troutbum Loc: north central pennsylvania

First make sure battery terminals are clean takes very little film between cable end and post to cause problems. Also put a analog amp gauge in series with positive cable to see if any significant current draw, if nothing major then do the same with negative cable. Next would be to pull a single fuse to see which circuit has above average current draw. My guess is your battery is near to biting the bullet and good load test is in order.

Dannj

Just want to share a story of the weird things that can lead to battery problems.
In the early ‘7Os, I drove the Chevy Nova I’d just picked up from the dealer to the gas station. After I filled the tank, the car wouldn’t start so we jumped it and drove back to the dealer. I tracked down the salesman who gave me a song and dance about the battery sitting while the car was in transit (this was at a time when you actually ordered what you wanted in the car) etc. and that he would have the service dept. charge the battery. I insisted on a new battery...which escalated to a conversation between the sales manager and the service manager..which I got.

That night we drove into mid-town Manhattan for dinner and when we left the restaurant the battery was dead again. It was late Saturday night so I had the car towed back to the dealership and left it in their driveway and called the salesman first thing Monday morning with my tale of woe. This is when I learned that once the car is in your hands, the sales folks want nothing to do with you...it’s now a service issue.

Anyway, to shorten this very long story it took them a week to find the problem. While working on the car, a service rep noticed that sometimes when he opened or closed the passenger door the dome light wouldn’t come on, or it would flicker, or sometimes it wouldn’t go off. Eventually he traced the problem to a screw in the door panel that at times would rub against the wire controlling the dome light from that door. Remember, this was in days before computer chips and sensors controlled everything so trouble shooting was essentially trial and error.
There’s more to the surrounding story that gave me a lot of insight into how the car business works but sometimes flukey things just happen.

stu352 Loc: MA/RI Border

If you can't do it yourself, have an auto technician read the current being drawn from the battery when everything is supposedly "off". There's so much electrical crap in cars these days that it only takes one failure somewhere...

I've heard of several of these, traced to such things as a sticking relay or a broken, "always on" trunk light switch.

Stu

Cykdelic Loc: Now outside of Chiraq & Santa Fe, NM

If you leave the smart key in the car it can continue to draw.

agillot

you are right , a totally dead battery is usually caused by a drain in car , common with modern cars , they are loaded with modules that must go to sleep after key off , doors closed , it make take 1/2 hour .if one stay on , it will drain battery .on rear cases , a battery can short internally and go dead with time .

Al Freeedman

You can make a simple test wire/light to see if there is a leak. or you can buy one at an auto supply store.
Disconnect the plus terminal then connect a test light between the battery and the terminal you disconnected.
With everything turned off, if you get a glow from the test light something is on. You can find
where the leak is coming from by disconnecting the fuse one at a time and you will be able
to determine where the leak is coming from.

Captain Al

G. Crook Loc: Linden, TX

I have a Ram with dual batteries. After repeated trips to the shop with “low voltage” showing on the dash and replacement of one battery with a dead cell, dash was still showing low voltage. Replaced bad alternator. Thoroughly cleaned all battery posts and terminals. After much probing and testing the problem was finally found: the clamping bolt on one of the battery terminals was corroded and not making proper contact between the post and attached wiring. Replaced one $.35 bolt, problem solved.

Difficult problem, simple solution. My out of pocket expense? Zero. Battery was under warranty as was the alternator. No charges by an excellent shop.

burkphoto Loc: High Point, NC

We drive Priuses — four of them. They use AGM 12-volt batteries located in the trunk, to run the computers and lights and audio gear. (Only briefly, or when in Accessory mode... an inverter powers everything from the high voltage battery after the car starts.)

The OEM batteries in the two 2009s lasted four and five years. The first one died without warning, in my garage. Jump starting couldn’t happen, because you can’t strap cables onto a Prius 12V battery — jump points are up front, under the hood, in the fuse box. It’s also a LOT of fun getting to the battery when the trunk is locked and the battery is dead! But changing the $220 battery is easy once you get the trunk open, via the emergency latch.

I bought a 2010, last May. It had been VERY gently used by retirees. It had been sitting for several months on a dealer lot. The 12V died two weeks after I bought it... with only a little warning. The dealer honored their 30-day warranty and replaced it.

My mother in law bought a used 2015. They had to jump it on the lot, because it sat most of the time for three months. They replaced the battery before she signed the deal.

Upshot: Monitor 12V AGM battery health carefully and proactively replace them. Toyota warrants their replacement for seven years, but five is more likely.

Jimmy T Loc: Virginia

Jerry, I had a new-ish battery go bad once and I could charge it and it was fine for a day or two then it would go dead again. I replaced the battery and shortly after that, the new battery went dead. I charged the new battery up and that night I opened the door from the house to the garage to see a light glowing inside the car. It was a light in the glove box. Years later I had a similar thing happen with an interior map light that had been left on. I felt kind of silly, however, it was a lesson learned the hard ($$$) way. You can admit it to your mistake to your photography fraternity because we won't tease you, grin.

Tomcat5133 Loc: Gladwyne PA

Could be the battery if original just died. Or their are hidden lights like in the trunk that
can get stuck on. Some cars like mine lose a small amount of charge like my old boxster.
You are always helping folks here. I solved the battery problem moved to FL.

Found this.
Reasons for quick battery drainage and how to prevent them
mechanic placing car battery into carYou may be making some errors. Hey, you are only human. We all make mistakes, and in such a busy world, it can be easy to accidentally leave the headlights on overnight or leave the radio on during a hectic evening. When you are done with your car, make sure all lights are off.
You are experiencing parasitic drain. Similar to leaving the headlights on, this could occur when some of the vehicle’s systems keep running after the car has been shut off. Some of this is normal, such as your clock always working, but there may be something else that is not meant to be running but continues to do so anyway. If you can’t find it yourself, you may need to check with a mechanic.
Loose or corroded battery connections. Have these tightened or cleaned, perhaps even replaced if need be.
Problems with the charging system. Your battery could be in fine shape, but the system that helps to charge it may be out of order.
Extreme temperatures. This one you can’t really help unless you move, but if you live in an extreme climate, that can really take a toll on a battery.

ChuckKarp

When my 4 year old battery died I pried off the sealed caps and the electrolyte was way lower than it should be.
The dealer said time to replace the battery because you can't add water to it. So of course I added distilled water
to the battery and charged it a few hours.
It worked perfectly after that. Maintenance free means the dealer does not maintain it they would rather you
pay them to replace it every few years.

Pepsiman Loc: New York City

Clean the posts and cables. The computer is always on and does run down the battery. Good luck...

PixelStan77 Loc: Vermont/Chicago

You may think it is sealed because you do not see those screws caps for the battery. If you look you will see a plastic block across each of the 3 cells. With a small screwdriver, you can pop that block off exposing the 3 cells. The ones that normally need water is the first and last.

polonois Loc: Lancaster County,PA.

I had the same problem in my Explorer. It turned out to be my glove compartment light was on all the time.

1Feathercrest Loc: NEPA

I believe that batteries now are all sealed and do not run low on electrolyte. Something caused a BIG drain on the voltage to cause it to completely discharge.