12 volt aux battery (testing a theory)

I ordered an Optima Yellow Top for my 2001 Prius and will let you know the results soon.

Here is what has been going on...
If the car sits over night or after working 13.5 hours, I get the red triangle if I try to start the car immediately. Also getting an ABS light.
If I shut off the car and then turn the key again, the errors may or may not reappear.
The next day I tested a theory. I turn the key to ACC. and wait. The error codes appear and I let it sit this way for 10 seconds or so. Then shut off key and then restart it or even go back to ACC. Errors are gone most of the time. I have a scan gauge and the error is a P1436 and the dash shows ABS fault.

I tested the battery using the diagnostic in the Prius. Static voltage is 11.8 or 11.9 upon running the test (done before starting the car and it sat for 13 hours). When I apply the lights, rear defrost and heater fan on high the voltage drops to 10.4 or 10.6.

I believe the battery is causing these errors. If I turn the car to ACC. and wait, I am getting the battery to have a chemical reaction and it becomes a bit stronger for the next try which then is enough to clear my codes and work correctly. I don't know how to explain the battery theory, but my dad taught me this for starting a car in below zero temps here in the mid west. The car will crank stronger if you let it react on ACC. for a bit then try to start the car verses an immediate try.

Once the Optima battery is in place, I will test the voltages again and compare the results of new and old. I am curious if the errors will go away also. It is consistant and I should have immediate results. The current battery looks like the original brand for a Prius and I am curious what year the battery was replaced or if it is original? I just bought this car and I am finding many original parts at 224,000 miles. I can't believe the battery is original, but will find out soon. There should be a manufacture date on the batteries correct?

Below is the test procedure from elearnaid and my test results are a bit different then what they say should be a defective battery. I would think my voltage would go below the 10.2 since my static voltage is so low.

Hoping to share what I learn and would like to hear of others experience. By the way, my milage is consistantly holding 41 mpg given the same driving pattern. I will see if a battery can raise mpg as some say it does. I will also find out if erroneous errors will go away.

From Optima battery and installation kit for Prius 2001 to 2003

Do this test after you have driven the car for at least 30 minutes. This will give the battery a chance to be fully charged.
Put the transmission in Park.
Turn ignition switch to off.
Engage the parking break
(2001 to 2003)Turn ignition switch to Accesory. (do not start the engine)
Push Display button. (2001 to 2003)Top rocker to the right of the radio 2004+ top button to left of screen - "DISPLAY" will now appear in the upper left corner of your screen.)

Push on the upper left(1) of the display just inside the box, withdraw, push on the lower left of the display(2) and withdraw. (see picture) Do this three times. Keep trying till the screen changes. If the word "Display" in the upper left hand corner of the screen goes away hit the display switch again.
Push on Menu in upper right of display screen.
Push on Display Check
Push on Vehicle Signal Check
You will see the 12 volt voltage displayed.
With no electrical accessories on including lights the voltage should be fluctuate between 12.2 and 11.9. The lower the voltage, the less of a charge your battery currently has. If the voltage is low do not proceed as the load test might totally discharge your battery. (If you see a voltage around 13.5-13.8 you are seeing voltage from the high voltage battery being converted to around 13.5-13.8 in an attempt to recharge your battery. This normally does not occur till after you start the engine but might occur earlier if the battery is very drained.)
You can also test the battery by turning on the headlights, rear window heater and the heater fan. For a new battery the voltage would be around 11.3. If the voltage drops below 10.2 it should definitely be replaced. For voltages in between the lower the voltage, the lower current charge of your battery.

 

Now I was curious again and tested the battery just now. I drove 6 miles to work and the car has now sat for two hours. This time I took the DMM and checked the voltage directly on the battery.
12.52 volts static.
11.61 volts with headlights, heater fan high, and rear defrost on.

Did the test with the Prius screen and this is the voltages.
11.6 static
10.8 under load.

I believe the battery needs to be replaced with these measurements? The internet is so conflicting with information. If a battery drops below 12 volts with the load, that is bad?

I plan on using a trickle charger with the Optima battery at least once a week. I read that short trips will not fully charge a battery and will destroy it over time. True? I drive 6 miles to work and consider this a short trip. Paid $180 for the Optima and want it to last. Thoughts anyone?

 

Is this a defective battery with 11.6 on load? I wonder if I jumped the gun and bought the Optima. I would like this car to run for awhile and doing the preventative maintenance seems to be where to start. I believe the Optima will ensure a long life but wonder how far this battery would stretch. If the codes go away, I made a great call. Until then, what did this voltage checking tell me?

 

I called Linear Logic (480-656-4089) and they are sending me an ISO cable. This will remove the wires that confuse the system. Heading home to change out the battery to an Optima and will hope for years of use with it.