rapid HV battery drain on startup hot days only

So you are getting 43-44 MPG now. What were you getting before ? Where you having any 80 degree days before this started ?

Sounds like dealer is trying to blow you off if your mileage suddenly plummetted and battery discharge characteristics changed quite a bit.

I achieved a new "first week of ownership" mileage records Friday morning of 63 US MPG with no AC and temps about 70-75. I drove with the same techniques home with AC and temp about 85 and very humid and I got about 18% less, about 52 US MPG. This was half city, half 35-45 MPH straights, some hills but even overall.

 

Your log is fascinating. Most of the time when you arrive at work you show 8 green bars.

• Is this because you live at a relatively high elevation and descend to the office?
• What is the approximate altitude of your home and your office?
• What is the commute distance and your average speed?

June 3 is particularly interesting, where you park the car in the morning with 8 green bars, and when you return to the car in the evening it shows all white - then jumps up to 3 blue bars. This definitely is not normal.

• If you have been averaging 43-44 mpg over the first 9K miles, how about when you go on road trips? Any difference when you are driving on flat ground?
• What temperature is your air conditioning set to achieve?
• What is the ambient temps in your area now: mid-80 degrees?

 

I'm seeing a troubling hot weather battery related low MPG complaint trend here. 3 different threads started in the last few days:

sudden battery discharge

rapid HV battery drain on startup hot days only

Drop in performance / mpg? Going to dealer, please help!

I'm thinking this could be a widespread "defect" in Gen-II Prii...

 

Of the three, I would say that Elizabeth's car is the closest to potentially needing a new traction battery, because of the big mpg impact which implies the ICE is running almost all the time. When her SOC gauge starts moving up quickly (as well as down quickly) then she should be very close to getting a master warning light and traction battery icon, which would allow her to get a new battery under warranty.

We really haven't seen many 2G owners report that their traction battery needed replacing. It is about time for a small % of owners to start reporting this failure. The summer is a good time to provoke failures, with the extra stress from ambient heat, running AC, etc.

I used to own three Toyota hybrids (sold the 2001 4 months ago) and out of the three, two needed new traction batteries. The 2004 Prius still has the original traction battery.

 

I don't see a problem here. The battery display is supposed to spend most of its time in the blue, not the green. Americans seem to think that FULL or MAXIMUM is always optimal for everything, but the nominal operating point for this battery is HALF.

Common things to check include:
1. tire pressure
2. oil level

 

Hi Mike,

Thanks for providing more detail. Your road trip mpg sounds quite normal.

I think that the Toyota hybrid system is stressed severely when it is necessary to regularly climb and descend hills. This may provoke a traction battery failure much sooner than flat terrain usage. (Certainly my personal experience will attest to this, as I live at 1,100 ft elevation and regularly commute to sealevel.)

 

It was a warm & humid day here the other day and the car was sitting in the sun all morning.

Came out and went for a drive to the park. A/C was going full blast trying to get the temps down to 72*. Got stuck at a couple lights. Notice the battery down to the purple and the engine started up immediately when going for the green light.

Seemed to be fairly normal to me? First 5 minutes indicated ~20 mpg which did not surprise me. Average for the tank is 47mpg right now. Had it a bit over 50 over 70 miles before a few short, hilly, hot trips like the trip to the park brought it down.

If you frequently have shortish, hot trips which require extended time at full A/C to cool things off, I'd expect to see low 40s mileage.

If you are doing city driving with full A/C, I'd expect to see the battery go into the purple fairly frequently, too.

 

I have a 2008 Prius with 50k miles. My hybrid battery completely drains when my car is sitting in the hot sun. I did not realize this was a problem as I live in San Francisco and it only happnened very occasionally. Recent road trips to LA and Palm Springs have brought to my attention that this a severe problem.

Interestingly, a friend of mine in LA also has a 2008 Prius with 50k miles. We parked our cars side by side in the hot sun. Both with all green bars. When we came back, his was fine. Mine read green for two minutes, then dropped to nothing and the gas engine was on overdrive for some time while it recharged the batteries.

Apparently they do not all have this problem. Now the challenge is to convince the dealer that something is wrong. They say it passes all diagnostics and that it is just the display going up and down.
Wish me luck.

 

In your test, your battery was much hotter than your friends, for some reason. I personally think it is harmful to park the car when it has 8 green bars, because the NiMH tends to suffer increase in temperature near full charge even after charging current is removed, but the hv battery fan doesn't run when the car is turned off. I suppose everyone here will call BS on this theory and I'll have to prove it. Someday.

