Prime Battery, how low does it go?

Today I took my PPPXP (Pretty Prius Prime XSE Premium) from Denver over the continental divide (5,000 feet to 11,000 feet). BTW, it was a dream driving it, it felt like it never really even broke a sweat, I'm sure I could have gone a lot faster than the speed limit, but hey, I'm still a Prius driver!

In my Gen1, that hill was a traction battery killer for good reason, the final 6+ miles is a continuous climb at interstate speeds. For the Prime I was clearly in HV mode well ahead of the final climb, so was expecting it to get drained too. It didn't! With my previous limited driving in HV mode on littler hills, I've never seen the charge level on the traction battery get to less than about "3/4" of the HV range on the battery indicator. There aren't tick marks, so it is hard to guess. Even with this big nasty hill, it still never got below that level.

Hence the question for others: Have you ever seen the battery get lower than roughly 3/4 of the HV range on the battery? If so, what were the circumstances?

Given Toyota's super-conservativeness on battery maintenance, I can see them not letting it get close to zero since they can control when the ICE comes on. I'm certainly not complaining either, my Gen1 lasted 20 years and 220,000 miles on the original battery and I still gave it away in good working order.

will

 

Mr.Vanvandenburg: Good point on when manually switching to HV mode. For this time I was just in auto EV/HV which meant it drained the battery down to the 0% EV line, then switched to HV mode. From then on mostly stayed at at that line (0% for EV, 100% for HV) until the big hill, then only dropped by about a quarter of the HV capacity. On my older car that hill would completely drain the (only) HV battery capacity. Hence the question on what other folk have seen, does the car just keep the battery close to that EV/HV transition level or does anyone ever see it go much below it?

will

 

HacksawMark: Yea, that was the cool part, even with it 1/4 below the EV/HV threshold at the top, I got back up to 16% at the bottom of the hill in Silverthorne. That wasn't quite enough to get me to Keystone (another 1,000 feet up), but a good part of it. In my Gen1 the battery would fill fast then just resort to engine braking for the rest of the decent. That always bugged me, wasting all that energy. Not so with the Prime! I head back to Denver today, so curious if I will do any better. I suspect not given there are two hills to descent that don't seem as steep with a lot of level driving in between.

will

 

HacksawMark: On the drive back to Denver I only got up to 8% charge, but twice. First on the initial hill by Loveland pass, drained the battery again and back up to 8% on the final hill down to Denver. See "Primed at 12,000 feet" post too!

 

While trying some acceleration tests with the car, I actually got the car to show only about a half charge on the HV part of the scale! Before that I've never seen it more than a few pixels below the EV/HV separator. The circumstances take a bit of explaining though...

There is a hill on I-25 from Colorado Springs to Denver that is a nice incline, perfectly straight, a bit over a mile long and has extra lanes mainly for trucks. Since long before I even got my Gen1 Prius, this was my "test hill" where I could compare my cars. At the bottom of the hill I go 65MPH, then just floor it and see how fast I'm going at the top of the hill. For my Dodge Colt and Toyota Tercel, I was lucky to maintain 65MPH! For my Gen1 Prius I could get to 85 if the battery didn't conk out, otherwise it was 65. My wife's Gen3 Prius V could get a bit above 85, but not 90. For the PPPXP I don't know because I keep on chickening out. At first it was 90 as I thought the tires were only rated to 85, but after some friends explained how to read tire codes, the stock tires are 130-ish (forget the exact speed).

Knowing the tires were OK, I re-ran this test a few days ago, but this time chickened out once I saw a 3-digit speed! However, for the purposes of this thread I also noticed that the battery gauge showed half the HV charge gone! I started the trip in Denver, so had depleted the EV range on the drive to Colorado Springs. For the drive back I was already in HV mode and at the bottom of the hill it was right at the EV/HV separator. So, if you have a case where you are asking for a lot of power for an extended period of time, the car will indeed drain a lot of the EV charge.

On my Gen1 and wife's Gen3, that hill is long enough that unless I start with nearly a full battery, it won't last until the top of the hill, so if this hill only drains half of the battery on the PPPXP, that correlates pretty good to the extra capacity they have in the Prime vs the older HEVs. However, unless doing whacky experiments like this, the car clearly prefers to use the engine over the battery. Fine with me, just an interesting observation. If driving normal highway speeds up the hill, the battery gauge barely budges below the EV/HV separator just like anywhere else. That includes many MUCH longer hills like over the continental divide. At regular steady speeds, I guess there is no need for extra battery power. Definitely NOT the case for My Gen1 or wife's Gen3, they needed electric power just to maintain speeds at those inclines.

"But officer, I was conducting important scientific data gathering!"

will