I had this happen twice. The Prius will run the ICE non-stop to recharge the battery. Even after the Energy monitor shows the battery to have a full charge (yes, 100% green), the ICE just keeps working to charge it up. Accelerating even slightly, which would normally use the battery only, uses the ICE instead. Turning the car off for 20 seconds and restarting seems to fix this, but why does it happen? It reduces MPG. This is a 2002 Prius Classic.
bisco is on a roll today; BEWARE. There are several things that can cause the ICE to run and charging the battery is only one. Others who are really familiar with that model can probably give you some specific advice.
Reduced battery-capacity due to old age is to be expected. This is a good time to come up with a "next step" plan. Since you purchase a used Prius, you have no idea of the battery's past either. If the former owner drove a few times after running out of gas (a common issue with Classic owners), the deep-discharges would have accelerated the aging. Whatever the case, watch for signs other than reduced MPG. If all it's doing is running the engine more, replacement need hasn't arrived yet.
There are reports of a 'rebalance' cycle that sounds similar to what you've experienced. But I concur that it is likely a rebuilt traction battery should be in your long-term plans. In the meanwhile, "heat is the enemy:" try to park where the sun won't heat the pack avoid speeds over 65 mph avoid driving up tall hills with the battery showing a discharge to the wheels These are not 'cures' but keeping the traction battery cool is the best way to slow down the rate of aging. Read the sticky about "Who should buy" one of these cars and think about where you fit in that essay. There is nothing about this car that is not basic engineering but it is different than ordinary cars. This is one of the rare corners of the Internet where you will find owner, operators, and mechanics who still keep these cars running. It is the only compact, sedan hybrid. Bob Wilson
The Classic traction battery gauge should normally read either 50% or 75%. Any more or less, means the gauge is giving you an early indication that the traction battery is about to die.
Normally, it is either 50% or 75%. The first time this happened was in very heavy traffic where I ran on battery for a while. It is the first time I saw the battery gauge dip to 25%. As expected, the ICE started up and charged the battery. But then it didn't stop even after reaching the never-before-seen 100%. Parking the car and restarting fixed the problem, for a while. It later happened in regular traffic (about 2 weeks later) and again the only way to stop it was to park the car, turn it off for 20 seconds, and restart. I should also clarify the MPG issue. I simply saw my MPG average dropping when the ICE kept running non-stop, as expected since ICE idling is inefficient. The average probably went from 57 MPG to 54 MPG. I have not had that problem for a few days so the average is back to 56-57 MPG. It seemed like an odd issue and I almost thought the car was doing some kind of maintenance by charging the battery all the way. Does it really mean the battery is going? What is a good place to get a rebuilt battery? Can I install it myself?
I've had this happen three times in two years on my 2001, last time was close to a year ago. It's been discussed before in this forum. The behaviour for me was pretty much exactly as you described, and it does appear to be an intentional act by the car - the first time I shut down, but the next couple of times I let it run its course. It may be related to battery age/degradation, but unless it's happening often there doesn't seem to be a need to panic about it.
So you let it run its course and it actually stopped without your having to shut down the car and restart? Remember how long it took?
It just keeps charging to close to 100% SoC, keeps it there for a few minutes, then stops, and the battery returns to the normal ~60% SoC shortly after. See Sudden HV overcharging | PriusChat
I agree with Jeff F on this. I personally have also noticed this but, I wasn't brave enough to let it run its course but the last time this happened was about 2 years ago and I'm still running on the original HV battery. So it is not necessarily an indication of your HV battery going dead.
