Mystery Problem

Yes, there have been quite a few reports of this behavior with Gen2's as they age. Basically it's the HV battery losing capacity as it ages. They all do it, some more than others. Also some people will simply notice it more than others due to the terrain and conditions in which they drive.

My HV battery was estimated at about 50% capacity after 160k miles and 10 years, and to be honest I don't think there is anything unusual in that. Fortunately with the terrain that I travel it's not a huge problem, but I can definitely see that it would be for some.

The dealership won't do anything (and it wont qualify for warranty replacement) unless it throws a code. The bottom line is that you can lose A LOT of capacity on the HV battery without it throwing a code, provided that the cell balance and internal resistance remains reasonably ok.

BTW. I cant find the post right now, but from memory only one guy here has ever reported getting a warranty replacement over this issue. Essentially he kept taking it back to the dealers and bugging them with it. They even got specialist Toyota techs in and test drove it extensively, but they gave it the "all clear". Still he kept at them and eventually they caved in and gave him a new HV battery, which fixed his "hill" problems straight away. Anyway, I think it would take very good luck (or a lot of persistence) to get similar treatment to this "one off" case.

 

Yeah the hills and mountains can push the batteries pretty hard. At 220k miles this would definitely just be normal "wear and tear". The Gen2 really does rely a lot on the battery to "cover" for the lack engine power (in relation to the car's weight) when hill driving. The problem is that the battery can only cover this for a short time, and if you continue up a very long hill at high speed (with the battery having to supplement the engine) then state of charge will fall until the point where it will no longer supply power, and has to try to recharge itself by draining engine power.

At that point you basically get a "double whammy". The battery stops assisting, but it also starts draining some engine power as it desperately tries to recharge. At this point the Prius is most definitely sluggish.

It could be if the rest of the car is ok. I think some dealers have been selling new Batteries for as little as about $2k. There's a thread about the best place to buy a replacement battery somewhere here.

 

Hi

My battery depletes (1-2 purple bars) after about two miles of aggressive hill climbing particularly at highway speed then the engine works hard to compensate, I know my battery has excellent capacity, have never compared it with a brand new car but would expect any hybrid to act similar.

When battery fails totally charge will very rapidly swing between full 8 green bars of power down to 1 or 2 bars even in normal city driving conditions.

 

Yeah, there's no reason why it couldn't happen even with a totally new battery. It all comes down to driving with a power demand that exceeds what the engine can output. The Prius HV battery can cover for this extra power for a minute or two, but when it's gone it's gone, and then you've got to live with the reduced output or give it a chance to recharge.

One other thing to consider before looking into a new battery is that a decline in engine power can cause the same situation. So at 220k miles it could well be a combination of both reduced battery capacity and reduced engine output.

 

Hello everyone I am new.... Don't know much to use this site...... I drive prius 2011 3rd Gen. Yesterday while driving I heard a bang sound and after that car was filled with smoke arising from battery pack.... I de-assembled the battery pack, cell number 20 got exploded, damaging 19 and 21. Cooling fan is working perfectly fine, All battery cells are showing 7.8 or 7.7.... The one got exploded is now at 6.4....i changed three cells now it's working fine but I am worried why it exploded at first instance.