Mileage dropped from 46 to 39!!! How?

It has been 4 years, have you checked your 12 volt battery?

Weird stuff happening? MPGs dropping? Test The Battery | PriusChat

 

how about the weather?

 

no need to rub it in.

 

I believe the sequence is:

- Press and hold the MFD Info button, then turn the headlights on and off three times to enter Maintenance mode; release Info

button

- Press “Menu” (on screen)

- Press “Display Check”

- Press “Vehicle Signal Check” - the battery voltage is shown and should be about 12.4 to 12.8 Volts (normal for an unloaded

battery)

- Again without brake pedal, press Power button and release to put a current load on the battery - the voltage should stay

above 12.0V (if less than 12.0V the battery is not well, or there is a fault or unusual load somewhere)

- Press brake pedal and press Power button once to enter "Ready" mode - the battery is now charging at about 14V (if less than

13.6V or more than 14.4 there may be a problem with the charging circuit)

- Turn car OFF to leave Maintenance mode


Read more: http://priuschat.com/threads/weird-stuff-happening-mpgs-dropping-test-the-battery.73400/#ixzz2ENuBCSHk

 

You have tree safe choices:
Toyota's OEM battery
Optima Yellow top Optima DS46B24R Optima battery direct fit replacement for Prius 2004 + with Instructions
Exide Edge
Exide AGM Car Battery (Group S46B24R)

 

I did this check and got the following results, do these indicate an issue or just that I need to keep an eye on the battery as we enter winter here in Kansas? I have owned my 2006 Prius for a little over 2 years and am not sure when the current battery was installed. Thank you for any assistance you can provide.

Press “Vehicle Signal Check” - the battery voltage is shown and should be about 12.4 to 12.8 Volts (normal for an unloaded battery) (MY READING WAS INITIALLY 12.1)

- Again without brake pedal, press Power button and release to put a current load on the battery - the voltage should stay above 12.0V (if less than 12.0V the battery is not well, or there is a fault or unusual load somewhere) (MY READING WAS 11.8)

- Press brake pedal and press Power button once to enter "Ready" mode - the battery is now charging at about 14V (if less than 13.6V or more than 14.4 there may be a problem with the charging circuit) (MY READING WAS 14.1)​

 

I would not worry unless I had other symptoms, then I would mail order a Optima from elearnaid at the first real symptom. Think of the test as a way to know if your symptoms are battery related.

 

As a point of interest I've discovered this sequence also works just turning on the parking lights 3 times instead of the headlights. I like that much better. I hope your MPG 's improve also.

 

I have a 2005 prius w/ 105,000 miles on it. My summer gas mileage was around 48ish mpg. I do a lot of mountain roads. In Dec it dropped to 39mpg. After reading these threads last week I checked the start Batt (11.9 after sitting a few hrs) and 13.9 while on. My dealer replaced the batt last summer. I also replaced the spark plugs (this got me more power while driving and better gas mileage. Thanks for the tip!! Is there a sensor I can check for carbon build-up?

 

We would expect the mpg to drop some in the winter but that may be too much. It is not clear how you got your battery readings. You should report all 3 readings in the sequence outlined above. If you did it this way your 11.9V is low. The range between the 1st and 2nd number (that you didn't give) gives an indication of the health of the battery, as does the last number that indicates the charging amps.

A new battery is not necessarily a fully charged battery. After you report all 3 numbers you could try slow charging with 2 amps or less. You can do that at the jump point under the hood. Be very careful to connect it correctly the first time. You may not get a second chance if it is connected backwards even for a split second. The cost of repair can be 4 figures.

 

Thanks for responding Steve. After a cold night the 1st batt reading was 11.9 with a load on it was 11.5 and powered up was 13.9. I fear the 11.5 for the loaded batt is weak especially for a 6 month old dealer battery. I talked to my dealer guy and he said those readings have nothing to do with the battery life. He gave me some line about it has no alternator and there is something else thats is pulling power from it. I think they are trying to get out of replacing a bad battery they put in. What simple explaination can I tell them so they look at this battery seriously?

 

Well, they do have to do with present battery health. The 11.9V is about 50% SOC and much lower than it should be considering the age of the battery if the car is charging, which it is as we see with the 13.9V reading. It's true it has no alternator but it does charge this battery and it is doing that. The range between the 11.9 and 11.5 readings doesn't seem to be an unusual drain. I'm not a battery expert but others here are very knowledgeable and with these readings should be able to give more info. I would probably try trickle charging it to see if it will hold a higher charge. It should not be reading 50% state of charge at 6 months old. What is the warranty period for the battery? I doubt this is the car's fault.