20amp 12v lead acid battery overcharging ?

Thread Starter

MeGuinness

Joined Mar 17, 2015
5
hello, wondering if you guys can help me,
i have a 2x identical 12v 20amp lead acid batteries , one of them due to been left in the garage unattended for about 2 years had a voltage output of about 1V ,i know practically dead,anyway in trying to salvage it before go and buy a new one i decided to top it up with some deionised water and put it on charge using a RC charger in Pb mode .
Due to the low voltage the charger would not start the charge.
After some thinking ....I connected the good and the dead battery together in series and left them for one hour.. .....once I removed the connections the dead battery voltage was up to about 12.40V ,so I quickly connected the charger and yes it started charging no problem. I put the settings at 0.5amp charging .

Now the fist battery was still at 12v and using the same charger i had no problem in fully charge it ,the charger did put about 6000mah and stopped when it was time to.

My problem is with the second so called dead battery ,yes i managed to start the charge but the charger will not stop charging even after putting in about 28000mah in it and a voltage of 13,20V.
If the battery is rated at 20amp how is that the battery could take 28000mah??? what is wrong ?is it overcharging ?
i left the battery off the charger for a day and when i checked the voltage is at 12.46V .
Any ideas ?thanx
 

tcmtech

Joined Nov 4, 2013
2,867
First off recharging a battery is not the same as charging up a capacitor so be expecting considerable ah discrepancies between the batteries AH rating and how many AH go into recharging it.

Basically regenerating a near flat dead battery takes a lot more charge than just what its AH rating is.

Personally if it was me when I try to regenerate dead batteries I try to hold them at around 14.4 volts give or take a few 10ths for a good day or two before concerning myself with what their amp draw is or what their voltage stays at.
 

Lumenosity

Joined Mar 1, 2017
614
Old thread....but still a good one.....for the benefit of others who find this thread....

Also, remember that a battery's capacity is a much better indicator of it's condition than it's voltage.
You can buy a 12v battery that is nearly the size of a AA battery.....but do you think that will start your car? Why not?
It's also 12 volts...... The answer is capacity. Technically the ability of the battery to hold electrons on it's plates and move them across the plates.

So a car battery might charge to 13.3 Volts ....but have the capacity of a VERY small battery because the plates inside no longer have the ability to hold and transfer electrons (or very few relatively speaking).

In addition to what tcmtech said, I use 20watt 12v solar panels on larger batteries and 10watt, 12v solar panels on sulfated smaller batteries.
The solar panels peak at around 20v in the brightest sunlight but it "pulses" somewhat as clouds pass. I've rejuvenated quite a few batteries this way. But I think it's a matter of expectations. If you expect to rejuvenate a 5 year old battery to near full capacity you are going to be disappointed. I have 80AH batteries that finally went flat with only 1Ah capacity remaining and have brought them back up to 20-30Ah with Solar panel desulfation. Plenty good enough for battery backups and a few other similar purposes.

But eventually a battery will become so damaged inside that nothing can bring it back to life for any intent of useful purpose.
 

MisterBill2

Joined Jan 23, 2018
18,061
hello, wondering if you guys can help me,
i have a 2x identical 12v 20amp lead acid batteries , one of them due to been left in the garage unattended for about 2 years had a voltage output of about 1V ,i know practically dead,anyway in trying to salvage it before go and buy a new one i decided to top it up with some deionised water and put it on charge using a RC charger in Pb mode .
Due to the low voltage the charger would not start the charge.
After some thinking ....I connected the good and the dead battery together in series and left them for one hour.. .....once I removed the connections the dead battery voltage was up to about 12.40V ,so I quickly connected the charger and yes it started charging no problem. I put the settings at 0.5amp charging .

Now the fist battery was still at 12v and using the same charger i had no problem in fully charge it ,the charger did put about 6000mah and stopped when it was time to.

My problem is with the second so called dead battery ,yes i managed to start the charge but the charger will not stop charging even after putting in about 28000mah in it and a voltage of 13,20V.
If the battery is rated at 20amp how is that the battery could take 28000mah??? what is wrong ?is it overcharging ?
i left the battery off the charger for a day and when i checked the voltage is at 12.46V .
Any ideas ?thanx
 

MisterBill2

Joined Jan 23, 2018
18,061
My experience with quite a few lead-acid batteries is that eventually they reach a condition where they will continue to accept a charging current but they will not hold much charge. At that point it is time to replace the battery, or, if you have some method of rejuvenating it, to use that, because the battery has failed. This is why it is important to recharge batteries that are being stored every few months.
 

dl324

Joined Mar 30, 2015
16,788
What is the point in necroposting (reviving a long dead thread) if you have nothing useful to add?

The original poster has a grand total of one post, lost interest in his thread, and is long hone.

Edit: referring to post #5.
 

MisterBill2

Joined Jan 23, 2018
18,061
What is the point in necroposting (reviving a long dead thread) if you have nothing useful to add?

The original poster has a grand total of one post, lost interest in his thread, and is long hone.

Edit: referring to post #5.
The reasons for responding are two: First, this information would also be useful for other folks, aside from the original posting person, and Second: I did not examine the thread date adequately, as I am new to this web entity. OK?
 

dl324

Joined Mar 30, 2015
16,788
The reasons for responding are two: First, this information would also be useful for other folks, aside from the original posting person, and Second: I did not examine the thread date adequately, as I am new to this web entity. OK?
Welcome to AAC!

Just so you'll know, some members receive email when a thread they've contributed to has a new post.

The blame for resurrecting this thread goes to @Lumenosity. He knew it was over 2 years old when he posted and ignored the old thread warning because he thought he was adding something useful.
 
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