# 6 volt lead acid battery Question; please help.



## Longrifle2506 (Sep 19, 2009)

I know it is said that you shouldn't completly drain or deeply discharge a rechargeable battery or it can shorten the batteries life. I just bought a brand new 6 volt non spillable lead acid rechargeable for my Optronics Varmint Light kit and I came home and wanted to discharge because it seemed to have a lot of charge. WELL, I LET IT GO TOO LONG AND IT WENT COMPLETELY DEAD. DO YOU THINK THAT IF I DON'T DO IT AGAIN WILL MY BATTERY BE OK? thanks in advance


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## filibuster (Sep 19, 2009)

To preserve the life of any lead acid battery it's best not to discharge it more than 50%. 

When a lead acid battery is over discharged the lead plates inside the battery get coated with sulfur compound which can permanently limit the capacity of the battery. 

The longer a lead acid battery remains in the discharged state the worse it is for the battery. 

Most lead acid batteries are shipped fully charged from the manufacturer but depending on how long they are "on the shelf" will determine their charge state when you buy it. 

As best as possible, after use always recharge a lead acid battery as soon as possible leaving it in a completely charged state until next use. This is much more important for lead acid type batteries than other battery chemistry because in a discharged state is when sulfation occurs.

Your battery may not be ruined but it could have suffered some ill effects from being over discharged.

Here's some info that may help with this question:
http://www.batteryuniversity.com/parttwo-35.htm


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## Mr Happy (Sep 19, 2009)

Longrifle2506 said:


> I know it is said that you shouldn't completly drain or deeply discharge a rechargeable battery or it can shorten the batteries life.


It depends on the kind of battery. There are many kinds of rechargeable battery such as lead acid, NiMH, NiCd, lithium ion etc. Some can be deeply discharged better than others.



> I just bought a brand new 6 volt non spillable lead acid rechargeable for my Optronics Varmint Light kit and I came home and wanted to discharge because it seemed to have a lot of charge. WELL, I LET IT GO TOO LONG AND IT WENT COMPLETELY DEAD. DO YOU THINK THAT IF I DON'T DO IT AGAIN WILL MY BATTERY BE OK? thanks in advance


This does not make any sense at all. How can a battery have "too much" charge?

It is a bit late now for your battery, but remember that lead acid batteries last best when they remain fully charged. Every time you discharge one of those batteries you shorten its life a little. Use a proper battery charger and keep your battery _fully charged_ at all times.


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## fivemega (Sep 19, 2009)

Longrifle2506 said:


> I know it is said that you shouldn't completly drain or deeply discharge a rechargeable battery or it can shorten the batteries life. I just bought a brand new 6 volt non spillable lead acid rechargeable for my Optronics Varmint Light kit and I came home and wanted to discharge because it seemed to have a lot of charge. WELL, I LET IT GO TOO LONG AND IT WENT COMPLETELY DEAD. DO YOU THINK THAT IF I DON'T DO IT AGAIN WILL MY BATTERY BE OK? thanks in advance



*Draining a lead acid battery won't help and shouldn't be done after it is overcharged.
Your battery already has some damage and will effect its life but since it is new, I guarantee it will work assuming it was not too long in deep discharge position.*


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## Flash_Gordon (Sep 19, 2009)

Please define "too much charge" for us.

A lead acid cell will read about 2.2 volts when fully charged. Your 6V battery should then be about 6.6V.

Significantly more than that might indicate a problem with your charger.

Mark


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## Longrifle2506 (Sep 19, 2009)

All I mean is that usually when I buy a new battery it hardly has a charge, so I have to charge it. This particular battery seemed to be fully charged. I am use to giving them a good first charge when I bring them home, so I was just trying to drain it until the bulb went dim, and in doing so, it went past dim; but it did not remain in this state for over 30-40 minutes before I hooked it to the charger.


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## Mr Happy (Sep 19, 2009)

Longrifle2506 said:


> All I mean is that usually when I buy a new battery it hardly has a charge, so I have to charge it. This particular battery seemed to be fully charged. I am use to giving them a good first charge when I bring them home, so I was just trying to drain it until the bulb went dim, and in doing so, it went past dim; but it did not remain in this state for over 30-40 minutes before I hooked it to the charger.


When you buy a new lead acid battery it is supposed to be fully charged. If you buy one and it is not charged, you probably have bought an old, poor quality or defective battery.

Draining a lead acid battery until the bulb goes dim is otherwise known as "damaging the battery and shortening its life". Nothing good can come of that.

There are some more expensive "deep cycle" batteries that can cope better with being drained than others, but they will still be happier if you don't.

When you get a new battery home you should put it on float charge using a proper lead acid charger to top it up. If you are not going to be using it immediately, you should keep the battery topped up on a regular basis. Lead acid batteries want and need to be kept in a charged state at all times.


