Feeling that my HV Battery is going to die

Yeah, as long as you're some distance from the end of warranty, a long lingering death is not what you want. We had similar issue with previous Civic Hybrid, battery obviously deteriorated but took forever for a warning light to come on. Did finally...

What with the oil burning issue (in your other thread), sounds like you've got your hands full.

 

There is a procedure to check battery health under load BEFORE it codes. I thought it was a common knowledge?

 

..in fact it might be a good time to repeat that 9hr 110deg F journey?

I am curious, when you had a good look at the batt cooling fan, was it totally clean or some lint on there?

 

My SOC display often has a slightly delayed response to a regenerative event (eg going down a hill or stopping). Sometime I stop at lights and it's 6 bars just as I stop, but then jumps to 7 a few seconds later. I'm sure it's just a delay in calculating and updating the state of charge. A change of one bar doesn't sound like anything serious to me.

The thing to watch for that's more of a sign is rapid swings between very low (red) and very high (green) SOC. Many people do sometimes get a rapid drop in SOC in the first few minutes of driving, and this tends to be exacerbated if the HV battery is aging. The solution is surprisingly simple, just let the engine warm briefly (30 to 50 seconds) before driving and it takes a lot of the initial strain off the battery.

Another thing to watch for is overshoot and undershoot. Overshoot is less noticeable, but corresponds to the SOC rising more rapidly than it normally would (typically from 6 to 8 fairly quickly) when descending. Undershoot is more noticeable and typical occurs after the battery has previously been at 8 (or sometimes only 7) green bars. With undershoot the SOC declines only gradually from 8 back to about 5 or 6 but then drops very rapidly to about 3 or so, even with the engine running (and sometimes even with the engine running and the green arrows showing charge going in to the battery).

The battery in my 2005 Prius is old and tired and has had this behavior for a few year. Several other users with aging batteries have also mentioned it here. In my opinion it's a very sure sign of a tired battery. Mine's out of warranty (both time and mileage) now anyway, so I just nurse it by using "B" mode on larger descents and warming the engine briefly before driving. So far it's keeping on going and I haven't noticed much further deterioration over the last two years or so.

 

All this talk makes me wonder about the state of my battery in the old Gen I. The Gen I SOC gauge (if you wanna call it that) is less than accurate to say the least. All I know is that it pretty much drives the same as when I got it (at 87k miles in 2009) and gets about the same gas mileage as well