- My Forums
- Tiger Rant
- LSU Recruiting
- SEC Rant
- Saints Talk
- Pelicans Talk
- More Sports Board
- Fantasy Sports
- Golf Board
- Soccer Board
- O-T Lounge
- Tech Board
- Home/Garden Board
- Outdoor Board
- Health/Fitness Board
- Movie/TV Board
- Book Board
- Music Board
- Political Talk
- Money Talk
- Fark Board
- Gaming Board
- Travel Board
- Food/Drink Board
- Ticket Exchange
- TD Help Board
Customize My Forums- View All Forums
- Show Left Links
- Topic Sort Options
- Trending Topics
- Recent Topics
- Active Topics
Started By
Message
How much voltage drop overnight is OK in a car?
Posted on 11/30/22 at 9:44 am
Posted on 11/30/22 at 9:44 am
Have an 07 Accord. Couple months ago the battery died a couple times. Jumped it and checked the voltage while running and the alternator was throwing 14+ volts, so that's good. Bought the battery from Costco, so took it down and exchanged it for a new one.
Yesterday, the battery died again. Jumped it and got it home and the voltage yesterday afternoon was 12.6. Just went out and checked it this morning and the voltage is 12.38.
Is that a normal ovewrnight voltage drop due to alarm, onboard computer etc, or does it sound like I have a short?
Yesterday, the battery died again. Jumped it and got it home and the voltage yesterday afternoon was 12.6. Just went out and checked it this morning and the voltage is 12.38.
Is that a normal ovewrnight voltage drop due to alarm, onboard computer etc, or does it sound like I have a short?
8
Posted on 11/30/22 at 9:45 am to Ajo Devil
12.38 will struggle to start the car, that isn't normal
Posted on 11/30/22 at 9:46 am to Ajo Devil
You might see voltage variation like that as a result of changes in temperature.
I’d monitor over the course of a few days to see if it’s a consistent drop.
Posted on 11/30/22 at 9:51 am to Ajo Devil
Your battery is failing; probably a bad cell or a faulty alternator.
It’ll only get worse as it gets colder.
It’ll only get worse as it gets colder.
This post was edited on 11/30/22 at 9:54 am
Posted on 11/30/22 at 9:51 am to Ajo Devil
Is this local? The temps down here haven't been anywhere near low enough to put a stress on a new battery.
My bet is a short or that alarm is drawing more than it should. Can you disconnect the alarm for a day or so and then re-test?
My bet is a short or that alarm is drawing more than it should. Can you disconnect the alarm for a day or so and then re-test?
Posted on 11/30/22 at 9:57 am to Ajo Devil
I had problems with my 2004 Honda Civic. I bought a new alternator and after removing the power steering unit to access the alternator, I discovered a loose wire to the alternator. It was completely severed, just hanging there making occasional contact, enough to keep me baffled. I reconnected it and haven't had a problem with it since (returned the new alternator for a full refund).
So check all your wire connections first. Good luck!
So check all your wire connections first. Good luck!
Posted on 11/30/22 at 9:58 am to Boudreaux35
quote:
Your battery is failing; probably a bad cell or a faulty alternator.
I just put a brand new battery in a little over a month ago.
quote:
Is this local
It's in Arizona, definitely not cold.
Posted on 11/30/22 at 10:08 am to Ajo Devil
quote:
a faulty alternator.
A quick check for a faulty diode inside the alternator, start the car, and with a multimeter and the AC scale selected (not DC) check for voltage across the battery terminals. Should read 0.00
Any voltage read is a voltage leak through the diode and will cause a parasitic drain on your battery when shut off.
Posted on 11/30/22 at 10:45 am to Ajo Devil
quote:
I just put a brand new battery in a little over a month ago.
Doesn't mean it isn't faulty. I went thru 3 batteries last spring that would not hold a charge. The guy at the store got pissed at me and swore it was not the battery. So he put it on their charger. After 2 hours it still would hold a charge. He gave me my refund because I was tired going back. Went down the street and bought one from a different store and everything has been fine.
If you tested it running and got 14+ then the alt is PROBABLY not the issue.
Posted on 11/30/22 at 11:14 am to Boudreaux35
quote:
Doesn't mean it isn't faulty. I went thru 3 batteries last spring that would not hold a charge. The guy at the store got pissed at me and swore it was not the battery. So he put it on their charger. After 2 hours it still would hold a charge. He gave me my refund because I was tired going back. Went down the street and bought one from a different store and everything has been fine. If you tested it running and got 14+ then the alt is PROBABLY not the issue.
Your battery should hold 13.5 volts for cranking.
Posted on 11/30/22 at 11:17 am to Ajo Devil
7
Posted on 11/30/22 at 11:27 am to Bigfishchoupique
quote:
Your battery should hold 13.5 volts for cranking.
Posted on 11/30/22 at 12:10 pm to Ajo Devil
quote:
Jumped it and checked the voltage while running and the alternator was throwing 14+ volts, so that's good.
Voltage alone is not a reliable test for an alternator. You need to get someone to actually run a charging system test on it. Just because the voltage is adequate doesn't mean the amperage (current) is adequate.
Posted on 11/30/22 at 12:15 pm to Ajo Devil
Possible you got a bad battery. Happens a lot nowadays.
Posted on 11/30/22 at 1:07 pm to Tridentds
With the car off put an ammeter inline between the negative terminal and the negative lead. Determine if it's a load draining down while sitting. If it's drawing a substantial amount of power, eliminate one circuit at a time (pulling fuses) and determi e what and why.
Posted on 11/30/22 at 1:10 pm to dakarx
quote:
With the car off put an ammeter inline between the negative terminal and the negative lead. Determine if it's a load draining down while sitting. If it's drawing a substantial amount of power, eliminate one circuit at a time (pulling fuses) and determi e what and why.
This.
Sounds like a parasitic loss. Find out what is drawing the amps with the key off.
Posted on 11/30/22 at 1:32 pm to Traveler
quote:
quick check for a faulty diode inside the alternator, start the car, and with a multimeter and the AC scale selected (not DC) check for voltage across the battery terminals. Should read 0.00
Any voltage read is a voltage leak through the diode and will cause a parasitic drain on your battery when shut off.
Almost word for word what I would have suggested... Except I didn't know any of that.
Traveler knows his stuff.
Page 1 of 1
Popular
Back to top
Follow TigerDroppings for LSU Football News