Uses for Dead Car Batteries and Sealed Lead Acid Batteries




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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.

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Step 1: 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. 

There are cheaper charge controllers but after reading about several of them I went with this one.  The 20 watt solar panel is currently (9-24-12) $52.99 plus shipping at

Step 2: 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.


Step 3: Sealed Lead Acid Battery Powered Lamp

Here is a nice little battery operated 12 volt clip on light I made from a 120 volt light.  The 12 volt led board has four 20 milliamp type LEDS in series with a 33 ohm resistor.  So this lamp draws 20 milliamps at 12.5 volts (1/4 watt).  On the back of the board is an RCA plug that plugs into an RCA jack inside the lamp.  If I want to go brighter or use different LEDS I can unplug this board and plug in a different board.

Step 4: Lamp and Charger

I also made a desk lamp with a completely enclosed battery.

I decided to go green with these lamps and other low voltage devices I have made, so several years ago I bought a 5 watt solar panel. We do not use our chimney because we have birds (they are sensitive to smoke) so I put the solar panel up on the top of the chimney. Since the current is so low I used cat 5 cable to run from the panel to the garage. Since I only need to charge one of my other un-dead car batteries for about 4 or 5 hours about twice a month (as needed) I made a battery charging board with a linear regulator. It is a 15 volt regulator. The battery never gets up to 15 volts. I charge the battery when it gets down around 12 volts and I charge it back up to around 12.5 volts. I check both lamps every couple of weeks. They have a really long run time. A 7 amp hour battery is kind of overkill for a 20 milliamp load. It’s great. Both lights get used daily. One of them gets charged about every 6 weeks or so. Keeping the batteries above 11.5 volts makes them last longer.

The charging board also has a 12 volt regulator so I can run 12 volt devices off of the solar panel directly.

So there you have it. You can run whatever you want off of one of these un-dead car batteries. If you buy a 12 volt to 120 volt inverter you can power many 120 volt devices. Also you can run any device that has one of those plugs that pug into the car cigarette lighter jacks. You can be ready for some quick and easy camping at home in a power outage with the 5 watt set up for under $50.00 or take it up a notch with a 20 watt set up for a little over $100.00.

If you want to go really simple and cheap, may I suggest this for really simple emergency LED lighting:



Technical information on the Sunguard charge controller:


LEDS for Beginners:

It is a good idea to check your results after you make your circuit to be sure that you do not exceed 20 milliamps in the circuit. You do this by measuring the voltage across the current limiting resistor by the resistor value (ohms).


Data sheet for linear regulators:

Lots of companies make these.

Here is a link for a 12 volt linear regulator:

Cost: about 18 cents. You may need a heat sink to get the full 1.5 amps.


Cheap low power fans (added 11/3/2015)

Low wattage 12 volt fan:

0.12 watts, 50 cubic feet per minute, under $11. This would be for a regulated 12 volts since the data sheet says 17 volts max and some panels will exceed 18 volts.

Lots of other fans are available at

Cheap Duracell Batteries:

D cells for under $0.70 etc.

Step 5: See Also.... (More Energy Saving Ideas)

Check out my LED light bulb video: LED Light are good but not great. My bathroom light should ast 30 to 40 years.

This video looks at the engineering shortfalls of most off the shelf screw in LED light bulbs.

Perhaps I will do an instructable and redesign one.

See also these instructables.

LED Lighting: One "Dead" D Cell at a Time:

Super Size Your Battery Run Time: D Cell Battery Packs:



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    77 Discussions


    4 months ago

    Very cool, Recycling dead Car batteries to work with charger and Solar cells on the roof.


