July 19, 2024

The following described method is for those of us with more time than money. But this may be an increasingly valuable skill in a prolonged austere environment. Note that this pertains only to 12 VDC flooded lead acid batteries, including semi-sealed or “maintenance-free” batteries. This will be a succinct tutorial.

This is an old-school method, a technique of a bygone era. It is nothing new, but old school and time-tested. I have more than 40 years of experience in the automotive world. I’ve known about this since the early 1980s. My success rate is now at 70 percent, yet how I define what is a success is highly imprecise, or generous. Given the high cost of a typical automotive battery is now between $150 to $175, and given that in an austere environment any battery that contains a useful amount of electrical power, that battery has more value than what is considered serviceable today. If it can hold enough power to run a single transceiver for several weeks, then it is useful in my book.

To restore a battery to near new or to a level that it will reliably start a vehicle in cold weather, then my success rate is about 50 percent. I have also restored 10-year-old deep cycle flooded lead acid batteries used for a PV System from completely “dead” to a good condition where the resting voltage is 12.6VDC and its capacity is about 90 percent of what factory fresh batteries provide. Large deep-cycle batteries are now quite expensive. In the last month, I’ve recently restored 20 batteries back to serviceable levels. This means that I have saved a significant amount of money and I now have a stockpile of batteries for the coming collapse of society. Many of the batteries were purchased at an automotive parts store for just the price of a “core” charge — which is based on the scrap value of lead.


Working with lead-acid batteries is potentially dangerous. At a minimum, the acid from these batteries will burn flesh and eyes, and ruin clothes. Wear protective goggles, gloves, and old clothes with long sleeves whenever working with lead-acid batteries. The electrolyte is highly caustic and will burn quickly burn flesh and eyes. Therefore I always have lots of water handy to wash away any electrolyte that might somehow make contact with the body.

The Required Equipment

The most important tool you need to get is what works most of the time, and that is old fashioned ‘dumb’ battery charge that applies constant high voltage will enough current to sustain a voltage that as close to 14.6VDC as possible and yet does not exceed 16 volts. Essentially, we are attempting to overcharge the battery. Flooded lead acid batteries are tough, and can tolerate long periods of overcharging if the water is replaced so that the electrolyte covers the plates. The link should take the reader to a photo of an old-school charger which is the kind of battery charge that is usually all that is needed for batteries that do not have a bad cell:

SCHUMACHER Trickle Battery Starter Charger Model SE-10-52 2 / 10 / 50 Amp 12V

If one of the cells is not bubbling, then this battery will require more time to recondition or it may not be recoverable. A ‘bad’ cell can be made good in time with this charger, but it will require many days of constant charging if it would be made good again. If this doesn’t work, then go to Method #2. Be very patient as eventually most batteries can be improved or greatly improved after a week of charging. However, if this method does not cause the ‘bad’ cell to bubble, then the battery will not generate 12VDC or higher, but it still could be useful in certain and other applications. A battery can also be internally damaged and be shorted out. This battery condition is seen in less than 5 percent of what will be found.

Locate the batteries outside, remove the caps, and connect the battery to this charger, and let it bubble for the next few days, and possibly up to a week. this can require many days to a week to see the best results. Once every 12 hours, add distilled water. This is the old-school way to recondition a battery using the Schumacher brand battery charger that I mentioned. I paid $8 for mine at a thrift store.

Use a volt meter, load tester, and a hydrometer to monitor the progress, or lack thereof. We hope to see a steady improvement in the number that our test equipment indicates. The target voltage we hope to eventually see is 14.6, VDC, while charging. We are looking for a specific gravity of 1.26 to 1.30. And a load tester, if it is either the old-school resistant type, or the modern battery analyzer will indicate its reserve capacity, or cold-cranking ampere hours.

Of course, if the battery can not be completely restored, it can be restored to a level considered good enough for a function such as powering a single transceiver or an LED lamp. Consider that a package of 6 AA Eneloop rechargeable batteries now costs as much as the core charge for a ‘bad’ battery. When there is no way to purchase a new battery, then any working battery would be priceless.

Note:  Any restored battery should be tested over several subsequent days, to see if it properly holds a charge.

Method #2, The Arc Welder Method

An inexpensive arc welder can be purchased on eBay for only $75. I shopped long and hard to make sure the one I purchased is also good enough to stick weld with and mine cost only $75. It welds just fine, but some do not produce enough power to start a weld when set to lower amperage. If you are going to buy one, get a decent one for a little more money. And use the proper eye protection, goggles, or face mask. And then you can pick up another valuable skill, welding. If you can fix people or things, we have a barter-able skill. Never stop growing your list of skills and be indispensable.

