Traction battery discharged

The HV (traction) battery is completely disconnected when the Prius is powered off. The most common cause of the situation you describe is forgetting to shut off the your Prius when you exit the vehicle. In this situation the Prius will run down the HV battery until it gets into the purple zone, and then run the ICE as necessary to keep the HV battery from being completely discharged.

Alternately, the displayed SOC sometimes drops when the car is off. This isn't because the battery has really lost charge, but because one of the factors for calculating SOC has changed, such as having a hot battery.

Tom

 

+1

There is a simple scenario that leads to the HV battery being at one
purple bar -- this is the "bottom" of the batery's useable range, but is
40% of the battery's capacity -- that results from a simple operator
error or oversight.

If you leave the car in the Ready mode, the cars systems gradually
discharge the 12V battery, which in turn is recharged from the HV
battery via the DC-to-DC converter. As these cycles repeat, the HV
battery slowly runs down.(Depending on how may bars you had when
you left, it might take an hour or so.)

Eventually, the HV battery is at one purple/magenta bar, and the HSD
starts the ICE to recharge the HV battery back up to one blue bar.
Then the little dance starts over again... and repeats until the car runs
out of gas. There is no way of telling how many HV battery
charge/discharge cycles occurred before you returned. IIRC, from one
blue to one purple/magenta bar takes about 25 min.

This would be the simplest explanation; no damage what so ever to
the car.

Just some minor bruising of the ego for that initial oversight.

Other than this, I can't say for sure...
but suspect it would be a costly malfunction/failure in the HV circuitry.

 

I did this at Easter. I took the prius camping but sadly I arrived at the camp site after dark and in the rain.

I parked the prius pointing into the campsite and left it in ready mode with the headlights on while put up the tent etc. I thought everything was sweet and it would just run the ICE to keep it charged if neccessary but unfortunately I left it in neutral instead of park! (Yes I know it warns you and beeps and everything but I somehow I managed to ignore all that). :embarassed:

Anyway I managed to run the poor traction battery right down to zero bars. I was panicing when I realized what I'd done as I thought it probably wouldn't start and I'd be stranded there. Fortunately however it started straight away and I just let the ICE run for about 10 minutes until it got back to the first blue bar then I shut it off. It doesn't seem to have caused any ongoing problems.

 

I have on several occasions (cold outside) left Pearl in "ready" while parked (in "P"). The traction battery indicator has -never- gone as low as to display purple bars. It usually keeps the battery in the three blue bar level by running the ICE as required.

I would suggest the one purple bar is probably a result of temperature messing up the calculation, not actual charge level.

Once again, do note that even if the display was accurate, the battery was not "dead". It was probably no lower than 40% of full charge.

You can take it down to no bars, and it will still start the ICE five or six times in a row. But don't do this if you can avoid it! Discharging the traction battery below about 30% is to be avoided whenever possible! In this state it's possible to "reverse charge" one or more cells, which can destroy them, dramatically shortening the life of the traction battery.

 

Most likely you don't have a problem. Call the dealer if it makes you feel better, but the odds are 99.9% that your "problem" is one of the two listed above.

Tom

 

Just keep your eye on it for a few days and see if the SOC behaves normally. If so then I wouldn't worry about it. You can pretty much bet that if everything is currently behaving normally then the dealer is not going to be able to find anything.

BTW. There's another way you can get the SOC right down low like that. If you make a few really short trips with the engine cold then it often runs the SOC down to purple because it uses mostly battery while warming up the ICE. If I drive a short distance to the local shops (0.6 miles) park for an hour and drive home then it will usually pull the SOC down to purple because it does the trip each way on battery even though the ICE is running (a very inefficient use of the car which I should add that i try to avoid). Also note that the the SOC seems to lag a little behind the true battery state, so it can drop a bar after you stop!

 

Always lock the car. It will give a long warning beep if it's not OFF or if a door is open.

 

Very helpful thread. my 05 is in shop this weekend waiting for the "hybrid specialist" (LOL) to diagnosis possible drawdown of battery due to AC or other drain on system. Most people on the forums say the AC depends on the hybrid battery but dealer says the AC draws power first from the IEC... then, i.e. secondarily, from the battery - if the engine drives the AC, car draws more power from the battery to make up for what the AC is using... net effect, of course, is that with both the IEC and the battery being used, fuel efficiency drops, etc., etc.
One related issue to this thread about battery recharging, making sure you have turned OFF the vehicle, etc. - is anyone aware of any condition which would cause one warning short beep when you've turned off the car, in park? This does not happen all the time - but intermittently, starting about two weeks ago - right around time weather got warm here and I was also starting to use the AC. No dashboard warning lights or messages of any type during these episodes.
Will be interesting to see what the techs report back today.

 

Your dealer is wrong. Well, not really wrong, but misleading in his statement. The AC compressor is powered by the HV bus. The HV bus is powered by both the HV battery and the MGs. When the HV battery gets low, the Prius spins an MG with the ICE to make electricity. In this case you can think of the engine (ICE) as directly powering the AC compressor. If the HV battery SOC is high enough, and the ICE is not otherwise needed, then the AC compressor is powered solely from the HV battery.

It doesn't make sense to say that the AC is powered principally from one or the other, except in the sense that *all* power in the Prius ultimately comes from the gas engine.

Tom

 

It's pretty easy to run the traction down to the purple in warmer weather, particularly if the AC is running. I suspect that your engine was starting earlier due to the cold - because another reason the engine starts is to keep the coolant and exhaust system in the normal operating temperature range.

 

Oh, *now* you tell us about the recent front end damage. Sheesh. Yes, the body shop either failed to repair something or they broke something themselves.

One candidate is that they didn't isolate the high voltage system before welding, but there are too many possible somethings to be worth guessing about. Take it to a Toyota dealer for proper diagnosis and repair.

 

Equally important, DO NOT worry about being in the purple zone. The battery is even designed to dip down to NO color. I've had that happen on a couple occasions over the years. The traction pack STILL has about a 20% SOC at that point, and will still start the car.

 

If your statement of a 40 mile Highway drive then in the am it was purple is troubling. That jaunt should have charged it up real good maybe even all but one green bars.

It can't be real bad or it would throw a code. Try this. Take it for a nice long spin again and make a note when you stow the car of exactly where the bars are on the MFD. How many bars. Check that when you re-start it in the am. Shouls have no storage loss.

For reference my 07 with 27,000 miles if stowed for even 4 days has the exact same battery mfd level when started 4 days later. No storage loss.

Full green will be full green. 3 blues will be 3 blues.

Track that. If its not tracking like that and it should you may have an unhappy cell in the Traction Pack. Which is rare.
You need historical data to prove your point.

BTW, where do you keep the SMART Key Fob Alarm after you stow the car?

Good Luck!!

 

Efusco pretty much nailed it.

But I must say one purple bar is pretty low. For my 2007 that would be a long stop and go on a super hot day with the radio on and the ac at max but a short run up on the highway after that charges it right back up to maybe 2 blue bars. I guess my point is on my car it is very unhappy at one purple bar.
You may just have some very hot day short runs super on and off kinda stuff. A couple of days of that will wack the battery out and will only get back properly charged on a nice long highway run.
I notice if the wife spends 2 days doing local errands the mileage is very bad the battery is low and will take 2 days of semi hyper highway runs to get it back together.
Bottom line is I have never parked my car with one purple bar so do not know how unhappy that traction battery gets about that.

But again...it cannot be to bad as it has not thrown a code.
And if anything is abnormal with the traction battery it will throw a code.