    6 years ago on Introduction

    i had a lot of batterys, what i use to charge it it's a normal transformer to 13.9 volt to charge them, i had aprox 5 batteries, i used to test hig power brushless motor or to cut foam with large hotwires of nicrom and use clamps to atacth or release batteries to give more or less temp, and a transformer its more cheap than any solar panel

    18 replies

    Reply 6 years ago on Introduction

    Cheaper Yes but:
    1. Solar panels pay for themselves over time if used in an application that replaces or reduces the power you use from the grid.
    2. In regard to emergency power, solar panels are green, quiet, and last decades.


    Reply 6 years ago on Introduction

    It takes a loooong time for Solar panels to pay off even for the terminal consumer.. The entire industry is subsidized all across the supply chain so the terminal consumer is paying only a portion of the entire cost.

    Solar panels aren't particularly green. From the environments prospective, it only matters how much C02 as system produces over its operational lifetime. Solar panels rack up an enormous carbon debt in their manufacture, distribution, installation and maintenance. It takes years for them to pay off that carbon debt even if they work in isolation.

    However, very few panels actually do work in isolation so you have to figure in the carbon emissions of the grid power that backs the panels up. Worse, just because you aren't drawing power from the grid, doesn't mean that grid operator doesn't have to keep generators spun up just in case you do. So, even though you aren't drawing down power, just the fact that you might cause significant C02 emissions.

    People have an intuition that an electrical grid works like a water system and think, "Well, if collect rain water that means that I save water from the city supply." But electricity doesn't work that way. It's a giant circuit that has to constantly balanced between load and source. To buffer high variability in the load, the source must run at excess, usually with fast spin up natural gas generators. The solar panels are causing the generation of C02 and other pollutants constantly, not just when the panels are offline.

    Neither would I plan on them lasting decades. One good thunderstorm with hail can wipe out solar panel systems across a wide area. Happened here a few years back.

    By the time you factor in the cost and carbon debt of replacing destroyed installs with the initial carbon debt and the secondary/backup generator carbon debt, it is highly unlikely that solar panels ever save carbon emissions at all.


    Reply 6 years ago on Introduction

    The carbon footprint is a popular political theme these days. But its time will pass.

    "Carbon dioxide accounts for only one in every 4000 molecules in the air; water vapor accounts for one in every 20. Carbon dioxide absorbs only a quarter as much energy from sunlight as water vapor, molecule for molecule; suggesting that water vapor is responsible for the majority of atmospheric heating."

    Guess we have to stop using so much water. And seal off the oceans as well. A nice big oil slick should do the trick. I mean a really big one. Got to get rid of that water vapor.
    And the naturally produced methane:
    "Methane is 21 times more powerful a greenhouse gas than CO2."

    Here's a question for you: If the carbon in hydrocarbons came from all the dead animals which ate other animals or grass and other vegetation, then the carbon that's sequestered in the oil fields must have come from the plant world. Now, if the coal deposits around the world came from all the dead plant life over time, and knowing that only photosynthesis can capture the carbon from the carbon dioxide in the atmosphere, where was all that carbon sequestered before it got into the atmosphere? And from the dinosaur evidence, there must have been huge amounts of vegetation available on a daily basis to support those huge animals. There must have been a lot more carbon in the atmosphere then than there is today to support that level of plant growth. The carbon that is now sequestered in the coal fields and the oil fields had to get there via the atmosphere. That must have overheated the planet and they all died off every year, year after year. Or it was lush and very green and everything grew at astonishing rates which is most likely the case, even faster that in the jungles of the tropics. They probably died off because they starved to death once the carbon levels dropped in the atmosphere to a point that it could no longer support the level of plant growth necessary. The oceans could absorb enormous amount of CO2 if we would seed it with iron in the right amounts, populate that area with fish, and feed the world. The atmosphere and the oceans are starved for CO2. And its presents in the atmosphere has little or nothing to do with the temperature aside from politics. Just thinking out loud. Don't mean to offend.


