Generic question about charging amps
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Elder User
Joined: Mar 2003
Posts: 999
Likes: 1
From: Willamette Valley Oregon
Generic question about charging amps
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How do you figure how long it will take to recharge a dead battery? For example:
You have a 600 cranking amp 12 volt battery
and
a 10 amp charger
I assume it would not require 60 hours to charge the battery . How long should the battery be charged and what is the formula for determining that?
How do you figure how long it will take to recharge a dead battery? For example:
You have a 600 cranking amp 12 volt battery
and
a 10 amp charger
I assume it would not require 60 hours to charge the battery . How long should the battery be charged and what is the formula for determining that?
Senior User
Joined: Feb 2003
Posts: 215
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From: The best is the U.S.
Lead acid batteries take on a charge exponentially. The initial charging rate will be much greater than your final charging rate. With a regulated 10A battery charger (voltage applied is fixed) you should see a gradual decrease in the ammeter display as the battery takes on a charge due to the increasing potential/resistance. When your charger registers a minimal reading for 30minutes to an hour your battery should be charged. To calculate an exact charging time would just fall short of a graduate study in mathmatics/chemistry. Ball park figures of charging times can be calculated but they will be of little use to you if you do not use careful consideration when selecting the proper values of all variables. I spent several years on a nuclear attack submarine as a Nuclear Electricians Mate and got to spend MANY personal hours with the ship's battery. Although batteries are fairly low on the technology totem, taking proper care of batteries is fairly complex.
Post Fiend
Joined: Apr 2002
Posts: 7,157
Likes: 1
From: Central Kali
Don't be confused by the cranking amps rating and the amp hour rating which you hardly see any more. I think they are about a 100 amp hour at a 20 hour rate. (you can discharge 5 amps for twenty hours without damage).
If I remember correctly, the last 10 or 20 percent to full charge takes 24 to 48 hours. Don't leave a cheap battery charger on un-attended, it may over charge.
If I remember correctly, the last 10 or 20 percent to full charge takes 24 to 48 hours. Don't leave a cheap battery charger on un-attended, it may over charge.
Posting Guru
Joined: Jun 1999
Posts: 2,007
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From: Oregon
It's a bit over 12 Vdc for an automotive battery. Battery chargers and your alternator charge at about 13.8 Vdc. Your battery has an internal resistance that you have to overcome or it won't charge. That's why your rig has a 12 Vdc system, but the voltage is higher when you check it while running.
Last edited by Howdy; Dec 2, 2003 at 09:39 AM.
