Dying Battery Extender

Published by: Nick Meissner

When we purchased our new (to us) homestead, it came with an old dilapidated off-grid power system.

It didn’t take much expertise to see the writing on the wall—this power system was a relic from the past and was on its last leg. We would need to replace it soon...

But purchasing a homestead can tend to stretch one’s finances, so we decided to try and make the old power system “stretch” for a year or two while we saved for a “real” solar power system. We’ve been slowly whittling away at replacing one component after the next. But still, the batteries kept cruising. One year…two years…three years. Finally, they are officially biting the dust.

My initial assessment was that the batteries wouldn’t even last one year, but with some careful management and a few tricks up my sleeve, we managed to squeak another 3 years of life out of an almost dead bank of batteries.

Our "Dying Battery Extender" Strategy

So, how did we do it? What are those tips for stretching more life out of a dying battery bank?

Our strategy wasn’t all that revolutionary, but I think you’ll find it really helpful to see what we did—in case you find yourself in this position.

Here’s a quick video I just shot that walks you through it all…

No Actually 5 Options For Extending Dying Batteries

There are 5 things we did to squeak extra life out of our dying battery bank.  Be sure to check out #5 especially as I forgot to mention it in the video.  PLEASE NOTE:  This list is NOT for maintenance of a healthy battery bank.  It is for dying batteries that would otherwise be unusable.

  1. Triage - Don’t assume that a battery bank is entirely dead just because it is misbehaving.  Investigate whenever strange things happen.  How?  Your primary tool is a hydrometer (which measures the specific gravity of each cell).  Check each cell, looking for particular cells that are reading dramatically lower than the rest.  Remove each battery that has even one dead cell.
    How many do you have left?  Based on that, reconfigure your battery layout.  Remember that it takes four 6-volt batteries to equal 24 volts (or eight of them to equal 48 volts).  If you are dealing with industrial type 2 volt batteries, it will be strings of 12 (for a 24 volt system) or 24 (for a 48 volt system). Removing the dead cells will save the good ones from being killed by it, and will dramatically improve the overall performance of the battery bank.
    We whittled our old battery bank from 12 down to 8 and then to 4 batteries.  Now that the last 4 batteries are spent, we have reached the end of our rope :-).
  2. Use a desulfator - This is a little device that helps to dissolve the sulfate crystals that can form on the plates of a battery and greatly impair the performance and capacity of it.  But not all desolators are created equal.  My favorite brand is Battery Life Saver.  We’ve been using it for many years as preventative maintenance.  I think it is one of the factors that caused this old battery bank to last as long as it did.  I have heard of some folks having success with rejuvenating old sulfated batteries with it also, but there is some debate about this.  It’s best used for preventative maintenance.
    Battery Life Saver makes a number of models, but I’d suggest this one for 12/24 volts systems (with an overall capacity of less than 1,000 amp hours), this one for 48 volt systems (less than 1,000 amp hours), this one for large 24 volt systems (larger than 1,000 amp hours), and this one for large 48 volt systems (larger than 1,000 amp hours) [those are affiliate links to reasonably priced options].  I don't suggest going with a different brand for your desulfator as I have heard mostly poor feedback about the others I've heard of.  Battery Life Saver is what we have used personally for years.
  3. Equalize more frequently? - When trying to stretch another year out of a dying battery bank, most of the rules are out the window.  So you might find that the only way to get a decent charge into the old batteries is to equalize them more frequently than typical.  Equalizing is a controlled overcharge.  You definitely don’t want to do this too frequently with a functional battery bank, but you may have to do it a lot more frequently when batteries are dying.
    You'll notice that I put a question mark at the end of this subheading.  That's because equalizing an old battery does not come without risks.  If you have used the batteries hard and worn the lead plates thin, then equalizing a lot could finish them off.  Also, equalizing knocks sulfate crystals off the leads plates, adding to the sediment piling up in the bottom of an old battery.  When the sediment gets high enough, it can short out the cells.  So there are risks to this, but if you are unable to get a decent charge with the typical settings, then you really have nothing to lose, right?
  4. Keep them watered - You’ll likely find that worn out batteries use more water than new ones.  This is especially true if you are equalizing more frequently.
  5. Kill any corrosion - Corrosion is the enemy of free-flowing electrons.  In the highly corrosive air present in a battery bank, almost any piece of metal is at risk, especially any electrical connection (where wires or cables connect together).  This is especially true with old batteries.  You will often find that old batteries are dealing with serious corrosion issues.  Since the symptoms of corrosion issues and dying batteries are sometimes similar, it can be difficult to tell one from the other.  But here's how to do it...
    Use a wrench to take apart EVERY cable and wire connection in the battery box (specifically, the battery interconnect cables and the main cable that connects the battery bank to your inverter or power center).  Then you'll want to use a wire brush to clean all of those connections and battery terminals.  Then put it all back together and tighten them down.  You probably don't have to worry about wire brushing connectors that are outside of the battery box, but it never hurts to snug up those connections with a wrench.  Anytime you have heating and cooling occurring frequently, it's possible for the nut to work its way loose.
    After you have cleaned and tightened everything, apply a liberal dose of battery terminal protectant.  My favorites are generally a gel or grease type consistency and have additives that neutralize battery acid.  I have used this one with great results, and this is another great option.

That's about it.  As you can see, this is not some revolutionary new method.  It's pretty common sense if you understand how batteries work.  It worked well for us and bought us a significant amount of extra time.  Hopefully, you won't be in that position, but if you are, I hope this helps!

question mark
Any questions or comments about stretching the life of dying batteries?  Let me know below:


  1. Nick Meissner

    Any questions? Anything you'd like to discuss about dying batteries? Fire away!