Here is an example of the kind of welder you’ll need at a minimum:

HONE Smart Welding Machine, 110/220V, 140Amp IGBT Inverter

I also recommend getting a supply of a general-purpose welding rod that is good enough for most home projects:

DURA ARC 6-Lb E6013 14”x1/8″ Stick Welding Electrode Mild Steel Rod

Using an arc welder to overcharge batteries is dangerous so see the demonstration videos on YouTube before attempting this method. The battery will off-gas dangerous amounts of flammable, or in high enough concentrations, potentially explosive hydrogen gas, and gases that are toxic and should not be inhaled. Remove the caps from the battery to allow these gases to escape. When using either battery charger, the battery must be outside of any contained space.

While the battery is being charged, never remove the clamps from the battery as sparks will be emitted at the terminals and potentially cause an explosion. The 50 amp automotive charger is not quite as dangerous if the battery is charged outside. It is my preferred method that I always use and have had good success with. Use an arc welder to apply upwards of 100 amps if needed to quickly remove the lead sulfate that is built up on the lead plates. This method is for the most hard-to-recondition batteries. Use this method at your own risk. Keep replenishing the battery cells with distilled water when using either charger.

If one of the cells is not bubbling or the battery is not improving, then briefly use an arc welder that delivers 75Ah. This method is dangerous and can even melt the lead terminals so make sure the connection at the terminal is as good as possible. Clean the terminal until the lead is shiny, and clean the clamps or any part that will connect the arc welder leads to the battery. Be sure there is enough clamping force to make a solid connection. If you see any smoke, the connection is not ideal and it will generate excess heat and could melt the lead terminals on the battery. Apply this level of power briefly until the battery is warm to the touch, perhaps 5 to 10 minutes, and then let it cool off for several hours before repeating this treatment. Repeat up to 5 times. If not enough improvement is made, then place it back on the 12 VDC 50 amp charger, and “cook it” for several days.

Why These Methods Work

We need to use enough power over time to cause at least a small portion of the lead sulfate to dissolve back into the sulfuric acid of the electrolyte. When we remove layers of lead sulfate that form on the plate when the battery is discharged, the lead plate is better exposed to the electrolyte. The electrochemical conversion of sulfuric acid to lead sulfate and back into sulfuric acid is process that produces electrical power. When power is applied to the battery the lead sulfate is converted back into sulfuric acid and creates the potential power that can be produced by the battery.

The electrolyte is about 35 percent sulfuric acid and 65% water. Using water that is not distilled may contain compounds that are alkaline that can neutralize the acid in the electrolyte. Therefore, whenever possible, use distilled water. If there is no distilled water available, filter the water if possible and use it. Using water that is not distilled could potentially degrade the performance, but it is better than no water at all.

The level of sulfuric acid in the electrolyte is what increases the specific gravity. A higher specific gravity strongly correlates with a higher potential to make power once a demand is placed on the battery. The hydrometer tests the specific gravity and the presence of sulfuric acid. If the battery has all good cells and when both methods fail to further improve the battery’s capacity, or when the specific gravity is less than 1.26, then instead of adding water, add electrolyte that can be taken from a bad battery, or purchased at an auto parts store. This will replace the sulfuric acid that has been bubbled out of the electrolyte over many years of hard service or weakened by the use of non-distilled water. Note that concentrated sulfuric acid has a specific gravity of 1.84. If there is a proper balance of acid in the electrolyte, then the voltage of the battery after it rests for 48 hours will be between 12.6 to 12.7 VDC. These two indicators are a sign that the battery is ‘healthy’ and has a useful amount of capacity near to a fairly new battery. A load test will confirm this.

Battery Selection and Maintenance of Batteries in Storage

With experience, I will now choose better candidates and my success rate might improve and less of my time is wasted on a battery. This method is for those with more time than money. In an austere environment where no battery chargers are available, given my experience, I believe I can use a PV array that can produce 50 amps and voltages of 15 to 19 VDC, this process can be duplicated. Another method might be used as well. If we can produce 40 VDC at less than 1 amp, batteries might also be improved. To help maintain any lead acid battery that is in constant use, 16 VDC should be applied for several hours each month to equalize batteries in a nominal 12VDC PV system.

High-quality charge controllers will equalize a battery bank on a 30-day schedule in this way. We can do the same or similar for batteries that are being stored. Flooded lead acid batteries not in use, or in long-term storage should be charged every few months using the 12VDC 50 amp charger to keep the lead sulfate from becoming thick and hardened like plaque on artery walls, and thus impairing or degrading the battery’s ability to provide power. I would not be afraid to use this method on batteries that are less than one year old, for fear of damaging them. In the austere times ahead, any battery that holds a useful amount of power will be priceless and can be used in innovative ways. And if the battery is no good, then the lead inside will also be priceless. I can think of a number of ways to recycle lead.


So there you have it, another redneck hack. I suspect in the future bad times ahead, rednecks will rule, because we can innovate, adapt, and overcome like Americans have done in the past. Without this unique American trait, we would not be Americans. It is good to stockpile enough essentials so that one does not need money. And we should also be adding to our knowledge base, and list of useful skills. If I do not have the money to buy stuff, then I use my time to learn how to do stuff that makes me money or can produce barterable goods now and in the future, or otherwise increase my odds of survival.