What does 50% battery life mean in daily use?

Run. Don’t walk, run.

 

Was the hybrid system throwing battery codes or performing badly?

50% battery life on a high voltage battery is a pure guess, especially if it has three modules that need replacement because they are out of tolerance. Something does not add up with the diagnosis.

The reality is Toyota has no metric to determine battery life. There is a third party phone app called Dr. Prius that attempts to make a guess by having the driver fully charge it and then measure how long it takes to discharge. It is of questionable utility even if all the modules were close to each other.

 

What did he use to test the battery? Is it at 50% charge? How did he determine that
6 cells need replacing? Driving it will charge the battery, and depending on the real condition of
the hybrid battery those cells will be okay. It will be low since it's been sitting for so long.
How is the 12v battery? You may need to replace that one because it will probably have
completely discharged from sitting for a year.
$800 seems like a lot just to replace those few cells.
With only 65,000 miles on it, it might be a bit early to clean the EGR system, but it wont' hurt.
And if you can do that, you can do the hybrid battery yourself. For $1600 you can get new cells.

Charge the 12v battery, test it. If it tests good, then drive the car for a while so the hybrid battery can
be used, charged and discharged. Then test the battery again. You might find you'll be okay for a long time.

 

i wouldn't do anything until you get a trouble light and corresponding battery code.

it is more than likely that all your car needs is to be driven regularly, and everything will balance out on its own

 

wouldn’t that be covered under Toyota’s warranty with cel pretaining to bad hv bat?

 

New for the hv battery means new cells at least and any other option is a waste of money unless you just want to flip a non-operable car. If and when it provides a battery fail code, do something about it. Assuming the car was run weekly as you note, there is little concern about non-activity. As Grit mentions, it is likely still under factory warranty but Toyota will not change a good battery. A third party working on that battery voids the warranty.

The truth of the matter is batteries are the least of the issues on this generation of Prius. Piston rings causing huge oil consumption, head gaskets leaking, brake by wire systems and inverters failing are too common. All of these are all more expensive and more likely to strand you than a hv battery. The egr system is a unique first time design in a Prius and has flaws as well. The intake manifold fills with oil from the pcv system. At least those two are more diy maintenance oriented.

The good news is your car is low miles. Most of the big problems show around 150k miles. Changing oil at 5k intervals, avoiding excessive idle states with the ac on, being aware of warranty and customer service programs can all make a decent car last many more years without issue.

 

Yes, it means nothing unless you can say how you measured "very rapidly." In steady state freeway driving you will see the battery go up or down a bit. But if you go uphill or accelerate a lot it will drain down quickly -- as in a few minutes. Same thing if you go down a steep hill...it will charge up quickly.

(This applies to the regular hybrid batteries. Plug in hybrids have a much bigger battery and it takes a lot more to charge or discharge them)

Mike

 

In your shoes, I’d buy a obd2 Bluetooth reader and get the free dr Prius android app, observe the real time driving voltage of the battery pack. There is a designated gauge that will tell you the voltage difference from the highest and lowest cell voltage while ready. If your pack voltage difference is within .2 volts most of the time, then your battery is still in good shape. Mine is a 2012 and still within .2 volts as I’m driving. My pack averages 67 mpg from the last 1,500 miles driven so my pack is still good, knock on wood. But adjust the fan temp on the app so the fan kicks on to speed 1 at 96F. Many people leave the default value as it is and their screenshots on here are always mid to upper 100F temps. Don’t be like them and prematurely kill the pack.

always check for the easy and no to low cost remedies first.

 

i would let it set for 5 more months and hope to get a code