My first hiccup after 6 months, 6000 miles

I bought my beloved Prius past November. It is a 2010 Prius III.
It has worked absolutely fantastic for the past 6 months and over 6000 miles. At times, I didn't stop by a gas station for a month

Today though I had the 1st hiccup. Went to a bank for a quick deposit. Came out(the car was driven about 10 miles from an overnight rest at this point), got into my car, pressed the Power button and Nothing!.. The entire display was dark.
Doing that several times in the past, I thought I didn't press the brake pedal hard enough. Tried again with no luck. But then thinking: Even not pressing the brake pedal would turn the display on!..
So something was up. I tired several more times with no luck. The entire display was entirely dark. Normally, I would see some red lights blinking even when nothing is turned on. I guess it is the remote key detection light.
It wasn't even there.
Got out, walked around the car. Was about to use the remote to lock it, changed my mind thinking it may not unlock again. Forgot at that moment that I actually had a physical key inside the remote
Got back in to try more. Pressed the brake hard, pressed the power button. Nothing...
At that moment, I realized the power button light was orange. I remember it would be green normally.
Leaned over to the Info Display and I kind of saw the remote key detection light but it was dim. I was about to call my roommate to come get me and power button worked. Car powered on. Got some relief but not entirely. I knew something wasn't right.
I put it into gear and started driving in the parking lot before getting on the road. At that moment, I realized something was weird on the Display. I wasn't able to see the hybrid battery level indicator and the energy bar.
I then realized the Multi Info Display was totally dark The left display (speedo etc.) was working.
I depressed the gas pedal and the gas engine started up and I decided to drive it to home. I wasn't far.
The car drove fine till home (about 5 miles) except the Multi Info Display was dark.

I was thinking of the Aux battery on the way home. It is the original one (8 years old).
Got home and checked the voltage immediately. It was showing 12.6-12.7
I know this doesn't exactly mean the battery is good. It wasn't under load voltage. But I was hoping to see it around 12.3v or below. I will check it again in a few hours.

I powered up the car a few times and No Multi Info Display.

Came here to read some threads. I found one that is talking about "Multi Info Display Not Working"
Multi Information Display not Working | Page 2 | PriusChat

The issue the OP having wasn't related but at the end of the same thread a user "andy post", (thanks to his detailed writeup) posted something that was very similar to what I have experienced.

So is this really the aux battery going dead?

It is just very hard to believe that with a weak aux battery everything but the Multi Info Display is working.

No problem for me to replace that battery but I would like to have some input.

Is that it?

Thanks

 

8 year old battery is old and overdue for sure. I will look into replacing that though I am about to go out of town for over a month. Just trying to think if this is the right move at the moment.

 

149k currently.
I am just hoping it wouldn't be a bad MFD.

Just went out to my car. I was going to measure the standing battery voltage after a few hours but I pressed the power button which initiates the aux battery charge (Call me stupid). Though the MFD was back online this time... The car started up and all was functional.

Weird symptoms for sure...

 

Well they really go for that long. I logged one 7 and one 8 year old battery before. All were in Florida

 

Hi Mendel,

That's the idea before replacing it. I want to make sure that is the cause. I don't have a load tester. I will try to turn the headlights on and see if the voltage will dip. It is tricky to load the battery on hybrid cars. With a conventional gas engine this would be a no issue just turn the engine over.

Will come back with an update...

 

I have many of those but voltmeter won't tell you exactly. Sometimes batteries (even when they are bad) show good voltage when there is no load. A simple voltmeter won't catch that.

 

After an hour sitting, the standing voltage is 12.65volts. Quite good...
Turned the headlights on and the voltage dipped to 12.15volts. No good for sure...
Pressed the power button in that state and the car beeped and the whole thing shut down...

Boosted the battery with a 12 volts supply for a few minutes then the car powered on but again no MFD.

So the battery is shot for sure and will need replacing. Is the MFD issue related to the battery? We will find out after the battery replacement.

I will let you know...

 

Wow... Bisco you beat me by two years man
I have never passed the 8 year mark so far. I was very close but didn't happen...

 

Alright...

I got the new battery last night and put it on this morning.
As I guessed, the car powered up without an issue and the MFD is alive.

The new battery (without giving it any charge) shows 12.7volts (standing voltage) and with the headlights on, it doesn't go below 12.35volts.

Let me drive it a few hours and I will be able to tell you 100% if the MFD issue was directly related to the battery. But so far my guess is 99% yes...

 

It could very well be the reason. Toyota engineers might have thought that MFD wasn't vital and let the other more important electronics run instead.

Anyways, I drove the vehicle 50 miles yesterday and all working fine