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Restoring AGM Batteries

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  • Restoring AGM Batteries

    Hi Everyone,

    I was talking with JB about AGM batteries and the particular problems they pose with the SG circuit, the ferris wheel, and how they do not like Radiant in general. He gave me a bit of insight into how he turns AGM batts into a hybrid AGM/LAB device. if your AGM is dead you can try the following:


    1- pop the caps to expose the cells
    2- go down to the local auto parts store and get some battery acid, they sell it in bulk sometimes.
    3- take a small syringe and add 10 CC of acid to each cell.
    4- wait a day for it to absorb the acid, then do it again.
    5- do this each day until the mat does not absorb any more acid
    6- drill a very small hole in the top of each cap to allow it to vent and replace the caps. make sure the battery is at zero volts.
    7- REVERSE CHARGE THE BATTERY !!! yes that is what he said REVERSE CHARGE. this changes the lead plates. 10 minutes is a good estimate.
    8- now drain it to zero with a load such as a resistor or dc bulb.
    9- charge it with a regular charger that has a variable supply for current in the correct direction.

    John said the fully charged resting voltage will be between 12.2 and 12.6 and it will behave like a standard LAB. water will have to be added peiodically as it will begin to offgass like a normal battery. this is all I was given, perhaps Chuck can chime in on this, and correct anything that is wrong with these steps.

    have fun and be safe
    Tom C
    Last edited by Tom C; 08-16-2012, 03:21 PM.

    experimental Kits, chargers and solar trackers

  • #2
    AGM Batteries

    To All,
    The AGM batteries may be converted, but what if the battery is Sulfated, your in trouble.
    The only way I ever found to help the battery is make sure the battery voltage is zero. To do this you must use a supply you can dial in for current. The first thing is to test the battery to make sure it is at zero volts. By reversing the charge you can move the lead in the reverse direction, and you only want to do this for a very short time as the battery may heat and you want to keep this at a minimum, say 10 minutes. Then drain the battery to zero and charge again with a variable supply for current in the correct direction. Now we are talking about AGM cells here and not anything else. Be very careful when doing this, as this is done at your own risk.

    You should be able to recover at least 55% of those useless batteries. This type of battery dries out and you cant do a thing with it. You can get it to work as we have done this at the shop. Make sure you drill a small hole in the caps that you pop off for the gases to escape.

    A Sulfated Battery

    How many times have you heard the expression, "The Battery Won't Take A Charge" or "The Battery Won't Hold A Charge?" More often than not, the culprit is hardened sulfate on the battery plates. Below we will attempt to explain what that means, what the causes are, and some measures to prevent the sulfate from permanently damaging your battery.

    Let's look inside a battery cell. Basically, there are the positive plates, the negative plates, separators (to keep the plates apart), and electrolyte (sulfuric acid and water).

    In normal use, battery plates are getting sulfated all the time. When a battery is being discharged the lead active material on the plates will react with the sulfate from the electrolyte forming a lead sulfate on the plates. When there is no lead active material and or sulfate from the electrolyte remaining the battery then is completely discharged. After a battery reaches this state, it must be recharged. During recharge, the lead sulfate is reconverted into lead active material and the sulfate returned to the electrolyte.

    When the sulfate is removed from the electrolyte the specific gravity is reduced and the reverse takes place when the sulfate is returned to the electrolyte. This is why the state of charge can be determined with the use of a hydrometer.

    If a battery is left standing in a discharged condition the lead sulfate will become hard and have a high electrical resistance. This is what is normally called a sulfated battery. The lead sulfate may become so hard that normal recharging will not break it down. Most charging sources, engine alternators and battery chargers, are voltage regulated. Their charging current is controlled by the battery's state of charge. During charging, battery voltage rises until it meets the charger's regulated voltage, lowering the current output along the way.

    When hard sulfate is present, the battery shows a false voltage, higher than it's true voltage, fooling the voltage regulator into thinking that the battery is fully charged. This causes the charger to prematurely lower it's current output, leaving the battery discharged. Charging at a higher than normal voltage and low current may be necessary to break down the hardened sulfate.

    Hardened sulfate also forms in a battery that is constantly being cycled in the middle of its capacity range (somewhere between 80% charged and 80% discharged), and is never recharged to 100%. Over time, a portion of the plate's active materials turns into hard sulfate. If the battery is continually cycled in this manner, it will lose more and more of its capacity until it no longer has enough capacity to perform the task for which it was intended. An equalizing charge, applied routinely every three to four weeks, should prevent the sulfate from hardening.

    In both cases, the fact that the battery "won't take a charge" is a result of improper charging procedures which allowed the sulfate to harden. In most instances, it is possible to salvage a battery with hardened sulfate. The battery should be charged from an outside source at 2.6 to 2.7 - volts per cell and a low

    current rate (approximately 5 Amps for small batteries and 10-Amps for larger ones) until the specific gravity of the electrolyte starts to rise. (This indicates that the sulfate is breaking down.) Be careful not to let the internal temperature of the battery rise above 125 F. If it does, turn the charger off and let the battery cool. Then, continue charging until each cell in the battery is brought up to full charge (nominal 1.265 specific gravity or higher).This time needed to complete this recharge depends on how long the battery has been discharged and how hard the sulfate has become.

    The next time your batteries don't seem to be taking or holding a charge, check the specific gravity with a hydrometer. If all cells are low even after a long time on charge, chances are you've got some hardened sulfate that has accumulated on the plates. By following the instructions outlined above, the problem may be corrected.
    John Bedini
    My homepage:


    • #3
      thanks for the clarification John,
      Tom C

      experimental Kits, chargers and solar trackers


      • #4
        John B,

        I know you said AGM only, but will this work for gel-cells?

        Also on the variable supply what voltage and current should be used? 2v over the battery and the current at the c20 rate?

        John K.


        • #5
          Originally posted by John_Koorn View Post
          John B,

          I know you said AGM only, but will this work for gel-cells?

          Also on the variable supply what voltage and current should be used? 2v over the battery and the current at the c20 rate?

          John K.
          2v Over the battery may not be enough to salvage. You talking about 14v range. To rejuvenate you need at least 15.6 at low current of about 5amps. You cannot do that to a Gel battery without drying it Up and making it useless