Prius runs fine when (cold), but low MPG and engine stays on when hot (MarieAnie's thread)

you need a new battery, how many miles on her?

 

MarieAnie - is the car itself actually overheating? Does it have any warning lights?

 

changing cells doesn't work, you need a new battery, or at the very least, a complete balance procedure

 

i suspect her battery is overheating, and self protecting limiting of output.

 

I strongly suspect this too - it would be awesome if the problem was that the battery fan wasn't spinning and that was the cause of the problem, as the car could be saved quite easily!

(I assumed Gen 2 but it could be Gen 1. I hope it isn't Gen 3 otherwise we need to consider the fact that the (E G,r) I think, gets blocked, and destroys the he G). I have deliberately obfuscated those terms because they would induce fear in most car owners! Hopefully it is a Gen 2

 

To MarieAnie (and others where applicable):
When you say the problem is only when hot, can I ask:
-> Is the problem only when the weather is hot outside?
-> Or do you mean, the problem only happens when the car has been driven for a few minutes?

Also - where do you stay? Are you in the USA, Georgia, or somewhere else?

Also, what year is your car made? It is somewhere between 1999 and onwards, probably 2001 or later...

 

There should be warning lights for these conditions. Is the dash working, as in is the combo meter up and running?

 

Seems odd that we have no 'codes'. Might try a new "tech", or buy a $1 USD OBD2 bluetooth adapter and the appropriate App.

Given the problem (read the thread) and the steps taken (HV battery / HV fan), it sounds like a failed inverter pump or trapped air

There should be some DTCs logged, somewhere.. or not