Battery Self Discharge

[Gjac]

Would the rate at which a battery self discharges be a way of determining the health of a battery? I have (2) 7 year old Sam's Club GC batteries that have been sitting without charge(battery disconnect switch on) since Nov 4 2014. On Jan 10 2015 they read 12.48 V at 20 degrees F. I know a load test would be the normal test, but I am in Fla now and the MH is in Ct. So is there a direct correlation between the rate of self discharge and how many more years a battery would last assuming the same usage as the previous years?

[Gjac]

MEXICOWANDERER wrote:
Overcharging is overwhelmingly the inpreferred way of poisoning the negative plates with antimony and GC batteries have 5% antimonial positive plates.

Are you saying over charging is the cause of antimony poisoning which in turn causes 90% of " advanced age accelerated self discharge"?

[Gjac]

jrnymn7 wrote:
Last winter, in cold storage, my 6v's were holding strong for 3-4 weeks at a time, without any noticeable self-discharge. This past summer they were over charged a lot, which resulted in excessive gassing, overheating, and electrolyte levels dropping below the tops of the plates on a few occasions. The result is now they are discharging at about 1-1.5% per week, as far as I can reckon. So abuse does seem to affect self discharge. As far as I can tell, charge-ability and discharge under load have not been affected to any great extent.

But as others have said, there are more reliable ways of determining overall battery health.

OP, Did you happen to put a good top charge and/or EQ on those batts before putting them into hibernation? That can make a big difference.

Did not put a top charge on before hibernation. What I do is charge it with my B&D 40 amp charger until it reads FUL then float for a couple of days after with my Magnatec 950 converter at 13.8 v. I do equalize several times a year. If I am home I will recharge when the the batteries reach 80% SOC. The B$D never seems to fully charge them I can get 2 more days of dry camping when I float for several more days before using.

[MEXICOWANDERER]

Overcharging is overwhelmingly the inpreferred way of poisoning the negative plates with antimony and GC batteries have 5% antimonial positive plates.

[jrnymn7]

Last winter, in cold storage, my 6v's were holding strong for 3-4 weeks at a time, without any noticeable self-discharge. This past summer they were over charged a lot, which resulted in excessive gassing, overheating, and electrolyte levels dropping below the tops of the plates on a few occasions. The result is now they are discharging at about 1-1.5% per week, as far as I can reckon. So abuse does seem to affect self discharge. As far as I can tell, charge-ability and discharge under load have not been affected to any great extent.

But as others have said, there are more reliable ways of determining overall battery health.

OP, Did you happen to put a good top charge and/or EQ on those batts before putting them into hibernation? That can make a big difference.

[MEXICOWANDERER]

The majority and I am talking about 90+% of the cases of advanced age accelerated self-discharge is caused by antimonial poisoning of the negative plates.

Self discharge is a specific symptom. The symptom is loss of charge with the ability to take a recharge and restore a good percentage of the storage capacity of the battery.

This is easily confused with self-discharge of a battery that has little capacity remaining in it, regardless of the state of charge.

By itself rate of self-discharge is limited in it's value to determine a battery's state of health. But it is definitely a component of the array of tests used in testing a battery.

Poisoned batteries gas at a much lower voltage, can use 5-times the water of a new battery and of course self discharge. The rate of discharge can approach phenomenal levels. I have seen badly poisoned batteries lose 60% state of charge in an month's time.

[Matt_Colie]

Gjac,

The short answer is no.
The self discharge of a typical Lead/Acid battery is only a function of that batteries leakage rate. It has little to do with the actual capacity of that battery (cell). While it is necessarily true that high leakage (low leakage resistance) does indicate a battery in poor condition, I have seen batteries that had lost a great deal of their original capacity but still had acceptable leakage. So, the short answer is no.

A golf cart battery is a true deep cycle. It will have a terminal voltage at rest that may be less than an automotive battery's 12.6V. In your case, that bank has been sitting unattended for 2 months and is now at 12.48. I don't care where it started but that is good.

I did electric work on boats before the depression and one of my standard recommendations for boats stored for the winter was that the owner get (or I could get and he could pay me to set up) a small (5w) solar panel. This is enough to overcome the leakage of any bank that is still in serviceable condition.

Matt

[mabynack]

Not really. It has been my experience that the real killer for most lead acid batteries is shorting between the plates in the battery. It's cause by either warped plates that short or by solids in the acid that short across the plates.
Another cause for failure in non-sealed batteries is low acid levels that allow the plates to be exposed to air and oxidize.