Toyota Prius 2006 Slow to accelerate in heat?

you probably need a new battery, but start with cleaning the fan and the intake grille. prius protects the battery from overheating, and an old battery is more prone.

 

Sounds like your HV battery is very, very weak and about to give up the ghost. As bisco said, a clogged fan with poor flow wouldn't be helping matters.

Also, are you using A/C? The battery needs cooling so use a/c but the heavy a/c load makes it harder for a weak battery to stay charged.

 

New battery is $3500 at the dealer

 

100%. They don't have an infinite lifespan.

You'll need to asses your situation. Do you want to keep the car for many years with reliable battery operation or are you contemplating moving on, etc. New vs refurb (rebuilt).

 

new is almost the only option if you want reliability.
since you haven't thrown any codes yet, it may not be too late to reinvigorate your battery with a prolong system.

 

Below is the website of supplier @bisco is referring to:

Prolong Battery Systems. Extending the life of your hybrid. – Hybrid Automotive

The owner is an active member here: @jeff652 . You can PM him specific questions.

I had Jeff install the setup on our 2010 Prius II and have used it with good results.

Act now before it's too late .

 

had to press the like button 6 times for one like.^^^

 

Thank you for your persistence while the site is janky .

 

I always thought @Raytheeagle was a likable person, myself.

 

indubitably.

 

I agree with the weak battery theory but it would help to know more about the conditions the car is kept in prior to driving. For the first time we experienced a drive similar to yours in the same conditions the day before yesterday. We almost always park the car in the garage or the shade. My wife took the car to work and was forced to park in the 100+* sun all day for a change. Gas mileage immediately went down; the ICE ran much more than usual It was only the second time I've heard the fan run on high while driving. The battery had obviously heated up. After the car "cooled" overnight in the garage it was better in the extreme heat yesterday. Today it's back to normal.

As an aside, I started using the Prolong system in June and have been happy with the results on the road and on the MFD after the single use.