rapid HV battery drain on startup hot days only

[mikemartin9]

We are having a problem with rapid HV battery drain after startup on hot days,
from green to 2 or no bars in 1/2 mile the following relates our experience

Our car is a 2008 Prius package 2 purchased in November 2007 with 9000 miles

date

[hiremichaelreid]

Originally Posted by mikemartin9

We are having a problem wit rapid HV battery drain after startup on hot days,
from green to 2 or no bars in 1/2 mile the following relates our experience

Our car is a 2008 Prius package 2 purchased in November 2007 with 9000 miles

date

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.

[Patrick Wong]

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?

[hiremichaelreid]

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...

[Patrick Wong]

Originally Posted by hiremichaelreid

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.

[richard schumacher]

Originally Posted by mikemartin9

We are having a problem wit rapid HV battery drain after startup on hot days,
from green to 2 or no bars in 1/2 mile the following relates our experience

Our car is a 2008 Prius package 2 purchased in November 2007 with 9000 miles

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

[mikemartin9]

Originally Posted by Patrick Wong

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? A: Santa Clarita to Sun Valley, Ca
• What is the approximate altitude of your home and your office? A: Santa Clarita: altitude: 1200 to 1400 ft : Sun Valley: altitude: 810 feet good sized hill at the beginning in the morning
• What is the commute distance and your average speed?A: Approx 25 miles, approx 45-50 MPH

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? A: Road trips are significantly better (never have a discharge problem) to Palm Springs Ca 50 + MPG return 47-49
• What temperature is your air conditioning set to achieve? A:75 degrees
• What is the ambient temps in your area now: mid-80 degrees? A:91 degrees

I answered you inline. We are going to continue our log to be updated next Friday
:Mike

[mikemartin9]

Originally Posted by richard schumacher

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

Oil level is good. Tire pressure 42 front 40 rear. Battery does spend most of its time in the blue however usually ends up fairly high at the end of the morning commute. the problem is that the discharge seems to remain for the freeway portion of the return commute, 14 Miles, with the ICE racing trying to charge the battery which does not occur till off the freeway for the last 11 miles which is a long 300 foot climb.

Mike

[Patrick Wong]

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.)

[drees]

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.