U.S. Battery

The Truth About Reviving Dead Batteries

The Truth About Reviving Dead Batteries

When your deep-cycle battery nears end-of-life, it’s normal to want to squeeze as much out of it as possible before spending money on a new one. Numerous online videos show a variety of ways to revive a dead or dying battery using various substances and hacks. The truth is, there are many factors that contribute to poor battery performance and failure, and it is important to diagnose the symptoms of poor battery performance before determining a cure.  It is also important to understand that many of the supposed “cures” can damage the battery, while others can be dangerous and do nothing to improve battery performance.

Fred Wehmeyer, Senior VP of Engineering at U.S. Battery, has more than 50 years of experience in rechargeable battery design and development.  He says that many of these hacks claim to show some type of improvement, but the gains shown may simply be artificial. One of the more common ones is adding Epsom salt to the battery cells.  According to Wehmeyer, adding Epsom salt (magnesium sulfate) to a lead-acid battery will ‘artificially’ increase the specific gravity reading (SG), but because it does not increase the sulfuric acid concentration, it does nothing to improve battery performance.

“This is because the sulfates in the Epsom salt are tied up as magnesium sulfate and are not available for discharge to lead sulfate as the sulfates in sulfuric acid are,” said Wehmeyer. “If you filled a new lead battery with a magnesium sulfate solution instead of sulfuric acid electrolyte, it would have no capacity at all.”  Simply put, adding Epsom salt will not recover the battery capacity but does “artificially” increase the SG.

According to Wehmeyer, the result would be similar if you remove the dilute electrolyte from a discharged and/or sulfated battery and refill it with the electrolyte for a fully charged battery (usually 1.270). The specific gravity will be higher, but the battery plates are still discharged and/or sulfated. Doing this will probably kill a potentially recoverable battery (see below).

Baking Soda and Aspirin

Other popular hacks include adding baking soda to recover a dead battery. Baking soda mixed with water is often used to clean the tops of batteries and battery terminals because it neutralizes the sulfuric acid and acidic corrosion products. Wehmeyer says that pouring baking soda into the battery cells will neutralize the sulfuric acid in the electrolyte to sodium sulfate that cannot discharge to lead sulfate in the normal discharge reaction.  This will also permanently reduce the capacity of the battery, which was most likely already low.

Adding aspirin to the battery is another hack that is often seen in videos claiming to revive dead batteries. Wehmeyer says aspirin is acetylsalicylic acid, which eventually breaks down into acetic acid. Acetic acid attacks the positive lead dioxide plates in the battery and permanently damages them, leading to short battery life.  This may show a small, temporary increase in capacity but will quickly kill the battery.

Pulse Charging 

If your battery is sulfated, which results in low power and difficulty in recharging to full capacity, it can sometimes be recovered using proper pulse charging techniques. Wehmeyer warns, however, that there are an infinite variety of pulse charging techniques used by a wide variety of equipment sold for this purpose.  These techniques include DC (direct current) pulses using various voltages and currents, as well as AC (alternating current) pulses with a wide range of AC frequencies. “The problem is that if not done properly, it can do more damage than good,” says Wehmeyer. “Having said that, I have tested some very complex and very expensive pulse chargers that appeared to recover sulfated batteries more quickly than traditional methods.  Most pulse chargers use an external power source (wall AC) to power the device. Some, however, use the battery’s voltage to power the charge pulses. This can kill the battery if left connected for long periods of time without a separate charger.”

Ultimately the best recommendation for potentially recovering a sulfated battery is to save your money and try using a long, slow charge.  If you have a battery charger that has a reconditioning or equalizing charge mode on it, that may be your best bet. “Use the equalization charge mode regularly, about once a month, on deep-cycle lead-acid batteries to extend the life of the battery,” says Wehmeyer. “Regular equalization charges prevent sulfation and stratification by balancing the individual cells and properly mixing the electrolyte.  In addition, a long slow charge could help recover already sulfated batteries to make them last a little longer.  If your charger does not have an equalization charge mode, simply wait until the charger completes a normal charge and then restart it by unplugging AC power and reconnecting.  The charger should continue charging for an additional 1 – 3 hours.  If the battery is dead from poor maintenance, worn-out from too many deep cycles, overcharging, or excessive deep discharging; it probably can’t be recovered.”

Following manufacturer-recommended care and maintenance procedures will get you the longest life and best performance from any battery. For more information on how to care for your lead-acid batteries, check out the U.S. Battery User Manual.

18 Responses

  1. Thanks, I don’t have any money for anything but my battery’s still have a little life so all is not lost yet. Hope.

  2. My deep cell batteries for my RV trailer are messed up. They have both said “battery failure”. My Ampeak smart has been in the “battery repair” mode for approx. 12 hours. Is this going to help? Or do I need to spend all that money for new ones?
    Thank you if I can get your feedback.

    1. Hi Ross,

      The Ampeak Smart Battery Charger has an Analysis Mode and a Desulfation Mode in addition to normal charging modes. If the Analysis Mode detects potential sulfation which is common for batteries in RV applications, it will automatically initiate the Desulfation Mode. The batteries may or may not recover after one desulfation charge. If not, it may require several cycles of discharge and recharge with desulfation. If you can provide open circuit voltages and specific gravities after recharge and desulfation, we can better assess their potential recovery. Sulfation is caused by allowing the batteries to stand in a partially charged condition for long periods of time.

      -Mike Wallace, V.P. of Marketing

  3. I really wish I could count on a way to revive my 1 yr old US batteries ! They are dead, 5 friggin volts. 12 volt batteries should last more than a year.

