damage, but you're left with only the 76 HP gas engine to power you up the hill. When it happens, you'll have to join the trucks in the slow lane until the gas engine can recharge the battery enough to restore normal performance.

Towing a trailer at 80 mph up some of those grades in Colorado is just asking for it. It's probably why Toyota doesn't recommend towing with a Prius. The Gen3 has a more powerful gas engine than the Gen2, and thus is not as vulnerable to this situation.

 

As an FYI, per http://priuschat.com/forums/gen-ii-prius-main-forum/89320-advice-needed-2.html#post1254751, the 2nd gen Prius has FOUR coolant pumps.

 

Yes, but instead of saying 4 pumps I'd say 2 full time pumps and 2 part time pumps. Or you could say two high duty pumps and 2 low duty pumps.

For people in the south that heater core when engine off pump won't run much if at all.

And of course the turn car on / turn car off pump gets used more for short trips but less for long trips. Either way it only runs for a few seconds each time.

 

Thank you all for covering this issue. I had the same panicky feeling going over the Grapevine this summer. Can't they put something in the owners manual about this?!

 

They really should. Maybe it could just read "Just drive the damn thing and don't over think the system. We took care of everything."

 

It's an interesting that the grapevine is bad enough for this to occur. I drove up the grapevine at about 80 mph w/the AC on in my Gen III last month and I don't remember the battery getting down to 1 bar at all. I guess the Gen III's larger engine really helps.