    Reply 6 years ago on Introduction

    You are 100% correct my friend. I worked for Landmark Graphics (at the time a subsidiary of Halliburtion now is absorbed into the main corp) but it makes me laugh when I hear people use the term Fossel Fuels. hahahah See, I had to laugh just saying it. Any geologist (that knows their stuff, and is willing to spill the beans) will tell you that is a lie that was sold to the public in order to create the sense of scarcity. Its almost ludicrous that people think the dead plants and animals under pressure over time turn into oil. hahaha even if they did how did they get miles below the surface in large pockets. Its rather funny how those pockets keep on refilling too. But people will believe anything they see on TV. Just call it a documentary and you can tell them the titanic is at the bottom of the ocean. (oh wait that takes about 50 million to pay a hollywood director to create the scenes for you THEN you can tell everyone its really down there because you can show it on TV) right.

    But yes you are correct about the Carbon BS scam.


    Reply 2 years ago

    A fact I always enjoyed is this; all of the energy absorbed by a tree (by photosynthesis, & absorption of water and nutrients through its roots) as it grows will be returned when you burn it, or as it decomposes, BTU for BTU...


    Reply 2 years ago

    Hmmm, no, the Second Law of Thermodynamics dictates that energy (the capacity to perform work) always decreases. The energy return on burning wood is very low, somewhere in the 1%-5% range at most.

    Don't confuse the closed system of chemical element with energy. They're two separate phenomena. Chemicals in plants are essentially batteries which are charged by photosynthesis and discharged by biochemical work inside the living plant or, in this context, burning. The chemical elements remain, merely combining into different forms, but the capacity for work, the energy, always decreases.

    Good thing too, because if energy didn't decrease, it would build up in the biosphere, turning the entire surface of the planet into a giant bomb.

    So how did the hydrocarbons get there? I am interested to hear an alternate explanation. Did God (or aliens) just leave this stuff behind for us to find over time? Or was it formed from the natural elements and compounds that formed the earth? Can you explain the chemical reaction that might take passive substances and convert them to something with stored energy value? That could be a real money maker if we can patent it Kind of like a perpetual motion machine. You have one those right? Me too!


    Reply 6 years ago on Introduction

    I'm probably feeding a troll,but... I'm not typing this to try to convince hopeless causes I used to work in production. Just like you can see the strata when a road cuts through rock cut away for a road, Geologists can "see" the strata as the bit makes it's way down through the layers that where laid atop what are now producing formations. Underneath my feet there are several producing formations on the way to the Arbuckle, not to mention brine, and freshwater aquifers. When a field is shut down because it's no longer profitable to produce it the formation does appear to refill. However that occurs after years of sitting idle, and the production is nowhere near what it was previously, and only profitable to produce when the price of oil is very high. The logical explanation is that the fluid migrated from other area of the formation to the fractured zones around the well bores. Only ignorance would depend on that refilling  to plan our future with.  My guess if you, carmstrong2, and northcalgreens are old enough you where in that choir chanting, " the dilution is the solution to pollution" That solution really worked out well for those who depend on the oceans for an unpoisened food source.


    I couldn't but think of FFVII when I first heard this. It's the lifeblood of the earth. :-)
    For me, going green isn't about the environment, it's about green money. I like to live off the land as much as I can and hate paying someone for something I could do myself; I guess that's why I like instructables. Thanks all.


    Reply 6 years ago on Introduction

    You're dead-on! In fact, study of the geologic record clearly shows that CO2 in the atmosphere ONLY increases 200-400 years AFTER Earth has a global warming period!

    Those who have world influence, and money to preach any LIE that will make them more $$$$ from a SOUP-headed public, can do so if they tell their LIES often enough to alter a few who then, like mindless transmission repeaters, go blabbering the LIES to the world as if they are facts!

    I'm certain this world is at the point where humanity will destroy it, if allowed to!

    Its the monied interests that own all the media outlets and use them to create an echo chamber of lies that once repeated enough times tends to become thought of as the truth.


    Reply 2 years ago

    Except that "co2" is green. It being plant food an all, more co2 = more green...

