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Dr. Hamman
Dr. Hamman, Technician
Category: Classic Car
Satisfied Customers: 6286
Experience:  I have 30 years experience repairing, restoring, and customizing cars, and pickup trucks.
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Charging my dead car battery at 10 amps, how long should I charge it?

Resolved Question:

If I am charging my dead car battery at 10 amps, how long should I charge it?
Submitted: 7 years ago.
Category: Classic Car
Expert:  Dr. Hamman replied 7 years ago.

Hi, I will do my best to assist you. When you are finished please click on accept. I don't get paid unless you do. I don't know if you are a pro or a novice so we may have to fine tune the answer. I only know as much about your problem as you have told me in your post, so my answer will be based on what you have posted. Feel free to add any additional info you feel is needed.

There are a lot of variables here, mostly how big the battery is in amp hours. Also the condition of the battery factors in. If it has been dead a while it takes a bit for the chemistry to go back to normal. If it is freshly discharged then it starts saturating right away.

OK all that being said normally about an hour at 10 amps will do it, on an average battery in good condition. Now there are ways to check to see if the battery is charged. One is with a battery hydrometer, that is if you have the type the cells open up on. Battery hydrometers are very inexpensive. I will post a chart below with hydrometer readings for your reference.

The next way is with a Open Circuit Voltage (OCV) Test An OCV test may be performed with a voltmeter. Let the battery sit about an hour after charging. Then check the voltage. Use the Battery Voltage Chart below to determine the state of charge.

Also load testing the battery can tell you if it has much life left in it or if it is bad. Load testing takes a special test device, most places that sell battery's can do this test for you.

Battery Voltage Chart

12.66V 100%
12.45V 75%
12.24V 50%
12.06V 25%
11.89V 0%

Specific Gravity Chart

1.265 100%
1.225 75%
1.190 50%
1.155 25%
1.120 0%

If you have any more questions I am here to help. Good luck, and Thanks for using Just Answer.

I hope this helps, 100% satisfaction is my goal. If the answer is not clear, please reply and I will assist you more. When you're satisfied, click on accept. I don't get paid unless you do. A bonus and positive feedback are always appreciated, good luck and Thanks.
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