Exasperating misinformation on 12V battery

you could check it, but most people don't. there are some threads here if you can find them.
also on replacement size and available options.

 

i don't know much about 12 volt batteries. i do know you can get a free load test at most auto parts stores, or even turning on all the electricals and watching the voltage decrease over time, if you understand what's healthy and what isn't.
i'm old enough to remember checking electrolyte levels on a regular basis. but these days, i'm comfortable caring for the 12v as best i can and replacing when necessary.

 

It's flooded, right? Yes
I can check the electrolyte? Yes
I should check the electrolyte? Yes
There's a tool less likely to damage the caps than a screwdriver? Use a nickle or quarter, if you need to get a better grip
What exactly is it called or can I have a link? Huh??? fill with distilled water to the internal line

You stated the battery was at 12.5 vdc, so I believe it's in good shape and should last a good long while - if properly maintained...

FWIW; all gen4 batteries are under the hood - all other Prius are in the trunk or under the seat; past and present.

 

Love the title of this thread. If removing just the 12v battery from the title, the rest of the title could probably fit in 50% of the posted threads in this forum.

 

The battery model number (345LN1-MF), you would see the MF designation is "maintenance free" flooded battery. It is similar to one in my 2025 Camry. You should be able to use either a regular flooded battery or a maintenance-free battery. AGM does have a different charging profile.

 

The battery should be fully charged when checking the fluid and adding water.

 

What you need to know about 12v ICE (Internal combustion engine) in front end of Prius Prime is doesn't talk to the back-end of the Prius when traction battery gets charged.
It's a stupid story, but I had a 100k warranty so when battery died it replaced them because Dealer Technicians kept saying the car had a problem. They replaced the ICE every 18 months when they died - for 5 yrs, and they kept diagnosing the car and kept saying the car had a problem and I took them at their word.
After warranty ran out I finally gave it some thought and charged it myself, not having seen all the PriusChat articles saying to do it.
You have to put a volt meter on it once in awhile and manually charge it or it will come up with a Bad cell and leave you stranded. Or put a solar panel on dashboard hooked to battery directly, or waste the gas and put the car in CHARGE Mode on purpose periodically because that's the only time the car itself will charge the ICE battery-but you still have to test it to make sure your staying ahead of the problem.

 

i assume you mean the 12v battery, not the (ICE - Internal Combustion Engine) engine (!)

 

For checking the electrolyte level on a flooded-acid battery, I've found the only way to see the level clearly is to haul it out of the car, set on a bench and put a light behind it. This is something I'd "sometimes" get around to, about halfway through it's lifetime. Clean off the case, the posts, the inside of the cable clamps, and blow the dust out of where it resided as well.

No clue. In addition to simple battery tests, I'm using a Solar BA5 battery tester* from time to time. It's a new generation electronic load tester, also gives a rudimentary verdict on it's condition. Current iteration is BA9 I think.

Google results said that, or was that bit hyperbole?

* There's more info on that tester, in the battery testing link in my signature. (If you're on a phone, hold it landscape-oriented, to see signatures.)

 

In most flooded batteries I've looked at, each filler 'well' has a neck that reaches down into the cell to the level where the electrolyte should be, and the bottom of the neck has a couple notches so it isn't a continuous edge all around.

When the electrolyte reaches the right level and touches the bottom of the neck, surface tension pulls the liquid into a kind of eye-shape (with the corners at the notches where it isn't touching) that you notice right away in how it reflects light.

 

How to Use a Battery Hydrometer: Avoid 6 Common Mistakes!✅

 

Putting the car in park at stop lights etc or in the driveway in ready mode charges the 12 volt. Engine off. Get a battery monitor.

 

If they knew the car had a problem, why did they not try to fix it? Was it cheaper for them to keep replacing the battery? Ideally you should have pressed for a repair and, if a Toyota extended warranty, call Toyota to get involved if they did not fix the underlying issue. It is too late for you now, though.

 

It's more profitable to keep you coming back for more, by managing the symptoms than fixing the root cause.
IMHO; They were 'milking' the extended warranty insurance company.

 

In hindsight, ideally the customer would have realized they would be left with the problem after expiry.