Correct Way to Fully Charge a Battery?

[AngliaGT]

A few of my cars don't get driven all the time.
Sometimes the batteries are low when I go to drive them.
I have a 2/10/50 Amp charger.

- Doug

 

[AweMan]

Doug:
2 amps is the best setting on your charger {yes it takes longer to charge} BUT ..... Hot shoting {Hard charging with high amperage} a battery can warp the plates causing it to short out! And ..... High amp charging also causes the lead on the plates to go sulfide much faster than normal. {sulfide is what causes shorted plates} eg. dead cells.
For vehicles that don`t get used much. A good battery tender is ideal, They keep the battery topped off with a full charge and will not over charge it. eg. cause the lead on the plates to sulfide.
Something along these lines is what you want
https://batterytender.com/
Yes there are cheaper brands on the market BUT ..... Make sure the one you get goes into "Float mode" after the battery is fully charged.
You can attach these right to the vehicle, simply plug them in when the vehicle is not in use.

 

[PAUL161]

Yup, I agree with Kerry. 2 amp float charger won't cook a battery, but will put a full charge in it over night, depending just how low it is. I have 3 big 100 lb batteries in my motor home and they get charged at the 2 amp rate when parked. Works very well. PJ

 

[texas_bugeye]

About this battery charging rate. What happens when you start a car?
Say the battery is low, It starts and you have a one wire Alternator with output capacity of say 45 amps. Is there any ill affects? What would be the differance than charging with a 20 amp charger?

 

[14dna]

I agree with Kerry, a slow charge is best for a battery.
When you start your car, the alt. then recharges to the correct level and the regulator controls the charge amount.
Because you take out so little when starting, the alt. doesn't overcharge it or quick charge it.
If it is low enough to be boosted, then a slow charge is likely recommended if possible, but on a one time basis, there should not be an issue.
If your battery constantly goes through a cycle or series of cycles of low and high charge, the life is seriously compromised.

Dave

 

[texas_bugeye]

So the regulator is not just a switch? How is that? Would it not charge at the output of the alt all the time to 14or so volt cut out?

 

[Twosheds]

So the regulator is not just a switch? How is that? Would it not charge at the output of the alt all the time to 14or so volt cut out?

The voltage regulator keeps the output voltage of the alternator or generator constant, but the current output of the alternator depends on the load it must power. The load is the sum of the current needed to run all the electrical needs of the car and the current to charge the battery.

The deader the battery, the more current will go to it to charge it. As the battery becomes more charged, this current will decrease. The regulator will also limit the maximum current the alternator puts out so that it is not damaged by trying to put out too much current. But the current at any one time is only determined by the load it has to run. A 60 Amp alternator does not always put out 60 Amps, only the Amps that are needed.

 

[tony barnhill]

Slow charger, yes...but, if you're charging the battery to get the car started, let the alternator completely charge the battery - not the charger.....at least that's how I do it.

 

[Guest]

Differing views on this. On allota new stuf, "they" say never let the alt charge the bat if it's low. Matter of fact, it's part of the disclaimer for alt warranties. (if you actually read them as few folks do.) I have done, and do this from time to time depending on my mood.

I'vee seen REALLy dead batteries not come back from a slow or low amp charge. They will, however; wake up if you hit it w/ 225 amp start setting till the charger kicks out. I learned this trick from our local bat and alt supplier and it does work and has saved a few "bad" batteries this way.

Slow is best. I've cooked several even at 20-40 amps cause my auto timer shut off didn't and overcharged them.

 

[tony barnhill]

I've never cooked an alternator letting it finish charging a battery!

Matter-of-fact: how many brand new batteries are sold fully charged?

 

[Don_R]

Matter-of-fact: how many brand new batteries are sold fully charged?

the rules at the 2 shops I worked at was to charge a new bat for half an hour either before install or after

 

[tony barnhill]

Matter-of-fact: how many brand new batteries are sold fully charged?

the rules at the 2 shops I worked at was to charge a new bat for half an hour either before install or after

That might or might not fully charge it!

 

[martx-5]

Differing views on this. On allota new stuf, "they" say never let the alt charge the bat if it's low. Matter of fact, it's part of the disclaimer for alt warranties. (if you actually read them as few folks do.) I have done, and do this from time to time depending on my mood.

I work for an electrical rebuilder, and yes, we put this disclaimer on the box. It's much less of a problem today, because the ratings for most alternators are 100+ amps. When the alternators were 60 amps and below, it is possible for it to run full bore for an extended period of time with a really low battery. Auto alternators are not designed to run full bore for extended periods, and they can cook themselves.

Having said that, a little common sense is all that's needed. I just take a voltage reading on the new battery, and if it's in the 12.5 Volt range, I just put it in without charging it.

 

[Guest]

Matter-of-fact: how many brand new batteries are sold fully charged?

the rules at the 2 shops I worked at was to charge a new bat for half an hour either before install or after

That might or might not fully charge it!

AMEN!!!!

Just bought one yesterday for Maggie that was on the shelf 2 months before I got it. The others were there for 4 months.

I've hurt some newer ones (alts) by pulling the jump box off of 'em too soon on dead auction junk.