Survival Skills Blog & Off The Grid Guides

How To Revive Dead Batteries


Today I have the privilege of bringing a great article to you from one of our own readers. Lux17 has written several instructables and has some great ideas on how to enhance some items that you may already have.  The article below is a great example of this; in it Lux17 has taken some old “dead” car batteries and brought them back to life with a new purpose.

Uses For Dead Car Batteries And Sealed Lead Acid Batteries

Many “dead” car batteries are actually perfectly good batteries.  They just can no longer provide the hundreds of amps needed to start a car.  Many “dead” sealed lead acid batteries are actually un-dead batteries that can no longer reliably provide a couple of hundred watts of power needed to keep a computer running in a power outage.

A couple of years ago I decided to add another small solar panel to the collection I have on my roof. I have a 5 and 10 watt.  This new one is a 20 watt.  It is dedicated to providing emergency power for lighting, a small fan and other misc. small low voltage devices.

For this setup I needed a battery since it would need to be able to provide power 24 hours a day.  I decided an un-dead car battery would be perfect since the largest load it would need to power for any extended period of time would be less than one half an amp.  There is quite a difference between 200 – 600 amps and a half an amp.

The battery pictured was one I replaced when it would no longer start my car.

Charging The Battery

I could have used a linear regulator to charge the battery with the solar panel.  The cost of a linear regulator is typically less than a dollar.  I decided to go with a charge controller instead because they more efficiently use the available power to charge the battery.  You get more run time at night when you use a charge controller.

The Test Fan

I did some extensive testing to make sure I knew how well the system would work in an extended power outage.  I ran the fan for several weeks, 24 hours a day a couple of summers ago.  The system worked fine.  Since then I have been running LED lighting out on the patio 24 hours a day for about 2 years.

The fan pictured is a 10” 12 volt, 5 watt, 2 speed fan that was on clearance at Walmart.  They still sell them but it was the end of the season.  I have 3 or 4 of them.

The LED board has 16 leds.  The battery is not even hardly trying to power this tiny 1 watt load.


Click here to view the full instructable with images and diagrams


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  • Lux says:

    Here is the link with all the steps on one page:

    Thank you Joe.


  • Wilma says:

    Survival seems to be the thoughts of the day and I appreciate any of these tips I can use to survive. I’ve thinking of solar panels to offset the price of fuel to heat my house. If you have any ideas on how-to-do such a project I’d appreciate that too.

    • Afungi says:

      The problem is the cost trade off is awful. 70 watts will cost about $700.00 and will give you the heat equivalent of a single light bulb. Putting a tremble wall on a south facing wall give you the best bang for the buck. A Nova Scotia man used aluminum cans and insulated box below south facing windows to collect heat small fan to move air. An Idea I have is to put heat ducting in the addict space with a thermostat controlled fan. The air in the addict can get very hot even in the winter. When the air gets over 100 deg. the fan moves air into living space. The problem is getting a good louvered shut off for the ducting.

    • tj mac says:

      We had made a solar water heater for a small cabin… not expensive for heat output.

      4×8 plywood, 2×4 to frame plywood, clear heavy plastic/plexiglass and copper pipe (you can use plastic pipe too for slight less heat vs cost )and the most costly part was a small electric pump (slow flow which we got used for $20,allows water to pick up heat as passes thru) Total cost was $50-60 as we used what we had. PS some auto antifreeze too

      Frame plywood with 2x4s, cut additional for two(short side of plywood) cross pieces inside of frame. Drill holes thru center of cross pieces for size of pipe used, about 1/2 – 1 inch space between holes…cut cross piece in half so you have sort of ‘stock-pillory’.
      Put pipe into notches across the length of plywood, put second half on top to hold pipes(screw in place). Connect each end of pipe to one below…( big “s” snake back and forth,top to bottom) spray all with flat black paint, then cover plywood with heavy clear plastic over outer frame.
      We placed it on the south roof and ran it with pvc into a salvaged hw base board heater of 10 ft… when running during day the water output from solar panel was over 130d… gave out good heat during day ( had to run the stove at night ) Worked so well, we added a second one in series with a second section of base board… we wired a thermostat to the switch for the pump later too. Prob savings were about 30% in heating.

      Hardest part was purging air during install, had one person on roof fill system to eliminate air bubble… prob easier to add some form of air purge valve at high point of system if I was to re-do(right off panel).

  • Lux17 says:

    Hello Wilma,

    I am planning on doing some testing with a 12 volt water heater element this winter. There is a company called SJH that makes among other things, 12 volt submersible water heater elements (for the RV industry). I am not sure if this is the best way to go, but for camping at home it is cheap and very scaled down. I forget all the wattage SJH makes but I know for sure that they make 300 and 600 watt elements. In a survival situation where people are stuck at home with no power and sub zero temperatures, the element is in a tank or large bucket of water. The water is heated all day and is radiating heat into the room or better yet into the tent in the room. Large amounts of water retain heat well, so if you were to heat up a 50 gallon drum of water during the day it would radiate some heat all night. This sort of thing could be scaled up for your application. This is not the only way to produce heat with solar panels. You can go the more traditional route and get enough panels for one 120 volt off grid circuit (and the batteries and inverter to go with them) and run an electric heater. Hopefully some others have some ideas. Here is one place to get an sjh heater:

    Typically submersible heaters have to be in water or they burn out. They need the water to dissipate the heat.


  • Chuck says:

    Water left in a black plastic bag in the sun will get quite hot. Not hot enough to sterilize anything, but certainly hot enough to wash with. Try to spread the bag out so that more of it is exposed to the sun. This will even work on a cloudy day. Same principle as solar water heaters only on a smaller, less expensive scale.

    • Chris Crow says:

      I have purchase the solar shower bags and do use those but also I use gallon milk jugs that are spray painted flat black and set them in the sun. It’s easy to take a shower with just one gallon of water. Also great for dishwashing. They are dirt cheap to make. And yes, sometimes the water is almost TOO hot to handle :)

  • Satchmo says:

    I saw you can also make fire with a AA battery too. It’s always a good idea to keep a stash of batteries for the BOB. They have some over at for pretty cheap.

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