Driving prius with bad battery

I just had a guy drive up from Abq on a bad HV battery, 55 miles and 2000 feet of elevation gain. I had to push it into the shop because reverse is basically doesn't work. It will be slow going but doable.

 

The computer does not use much the HV battery. That means that the engine is driving MG1 to send current to MG2, and then it gets complicated. How much actual power do you have? I don't know, certainly not 80 HP though.

 

HV battery has to have enough power to start the gas engine (ICE) or you won't be able to drive it at all.

 

Unless the car has been sitting for more than a year, it is fine for the HV battery. The 12V would be toast. Anyway, the HV battery will start the ICE, because there is plenty of potential in a car with a recently flagged P0A80, but it will not provide sustained current, because a bad cell acts as a resistor and heats rapidly under continuous discharge. The HV ECU drops into a fail-safe mode, similar to a limp-in mode for automatic transmission failure.

 

Do you have experience working with high voltages?

What do you mean by "rebuild"? Are you planning to change out the HV battery pack or do something more? Do you have the necessary equipment to at least read the DTCs?

 

Failed traction (HV) battery, what to do? - Prius Wiki under rebuild it yourself has some potentially useful links. (If you find more, you're welcome to create an account on the Wikia and add them to the page.) I've never done it and wouldn't bother.

If it were me and I wanted to bother w/fixing it myself, I'd likely go w/a rebuilt pack.

 

ts : how you now its a bad battery?

 

This method will fail if the battery has overheated several times in its life. A module with very low capacity due to electrolyte loss will still hold 7.2V+ for a long time, even if having less than half of it's original capacity. Best way to tell is to discharge-charge-discharge-charge, and measure the amount of Ah in the second discharge.

If you have 1 module with less than 7.2V, then it might work. If you have more than 1 with less than 7.2V, that's an indication that the entire pack may be bad.

 

I have to wonder how many people would buy a Prius with a battery that had been rebuilt by someone who had never done it before. Would they pay enough to make it worth your costs?

 

I wanted to see if I could get more details about possible problems of driving in limp mode? We bought a high mileage 2005 185k mile prius last week with no known issues. We since drove it 600+ miles over multiple trips int he past week and now the Christmas Tree lit-up - P0A80 (no second code of what pack for unknown reason). Problem is we are 300 miles from home and need to drive the car.

- What damage will occur if continued to drive in limp mode?
- Can we reduce the damage by continuing to reset or delete the code?

As the car behaves fine after first reset, I believe this is because it takes two trips to compare errors based on the P0A80 error message "Voltage difference between battery blocks is higher than standard (2 trip detection logic)".

Last question, we are getting different results from different OBD2 readers in our local auto part shops and I haven't yet figured out how to get the DTC Log to show me the specific battery details; but can I use the on-board Maintenance Mode to show me the battery details?

 

I doubt you will damage anything. On the highway, going on fairly level grade, the best efficiency is had at the speed where there are no arrows going to or from the battery. At that point there is not much concern about the battery's health. It's accelerating up to that speed which will be slower, due to the limitation of the current from the battery. You may not make folks happy by going too slowly.

As for codes readers, you must have a Prius specific reader to get to all the ECU's. A generic reader won't do it. The car will not display its own codes, which is somewhat lame, but that's how it is.

 

I have a question...I am new to the prius family. I bought my 2007 prius a few months bad and love it. (although the seat is pissing me off lol) but I was wondering what are the signs of the HV battery going bad? I was wondering because when I am driving it, the battery gets fully charged, but when I leave it parked for a day or so, that battery seems to be on the last 2 bars...I am worried that it is a bad pack...what kind of test can I do besides taking it to a dealer?

 

Fast and large changes in the state of charge level seen on the MFD while driving is a commonly reported symptom of a weak HV battery. Typical SOC while highway driving remains mostly in the middle to upper area of the scale. City driving is often lower. Below 41 mph in cruise you would expect to see the engine cycle off for around 1 mile then cycle back on to recharge the HV battery. How about the MPG? Have you noticed any difference since you bought it? When you say "fully charged", on flat lands I seldom see the SOC indicating all the bars charged. Next to the top yes. Very occasionally the top bar, usually when coming off an off ramp while coasting a good ways.

 

In an area with mountains, a dying HV battery will have its fan running on high a lot and have seemingly no power at a certain point when climbing a grade. Someone that knows what they are doing can estimate the amp-hour capacity remaining with the right scan tool. From the user standpoint, if you can avoid having situations where the battery fan comes on high, then you are doing your part to maximize the possible longevity. Otherwise, just drive it until it dies. If you don't want to fix it, then someone else will buy it for a pretty decent price. If you do want to fix it, find someone that does rebuilds with Gen III packs.

 

Jesse, also I would recommend cleaning the battery cooling fan, which procedure has photos and videos here and on youtube. It will help to extend the life of the battery a bit. Heat is the enemy of the battery, so keeping it cool is important. Run the A/C in hot weather.

Where is your location? Hot climate?