Could I have reconditioned my battery on a long highway drive?

I just finished a multi-day, 1000-mile drive through the Rocky Mountains. Every day I climbed two or three major grades of up to 6000' gain. Now I notice the battery seems to have better capacity than when I left home.

I bought this 2007 Prius one year ago with 100,000 miles and I noted then that the traction battery was in excellent condition, as compared to another '07 with more miles I traded in. But I've only driven the car 5000 miles since then, and have noticed a gradual but not alarming drop in storage capacity. I drive in foothills enough to gauge how it's doing.

I looked at the battery with my Mini VCI before I left home (no codes). Max delta V was in the 30 millivolt range, and internal R values were exactly equal. It looked good to me, so I didn't worry about the trip. But on every climb that first day, the SOC would drop from all bars to none within 500 vertical feet, too fast for my liking, then the ICE would pick up the load. Same on the descents, very rapid recharge rate, climbing though all the "blue bars" in less than one minute in "B" mode. I never heard the cooling fan.

The second day it acted a little better. Third day, it seems to be just like it was when I bought it a year ago. I climbed a 2000' grade today, sections up to 6%, without completely draining the battery.

Is it possible I reconditioned the battery on this long highway trip with repeated charge cycles? Is there a lesson here for battery longevity? Thanks for your thoughts, for reading through this long post, and happy Thanksgiving.

 

Yeah, I read in the threads about it taking a weekend or so. I did have some unusual charge/discharge cycles on this drive, like a 45 mile slight climb into a stiff wind where it stayed at one purple bar the whole time, followed by charging into green over a half hour on a long descent in to valley.

Actually, around town it seemed okay. But to be fair, it didn't get driven around town very much in the past year, less than 200 miles/month. The car would often sit idle for over a week at a time, probably not good for it from what I've read on other threads.

I was just thinking of starting to research the chemistry before investing in the grid charger. But after this last trip, I'm starting to think like Patrick.

 

HA is Hybrid Automotive. The company sells a high voltage DC smart charger for the traction battery. There's a recent thread on some experiences using it to recondition the battery.

You'll see at least one skeptic on this site. I'm tempted to try it, but I'll probably end up putting that money into the new battery fund. My recent experience tells me the car's charging system does a fairly good job. But I had access to driving conditions than many do not have, so there may be a market for the charger.

One of the reported failure modes is a bad cell, leaking electrolyte, and charging will not fix that.

Good mileage is a reflection of many things. Even a poor 12V battery can affect mileage. But if you're consistently getting 50 mpg it sounds like the car is in good condition overall.

In my limited experience, a failing hybrid battery will show rapidly fluctuating state of charge (SOC) on the dash display, and the cooling fan (grille in the back seat) will switch on fairly often.

Sorry if you know all this, but one of the main things to keep an eye on in an aging Gen 2 Prius is the engine oil level. If the car is new to you and you don't have maintenance records, consider a transaxle oil change, brake fluid flush, and coolant change in both engine and inverter/transaxle. Also keep an eye on the 12V battery (search for tips here on doing that from the driver's seat). If you're a DIYer, the Mini VCI adapter is a good tool to help you do all the above (as well as monitor the hybrid battery health).

Welcome to the site!