2008 Gen 2 Prius Dead 12v Battery

tough question to answer over the internet for someone with no tools.

best i can say is ask them to charge it again, buy a cheap voltmeter, bring the battery home, and bench test it every day for a weak.

otherwise, i would just get a jump pack in case it dies

 

Probably ought to have a jump pack anyway. No one is immune from accidentally leaving the dome lights on.

 

You really need to know three things...

1) Is there a drain on the 12v battery, seems like this *might be* the case (added stereo, alarm, radar detector, USB charger etc??)
2) What is the "health" of the 12v? Will it hold a charge overnight when disconnected?
3) Output voltage of the DC-DC converter? Should be 13.5V minimum while the car is "on" and having a "good" & charged 12v battery.

 

YES.
Unless you enjoy surprise adventures when your car fails to start at some random place and time...........
then GET A NEW BATTERY.

5 years is a pretty good run.
And sitting idle for long periods is hard on the 12 V battery.
Going completely DEAD is VERY hard on them.

If you try to "stretch" this and save a few pennies, circumstances might dictate that it ends up costing you a LOT more in the end.

 

I understand, after years of paying well under $100 for a new battery why people balk at paying $200, but when you need it, you need it.
kris

 

when you use the signal, there is a load on the battery. so 12v may or may not be good. it is useful to know the static voltage, as well as the loaded voltage, then track the daily changes.
a battery in good condition should be able to sit for weeks when disconnected without losing much voltage.

when connected, prius puts a small draw on the battery, but the daily drop should be very small.
it's a bit of a guessing game when it gets toward the low end. 12v and 11.2 don't sound awful, but what are those numbers after a week of not driving?

 

That is a VERY good thing!

Just to clarify, the 12v battery in a Toyota Hybrid does not start the engine, it simply provides initial power to the vehicle's electrical system, after which the DC-DC converter takes over.

 

Alas, it is not uncommon to get an inadequate test, even from a shop that should know better.
IF.....they had repeated the test several times in a row, the result might have been different.

 

I don't think it will add much longevity but who can really predict the future anyway?

For sure though, you will keep the battery in better condition by way of lowering the current draw by disabling the SKS when you know the car will sit for any time undriven for any period of time. The owner's manual advises doing exactly this when leaving the car parked up for any significant time.