Diagnose a bad/dying 12volt with scan gauge?

under 12.4 volts, after car has been off for a few hours.

 

Car will always show 13.8 to 14 volts when car in ready
Which is charging voltage. So disregard that.

U need to measure the battery first thing in the am before u start the car.

Try installing the SC and going into accessory mode which us foot off brake and 2 button pushes.

 

I am surprised that the car still starts.
You are WAY past needing a new battery.

 

11.8 is not enough with no load; neither is 12.0.
With no load the battery needs to be at least 12.4 and even that would indicate that it is getting a bit weak.

ALL of your readings indicate a bad battery........or one that isn't being charged long enough or often enough.

The only way to tell for sure is to charge it externally with an automatic charger and then take readings again.
If it is over 4 years old, you might as well just replace it.

 

I've never seen so much agonizing over anything so much in these forums as the 12 v aux battery. It's almost too simple to prescribe: If your battery goes dead much sooner than you expect, have it tested by someone who isn't biased in favor of selling you a new one, whatever it's condition.

If it checks out, stop fretting, because as long as it starts the car, it's fulfilling it's role in the system 100%.

P.S. By "start the car" I mean turning on ready-mode.

 

But if you check battery voltage in acc mode with MFD it isn’t no load condition. MFD and some other parts of car are draining battery so a bit lower voltages (compared to no load) are ok.

 

do what ed said in post #3.

 

Not true.

Many people have been down that road and advice like yours has caused them untold grief.
If the car only "starts" part of the time, it still could be a bad battery......regardless of the "test".
If it comes on accompanied by various, seemingly unrelated trouble lights and codes, it still could be a bad battery......regardless of the "test".

The simple fact of the matter IS that the standard CCA test is not good enough and never has been really.
In a conventional car, the "starter test" was much better; almost fool-proof.
A hybrid does not have a "starter test" so other indications are needed.

Ignoring those other indications is just foolish. (Yes Greg, I mean YOU.)

I will stop taking you to task for posting this........when you stop.
It is bad advice.

That's why I much prefer a $10 multimeter. Better control over the conditions.

 

Get a multimeter, check your 12 volt battery's voltage, with the car right off. It's not a load tester, but it will give you a decent idea of the state of charge.

A multimeter indispensable for so many things, even to check all the batteries (AA, D, etc) knocking around in your tool drawer. Or to make sure the power's REALLY off, when working on household wiring.

 

Yes, we've been down this road many times, and your opinions are well-known; so are mine. I'll continue to use my battery until it no longer activates the circuit that boots the computer into ready-mode.

That should be a long time in the future, because I don't use acc-mode at all, therefore my battery never needs to cycle, which shortens it's life. If I see any signs that the condition of the 12 v aux battery is having any sort of effect on the car, I'll be sure to let you know, and I'll be the first to admit my mistake.

 

My training and life's work is in Electronics.
Yours is in agriculture and the environment.
Which opinion on batteries and electronic equipment do you think should carry the most weight ??

 

That's no surprise.
In order to care, you have to be able to actually think.

 

BadaBing!