Car won't start unless I jump it and battery tested ok.

865 Views | 10 Replies | Last: 1 day ago by Bronco6Gen
CAR96
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AG
What is the issue?
agracer
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AG
How old is the battery?

A battery can test OK but still not have enough juice to start a car.

When the car is running, what is the voltage at the battery?

When the car is off, what is the voltage at the battery? What is it a couple hours later?
Waterski02
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AG
Second that. Have had batteries test good. Seem to hold
Charge but nothing left in them. Monitor voltage while cranking, or if you've got a DC amp clamp even better.
Stat Monitor Repairman
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You need a proper load test.


If that checks out, next step would be to check voltage drop at the starter post when you hit the ignition.

If that checks out you got to check both ends of your ground lead and ground strap for corrosion.

If none of that is it you got to be thinking about your starter and starter relay.
CAR96
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AG
Where can a proper load test be done?

Advance Auto Parts connect a device while car was off and said battery was good. The dashboard reads voltage as the same as always while car is on and running.

Then 30 minutes later it started with no charge but after 4 hours it wouldn't start until jumped.
agracer
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AG
How old is the battery?

Do you have a multimeter? Or a neighbor with one?

The voltage across the terminals should be ~12.5V when the car is off.

The voltage across the terminals should be ~13.7-14.5 while running.

Check it under both conditions.

The fact that it will start and run when you jump it, then start 30m later says, but then it's dead 4-hours later tells me it's a bad battery. Unless you added some new electrical component to your car that is draining the battery while the car is off, it's likely a bad battery. It can't hold a charge.

I have a car that does not get driven much and it's on a battery tender. Last summer I left it off the tender for 2-weeks on accident and it would not start. I charged it, and it ran but then a few hours later it was dead. It was 7-years old and just finally died.
CAR96
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AG
Battery is about 12-15 months old
CAR96
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AG
Car started This morning without a jump although on a second or third push button attempt. Got to an Advance Auto and battery tested as bad (yesterday at a different Advanced Auto it tested good). Was able to get a warranty replacement but had to go to another store to install (I am recovering from retina surgery)/.

Car is running and starting now.
Burdizzo
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AG
CAR96 said:

Battery is about 12-15 months old



There are a lot of junky Chinese batteries out there today, particularly the house brand batteries at most auto parts stores and Wal Mart. Buy one made in Mexico or the US. I prefer AC Delco. Most of the Chinese batteries are good for 12-24 months before they go bad. Today's cars with continual low amperage draws while "off" don't help battery life either.

A proper battery test puts a load on it while the voltage is cracked. There is also a recovery time for the voltage to come back up after the load is removed. All these these things tell you more than just checking voltage across the posts.
El_Guero512
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Had this happen like you this week, Die Hard silver battery. One day tested good and other day tested bad. Lasted 2 years and got a Interstate one from Costco.
Bronco6Gen
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I've had cables go bad, you can ohm them out and test the resistance...low resistance good, high resistance bad, I'd call anything above a .2 bad.
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