charging car battery

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Old 11-13-08, 11:22 AM
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charging car battery

I am wanting to charge up my two and a half year old 12V car battery as much as possible. The car hasn't been driven much for some time, only a few short quarter-mile trips now and then, not really enough for the alternator to put a keep a good charge to the battery. Now especially with the colder weather I'm noticing the battery isn't starting the car as powerfully.
So I've got the battery hooked up to the following charger, since it's all I've got, hoping this charger might be able to do the job, but not sure. NAPAONLINE®

It's a small automatic charger designed primarily to charge motorcycle and ATV batteries. It says 900 mA on the charger itself (as opposed to the webpage info which says 900 amp). So should it work or probably not?

Any comments appreciated.
 
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Old 11-13-08, 12:28 PM
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The charger is 900 miliamps which is a little less than 1 amp. If you disconnect the positive cable connector on the battery (so there is no draw at all on the battery) it may be ok. It will just take a while to charge. It's possible the battery could draw more than the 900 MA and burn out the charger.
 
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Old 11-13-08, 12:32 PM
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Unfortunately that charger isn't going to do much for a battery that's been discharged for 2 years. You would need a fancy charger that has a "regeneration" or "rehab" mode or some similar name. This type of charger uses a microcontroller to analyze the battery as it's charging and alter the charging current and voltage to recover the battery without "gassing" it. Based on the price of that kind of charger, you'll be better off just getting a new cheap-o car battery and recycling the old one.
 
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Old 11-13-08, 12:39 PM
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Originally Posted by lud477 View Post
The charger is 900 miliamps which is a little less than 1 amp. If you disconnect the positive cable connector on the battery (so there is no draw at all on the battery) it may be ok. It will just take a while to charge. It's possible the battery could draw more than the 900 MA and burn out the charger.
Battery is removed from vehicle (both pos and neg cables disconnected). You say it is possible the battery could draw more than the 900 MA. How might I found out for sure (other than from a result of the charger burning out) whether the battery could draw more than the 900 MA?
 
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Old 11-13-08, 12:42 PM
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A good garage or automotive electrical shop might be able to put yours on their charger (not in fast charge mode!) and be able to regenerate the old one a bit. Then you could put the little one on for a few hours a week. It would probably help.

This of course is assuming you have a good garage wherever you live out in the boonies.

I didn't mention in the other post, this is even more of a problem with newer cars that have all the electronics in them. They draw power to keep memory in things like radios, clock, and maybe the ECM, even when the engine is off. Not as big a problem 45 years ago. OMG I know about cars 45 years old?!!!?
 
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Old 11-13-08, 12:48 PM
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Originally Posted by ibpooks View Post
Unfortunately that charger isn't going to do much for a battery that's been discharged for 2 years.
To clarify, the battery has not been discharged for 2 years, as the wording in my initial post here may have seemed to imply. It's been starting the car every day twice a day for a long time (2 and a half years), including up to now, except that lately it has not been starting the car as powerfully as it used to. As I mentioned, the car has been driven only on very short trips less than a quarter mile each day, barely I think enough for the alternator to keep it charged up sufficiently with such short driving trips. Now that the battery has aged 2 and half years and with the short driving trips and with the cold weather, I wanted to see if I could maybe charge it up good with the little charger.
 

Last edited by sgull; 11-13-08 at 01:08 PM.
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Old 11-13-08, 12:52 PM
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Originally Posted by Gunguy45 View Post
A good garage or automotive electrical shop might be able to put yours on their charger (not in fast charge mode!) and be able to regenerate the old one a bit.
Can't I just use my little charger to "regenerate" the battery a bit? Leave it charging overnight, won't that do it?
 
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Old 11-13-08, 01:52 PM
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Well, as was stated..even a small charger can cause the battery to bubble off a little electrolyte if left on too long. I don't think it would hurt it to do it once and see if it helps.

We used to have to charge batteries for portable backpack radios and the charger had refresh, fast and maintenance modes (I think, its been a long time). The refresh was for older batteries that had seen plenty of use. I think it would ramp the current up (or down) over time to clean off the plates somehow. Of course we always had to add more pre-mixed electrolyte after they charged.
 