You only have a problem if your battery fan turns on in the middle of a trip, rather than the beginning, and you mileage fades by 5-10+ mpg. If you want to put your battery to a real test, go over Donner Pass and see of you have a problem maintaining speed. See this thread for more details of a problem that Toyota seems willing to address:

http://priuschat.com/forums/gen-ii-prius-main-forum/95641-power-loss-low-battery-during-climb.html

 

Our 2006 has the same problem. Only happens when it was left out on hot days. Has anyone gotten anywhere with finding out why this happens to some prius's and if there is a fix?

 

Tint your windows to the maximum allowed by law, and don't park it with a battery anywhere near to full. Check your battery fan for clogs. Is it hotter than the 9th level in Austin now?

 

That your parking it in green all the time means your in tight stop and go heavy urban traffic. Or your not managing the gas pedal all the time. Try to get to work without it being green as green is not good. That's accomplished by trying as hard as you can to not allow the car to go into regen when in traffic.
Its hard to manage the pedal correctly if you drive multiple cars alot. Then you get into the Prius and by default you let off the gas completely where in a Prius you shouldn't. That hurts mileage and forces constant regen. Don't mean to preach but not sure of your hyper mileage skills.

Now as far as your log where you mentioned "white screen". Thats not right which makes me think maybe the dreaded little 12 volt battery in the trunk is bad. I doubt your actually losing that much battery energy just sitting there without throwing a cel hybrid warning.
Its worth 5 minutes to check the battery.
Do the on screen mfd battery check and post those 3 numbers. We are most interested in the first 2: ign on and especially accessory mode.

If 12 volt ok if it was me I would spend $125 in diagnostic fee at dealer and have them hook up there Toyota Techstream analyzer to the hybrid battery and see what each module voltage looks like.
Post module voltage back here. At least you'll know and can deal with it and not be left stranded somewhere.

And like i said in the other thread and the poster above me you need to manage the cabin heat. Good tint...and most importantly windowshield cover and crack the windows about 1/4 of an inch.
The Priusshop on this site sells the best windshield cover. It fits perfect and going on 4 years of daily use and still excellent.
I don't let my car sit in the sun for 5 minutes without the windshield cover on. You have alot of expensive electronics in the dash that do not enjoy being boiled everyday.

Good luck and post back numbers!!

 

It has nothing to do with my "hyper milage skills". Most Priuses can be parked for 30 minutes in 90 degree weather without this occuring. A few of use have cars with an issue that I would really like to figure out. I have a new 12V battery. The fan works, but when the car isn't running the fan doesn't help. After the cabin cools from the fan running for a while and the ICE charging it's butt off the car will start to run normally again. I'm not talking about hours in the sun in Phx in 120 degrees either. 85 to 90 degrees for 30 minutes will do it. I suppose I could pay to get it tinted, then deal with the low visibility at night, and get a windshield cover, but those are all bandaids, because thousands of other Priuses owners don't have to do this. I want to find out what is wrong with my Prius. At the end of the day I need a good tech, but haven't found one yet.

 

Question, you guys are in NM and FL, do your Priuses behave like this. Can you leave your car in the sun for 1/2 hour? 1 hour, 2?

 

I wasn't even replying to you. I was talking to the original poster and if you took the time to read my post before busting my balls you would see I was refering to his excellent documentation of his issue not your whiny crap.

 

If parked in hot weather with a full (7 - 8 bars) battery, in an older car with a weakening battery, this will happen. Because the battery is older and weaker, it tends to get overcharged, which causes an exothermic chemical reaction. Turn off the car, and it has no chance to discharge the battery, nor does the battery fan run. So it sits there and cooks, venting electrolyte, and reducing capacity.

Park your car with 5 bars or less. There is a very simple way to do this: run the A/C on max. That will also help cool down the pack. It only takes a few minutes.

 

Hi mikemartin9--

I'm surprised nobody's mentioned the Prius's tendency to drain the pack in S1.

What exactly is your drive for the first sixty seconds or so? There's one coffee house that I like to go to that has me park on the street. When I leave, IG-on, pull away, 25 MPH speed limit quickly becomes 35, and then 45 while going up a decent incline. If you accelerate moderately, it's just enough to drain my pack from 6-7 bars down to 2 bars in a hurry because the Prius is still stuck in S1 hell for the first sixty seconds of the drive and refuses to draw power from the engine unless you press the gas pedal significantly (more than 2/3rd).

If this is your case, try accelerating more briskly up the hill (enough that you can hear the engine revving considerably) or waiting the 60 seconds until the car's out of S1 before pulling away. If you have a ScanGauge, make sure you have a gauge set to IGN timing. When the Prius is in S1, it likes to keep the IGN at -10 and TPS at 19-20. Press the gas pedal enough to force IGN into positive and it may solve your battery issues