Hybrid Battery Problem??

[DaveMan6610]

At 37,000 (3000 miles ago), my Prius battery status started acting different. The battery would routinely be fully charged in the green with a noticeable increase in charge time vs discharge. Fuel milage dropped about 10%. At times, the battery will even show charging while going uphill when fully green and warmed up, which is something it NEVER did prior to this.

I've been through 2 winters, so I know what to expect from a winter climate. But this activity was also evident in fall when temps were in the 60s and 70s and different from the first two winters.

Has anyone ever seen this or know what can be checked? Have the rest of you seen changes in the charge pattern of your Prius?

This winter, my milage dropped to about 39-40MPG with about 44 in the fall. Prior to this, my milage would be 44 winter, 48 fall.

Thanks in advance!

[tochatihu]

Welcome 1st poster, sorry you came with an 'issue'. I suggest that you have a Toyota shop scan for stored 'DTC' codes. If some are present, we can discuss them.

It may be typical for shops to charge for this service, but if you have a good relationship (or bring a bag of cookies) you might get it for free/cheap. Good luck and please post the results, even if no codes are found.

[icecoldmittens]

Hi! I am so glad you posted his, because i thought i was crazy. I am just now passing 37,000 miles on my 2007 Prius. I also have been through two winters with my prius. To start, I do both a lot of highway and around town driving, averaging about 150 miles a day. Recently, i haven noticed while cruising on the highway at about 70 mph, my battery will become Completely full, yet still charging. I have only had one full batter up to this point and i had been driving down a hill, and now it happens almost every day. WHen my battery is full, it does go down very quick. My fuel millage has dropped from an average of 45 to 35 in the winter. I do have snow tires, but when they were first put on, i still got about 45mpg. Last winter without snow tires, i was getting 50mpg. In the summer, i used to get 60mpg, but now with my 17 inch rims, i get 45mpg.

Also, when i am accelerating heavily when my car is cold, and i remove my foot from the pedal a large amount without taking my foot totally off, my RPMs stay high as if i was still accelerating.

[DaveMan6610]

I took it to the dealership and they didn't find any codes. I really didn't get the impression that they believed me that there was an issue, though, so I hope they checked.

The last week or so it's doing a little better, but I still can't do better than 42MPG. The charge / discharge behavior is more normal, but the engine still does not like to shut off as easily as before.

Like you said, Mittens, I did get green battery one in a while, but ALWAYS on long downhills with gradual braking. And once it was green and you were on the gas at all, it was ALWAYS discharging. I haven't noticed the RPM issue, but I will pay more attention.

Something is definitely not right, and it's a bit frustrating, because I love the car, but at only 40+ MPG and a lot more sluggish (without the battery helping on acceleration as much as it should), I'm not sure I'd buy another one.

[tochatihu]

A cause of 'sluggish' and low mpg could be dragging parking brakes. Doubt it would change the battery behavior as you've also reported, but since we are just gueesing now, please check the temperature of the rear brake drums a mile or two after starting out. Wet finger test.

[bwilson4web]

Originally Posted by DaveMan6610

. . .
The last week or so it's doing a little better, but I still can't do better than 42MPG. The charge / discharge behavior is more normal, but the engine still does not like to shut off as easily as before.
. . .

Perhaps the first step is to baseline your performance on a flat, no stop, road at a fixed, cruise control managed speed. I notice there are plenty of roads along or around the river bottoms. See if you can find one that allows you drive at a steady, cruise controlled speed for about 3 miles. Then do the following:

• accelerate to a given speed to be maintained by cruise control
• at the same entry point, reset your MFD mileage and a trip meter
• at the same exit point, note the distance with the trip meter and the MFD
• repeat the test for a total of six runs, three each way
• report your MPG and speed here, all six runs
• note the temperature (needed for a correction factor)
• note the wind direction and speed
• must be dry day

What we'll do is compare your values against this chart:

If your MPG is too low, we'll next address the likely suspects. If your MPG is high, we'll address the likely suspects. If your MPG is on the blue line, there is no problem.

Bob Wilson