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Old 11-13-08, 01:55 PM
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I see, that's a little bit different situation. It is normal to lose some cranking power over time -- usually about 8-10% per year for car batteries, so what you're seeing might be normal aging of the battery. You can top it off with the charger you have, but I'm not sure that it should be left on all night.

Does your charger say anywhere if it's regulated or unregulated? If it's regulated, then it's okay to leave on overnight because the charger will cutoff when the battery is full. If it's unregulated, then you need to check the battery as it's charging with a voltage meter. When the voltage exceeds about 15V then disconnect the charger.

You'll also want to check the fluid level in the battery and top it off if you've lost electrolyte.
 
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Old 11-13-08, 02:09 PM
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Originally Posted by ibpooks View Post
I'm not sure that it should be left on all night. Does your charger say anywhere if it's regulated or unregulated? You'll also want to check the fluid level in the battery and top it off if you've lost electrolyte.
The charger doesn't say specifically whether it is regulated or unregulated. However, it is an "automatic" rather than "manual" type of charger. That is, it has an LED on it that stays orange during the period while the battery is "charging", and another LED that turns green when the battery charge is "full." So I assume that means when the green light turns on the charging process stops, which I suppose would mean the charger is a regulated type.

I've checked the electrolyte level and its good, above the plates in the cells.

Thanks
 
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Old 11-13-08, 02:18 PM
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Originally Posted by ibpooks View Post
It is normal to lose some cranking power over time -- usually about 8-10% per year for car batteries.
So if we were to assume that because my battery is two and one half years old and that it was losing 10% of cranking power per year over that time, we could calculate that the battery has lost 25% of its cranking power. If that was the case, then how long should it take a 900 milliamp battery charger to charge it back up to at least close to its original cranking power?
 
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Old 11-13-08, 02:18 PM
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Ok squll...are we still talking about the same vehicle? You said before (other thread) that it was a sealed maintenance free battery. Some places might be iffy on any warranty if you pried the covers off the cells.

Doesn't really matter that much on the advice, just trying to clarify.

EDIT:
As to the cranking power question..than doesn't happen. It gets old, it uses up the available metal on the plates...eventually it dies. You can make it last as long as possible, but you can't make it new again. Batteries are like pets, you can take care of them or abuse them, but...eventually they die.
 
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Old 11-13-08, 02:23 PM
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Originally Posted by Gunguy45 View Post
You said before (other thread) that it was a sealed maintenance free battery.
Yes, sorry for that mistake previously. It is NOT a sealed maintenance free battery.
 
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Old 11-13-08, 03:59 PM
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Originally Posted by sgull View Post
we could calculate that the battery has lost 25% of its cranking power. If that was the case, then how long should it take a 900 milliamp battery charger to charge it back up to at least close to its original cranking power?
Once it's gone, you can't get it back. The compounds in the plates break down over time and eventually lose the ability to hold a charge. At that point the battery has to be recycled and replaced.

Car batteries are designed to start the vehicle at 60% of original capacity so that should provide about 5 years of functional life; higher quality batteries live maybe 7 years. Cold climates further reduce the battery capability so something closer to 4 years is reasonable.

If you take the battery to a DIY parts shop like AutoZone, they usually have a testing rig there that can measure the battery output so you can compare it to the rating on the sticker and see how much life the battery has left.
 
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Old 11-13-08, 04:44 PM
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Originally Posted by ibpooks View Post
Once it's gone, you can't get it back.
Probably wasting my time trying to charge it up, then? My thinking was that, over time, with only my quick short trip (10minutes max running time) that the alternator wasn't having sufficient time to keep the battery charged as good as would be the case otherwise (with longer periods of running the car and more frequently). So thats why I thought it might be worth a try to use the charger on it. Maybe it still has the capacity to be charged to a higher charge but the alternator has not had time to do it? Does that happen?
 
