Car WON'T START dead battery?
 

So here's the story...

I have had this car since May 2014 and I have done all the maintenance on it and a bunch of mods (exhaust, Springs, rims, tires etc.). I also installed a subwoofer after about a month of owning the car which draws probably a good amount of power from my battery.the car has ran beautifully since I got it with just the regular oil change and stuff.

Lately however since it got cold here it has been having trouble starting up. Sometimes it would take a few extra cranks to start. This morning I Whent out to my car and it cranked about 3 times then failed to start. I tried jumping the battery and that did not work multiple times. I tested the battery on a multimeter and it Read 11.9 volts. So I'm assuming the battery is completely dead. The windows won't even go down when opening the door.

So my question is I know the battery is covered under the warranty still from speaking to them today but I dont want to get it towed to them because knowing my dealership they will blame it on the subwoofer and make me pay for a new one.

Do you think I can just take the battery out and bring it to them? They said they need to test the battery before they give me a new one. I have roadside assistance but like I said I don't want to have it towed.

Thanks!

Just buy a battery at autozone or some store. You can then bring the old battery for core refund.

OEM battery is not a maintenance-free battery. Electrolyte level must be regularly checked and topped off with distilled water as required.

See pages 304-305 (32-33) of the Owner's Manual.

Wow I did not even know that :bonk: so maybe the level is low do you think if I top it off then try to jump it it would last any longer?

And why pay for a new battery if they said it's under warranty still and a battery is covered?

It's a crap shoot. If one or more of the cells dropped too low it might recover and accept a charge. It's worth a try and a valuable lesson either way. Good luck!

I just know the cells in mine do boil down. The term "boil" isn't really accurate. The water separates into molecular hydrogen and oxygen through electrolysis.

Oh, and as long as your sub amp is installed properly, it's not an issue.

Quick question it says to add distilled water, now it's below freezing Temps here. Wouldn't that water just be frozen in there?

I have a battery charger so I'm going to just try and charge it up and add water and then re-install it and see if I have any luck.

The electrolyte is a sulfuric acid solution so, like salt dissolved in water, the freezing point is pushed way down.

Add water first, then try charging it.

It's not just water in there, it's 38% sulfuric acid and 62% of water. This mixture freezes at around -60 C (-75 F), sources vary a bit. Interestingly, around this concentration the freezing point is the lowest. At a lower concentration it's higher as most would expect (about -32 C /-25 F for 30% sulfuric acid), but it also goes up for higher conecntratioms: about -40C (-40 F) for 50%, about 0 C (32 F) for 80%.

Normally a battery only loses water due to electrolysis and evaporation, so the concentration of sulfuric acid becomes higher than 38% and the freezing point goes up too. But obviously you normally should not reach concentrations at which the solution would freeze in winter conditions, you would have to lose a LOT of water. And by adding water to somewhat over-concentrated sulfuric acid you will actually bring it back to 38% and a very low freezing point.

If you are losing both water and sulfuric acid due to a leak then adding just distilled water will dilute the remaining solution below 38% and drive the freezing point up, but again even 10% (very much diluted) sulfuric acid freezes at ~25 F (- 4C).

And if you had a massive leak from the battery, you would probably know from sulfuric acid corroding through the chassis...

Okay so I just pulled the battery out in the freezing cold Haha dedication.

Water level is fine I guess the battery is bad I put it on a charger outside of my house and I'll just leave it overnight.

Guess I'll just take the battery to subaru tomorrow.

Bummer. Oh well. It was worth a shot.

Thanks for the help man!

So I charged it overnight and re installed it and it started. I'm guessing there is a few bad cells.


Is there a way to check the cells. I tried testing the cold cranking amps and it read 9.5 volts when I cranked the engine.


Don't want to buy a new battery unless I need one.


What should the voltage be reading when the car is off?

A fully charged car battery should read at around 12.6 Volts.

Get a float-type battery hydrometer. Inexpensive ones are available at all auto parts stores. That's the best way to test the health of your battery.

Google is your friend here. TONS of basic tutorials. I'm betting one or more of the cells is sulfated. Google "battery sulfation."