At what point do you replace the 12v battery?

Yeah I'm replacing the battery on our daughters pilot tomorrow. She's so busy I haven't had a chance to use my tester. She reports it's a little sluggish when starting. It's had at least 3 incidents requiring a jump start, and will be 5 years old in December.

 

Yes but they might not have booted up CORRECTLY and thus might not work right.
It is not a difficult concept.

 

are you implying that a prius can be made 'ready' incorrectly?

 

NO. I am flatly stating it.
And that possibility exists with virtually ALL new cars these days, not just the Prius or other hybrids.

 

Well did the swap yesterday. Surprisingly, the old one was still reading pretty good (with Solar BA5): CCA still a fair amount above spec, and "passed". The new one had about 100 CCA on it though. OTOH:

The battery's coming up on 5 years (and winter), and my daughter's been noticing it struggling on cold start ups. So no regrets.

 

fair enough. i have to disagree though, only because it has never been reported here.

 

SIGH.
It has been reported here many, MANY times.
Car runs but suddenly throws all kinds of seemingly unrelated codes after it starts.
You can disagree all you want but that wont' change the facts.

 

of course that has been reported here, but not the 12v being the problem

 

Your memory is failing.
Just stop, please.

 

au contraire. as usual, you have no facts

 

But you have plenty of insults to throw around.

The fact IS that there probably are somewhere around a hundred cases in this forum alone in which vehicles suddenly displayed various lights and codes and failed to start or started and ran bad or started and ran good for a while before failing........and the solution for many was a new 12 V battery.

YOU have personally participated in many/most/all of those discussions.
YOU also have personally recommended testing/replacing the 12 V battery in some of those discussions.

Having these pointless discussions with you is getting REALLY old.

 

yeah, it's tough typing into the internet, i understand. and yet, you always feel the need to have the last word.

the only time i have recommended testing or replacing the 12v is when the car won't become ready. it is my understanding that the inverter takes over after that.

 

Computer boards not booting up properly due to low 12V battery is prima facie evidence of bad computer design.

Various other systems requiring substantial power can have reasonable excuses for low-battery wake-up problems. But the basic computers and digital controls have no such excuse. If the available power is not enough to ensure proper boot-up and initialization of the digital logic, then the power-on reset circuit must not allow it to proceed.

 

It's oft reported here that the first inkling of a failing 12 volt battery is everything but a simple warning, say "12 VOLT BATTERY LOW". Instead, just a lot of weird behaviours manifest.

 

Yes, Prii don't give a clear explicit low battery warning. And they have numerous weird behaviors on low batteries. But I don't know those problems to be in the basic digital logic and computer boards vs the numerous power-hungry other electrical components. And I don't give them full credit for good software design in how problems in those other systems are handled and reported.

And I won't go quite so far as to say (from a professional insider viewpoint) that just because certain design practices are inexcusable, necessarily means that such flaws are absent from our cars.

 

Well, just replaced the 8 year old 12v battery, charged it with my battery minder & fired up the Prius-----No Joy!

I tried driving it & shutting it down multiple times & the warning lights did not clear

The HV battery shows 80% and the car drives normal, tho the steering & brakes are stiff.

Since it seems the HV battery seems OK I guess there is a problem elsewhere....

Brake ABS system or Brake accumulator? I hope not that's lotsa $$$$$$ !!!

I guess I gotta take it in to the Toyota Stealership...........Bummers.

 

Turn the car to ready, check the voltage at the terminals. Just verify the DC-DC converter is working properly, should be 13 V - 15 V.

moto g(7) power ?

 

Jzchen, I just measured 14.45 volts at the battery with the engine running, and 11.84 volts with the engine ready but off and the headlights on and measured 11.84...

What does that tell you?

Thanks, Jim

 

I strongly suspect that it is a matter of COST. GASP.
Having the code and hardware present to actually verify the sanity would be cost prohibitive.
You apply the power, wait an appropriate amount of milliseconds, make some very basic operational tests.......and pray.
This isn't rocket science after all.

 

It might tend to indicate that you didn't get the battery fully charged.......or that there is a "loose" main cable connection.
What does it read with everything OFF ?
With no load, 12.0 indicates roughly 50% discharged; 11.8 would be something like 70% discharged.