Is my traction battery going bad?

no load 12.1 is a bad battery. it either needs a charge, or needs to be replaced.

 

I was experiencing the same symptoms with the bars rapidly decreasing in charge then charging quickly back up. Noticed it for about a year or 2 before the warning lights finally came up. My car is now being fitted for a new hv battery. For me those were the symptoms that got me concerned. I didn't act on it though i put up with it until now.

 

12.4 is on the edge imo, although, may not be the cause of your problem. a new battery with a full charge will be 13+.

 

I'd say your 12V battery is fine. When I replaced my 12V battery a few years ago it only measured 12.3 to 12.4 volts no load (in car measured) even from new.

 

Yeah that didn't look too bad. Was still worthwhile cleaning it though.

JDonalds, you probably have a similar amount of traction battery capacity loss as my 2005 Prius has. These batteries don't always just go from full performance straight to failure. In the same way that power tools, mobile phone and laptop batteries go, many of us will experience a gradual decline in battery performance rather than a sudden death, and that is what you are seeing.

If you look at the true underlying state of charge versus the displayed bars it looks like this:

Notice how bars 4 and 5 are relatively short, especially compared to bars 6 and 7. This is why you can lose these bars so quickly as the traction battery loses capacity.

The following image shows how I believe an aged traction battery appears to operate. Notice where I have mark the "charging anomaly" and the "discharge anomaly". An aging pack like this operates in two distinct states, a "bottom referenced" state and a "top referenced" state.

After the battery has been discharged down to about 3 bars it enters the "bottom referenced" state. From here, as it charges up the bars 3, 4, 5 and 6 behave perfectly normally (that is, they hold a similar amount of charge as per a healthy battery). When however the charge level reaches the point in the 7th bar where I have marked "charging anomaly jump", the battery management suddenly realizes that the pack can take no more and transits rapidly to full 8 bars and it's upper charge limit. Notice that at this point it actually has about 10% less charge than it really should.

Now that the battery has maxed out, it enters the "top referenced" state. From here as the battery discharges bars 8, 7 and 6 appear to operate perfectly normally (similar amount of charge as per a healthy pack). When however it reaches the point I have marked as "discharge jump anomaly", then the battery management first starts to notice that missing 10% charge, and you get the relatively rapid readjustment of the SOC from 6 bars down to 3. This is not usually instantaneous, but typically happens over a short period like about 15 to 20 seconds, sometimes even with the engine running and the battery display indicating green charging arrows.

Given that you have quite a lot of mountains around you up there in Redding, I expect that you are quite often entering this "top referenced" battery state, and consequently are often seeing this "discharge jump anomaly", just as I do.

 

those were they same way my 2005 acted. exept mileage change was not as drastic change.park car with it still running run air on high watch display it will throw code also red symbol.good test for battery capacity under load also recharge capacity. if it failing it will fall do this

 

In my post #11 I suggested several possible areas for you to check. Have you checked any or all of them?

 

Are you saying your battery lost two bars of SOC while going downhill ? That does not sound good.

 

Worrisome for sure, but it is not a definitive test unless you can say with some confidence that the car in the past always gained SOC bars.

 

that can't be good. if it's green, it's probably gonna start burning off juice, but it should stay green i think.

 

I suspect you are seeing an artefact of your forced charging and I would not read too much into the test.

You can drive yourself crazy, or wait for the cable and do a proper test. I know which I would choose.

 

9,000 miles /45 mpg x $3./g = $600.

9,000 miles / 36 mpg x $3./g = $750.

$25./mo. ride it out.