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## tabetha (Sep 21, 2009)

It depends entirely on the battery type and make, if its certain AGM, it will be fine as no sulphation can occur, this is due to the acid being suspended in the gel and these are usually spiral coiled as well.
Traction batteries for example often are built this way, and can fully discharge without problem of shorter life, so long as they are not discharged so quick that the plates move.
tabetha


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## CosmicEnergy (Oct 11, 2009)

Hi folks, my first post here although I've read the led light threads from time to time. There are methods to desulphate or condition batteries such as lead acids. Myself, I have rejuvenated a 6 volt-4.5AH SLA that was at 2 volts and when an led load was attached it dropped to 0 volts and was in this condition for at least a year or more so it was very dead. When using the Bedini type radiant charging method, which in my case was using the flyback off of a Joule Thief with a single diode. I was able to bring the battery capacity to 60% at C/20 discharge rate using this method, though with continued conditioning I'm sure it could be raised to like new or better. Any comments are welcome.


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## SemiMan (Oct 11, 2009)

tabetha said:


> It depends entirely on the battery type and make, if its certain AGM, it will be fine as no sulphation can occur, this is due to the acid being suspended in the gel and these are usually spiral coiled as well.
> Traction batteries for example often are built this way, and can fully discharge without problem of shorter life, so long as they are not discharged so quick that the plates move.
> tabetha



This is not completely accurate. AGM batteries can sulphonate. They still have sulphuric acid in them and there is still a reaction and movement. Only a very small percentage of AGM batteries are spiral coiled as well (Exide brands).


...but back to your battery. You are worrying needlessly. Have you reduced the life of your battery? You bet! Have you reduced it very much from a single deep discharge? ...heck no! If you had left it fully discharged for an extended period of time... week+ then the damage would have been worse, but according to you, you charged it right away. Those small 6V sealed batteries are designed deep discharge usage. They are good for about 150 - 100% depleted deep discharge cycles. At 50% discharge that may go up to 400-500 and at 20% ...well you get the picture. Even lead acid batteries not specifically designed for deep discharge can still take a reasonable amount of fully discharged cycles...again if you don't leave them in the fully discharged state for any period of time.

- You will see most battery maintenance recommendations to never discharge a battery below 20%. The reason for this is a combination of the discharge and being left in discharge. Deep discharges definitely cause the battery to fail earlier, but it does not fail after 1 full deep discharge, it fails after 10s or 100s depending on the lead-acid battery type. 

Semiman


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## qwertyydude (Oct 12, 2009)

AGM and gel cell batteries are different constructions entirely. AGM is an absorbant glass mat, meaning the acid is absorbed in mats and won't slosh around. These are the ones likely to be spiral wound. Gel batteries are just that the acid is gelled and this significantly reduces electrolyte evaporation, though in either battery overcharging will still "boil off" ie electrolyze the water in the battery.


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## keithja (Oct 12, 2009)

My two cents. 

I was in the US Navy on submarines, so I have some pretty in depth experience with lead acid batteries. "Boats" have just about the most elaborate and large a lead acid battery system that you would ever come across. The battery is the last ditch source of power on nuke boats. After reactor scram drills, the battery is all that is available until you can reduce depth, snorkle, and start the emergency diesel engine (while you are re-starting the reactor...and starting turbine generators and main engines...it gets to about 130 to 140 degress F during "rigged for reduced electrical power" in the engine room...analogy: starting a reactor in a sauna while bobbing around like a bar of soap in a bath tub with kids playing in it...sea sick and puking too).

The other posts are pretty good info. I hope this helps tie it togther from a practical angle. Anyway, on an equalizing charge (a regular charge to non-boat types)...the charge is started at a very high charge rate (current) to shock the plate surfaces to counter the coating/plating mentioned in the other posts. Does it totally reverse it...heck no...but it does reduce it. I used the same philosophy on charging lead acid batteries at home every since. I started the charge on the high current "start" setting on my charger for 5 minutes, then reduce it to a normal charge setting. I actually go to a fast setting for the next 30 minutes and then slow setting. It has extended my lead acid battery life quite a bit. BTW, submarines do not use flat set charging rate for charging...there is a specific curve that is followed...my very rough home equivalent is start (5 min), fast (30 minutes), then slow until the charging amps get close to zero.

I have supervised tons of charges, "hopped gravities" in the battery compartment, bypassed low cells (jumpered)...done it all. 

The 50% thumb rule mentioned in another post is a good one. Remember, a typical battery is made up from several individual cells...the number varies with the desired output voltage. Push a battery too hard and a cell will "reverse" on you...then that battery is trash. Avoiding reversing a cell is the reason that you try not to go below 50% or so charge...to give each cell margin to "reversing". The battery is only as good as the weakest cell!!!!


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## qwertyydude (Oct 14, 2009)

I too was on a nuclear sub, I was an nuke ET so I only crawled around in the battery compartment a couple times but if you're trying to set an equalization charge at home the best way after your initial current controlled fast charge to break off sulfation is to finish off the charge with a hobby charger since it maintains constant 2.3 volts/cell which can technically be left on the battery indefinitely without risk of boiling off electrolyte. If you're only hooking up a trickle charger it'll keep pumping current into the battery beyond full, best alternative if you don't have a hobby charger is use a float charger but it won't be as good at cell balancing as a hobby charger's constant 2.3 volts/cell.


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