How abruptly do Gen 2 traction batteries fail?

I haven't had a traction battery failure yet with my 07, but it will occur someday. I expect it will still be somewhat driveable, just very sluggish. The realization that it may fail fairly soon has not prevented me from taking several cross-country trips in the last year. For my own comfort, I keep an old Android phone with the Torque Pro app in my console, and check the status of the HV blocks from time to time. (Check my last post here What is a good source for an OBDII dongle / reader software? | PriusChat for more information about that).

 

Typically before failure they get weaker and show some signs such as but not limited to: lower mpg (gas engine (ICE) runs more), less EV performance, battery meter drains fast and/or cycles quickly up/down, ICE starts are rough, battery cooling fan running more/louder, etc. Some of these signs can be easily overlooked as the loss can be gradual.

Failure can occur at any time, any place. The car can still run (poorly) on just the gas engine alone to get you off the road and limp around at low speeds but essentially game over till it's repaired or replaced with a new or rebuilt battery.

 

Although I have not had a 2G traction battery failure, I have personal experience with traction battery failures with my 2001 Prius and 2006 Highlander Hybrid (both covered under warranty). The car cannot be driven any significant distance once warning lights come on. At best you might be able to limp a short distance at low speed to a local dealer. So, don't expect to drive 400 miles at 70 mph in an effort to return from a road trip, if you have a failure.

 

I could be wrong because I don't know these things that well....but, sounds to me, based on what I have read on here, that your mechanic has absolutely no familiarity with the Prius....LOL @ the bars being low on the dash....From what I have read this basically means nothing...and they go high...they go low...they go in the middle...etc...and it is all normal...There is no "bad" because it's low and there is no "good" because it's high.

Someone that is more knowledgeable feel free to correct if that is untrue.

It is going to be an abrupt failure with a bunch of lights on the dash when it goes out...As Fotomoto said there are some signs before hand but it's not "my customers dash displayed 2 bars when he brought it into me"...

 

I've had the battery get so bad that I've had to replace modules twice and it's giving me problems again. This all started around 3 years ago. Please note that I'm no expert. And I'm likely tempting fate. But I have gotten several thousand miles on a failing traction battery. They way my car has been acting, it starts with throwing codes and getting lower and lower gpm. You may notice the state of charge on the display will move up and down more quickly than before (if you are familiar with the car). My car eventually starts shuddering and losing the ability to accelerate. That's when I park it and take out the pack to replace modules.

Posted via the PriusChat mobile app.

 

You should get another pack from a gen3 wreck at a wrecking yard

 

Before it starts failing, your mpgs will go to crap for a Prius (30's generally), and the battery will swing from full to empty to full to empty quickly. Additionally the battery fan may become more noticeable.

When the time comes that the car throws a code, the dash will light up like a Christmas tree. At this point the car should be driven only to be serviced.

Having said that I drove my 2006 with a failed battery at highway speeds (80mph+) for the better part of a year and a few thousand miles. Eventually it got to the point where it threw additional codes and the car was barely able to move and I could get it into a parking lot going 20mph or so max. When going up a hill, common in the mountains, it would drop to a few mph. But it would limp. After I shut it off, it didn't start again. I was able to come back a week later clear all the codes with a techstream laptop, and drive it back another 100miles at highway speeds. Again I drove for months like that, with codes being thrown more and more frequently. They could be cleared and be driven a bit and then come back. Before I replaced the pack, the car needed to be started, have the codes cleared, and then drive. Before leaving the driveway or parking lot, the lights would come back on but the car would work until it was parked.

So to answer your question, yes the car can be driven after most HV pack failures. The legal and safe answer would be that you should really only drive it to a safe location and tow it to the dealer. It is possible to ABUSE the car and continue driving it. My Prius is a mountain goat and not primary in any ways. If it dies, burns down, whatever, I don't care. If the Prius is your only car or you are tight on budget and don't want to ruin other things, DO NOT DRIVE ON THE DEAD BATTERY LIKE I DID. It will tax the hybrid system revving the engine high, it will elevate the battery temperatures, run the fan, put a higher strain on the inverter, and can be unsafe in traffic if you don't know what you're doing. A hot battery can just be a hot battery, or it can lead to the cells expanding and popping. This can cause lots of damage to the battery cover, seat, battery gas venting, etc. Most likely also invalidate your core so you won't get your $1350 back from Toyota.

And to clarify...

...the effect is true, but the reality of the phrasing is false. A layman reading this may assume that they could remove the HV battery from the vehicle and drive around in limp mode. That is not true. The HV battery is required to spin the engine to start it and for general motoring. You cannot remove it and make the Prius "gas-only" since it is a true hybrid system and not just an assist. But it will get you off the toad and allow you to limp and low speeds with a complete failure.

 

A gen 3 can be used in a gen 2?

 

Yes, you just have to transfer the modules to the gen2 case. The internal modules are the same

 

No, the cases are different but you can transfer all the gen 3 modules over to the gen 2 case. You shouldn't mix/match gen 2 & 3 modules either. Only gen 3 modules are still made so if you buy a new gen 2 pack from Toyota, it comes with gen 3 modules inside.

 

When my gen 2 battery failed, the lights came on and I could drive it to the mechanic about 5 miles away. Also, before I did that, I let the car sit overnight and it started the next day. I feel like I had good luck though when my battery failed. The car drove pretty well for having an unhealthy battery. So I think you can drive it for another 20+ miles; just take it easy though.

 

The traction battery in my 2009 Prius died very slowly and gracefully. Not wanting to be stranded in Egypt, I replaced the battery with new cells from Toyota before the Red Triangle of Death came on.

I knew that the battery was dying because the battery compartment's cooling fan was on (loudly so) much of the time and especially after passing and driving up a long uphill freeway on-ramp. This cooling fan blows out a vent in the rear passenger-side seat.

Additionally, I noticed that the engine was working harder at higher RPMs when passing other cars at high speed. When watching the energy meter I noticed that the battery bar graph would drop into the low voltage region (few bars) and remain there for 5 minutes or longer after heavy throttle.

After I replaced the battery pack all of these features disappeared. The battery pack was installed by ABY in Scottsburg, IN.