    Those that use the term "Green" hearken back to the days before CO scrubbers were added to all the power plants. CO being the particle that will coat the surfaces of a green plant, causing it to die. So now they only emit plant food. Ask any greenhouse owner why the install expensive co2 generators...


    Reply 2 years ago

    CO is carbon monoxide, a gas just like CO2, carbon dioxide. CO is toxic to vertebrates because it permanently binds hemoglobin. It is harmless to plants. CO is not scrubbed. Instead it forms under low oxygen combustion, its formation is prevented by proper mix of air in the combustion chamber.

    The major pollutants released from coal are actually unrelated to combustion and are instead trace elements occurring because coal is essentially a rock e.g. mercury, lead, sulfur, radon etc. These are actually valuable resources in themselves, particularly sulfur, and the attempt to trap them predates the environmental movement.

    Sheetrock used in the walls of all houses today was once made of mined gypsum, but today is entirely artificial being made almost entirely from the solid and gaseous output of burning coal. Must of it imported from the coal fired industries in China.


    What's up with the "carbon debt" nonsense? You buy the hoax about CO2 "greenhouse" gas silliness, based on altered "science" that's actually been proven many times over to come from political and commercial sources who will gain trillions of $$ for the world to BUY their LIES?

    As for Solar Panel pollution, ever wonder about the pollution you cause by your own trash stream? I dare you to tell us how much trash you personally generate! When you show you do not throw things away that have reuse value - everything - then come and talk about pollution.

    As for environment damage to Solar Panels, every hear about protection systems adequate for the task? Or, how to use other Solar Energy capture methods? Get away from the Al Gore idiots' think scam, and start living in reality!


    Reply 6 years ago on Introduction

    Hello Shannonlove,

    That was quite reply.  When I have more time I would like to respond to several of the points but for now just these:

    My response to Jorgeneo560 was “In regard to emergency power, solar panels are green, quiet, and last decades”  I still stand by that because I was referring to the use of a gas or diesel generator for emergency power.  Generators rack up an enormous carbon debt in their manufacture, distribution, installation and maintenance and then you burn through gas at a fast clip in an emergency. Solar panels are quite quiet and many have multi-decade warranties.  Check out UL-solar’s:

    My oldest one is 13 years and it works fine.  I recently purchased a slightly used 80 watt panel for $100.00.  I bought it from a company that manufactures portable traffic signaling device.  They could not sell it as new or use it on a new piece of equipment.  So I rescued this panel from being a loss.  It will be used to run an attic fan in the summer and a small heater in the winter.  It is a small scale version of what I hope to have in the future.  So in this regard I get to be green or potentially green twice.  Also another 80 peak watts will be helpful in an emergency.  Hail and lighting are not so much of a problem in southern California. 

    So I think this micro-solar thing is a great little hobby and fun in a geekish sort of way and I have been able to rescue a solar panel and a couple of car batteries in the process (green) and with my supercapacitor flashlights I have been not buying so many batteries (green):

    I suppose on the green scale these hobbies beat out jet skiing by quite a bit.

    Thanks for your response.  .



    Reply 6 years ago on Introduction

    The small one panel ones they use at natural gas sites to run the monitoring equipment on the head (at least the ones around my friends land) are 140watt. I was shocked to see that. I didnt even know they made ones that efficient and that was 6 years ago. I haven't looked recently, but I would assume those little panels must of cost a small fortune. Might try and talk to some well workers and see if they have any damaged ones from hail, that they would sell. Even a damaged one is worth the repair if it puts out that kind of wattage.


    Reply 6 years ago on Introduction

    Every solar panel ever made is still working.. lower efficiency rate, but it never stops. Electricity can be stored in batteries, and it has to be *greener* than using generators full time, coal, etc.

    I've heard stories about how solar is useless, but that was from a military guy that has been brainwashed a lot by the gov't.... Improvements have been made in the last 10 years... *shrug* I like solar.