Bad Battery?!?!

Well it sounds like you do have a bad traction battery. I would just take it to the nearest dealer to have them check it out. I think on your trip you stressed a pretty worn battery just a little too much. This would happen if you never shut it off but it doesn't sound like you have been leaving it on. Have you replaced your accessory battery before?

 

A failing 12V battery can cause this because the traction battery spends itself trying to keep the 12V battery charged up. Use the built-in selftest and see what results:
PriusOnline.com • View topic - how to put 12V battery in sleeping mode?

 

No it does not work like that....

You probably have corroded terminals on the traction battery. A known issue.Get a Chiltons manual which clearly describes how to safely access the traction battery compartment remove the cover and take a peek in there. Its easy and will take you a few minutes with simple hand tools. You may have corroded terminals on the interconnects. Easy to see.

And it may give you the courage to buy a good used battery and install it If not the corrosion issue but bad batts if done by the dealer will be very expensive...no so much if you do it yourself.

Knowledge.

Please be aware if you present yourself to the dealer and plead "Help me" they will take you home the long way.

Cabeesh?

Good luck.

 

I'd try the 12v battery first. I wasn't aware that there was an issue with corroded terminals, but that's an easy check, and likely and easy fix. Both of those options are very cheap compared to even a used traction battery.

 

My story is similar to the OP, but not a sudden change, just a slow trend toward more and more often seeing 2 bars and full green. Mileage has gone down as well, although not as much as his. My car is now at 86k. I see this several times a day whereas when the car was new (2005) I very rarely saw less than 3 bars and full green only if coming down a mountain. Lately, it's even beginning to show 1 bar, and coming off the freeway offramp will give full green. Also, my battery SOC will plummet when the system is cold, as in first drive of the day cold, not absolutely cold. My local dealer says they won't do anything until the computer puts out a fault code.

I hadn't heard that this was diagnostic of corroded terminals on the traction battery, I will have to check that out and report back.

 

One more thing, I replaced my 12v battery a couple of months ago as a possible fix, but that made no difference in the traction battery performance.

 

A mistake with the traction battery can kill you. Leave it to a dealer unless you know exactly what you're doing.

 

Yes, I also have noticed this with my 2004, 87K miles. I think the traction battery is losing capacity. It would be nice if it would fail before 100K miles, but who knows.

If you are serious about checking the traction battery, this is a pretty dangerous activity unless you observe all of the safety precautions found in the Toyota repair manual.

 

I'm not advocating the op does any work there just taking a look inside. At least he will know if thats an issue and can deal with it accordingly. He's oow so taking that issue $$$$$ to the dealer will have the service manger do a little jig.

 

heres what i noticed, my 05 prius would stay between 2 and 3 bars most of the time if i did a short drive, say 0-5 miles

but soon as i started a 40 mile a day trip my battery would stay at 5-6 even 7 all the time, even the next day.

my guess is on short trips there is a large current draw since the car is still warming up?

 

Yes. In Stage 1 the car is trying to bring the engine oil up to a decent temperature before putting any stress on the engine, so it uses battery power to move the car unless you really push hard. It feels as though the car is reluctant to accelerate, and then will suddenly accelerate hard if you keep pushing it. The engine will be idling even while you're accelerating and then suddenly rev up.

On my journey home from work, the speed limit is 30mph, then almost immediately 40mph, then after about half a mile, 50mph. I have to be aware of cars behind me wanting to accelerate up to the speed limit at this point, because my Prius won't, usually, be warm enough yet.

Air conditioning is an additional drain on the HV battery, so avoid that while warming up if you can.

I don't have much in the way of hills on my route, so I usually only see seven bars (green) if I haven't had a chance to do the full stop/very slow idle for ten seconds, necessary for the idle check to go from stage 3A to stage 4.

 

What did you buy?

There is no direct drop-in replacement aftermarket battery for the Prius. It must be vented, for safety, and the vent, terminals or clamps, and possibly the mounting will have to be adapted to fit.

 

Yes I've also noticed the same thing (as nicely explained above by Mike D). When I cold start in the morning it seems that it really tries to make as much use of the battery as possible, while presumably taking it as easy as possible on the engine as it warms up. (Which is not a bad idea when you think about it).

First thing in the morning when I pull up the (not particularly steep) hill outside my house it uses the battery heaps and often drains it by a couple of bars in those first few minutes. Going up that same hill warm it usually doesn't even draw on any battery power at all.

 

Is it down to two bars staight away (as soon as you start) or does it go down to two bars after a few minutes drving?

So far each morning mine has been pretty consistent in displaying however many bars I had on it when I parked it the previous evening - I doesn't seem to lose anything overnight. Once I start driving however it's a different story. Like I said before it uses the battery a lot in climbing the first few hills when it's cold (much more than doing those same hills later when the motors is warm). So yeah sometimes my battery has gone down to just two bars during those first few minutes.

If I were you I'd at least get the connections at the battery terminals etc checked for corrosion, this could definitely mimick the symptoms of a bad battery. BTW - If you do get this checked out at some time could you please post the results back here because I'm sure many people would be interested.

Here are some things I've noticed about NiMH batteries in general (not specifically talking about the prius here). You usually see one or more of the following symptoms if a battery is going bad.

1. Reduced capacity

2. Increased internal resistance.

3. Increased Leakage (as in failure to hold a charge so well when not in use).

If it's only that the terminals/connections are less than perfect then it will definitle mimick the second of those symptoms, but probably not the other two.