    1. Hi Kenny,

      I’m sorry you are experiencing an inconvenience with your U.S. Battery products. If you have not, please reach out to our engineers by filling out this form. They may be able to address your issue and advise you on how to remedy the problem.

      -Mike Wallace, V.P. of Marketing

    2. I have a 5 year old A. DELCO battery that was dead, dead & dead. I tried charging it again & again. However, after 10 or so attempts, it started holding charge and after 5 more charges it hit 100% charged with 60% HEALTH
      shown. It’s now back in my SUV and working fine.

  4. I have four 12 volt batteries for my 48 volt pontoon boat. they are 5 years old and I have used batteries before for 8 years, so I think there is still life in them. I charge them every month over the winter. I tried the recondition mode on my Tower Top recharger and it ran for 24 hours and then the message was “overtime charging”. However it initially read 12.4 volts before the recondition and now reads 12.8 volts. So do you think it will help to run the recondition again ? Do I add electrolite and if so, ow much ? Yes, I know, last part is buy a new battery, but there are four of them and the charger cost $100, so I want to charger to earn it’s keep too.

    1. Hi Raymond,

      Apparently, the recondition mode on the charger did recover the batteries somewhat. According to TABLE 8 in the US Battery User Manual, the batteries are fully charged at 12.73 volts. However, the best measurement of the State of Charge of flooded lead acid batteries is the specific gravity of each cell. At full charge, each cell should be 1.270 SG or higher. The specific gravity is measured using a battery hydrometer designed for use with deep-cycle batteries. There are several reasons that the Tower Top charger could result in ‘overtime charging’ depending on the charge setting and the condition of the batteries.

      • First would be the current selection on the charger of 2, 8 or 15 amps. The lower the current selection, the longer the charge time.
      • Second would be the battery condition. Older batteries require longer charge times, particularly if they are sulfated.
      • Third would be the battery temperature. Hot batteries may not reach the end of charge conditions set by the charger for charge termination.

      -Mike Wallace, V.P. of Marketing

  5. I have 8 us batteries in series connected to an inverter.
    They have all been good and worked better than other brands.
    Recently one of these stopped working suddenly.
    I reads about 4v and has absolutely no power.
    When I short the leads, there is no spark.
    It will not charge.
    My questions, why only this battery when all the others work great?
    And what is wrong with it?

    1. Hi David,

      Thank you for choosing U.S. Battery products! I’m sorry to hear you’re experiencing a problem with one of your batteries. Our Engineers said from the description it appears that the suspect battery may have developed an open circuit. This would explain both the 4-volt reading and the ‘no spark’ observation. It would also prevent the battery from accepting a charge. The most likely cause of this condition is a failed intercell connector. The individual 2-volt cells are connected in series inside each battery. If one of the intercell connectors fails ‘open,’ the battery will no longer be able to carry any charge or discharge current. Actually, the 4-volt reading is artificial. If the voltage is measured under load, it will immediately drop to zero due to the open circuit condition.

      This is literally a ‘one-in-a-million’ occurrence in the field, particularly after the batteries have been in service for over a year. Failures of this type are almost always detected during in-plant testing. In the extremely rare occurrence that one escapes in-plant testing, it usually fails very early within the one-year warranty period. Since it is a very rare occurrence, it is extremely unlikely that the other batteries will exhibit the same problem.

      Obviously, the failed battery will have to be replaced for the other batteries to continue to function. U.S. Battery does not normally suggest replacing a battery in a pack of older batteries with a new battery. However, if the older batteries have not been used extensively, a failed battery can be replaced with a new battery of the same type and capacity. All batteries should be fully charged separately before being connected in a pack. Unfortunately, the warranty on the new battery would be voided in this case.

      -Mike Wallace, V.P. of Marketing

  6. Ordered Revive Battery Rejuvenator. It comes with 1 bottle per battery. Probably won’t work, but only $27 as opposed to $119 per battery at Sams. I’ll post results.

  7. I have 8 us batteries in a polaris ranger ev I bought used. It was 3 years old with just 21 hours. My range is 1/3 of original after servicing the batteries and cables.

    I am wondering if a chemical desulfator would be useful to restore some capacity.

    1. Hi Geir,

      U.S. Battery does not recommend the use of ‘chemical desulfators’. Most are ineffective and end up contaminating the battery. If the Polaris EV has been used lightly – just 21 hours over 3 years – the batteries are probably undercharged and sulfated.The best way to recover sulfation is a long slow charge with shallow cycling and equalization charging after every recharge for at least 10 cycles.The capacity and driving range should gradually recover if the batteries have not been permanently damaged. You may want to try recharging each 12 volt battery individually with a 12 volt charger.

      -Mike Wallace, V.P. of Marketing

  8. Hello Team,
    I need Information to Revive Dead Batteries in my House. I Have too many dead batteries,

    Please Help Provide me information or descriptions to revive dead batteries



    1. Hi Maiyakes,

      I will pass your information and inquiry to our Engineering team. They will be happy to answer your specific questions.

      -Mike Wallace, V.P. of Marketing

  9. Hi Mike,

    Do you or the engineering team have a favorite “off the shelf” smart charger. One that has provided the best desulfating results?

    Thanks, Michael

    1. Hi Michael,

      U.S. Battery recommends chargers and charge algorithms from Delta-Q, Lester Electrical, PRO Charging Systems and Quick Charge Corporation (among others) as shown on the Charging Instructions page of our site.

      -Mike Wallace, V.P. of Marketing

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