Introduction: Old SLA Battery Recovery

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Any battery will die after some years,but you can give a 1up to it.Every thing is not permanent every thing will finish out after some time.You can use the things made from the big bang.Any thing is not vanishing its turning into a other substance that's the atomic theory.

Step 1: About Sealed Lead Acid Batteries

Picture of About Sealed Lead Acid Batteries

The lead–acid battery was invented in 1859 by French physicist Gaston Planté and is the oldest type of rechargeable battery. Despite having a very low energy-to-weight ratio and a low energy-to-volume ratio, its ability to supply high surge currents means that the cells have a relatively large power-to-weight ratio. These features, along with their low cost, makes it attractive for use in motor vehicles to provide the high current required by automobile starter motors.

As they are inexpensive compared to newer technologies, lead-acid batteries are widely used even when surge current is not important and other designs could provide higher energy densities. Large-format lead-acid designs are widely used for storage in backup power supplies in cell phone towers, high-availability settings like hospitals, and stand-alone power systems. For these roles, modified versions of the standard cell may be used to improve storage times and reduce maintenance requirements. Gel-cells and absorbed glass-mat batteries are common in these roles, collectively known as VRLA (valve-regulated lead-acid) batteries.

In a valve regulated lead acid battery (VRLA) the hydrogen and oxygen produced in the cells largely recombine into water. Leakage is minimal, although some electrolyte still escapes if the recombination cannot keep up with gas evolution. Since VRLA batteries do not require (and make impossible) regular checking of the electrolyte level, they have been called maintenance free batteries. However, this is somewhat of a misnomer. VRLA cells do require maintenance. As electrolyte is lost, VRLA cells "dry-out" and lose capacity. This can be detected by taking regular internal resistance, conductance orimpedance measurements. Regular testing reveals whether more involved testing and maintenance is required. Recent maintenance procedures have been developed allowing "rehydration", often restoring significant amounts of lost capacity.

OK now we are going to weak up the dried battery.You can recover 99% if its not left alone for more than 5 years.

If its left more than 5 years alone,without usage,you can recover it to about 50-75%.

Step 2: What Cause This Sleeping?

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Lead–acid batteries lose the ability to accept a charge when discharged for too long due to sulfation,the crystallization of lead sulfate.They generate electricity through a double sulfate chemical reaction. Lead and lead dioxide, the active materials on the battery's plates, react with sulfuric acid in the electrolyte to form lead sulfate. The lead sulfate first forms in a finely divided, amorphous state, and easily reverts to lead, lead dioxide and sulfuric acid when the battery recharges. As batteries cycle through numerous discharges and charges, some lead sulfate is not recombined into electrolyte and slowly converts to a stable crystalline form that no longer dissolves on recharging. Thus, not all the lead is returned to the battery plates, and the amount of usable active material necessary for electricity generation declines over time.

Sulfation occurs in lead–acid batteries when they are subjected to insufficient charging during normal operation. It impedes recharging; sulfate deposits ultimately expand, cracking the plates and destroying the battery. Eventually so much of the battery plate area is unable to supply current that the battery capacity is greatly reduced. In addition, the sulfate portion (of the lead sulfate) is not returned to the electrolyte as sulfuric acid. It is believed that large crystals physically block the electrolyte from entering the pores of the plates. Sulfation can be avoided if the battery is fully recharged immediately after a discharge cycle.A white coating on the plates may be visible (in batteries with clear cases, or after dismantling the battery). Batteries that are sulfated show a high internal resistance and can deliver only a small fraction of normal discharge current. Sulfation also affects the charging cycle, resulting in longer charging times, less efficient and incomplete charging, and higher battery temperatures. Desulfation is the process of reversing the sulfation of a lead-acid battery. It is believed that desulfation can be achieved by high current pulses produced between the terminals of the battery. It is believed[by whom?] that this technique, also called pulse conditioning, breaks down the sulfate crystals that are formed on the battery plates.Pulses must last longer than the resonant frequency of the battery. Short pulses simply feed energy wastefully into the resistive components of this resonant circuit and virtually none into the battery. Electronic circuits are used to regulate the pulses of different widths and frequency of high current pulses. These can also be used to automate the process since it takes a long period of time to desulfate a battery fully. Battery chargers designed for desulfating lead-acid batteries are commercially available. A battery will be unrecoverable if the active material has been lost from the plates, or if the plates are bent due to over temperature or over charging. Batteries which have sat unused for long periods of time can be prime candidates for desulfation. A long period of self-discharge allows the sulfate crystals to form and become very large. Some typical cases where lead acid batteries are not used frequently enough are planes, boats (esp sail boats), old cars, and home power systems with battery banks that are under utilized. Some charging techniques can aid in prevention such as equalization charging and cycles through discharging and charging regularly. It is recommended to follow battery manufacturer instructions for proper charging. SLI batteries (starting, lighting, ignition; i.e. car batteries) suffer most deterioration because vehicles normally stand unused for relatively long periods of time. Deep cycle and motive power batteries are subjected to regular controlled overcharging, hence eventually succumb to corrosion of the positive plate grids, not to sulfation. Extreme weather can also cause sulfation in batteries. Extreme heat in the summer increases the amount of sulfates that come from batteries. Electronic components putting a constant drain on a battery also increase the amount of sulfation. Keeping a battery in a cool location and keeping it charged help prevent this.

