engine struggles when battery is half full

Are you also finding that the HV battery will quickly lose charge and quickly top back up again? You accelerate and it drops one, two, three bars, you ease off and they top up again?

 

Gen 1 MFD display of battery State of Charge is pretty pathetic. Try watching SOC with a Scangauge Xgauge as you drive the car, ideally in reverse up a long hill...if the SOC moves quickly, your hybrid battery is on it's last legs.

 

Sounds weird. I have an NHW10 prius and it doesn't do this.
I know it costs money but it might be a good idea to get someone to have a look at it. In New Zealand I use a guy who only services hybrids. He picked up on many things that were not right with my Prius including wrong spark plugs, wrong air filter. It runs very quietly now and it's a 1998 dont 115K Kms.

Sorry I can't be of more help.

 

if HV battery is suspect and still under warranty, ask the dealer to test it...then at least they'll be a paper trail that you had concerns at 70k.

Some dealers may even change it out under warranty as a goodwill gesture...has your MPG been dropping? If MPG went from 44-45 to 37-38 it's often the result of a bad HV battery..

Another thing that can help rough ICE running is a thorough cleaning of the throttle body....usually you don't need premium gas in a Prius....maybe you just got a bad batch of regular?

 

What about the 12 volt? Is that an issue on the gen1 like it is on the gen2 & 3?

When was that last changed? It's a cheaper option to try before having the HV replaced. Just a thought.

 

I hate to just butt in, but; this is my first time and I don't know how to start a new HELP THREAD; I am having the same similar problem. 2002 Prius, My battery indicator drops very low when I am idling, then engine struggles for a bit, but then recovers and I am good to go.
I took it to the dealer and they said that without an error message they couldn’t find a problem. 1 month later of the same, I finally got an error warning light, which always happens when you are on the highway in the far lane, unable to get over. I got the car to the dealer, who said code indicates either the inverter or water pump. Suggested that I pay 5 hundred for the water pump, because it is cheaper than the inverter. It has been 10 months and now the car is doing the same thing. Today the battery indicator went to totally full and the Yellow Turtle light is on. I was not far from home, for once.
Can someone advise me; my car has 170k on it. I love my car.

Signed
Sad to have to let it go.

 

I am not an expert but, it sounds to me like the traction battery is getting weak.

 

Is it pumping water or not? They have to mean the pump for the hybrid cooling system. You can look at the reservoir next to the inverter to see if coolant is flowing when the ignition is on. The fluid level should be raised at the front of the tank where the return hose attaches, and show a step down by about an inch if it is flowing well.

It would help if you could get the dealer to tell you the codes and subcodes they read from the system, and post them here.

-Chap

 

Thank you so much for the answer, it took me a while to find my thread. I should have indicated that I did have the water pump repaired. But, the problem continued, while idling in a line at a fast food place or in heavy traffic, the battery indicator would drop very low and the engine would not kick in unless I turn on the air condition or I start driving. Then the battery indicator would charge back up. Last week, this happened again while waiting for a light to change, once I started the battery indicator crept back up till it cover the whole indicator, then a yellow turtle came on with the check engine indicator. I limped home 1 mile and got it in the garage. Later that day I turned on the car and I got the same warning lights and battery indicator is still high.

I am so sad.