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.

27 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

  10. Good day I have 4 – 12 volt deep cycle US batteries I have had in my golf cart for 3 years now. Up until this year they worked great. But because we had very smokie skies and bad weather last summer we did not get out golfing much and as a result the cart sat plugged in for weeks on end and upon one visit to the cart I could smell sulfur rotten eggs. Because We don’t golf during the winter I bought the cart home and the batteries were fully charged at the time. So The cart sat in the garage for 6 months. When I went to move the cart the batteries were all dead and the charger said ( Sul) I took the voltage form each battery separately after removing the battery cables and the voltage on the batteries ranged from 3.25 to 5.25. So I put the battery charger on each battery one at a time in the Sul mode and now there up to 12.10 volts . Now the golf cart battery charger recognizes the voltage in the batteries and what’s to charge them. Your thoughts please. Is all this new found Voltage just playing with me LOL or do you think in your Experience the batteries could have a second life. Thanks Jim

    1. Hi Jim,

      Deep cycle batteries self discharge at approximately one percent per day. After six months of sitting without charging they would have been completely self discharged as indicated by the open circuit voltage.
      In addition, the batteries would have been severely sulfated and would be difficult to charge as indicated by the full charge open circuit voltage. You should continue charging until the batteries are up to approximately 1.270 specific gravity per cell or 12.75 volts per battery. It may take several cycles of discharging and recharging to get good capacity back.

      -Mike Wallace, V.P. of Marketing

  11. HI. THere are a number of fluids marketed that suggest they’re more efficacious in restoring a dry battery than distilled water. Is that true?

    1. Hi Ryan,

      Our engineers do not recommend adding any fluids but distilled water to batteries.

      -Mike Wallace, V.P. of Marketing

  12. Hi Mike,
    I have a small personal aerial lift that I have owned for about a year and during that year I have charged the batteries after each use and at least 1 time every 2 weeks to prevent discharge and further sulfation. That said however, the lift sat unused and not charged properly for quite some time before I took over its ownership and care.
    The lift is using 8, 6 volt U.S. Batteries in series for a total of 48 volts, model 2200 deep cycle 232 AH with speed caps. The onboard charger is working fine and the batteries are charging in a normal amount of time using the onboard charger. When in use, the voltage of the batteries drops and I suspect that due to the excessive time it sat in a barn before I owned it, sulfation has developed on the plates.
    I also checked the batteries for a date stamp and cannot find one, can you please advise the location of the stamp? I suspect they are about 3 – 4 years old and have not gone through many discharge cycles as the lift is used infrequently for personal use only.
    Can you please advise the best method to recover the batteries to the best possible condition and what charger or type of charger would be the best choice?
    Also, with the speed caps is it necessary to open them for every charging cycle?
    Thanks in advance for all your great work!

    1. Hi Tom,

      Our engineer believes that you are correct and the batteries are likely sulfated from not being charged properly before you acquired them.
      Your procedure for charging them after each discharge is appropriate for non-sulfated batteries but may not be enough to recover your sulfated batteries. In addition to the ‘opportunity charging’ you are currently using, they would also recommend regular equalization charging – normally about every 30 days.
      However, in your case the best way to recover the sulfated batteries is to run an equalization charge every charge/discharge cycle for the next ten cycles or until the specific gravities in all cells read 1.270 or higher. Equalization charging is implemented by letting the charger complete a normal automatic charge and then unplugging AC power, wait 1-2 minutes for the charger to reset and plug AC power back in. The charger should continue charging for 1- 3 more hours depending on the amount of sulfation to recover. If all the cells recover to 1.270 SG or higher, normal charging can be resumed.

      U.S. Battery uses a stamped code on the terminals of its flooded lead-acid batteries. The top left letter stamped on the terminal correlates to the month it was manufactured (A-L refers to January to December). In this example, the letter “K” is the 11th month indicating the battery was manufactured in November. The number indicates the year 2014, and the bottom letter specifies the U.S. Battery plant where it was produced.

      U.S. Battery Mfg. Co. Plant Codes

      The letter “X” is for Corona, California plant.
      The letter “Y” is for Augusta, Georgia plant.
      The letter “Z” is the Evans, Georgia plant.

      The SpeedCaps contain flame arrestors that are designed to prevent ignition of flammable gases in and around the batteries. They should always be installed and properly tightened on the batteries when in use and removed only when watering the batteries. The SpeedCaps should not be removed when charging or discharging the batteries.

      -Mike Wallace, V.P. of Marketing

  13. i have a 12v 100ah chinese solar bank battery that claims to be “gel” brand name JSL II… i didnt know better so i added battery acid to most of the cells.. commonly called “battery solution” here in Philippines.. ive ordered a “smart” battery charger with a 6a, 10a, 16a and :”repair” option.. ive topped all the cells of said battery with local distilled water .. is there any chance that the repair function will DEsulfate my heavy sulfated graphite cathode and anode ? the first cell was very thirsty.. when i first got this battery i just clamped a solar panel to it without a solar charge controller and forgot about the battery for 2-3 months…

    PS the “smart: charger is also.. very Chinese.. yes i said Philipines however i was born in Montreal, Canada…

    1. Hi Christopher,

      Our engineers don’t believe that desolation will help much. They feel that the batteries are most likely going to need to be replaced.

      -Mike Wallace, V.P. of Marketing

  14. What great response and customer service from a company. I’m really impressed. I have an old dead car battery that I use to power auxiliary items that I just leave in the back of my jeep. It’s on a black and decker reconditioner/charger now that’s been running for almost 24 hours. I’ll see what happens. This is a great resource:)

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