There is an 8th battery segment!!

I found it interesting to see how easily our V climbed the mountain going in a Westerly direction! Maintaining the 55 MPH limit was effortless.

 

I feel like it's a good idea to shift into B mode manually before the car does so. I also run the A/C higher on long downhills. Both keep the batteries a little cooler, which increases lifespan. I traverse mountainous terrain all the time, and that 8th green bar is lit often. I wish there was a drogue chute I could deploy.....

 

I agree... The appeal of having more power due to a fully charged (80%) HV battery led me down a path where I had two instances of the battery spontaneously losing 3 or 4 bars of charge, which is the very first warning sign of HV Battery failure. So I learned my lesson and now as soon as I get to 8 bars I prevent the battery from charging any further. Sometimes on really steep hills I use B mode, but mostly what works for me is a technique I like to call: brake and glide...

I also have found that using full EV mode with 8 bars to cool things down puts too strong of a drain on the battery when its most vulnerable, so I don't do that anymore either... Here's the details of it that myself and 'uart' in Australia have experienced: Why is engine still running at 8 bars charge? | PriusChat

 

Yes it does... That's why the car won't charge more than 80%... Also likely why they removed EV mode in the GenII in USA version, which in some states require a 150k mile warranty on the battery.

In general, Toyota does a great job at taking care of itself and if I wasn't watching all my instruments like a hawk I'd of never even knew this problem existed, nor would I of exacerbated the problem by goofing around with overusing the battery. And the car is at 117k and the battery will likely last beyond its 150k warranty as long as I take good care of it by not overusing it.

So it's better to see these battery care efforts as additional preventative measures. So to recap the ways to extend life of your HV battery:

1)Make sure the car isn't shut down when battery is at full charge (80%) especially if cooling fan hasn't had a chance to work long enough on a hot day. Most people on here recommend running the AC and headlights till you get the battery back down to 7 bars. Draining the battery down to 7 bars really fast via EV mode, might be counterproductive in this regard because a fast discharge creates more heat.

2) Driving in warm weather and not using the AC may get you better gas mileage but it makes your battery run hotter, which shortens the lifespan of the battery.

3) Don't drain your battery down really fast in EV mode very often. (Note: GenIII Prius have a better management process in EV mode that largely addresses these concerns so you don't have to)

4) When driving don't be inspired to keep your battery charge in Green (7th&8th bar) instead of blue because you'll end up fully charging the battery more often and when you do this it makes for more heat, which as said before ages a battery faster. It's important to always have a battery discharged enough that the next long downhill recharge happens for the duration of the downhill section rather than just the top part of the downhill section.

5) If you think you're smart enough to not kill yourself while working on a high-voltage battery make sure all terminals are kept clean and corrosion free and also check volt levels and makes sure bolts on each battery cell aren't loose.

6) Torque app and I believe Scan Gauge can give you readings for each cell in the HV battery pack. If one cell starts to go you can save the rest of the battery from dying on you by getting that one cell fixed right away. Of course until the car throws an error code, Toyota isn't going to replace the HV under warranty. Though one very persistent Prius chat person did get a new battery without an error code, so it is possible.

PS: I'm still a newbie and the last couple items on this list I don't have firsthand experience with! I hope someone more experienced than I can look thru this list and correct any errors, omissions or inaccurate statements.

 

As amazing as all the software is, that works together to make the car go, it is not necessarily perfect. I think they make things work well enough not to have excess warranty issues. But there are reports of smells generated by the HV battery getting warm, for ex. Prius battery exploration (about 2/3 of way down the page). I've also smelled this after a long downhill run when I first got the car. While it looks not to be a problem, I still feel, and this is just my opinion based on 30 years of living from battery power, that the cooler the better ( up to a point ). So I manually use B mode even though it does rev the engine a bit more. Most Prii are not running up and down mountains regularly.

 

I think that the Prius generally does a good job of protecting the battery, but there's one time that it cannot do so, and that's when the Prius is off. I think that my battery has been somewhat damaged by parking it in the hot summer sun with 8 green bars. Unfortunately it's very hilly around here, and many of my journeys end at the bottom of one of those large hills, with 8 green SOC showing. In this high charge state the battery can give off a fair bit of heat, but if you park then the cooling stops but the battery temperature can keep rising!

I had a few instances where I did this and when I returned to the car an hour or so later the battery fan came on full blast and the Prius acted kinda funky (running the ICE all the time, really poor MPG, lack of EV capability and general symptoms of an overheated battery) for the next 30 minutes or so.

After having this happen a few times last summer I'm definitely noticing a loss of capacity of my battery. Eight green bars comes up a lot more quickly now than it used to do when I first got the Prius. Actually I see 8 green bars pretty much on a daily basis these days.