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Old 11-13-08, 04:58 PM
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Originally Posted by ibpooks View Post
If you take the battery to a DIY parts shop like AutoZone, they usually have a testing rig there that can measure the battery output so you can compare it to the rating on the sticker and see how much life the battery has left.
In my community there is no Autozone but the local NAPA store says if I bring the battery in and leave it for about three hours they can put it on a charger and charge it to its full charge and then put a load test on it to see how its going to hold up under load. They said they can look up the specs on the battery such as cold cranking amps, etc. and I forgot what he said they can do with that info. But he said they dont have a way to see how much life the battery has left.
Comments?
 
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Old 11-13-08, 05:40 PM
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Drop it off...the 3 hr thing is a good indication. Most NAPA's are a little better staffed with good people than some of the other chains. Of course they can't tell you how much time you have left on it, but it will give you an indication of how bad off it it.

You won't be any worse off than before. You must have things more important than a battery that MAY fail in the future. They all do eventually.
 
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Old 11-13-08, 05:55 PM
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Originally Posted by Gunguy45 View Post
Drop it off...You won't be any worse off than before.
ok. sheesh if I had known they would do all this (and for no charge too!) I probably wouldn't have even bothered trying with my dinky charger, which is still out there with the indicator saying its "charging" just like it has been for the past ten hours.
 
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Old 11-13-08, 06:08 PM
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I have a charger like yours--I use it on my lawn tractor.
I shuts off when it turns green.
When it drops down it turns back on.
I got 7 years on my last battery using a unit like yours.
 
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Old 11-13-08, 06:24 PM
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Originally Posted by j HOWARD View Post
I have a charger like yours--I use it on my lawn tractor. It shuts off when it turns green.
When it drops down it turns back on. I got 7 years on my last battery using a unit like yours.
That's great. But are these units any good AT ALL for trying to charge up a CAR battery from a low state of charge, if the battery still has the capacity to be charged? I kinda doubt it, but don't know for sure.
 
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Old 11-13-08, 06:59 PM
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Originally Posted by sgull View Post
That's great. But are these units any good AT ALL for trying to charge up a CAR battery from a low state of charge, if the battery still has the capacity to be charged? I kinda doubt it, but don't know for sure.
Why don't you try it--let us know what happens.
Also: do you have a trouble light on that unit ?
 
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Old 11-13-08, 07:13 PM
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Originally Posted by j HOWARD View Post
Why don't you try it--let us know what happens. Also: do you have a trouble light on that unit ?
Okay, I've had my car battery on that charger for ten hours, and tried starting to see what happens. Before doing the charge on the battery, it seemed recently as if the battery were much weaker the car would not have started, especially on cold mornings after sitting all night outside. Now, after the ten hour charge with this charger, it seems better. Will be able to judge with little more certainty when I go to start the car tomorrow morning. By the way, these cold mornings I'm talking about are not super cold, 32 degrees or slightly above.

No, this unit does not have a trouble light, does yours? It just has three LED lights; a red light which indicates it has power, an amber light which indicates its chargingthe battery, and a green light which indicates the battery is fully charged.
 
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Old 11-14-08, 07:05 PM
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When my trouble light comes on----
the battery is usuall dead.....................
 
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Old 11-15-08, 08:15 PM
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Another option would be to leave the battery in the car and every now and then go for a nice long Sunday drive and give the alternator a chance to do it's job.
 
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Old 11-15-08, 08:23 PM
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Originally Posted by Buzz View Post
Another option would be to leave the battery in the car and every now and then go for a nice long Sunday drive and give the alternator a chance to do it's job.
Yes you're right I should be doing that. How often and for how long might you suggest? Is 45 min once a week good enough you think?
 
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Old 11-16-08, 08:05 AM
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Originally Posted by sgull View Post
Yes you're right I should be doing that. How often and for how long might you suggest? Is 45 min once a week good enough you think?
I would think 45 min once a week would do the trick, but you will be able to judge this by the ability of the battery to start the car. If the battery doesn't improve after a few weeks I would consider a new battery.

The link below will provide you with some good info.

Battery Tutorial | Batterystuff.com
 
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Old 11-16-08, 09:15 AM
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Originally Posted by Buzz View Post
The link below will provide you with some good info.url=http://www.batterystuff.com/tutorial_battery.html]Battery Tutorial | Batterystuff.com[/url]
Thanks for the advice and that helpful link
 
 

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