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battery question

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QueBert

QueBert

Lifer
Pep Boys tested it and it was good, so I got a jump and drove around for a bit. A person on taurusclub is telling me basically I have to have the battery slow charged for 24 hours on a 2amp charger. And without doing that the battery won't charge back up fully even if I drove for 4 hours. I have never in my life slow charged a dead battery and I've never had problems. How accurate is what he's saying? This is part of what he said

Here is the problem. You need to MANUALLY charge the battery with a good slow 2amp charge rate for 24 hours or so. Just driving it around the block won't charge it up. Not even driving for 4 hours is enough. Bottom line, the alternator is not capable of charging a completely dead battery.

He's making it sound like I could drive around for a month and it still won't be at 100%. I've been having stereo problems (it's totally disconnected) once I get the cause of the problem diagnosed I'll hook it back up when I'm comfortable my car's back to normal.

How much better are these slow charges? I don't have a trickle charger and none of my neighbors do. I'm not really interested in spending even 40 bucks on one if it's not going to do much.
 
Your alternator was not meant or designed to charge a dead battery. It was designed to keep the battery topped up after the drain of starting the engine.

It can charge a dead battery, but it will take it a long time to do so, and it is not good to ask it to do so repeatedly.

The best thing to to do with a dead battery is to charge it with a device that was made for the purpose. A battery charger.

Having said all that, you have probably done no harm doing this once, and you will indeed need to drive the car for a while to fully charge the battery with your alternator.

Do not expect the battery to be charged up just because the car started and you drove it to the store and back.
 
I've heard both stories. If it's possible, I would slow charge it for 24 hours--like he said. But I also completely drained my battery several times, and did not slow charge it--just jump and drive around for an hour. The alternator in my car is 80amp. Unless I run all the lights and accessories, I don't think that the whole 80A is used up. IMO, during day time driving with a dead battery, a significant amount of the power from the alternator is going to recharge the battery.
 
Originally posted by: LTC8K6
Your alternator was not meant or designed to charge a dead battery. It was designed to keep the battery topped up after the drain of starting the engine.

It can charge a dead battery, but it will take it a long time to do so, and it is not good to ask it to do so repeatedly.

The best thing to to do with a dead battery is to charge it with a device that was made for the purpose. A battery charger.

Having said all that, you have probably done no harm doing this once, and you will indeed need to drive the car for a while to fully charge the battery with your alternator.

Do not expect the battery to be charged up just because the car started and you drove it to the store and back.
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good reply thanks, I understand it's better to slow charge but some people make it sounds like without a slow charge you can never get the battery back to 100%. I'm fine with it taking a few days of driving around to get it good enough. I'm leaving the stereo unhooked and almost always drive during the day. So I won't be using headlights or anything extra. I'm curious at how long it takes, one person will tell me "drive 20 miles on the freeway and back during the day and it should be good" the next "slow charge only, or it will never work right!" lol.
 
The problem is that with a dead battery, you are asking the alternator to run at high output for a while. You may get away with it, but it's not good to do it often.

How long it takes to charge the battery depends on many variables. How depleted was the battery, how much idling, how much highway driving, what is the battery capacity, what accessories were running, etc., etc.

I would drive it for 30 minutes on the highway to feel comfortable.
 
Originally posted by: LTC8K6
You guys must be psychic.

The VOLTS light just came on in my company car... 😀
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See what happens when you bad-mouth alternators and doubt their ability to charge? 😛

To the OP: Even at idle the alternator will be putting out slightly more power than is necessary to run the engine. In theory it will be perfectly capable of charging the battery, but it would take a very long time. However, as others have very accurately pointed out, an alternator is not designed to put out full power for extended periods and it's generally best to use a bench charger to top the battery off again.

I use a charger that has a microcomputer in it to evaluate a battery's state of charge and adjust output appropriately (will start charging at 10 amps and reduce as the battery nears a full charge). The type is widely available at auto parts stores and shouldn't cost more than $50-$60. Even the cheap manual bench chargers are OK, but you need to be careful not to overcharge.

ZV
 
Originally posted by: QueBert
good reply thanks, I understand it's better to slow charge but some people make it sounds like without a slow charge you can never get the battery back to 100%. I'm fine with it taking a few days of driving around to get it good enough. I'm leaving the stereo unhooked and almost always drive during the day. So I won't be using headlights or anything extra. I'm curious at how long it takes, one person will tell me "drive 20 miles on the freeway and back during the day and it should be good" the next "slow charge only, or it will never work right!" lol.
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If you completely discharged the battery even if you did a slow charge it will never be 100%.
 
I agree. The best and proper way to charge a really dead or low battery is with a proper battery charger. Sears, has good one and not very expensive.
 
The battery isn't kept at 100% by the alternator though, is it?

The slow charger will get it to 100%, but it won't stay there anyway. At least that's my understanding.
 
Originally posted by: LTC8K6
The battery isn't kept at 100% by the alternator though, is it?

The slow charger will get it to 100%, but it won't stay there anyway. At least that's my understanding.
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An alternator should be able to "top off" a battery to 100% of remaining capacity unless you are continuously driving for only 5-10 minutes. Remember that as batteries age, their capacity drops so even a bench charger isn't going to bring a 2-3 year old battery up to rated capacity (in terms of amp-hours).

ZV
 
thanks for all the replies, I believe I'm going to get a kenitik battery, reading up on them today they're supposed to be really awesome, going to upgrade my big 3 too.
 
At least you have choices. Limited selection for a Lincoln LS (trunk mounted with vents) - I only know of the factory Motorcraft, Optima and NAPA batts.
 
Well, alternator has died in my company car.

Karma is a bitch.

The battery is 7 years old, so I'll just replace that too.

Thank goodness for company credit cards!
 
Originally posted by: ChaosDivine
At least you have choices. Limited selection for a Lincoln LS (trunk mounted with vents) - I only know of the factory Motorcraft, Optima and NAPA batts.
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I'd rather have an LS with little choices than a Taurus with a bunch 😉 And Optima's are SWEET batteries.
 
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