W/PICS HV Battery below normal, then maxed out, then comes the turtle

I have a Gen 2, but w/readings like what I see on your MFD, your 12 volt is toast. Replace it ASAP.

The other HV battery symptoms aren't good either. Did you hear the battery fan running? Was acceleration sluggish too? It'd be interesting to know if the probs go away w/a new 12 volt.

 

Mine has occasionally (not very often) done the same thing. Last time was last month, on a trip to Milwaukee. I was stuck on a Chicago interstate ... stop, go ... stop, go ... and noticing all my 'go'es were getting more sluggish. SOC on the ScanGauge II was down below 40% and dropping. I pretty much never see SOC much higher or lower than 60%, the ECU seems to hold it very tightly right there, maybe 55%, maybe 65%, but mostly 60% on the nose. So 40% was pretty weird, and the ECU kept allowing it to drop. I figured it was either some deliberately programmed behavior or a bug, so I watched it for a while. I don't remember how low it eventually got, but at one point I force-charged it back to maybe 40% because I was in stop/go interstate traffic and I didn't want to end up with no 'go'.

At some point shortly after that, the ECU seemed to change its mind completely and start charging. Really charging, running the ICE hard and charging at 10+ amps. 50%, 60%, 70%, and still charging. I got past the congested traffic and back to highway speed and the heavy charging continued. 80% ... 90% ... 99% ... and at 99% the charging still continued for several miles and double-digit amps. After several miles another abrupt switch happened, the ICE revved down, battery current went from charge to discharge, it smoothly dropped from 99% back to the usual ~ 60% and has been tightly controlled there as usual ever since.

I'm pretty sure the whole thing was a designed-in rebalance cycle that must happen on some rare schedule that I don't know. If I had not been in the stop/go traffic and didn't have a scangauge to obsessively look at, I might never have noticed. The only way I interfered with it was when I did the force-charge because the SOC was low enough to spook me, but probably if I had never interfered it would have gone through the same cycle and been perfectly fine.

-Chap

 

NinnJinn,
This exact thing has happened to me before. Although it happens seldom (once or twice since I've owned it). The last time was about four months ago. The thing you need to know is, the Gen I is finicky and will sometimes do unexpected things. That's why I don't take any DTC's/errors (turtles etc) seriously until they are consistent (I know some will say I'm crazy for doing this).

I do agree that your 12V may need changing and could be the cause of this problem. I have found when I get a problem on my Gen I, the first thing I do is pull over (ASAP), turn it off for about 1-2 minutes and restart. This has been the cure on nearly every occasion. So far I haven't had a consistent problem with it that restart or resetting the codes didn't fix (nearly 4 years of ownership).

Another thing for you to be aware of is: If you put the car in D or R before the ICE starts, you will enter OutofGas mode and get all the lights (triangle, turtle, Check engine). The car will only drive in electric mode and top speed will be limited to 52mph. You will only be able to drive about a mile before you run the battery down. The fix for this is the same, turn it off and back on. The lights will stay but the car will drive normal. Cycling it off and on 4-5 times will reset all lights/errors.

I think the trick to owning a Gen I is getting to know all the idiosynchrosies of it and avoiding panic at the first sign of trouble. The only thing I don't take a chance on is inverter cooling. If I get a DTC/warning light, the first thing I always check is the inverter coolant pump. Inverters are just too important (and expensive). They are the one thing that the system/car will let you run until you burn them out.

 

If the 12 V battery is bad, it can lead to a host of problems. The first step is to use a meter to measure the battery without the car running. If it has gone bad, nothing the car reports can be believed.

Start the car and then read the 12 V battery voltage, it should be ~13.8-13.9 V. If not, then the charging circuit has a problem, again, leading to problems with the rest of the car. A shorted cell in a 12 V battery could cause this. Worse, the 12 V battery will soon get very warm to hot.

Next, I would like to suggest getting a Prius friendly, scanner. Either a ScanGauge II ($100-150) or AutoEnginuity ($500+your Windows laptop.) This will access the information needed to diagnose what is going on. If I sound like a broken record, it is the difference between a modern car, especially a Prius, and simpler, earlier generation cars.

Bob Wilson