Modded Mustang Forums banner

1 - 17 of 17 Posts

·
Registered
Joined
·
4,366 Posts
Discussion Starter #1
Whenever I let my car sit for 3 or more days it won't start because the battery is dead. Is this a battery problem or is something draining the battery while it is sitting? It is an optima yellowtop.
 

·
Registered
Joined
·
1,619 Posts
Could be either. Do this.

Disconnect the negative terminal on the battery and let the car sit for however long this usually takes. When the time is up, hook the battery back up and see what happens. If it's dead, then it's the battery, if it starts right up, you have a drain.
 

·
Registered
Joined
·
4,366 Posts
Discussion Starter #3
Could be either. Do this.

Disconnect the negative terminal on the battery and let the car sit for however long this usually takes. When the time is up, hook the battery back up and see what happens. If it's dead, then it's the battery, if it starts right up, you have a drain.
Damn that would mean I can't drive my car for 3 days. Is there a faster test?
 

·
Registered
Joined
·
4,366 Posts
Discussion Starter #5
I've had places lie and tell me the battery was bad when it wasn't though. I just tested the voltage and it's 11.83V. If I leave it disconnected and it drops it means the battery is bad right?
 

·
Registered
Joined
·
1,388 Posts
sounds almost like something else is draining your battery. Do you by chance have an aftermarket stereo system or have you do any electrical mods to the car at all?

With doors shut and key out of ignition...disconnect the negative battery cable, then put it back on slowly...do you see a decent sized arc? if so you could have a short some where.

And to answer your question, yes if it drops below 11 volts you have a bad battery.
 

·
Registered
Joined
·
4,366 Posts
Discussion Starter #8
Yeah but it could get worse and I could get stuck out somewhere with a dead car. What could be draining the battery? The voltage went up from 11.83 to 11.86 when I disconnected it.
 

·
Registered
Joined
·
1,388 Posts
Yeah but it could get worse and I could get stuck out somewhere with a dead car. What could be draining the battery? The voltage went up from 11.83 to 11.86 when I disconnected it.
.03 volts is not anything to be worried about...that is an extremely minimal amount, its only a 30 milivolt difference. If for some reason you get stuck somewhere, you can always jump the car the alternator takes car of everything once the car is started.

BUT voltage doesnt mean a battery is good...amperage is what determines if a battery is good and only way to test that is have the battery load tested.

like i said before, it sounds like you have something draining the battery.
 

·
Registered
Joined
·
1,619 Posts
.03 volts is not anything to be worried about...that is an extremely minimal amount, its only a 30 milivolt difference. If for some reason you get stuck somewhere, you can always jump the car the alternator takes car of everything once the car is started.

BUT voltage doesnt mean a battery is good...amperage is what determines if a battery is good and only way to test that is have the battery load tested.

like i said before, it sounds like you have something draining the battery.
+1.

A voltmeter on a battery doesn't mean anything. When the battery is being put under a load, i.e. starting your car, it draws amperage, which in turn starts your car. Or in your case, doesn't start the car.
 

·
Premium Member
Joined
·
11,367 Posts
I just had a year old Optima red top do this. They have a 3 year replacement warranty. Mine would go dead after 2-3 days. There was no draw so I disconnected the battery to see if it would still go dead and it did. I took it back and exchanged it for a new one.......free of charge. That is the nice thing about Optimas and what makes them worth the extra money.

I've had places lie and tell me the battery was bad when it wasn't though. I just tested the voltage and it's 11.83V. If I leave it disconnected and it drops it means the battery is bad right?
Yep, many years ago when I used to manage a corporate auto parts store they had us using a rigged battery/alternator/starter tester. New parts off the shelf tested bad.
 

·
Registered
Joined
·
927 Posts

·
Registered
Joined
·
1,388 Posts
have an aftermarket alarm or other item ?

multimeter is your best friend .

Multimeter - Wikipedia, the free encyclopedia
he already used the multimeter on it, thats how he got the 11.83 volts. It will give him an amperage but with the amperage of a battery, it would blow up the internal circuits of most multimeters (under load)...unless he has an amp probe. Keep in mind most car batteries are over 500 amps.

And yeah things like aftermarket alarm or stereo if not properly installed can drain a battery.

But he might be in the same situation that Darrel was in...just might have a defective battery...if taken to a reputabile parts store, might be a good idea

BTW i'm an electronics technician, so if you have questions feel free to ask me.
 

·
Registered
Joined
·
1,544 Posts
I just had a year old Optima red top do this. They have a 3 year replacement warranty. Mine would go dead after 2-3 days. There was no draw so I disconnected the battery to see if it would still go dead and it did. I took it back and exchanged it for a new one.......free of charge. That is the nice thing about Optimas and what makes them worth the extra money.



Yep, many years ago when I used to manage a corporate auto parts store they had us using a rigged battery/alternator/starter tester. New parts off the shelf tested bad.
not all of the optima's doo. just the starting red top. well at autozone at least, the yellow top only has a 1 year. i work there, it's retarted.
 

·
Premium Member
Joined
·
11,367 Posts
not all of the optima's doo. just the starting red top. well at autozone at least, the yellow top only has a 1 year. i work there, it's retarted.
I must have spaced off the yellow top part of that post. The yellow top still has a 1 year free and 1 year prorated after that. If its bad and still in warranty, exchange it. If its bad and out of warranty get a red top and be done with it.
 
1 - 17 of 17 Posts
Top