Power Loss in Mountains: SOC Wild Swings: Batt vs VVT (Gen 2)

Just returned from 4-day trip through Northern California in my 2006 Prius and about halfway through I became obsessed with the State of Charge...SOC...on the MFD. So much so, it turned a 7-day trip into a 4-day trip. Muy malo. Specific details will be in the next post in the thread, to help manage replies.

Problem: The SOC was swinging from 1 purple bar going uphill to 6 blue bars going downhill and back again within minutes/seconds, which I had never experienced. Q: Is this in any way normal/acceptable?

Note: *Traveling speed* wasn't really an issue. I was able to maintain whatever speed I carried into the hill/grade (commonly 65, 70, 73mph) and was still able to accelerate if needed (unless/until there was only 1 purple bar) if less than 73mph...worst case was stuck at a certain speed until a flat/downhill area where I could increase again...I made it home safely and SOC returned to 6-9 blue bars on SoCal freeways. I don't feel the wild swings are normal when long mountain passes/grades are involved, but I've never done them for days on end (just once over the Grapevine and back a week later every now and again). It's my 2nd Gen 2 (bought 1st in October 2003), this is 1st time I've freaked out about SOC. I could *feel* the problem first, verified by MFD/SOC screen.

My research focus:
Q: Is this an indication I need another traction battery rebuild-replacement?
Q: Is this a problem that grid chargers solve?

While researching the issues I experienced, this thread about the VVT caught my attention. I've never heard of a VVT, but the title and the description in the post seem to hit the target. I will replace the VVT either way, but still have the Q's/thoughts about realistic expectations for the battery that's been sitting unused and has experienced these wild swings.
No power on hills, MPG down, SOC low, PROBLEM FIXED | PriusChat

The current battery is rebuilt, installed in early 2018, but about 2 months after it was installed the car sat unused until last month. So I'm wondering about the pitfalls of a ("better quality") rebuilt battery in a car sitting unused for a couple of years.

MPG for trip: 38.3mpg overall after 1300 miles, was at 47mpg after Grapevine near beginning of the trip, 42mpg when I noticed "the change" halfway through and it continued to drop from there. Still good, by my standards.
*

 

Symptoms: As I pulled into the McArthur (logging roads//Forest Service/BLM) area North of Burney Falls I knew something was wrong with the power/speed/acceleration. The engine was howling and power was low. I nonchalantly checked the 'energy' screen and there was only 1 purple/pink bar! I was sitting still and it was not charging. I put the car in 'park' and sat there, nothing changed...1 bar. Turned on/off AC to see if I could get some energy flowing to start battery charging, nothing. Ugh. Nonchalant gone. I've never seen 1 bar before, although it's possible It has happened...I don't know because I don't hawk the energy screens.

So I'm alone in the middle of nowhere about to go up logging roads (to test out my new PriusOffroad lift kit) and nobody will find me for days if something happens. No cell signal for many miles, so checking the internet was out. I bit the bullet and turned car off, back on again after a minute. ICE came on and then started charging...up to 2 purple bars and that was it. Ugh. So the system was working to that extent.

I decided to try to force some more charging and drove back and forth on a relatively flat part of the road nearby, which worked. At 3 blue bars, I decided to go for it and took a drive up some logging roads and took some pics/videos...it was relaxing. The SOC fluctuated from 2 to 3 bars, purple/pink to blue and back again.

From then on, it was easy to tell when the SOC dropped to 1 or 2 bars...the engine got loud and the gas pedal far less responsive. I got to the point I could tell when the grade was up or down (even pretty slightly) by listening/pedal response, verified by checking the SOC on the MFD. Very quick response from 1-2 bars to 4-5 bars...minutes at the most, maybe a minute per bar added and less than that to lose bars going up-grade...from 5 blue bars to 1 purple bar in 1 minute. This is where the "Would this be a lot different with a new/better battery?" question boiled up.

I remember going over the Grapevine (I-5 SoCal nightmare 6% grade) over the years in both of my Gen 2 Prii and hearing the engine louder at times...and wonder if I had been checking the SOC if I'd seen only 1 purple bar every time and this is completely normal, or am I experiencing something bad like I think is happening?

After I made it out of the mountains, it's blue bars all the way. Driving freeways the last 2 hours home it went up to one-less-than-all blue bars (9? It's the same/highest this rebuilt battery has *ever* shown, other than turning the same number of bars green for short periods of time).

Over the next week or two, I'll see if my theory about it working fine unless it's going up long mountain grades/passes is correct. If SOC stays blue/green I'll go back over the Grapevine to see what happens to power/battery and SOC/MFD. It will be helpful to know what a regular Gen 2 with decent battery does over long mountain passes for days as a baseline, for sure.

MPG for trip: 38.3mpg overall after 1300 miles, was at 47mpg after Grapevine near beginning of the trip, 42mpg when I noticed "the change" halfway through and it continued to drop from there. Still good, by my standards!

 

Prices/availability of VVT:

Amazon won't ship me one in California! No $25 parts for me.

The Red Bullet site says they're rehashing everything, left them a message to see what that means.

Local parts stores carry the most expensive aftermarket part only...about $85...could buy today.

Toyota OEM online is about $85, plus shipping.

 

I guess the question I forgot to ask is "If it runs fine and stays in the blue bars most of the time, and gets down to 1 bar on the SOC when I go over mountains every now and then, am I doing anything bad to the car other than lowering gas mileage?"

The replies so far have been helpful, thanks.

 

It had a 3-year warranty, but that was 3 years ago.

 

Thanks!

 

This is good information, thanks. I think the reason I noticed it this weekend is because it didn't use to act like this, but I haven't done these sustained mountain passes. Heh.

These were substantial mountain passes, I'm hoping to get more feedback from others, too. Thanks again!

 

This is a very helpful reply, thanks!

 

Just tried this several times from 5 bars and from 6 bars. 1 bar dropped either way and was pretty quickly recovered when I backed off at 60.

 

This is a prudent suggestion, elegantly simple. Thanks!