    • Caleb Hill

      Hi Nick
      A way to reuse a standard 12 volt lead acid is as follows.
      Remove all acid then slow charge it with distilled water several days and repeat about 3 times. Then install new fresh acid. An ordinary car battery was working more than 30 years and still working.

      I purchased a new battery for my truck 4 years ago. 610 CCA
      I installed about $.10 of chemical and slow charged it over night.
      The next day I took it to the store for a check up.
      Man was very shocked and asked what in the world I did to my battery! The strongest battery we sell is not this strong!
      I was given the print out.
      Battery rated 610 CCA
      Battery tested 1110 CCA

      The chemical I used was 3 oz white sugar in 3oz water and boiled to make syrup. 1/6 added to each cell.
      You MUST charge the battery as soon as syrup is added. This makes black carbon that coats the possitive plate and too much sugar will cause the plates to touch and damage the battery. I find that China uses carbon in their batteries that gives them about 15 years of use.

      Caleb Hill
      Electrician, Inventor

      • Nick Meissner

        Hi Caleb,

        Many thanks for the tip. No, I haven't heard of this one before. I wonder how it impacts the longevity of the lead plates? And also the amp--hour capacity of the battery (as opposed to the CCA)?

        For me, it would be too risky to try on a very expensive battery bank in operational condition, but may well be worth trying out on a dying battery to see if it can help get a little additional life. Maybe I'll give this a shot sometime.

        Thanks again,

  2. Riesah

    You mention grease and gel at the end of your blog, but failed to name them. Would you please do that.

    • Nick Meissner

      Hi Riesah,

      Thanks so much for giving me a heads-up. For some reason those links didn't make it in the article. Anyhow, they are added now.

      Take care,

  3. Hank Laderach

    One also important factor....when adding water go the battery, use water that has been filtered to remove desolved minerals (zero water filters) or distilled water.

    • Nick Meissner

      Very good point, Hank! Using water with any solids (minerals, etc) in it can cause "stuff" to pile up on the bottom of the battery. If enough of it piles up over the years, it can eventually cause cells to short out. Also, my understanding is that using water with solids in it can encourage the formation of sulfate crystals. That's bad news!

      Thanks again!

  4. Rick England

    Hi Nick, I have ten 12vdc batteries which have been sealed in their cardboard boxes. I would like to use them in a string. Haven't looked them over in years, DO you think I might still be able to recoup them for use or Mayne they have Sat too long?
    Rick England
    Des Moines, Iowa

    • Nick Meissner

      Hey Rick,

      Sorry to say that they are most likely beyond repair. Pretty much all batteries will self-discharge a certain amount every month. This can range from as little as 1% per month (some lithium batteries) to as much as 20-30% per month (with Nickel Iron batteries). For a typical lead acid battery, you would probably be looking at somewhere in between those two extremes--10-15%. A lot depends on the condition of the batteries and all that, but you get the idea.

      So, after batteries have sat unattended for months on end (let alone years), they will become so discharged that they will likely suffer from extreme sulfation and crystallization. Also, the electrolyte will "stratify" (settle out in layers kind of like what happens when you mix oil and water and let it sit). So while you could try changing the electrolyte, your batteries would likely be dead from the sulfation issue. And if somehow that didn't kill them, they probably froze if stored where the temperature can get below freezing. While a fully charged battery won't freeze until Alaska type temps, a discharged battery can freeze in the 20's°F or maybe even low 30's°F.

      But, just to make sure, I would check all the cells with a hydrometer and see if there appears to be any life left in them. If so, then make sure the water level is not dangerously low and try equalizing them (a controlled overcharge). If you seem to be able to get some charging done, you might try discharging and then equalizing multiple times.

      Anyhow, I hope that helps. If all else fails, you could try scraping them out for the price of lead (which is pretty steep these days) so it's not a total loss. With enough scrap batteries, it can add up.

      Take care,

  5. Jeff McCrea

    Something that I've been seeing around the internet lately is "cheap battery rejuvenation" for flooded wet cell batteries. There's even a car repair shop in town that sells "reconditioned" car batteries for $48.00. It's done on sulfated batteries. What I've been seeing on Youtube is people draining the acid from dead car batteries and replacing it with a solution of epsom salts, (Magnesium Sulfate), and water. (I'm not sure of the ratio of epsom salts to water.) When they finish, they all put digital voltmeters on the batteries and they read 12.XX volts but no one ever shows what kind of current they are capable of outputting. I don't have an available dead battery to experiment on or I'd try it and report back to you. This seems too good to be true but if it does work, it could be another last resort if one gets into a bind with batteries that are ready to go the way of the recycle pile. With my luck, my batteries would catastrophically fail the day of the super bowl. If this works as advertised, it might stretch another day or two out of a dead set. BTW, LOVE the newsletters. Thanks again.

    • Nick Meissner

      Hi Jeff,

      Reconditioning a battery means many different things to many different people. It could be as little as changing the electrolyte and repainting the case, to as much as a full scale electronic desulfation and load testing and electrolyte replacement. I have no experience with using Magnesium Sulfate in a battery to desulfate it. As you alluded to, one would not even want to try it unless the battery was practically dead. But by the time you get to that point, you have nothing to lose. I will say that many batteries die from the lead plates wearing thin or shorting out from too much debris on the bottom of the battery. In my experience, while you will see a gradual decline in performance from sulfation, it's the cells short circuiting that seem to be the "nail in the coffin" from which there is no return. But maybe when I replace some old batteries I'l give old epsom salts a try and let you know. Please let me know too if you ever give it a try.

      Take care,


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