You can see the lead plates in the picture,they are inside the battery.I got them from a 6v lead acid battery.When they get reacted the supply voltage is getting low.So it this instructable im only recovering batteries which is dried off.We can't recover the broken lead plates.

You can see the battery voltage is 0v now.We will see the change after the recovery!

Step 3: Required Supplies

Picture of Required Supplies

1. A Sealed Lead Acid Battery

2. A Syringe

3. 50% Sulfuric Acid (H2SO4)

4. Pure Water (not tap water,its rain water or battery water)

5. A Y tube (optional)

6. A Beaker (Plastic or Glass)

7. DC Power Supply (It must be as your battery)

8. A Sharped Pointed Tool

9. Wires or Clips (optional)

10. A Multimeter (To see the change but its optional you can use a LED instead)

11. Self Confidence (You can't buy it!)

12. A Clean Workplace


Please use safety gloves and goggles when doing this.Because battery acid might leak,this is important when doing the 2nd way.Sulfuric acid is corrosive it gets hot when splashed to skin.It can eat through your skin in a one minute.NOT IN SECONDS!!!

Step 4: Open the Cap!

Picture of Open the Cap!
  • In this instructable im using a 4v+6v battery.Using the pointed tool open the cap.And then you can see some rubber lids.Remove them too!You can hear a pop sound when opening it.Its normal!

Step 5: Pump in Some Water

Picture of Pump in Some Water

Using the syringe pump some water.The amount changes as your battery. So pump water until every cell is full.And let them sit for a while and close the lids and caps.Shake your battery and if you can hear water like when you shake a drink it means too much water so be careful not to overfill.You can use a Y tube instead of a syringe

I recommend using acid for batteries older than 5 years.Or you can do the both ways,but make sure to dry the battery to low down water.

Step 6: Charge the Battery

Picture of Charge the Battery

Use a proper matching charger to charge your battery.Do not overcharge!,And you can use about 1v more than the battery voltage.The battery might get hot.But its not a bad sign its good.

Step 7: Test the Battery

Picture of Test the Battery


My battery had recovered well!

You can use a multimeter or a LED,DC motor to judge its recovery.If your battery didn't got well you will have to again pump sulfuric acid instead of water.If any of these ways didn't work for you it means that the battery plates are finished!!!

Thanks for reading!

Comment and Vote!

This is my first instructable please request for new instructables.


lmlisak (author)2015-12-05

I had the same question... I believe you are just wetting the cells and not flooding them.

I am experimenting with using 5ml of water in each cell, and then charging ;them at 14.5 for 8 hours... then change the voltage to 13.5.. which is a "float voltage"... until I can test them.

I then will put a load on it for a few minutes using a,car headlight... then charge again...

these are the 7AH batteries im working with for now

BillsVX (author)2015-11-11

I've revived a few VRLA's like this and had checkered results but, looking back...I may have kept the water level too high. After messing with Wet cells for a number of years, it's all too easy to flood the cells when it comes to refilling them. Should there be any water visible when inspecting the cells after filling and they have settled for a few hours or so?

Science Tower (author)2015-08-24


seamster (author)2015-08-24

Interesting, thanks!

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