A theoretical battery from locally gathered materials
This post is very much a work in progress detailing some of the ideas I've considered about how to deal with both creating a useful trade item post-SHTF, helping a struggling community, and realistically creating a light source. It has applications in creating sustainable development in the real world too.
In a SHTF scenario, it's very possible that batteries may become unavailable. Batteries are really technically cells, usually of 1.5 volts dc (vdc and the power of a battery) and low amperage (current which is the flow of electricity in the battery). While the batteries will eventually and pretty quickly wear out (given lots of people using them carelessly), the LED or small incandescent lamps won't for awhile.
Lots of videos or pdf files describes ways to make a battery. Batteries are typically small galvanic cells that rely upon two dissimilar metals and an electrolyte either in a strong salt solution, or paste. Large batteries are often made of a lead acid composition (lead and strong sulfuric acid).
Which it's probably beyond the standard person making sulfuric acid from common materials, in addition there are safety concerns from its corrosive properties and very strong current produced. In an ideal world, we could recreate them. Ordinarily alternators spin from mechanical motion, and these continually top off the electrical charge capacity of a battery.
There are simple solar panels which can trickle charge a small dc voltage, and these can be utilized to get them back up to power when drained of their useful voltage. In combination with an inverter, a typical ac device of very low power use, or a device that uses a complex dc power source like a laptop can use an solar battery setup to power an inverter and this will produce the power to the laptop. For common devices that need simple dc power, they can be hooked up and powered by the battery directly.
But...it's not very portable. This would be immensely helpful and practical. People will run out of paraffin oil (really kerosene) to power small oil lamps, or candles. While candles can be remade with immersed mature cattail head in tallow, or oil lamps that on birch oil or pine resin, these all create fire hazards (heat and light).
If we could make small scale batteries from common materials found within a home, or produced in a survival situation, then we could really help a lot of people. Any battery will commonly corrode as the metals get used up in the corrosive electrolyte, however they could produce temporary dc power.
An aluminum soda can
hardwoods like oak
copper wire with a means of clipping or securing it on (alligator clips while perfect are not common)
an LED lamp
Tin snips or scissors
A coffee can or better a metal canister with a metal lid
When wood is burned, it leaves behind wood ash. When water is added to wood ash it produces lye. This can be made properly by pouring water through a sieve of ashes, but not necessary. Making a paste is suffice. Wood that is placed in a metal canister (like a Christmas cookie can) and heated but starved of oxygen produces wood gas (that will escape and ignite) and charcoal. This charcoal will be purer than simply incompletely burned wood.
Using the scissors, carefully cut a piece of the aluminum can. Leaving a tab at the top will allow a place to clip on. Scoop up some of the lye paste and spread it on the aluminum. Place a piece of charcoal on the lye paste. Now you have a weak battery, probably a 0.6 vdc battery. By clipping several of these in series i.e. the positive to the LED lamp, and then the negative to another positive and the negative to another positive and on and on, then eventually when sufficient strength is achieved hooking the last negative to the negative lead of the LED lamp, you should in theory produce light. It will be awkward to handle unless you can mount the battery in some way to stabilize it.
Look at your flashlight and you'll see that this is how batteries are stacked to produce sufficient power.
Many homes might contain lye or sulfuric acid under their sinks to be used as drain openers. Since that's already prepared, we might be tempted to use that for this purpose. Indeed the sulfuric added to a paper towel and placed between an aluminum tab from a soda can and a stainless steel paper clip will definitely produce a battery, but we might need that sulfuric for something else. Since that sulfuric is hard to make, we'll have to dissuade people from using it.
Proof of concept
This video demonstrates how to make a wood ash battery from an aluminum can, however it uses a joule thief. That might or might not be able to be made in the field. This can be avoided by making several instead. A joule thief will work but will burn out the battery quicker.
The joule thief requiring multiple electronic components (resistor, transistor, torus, coil)
Or simply a wood ash/alumnium/charcoal battery
The 2nd video from Tom Culhane shows how to make the aluminum pop top/paper clip/sulfuric LED flashlight.
Most battery videos describe ways to make batteries based upon using up materials that could be better utilized. For example, there are many which discuss using earth and an acid, or salt and two metals like a piece of copper and a galvanic bolt, but those materials could most likely be hard to replace. The potato battery uses metals and a potato, but it would be far better to eat it then waste it as a battery.
You can see that very low voltage and amperage can be developed from a plain earth battery, which is a piece of copper and galvanized, usually hammered into the ground, and without an electrolyte but with moist soil, then 0.3 to 0.6 vdc can be developed. Still it's too low to power an LED and isn't portable. Sure you could run wire into your home, but the length of a piece of wire will create voltage drops. It's the same reason that a long extension cord will get hot and kick out a breaker.
While there are many outdoor solar lights that run off off batteries and an LED, again most of these will usefully recharge some old dead alkaline batteries, they eventually will not work. That means in the interim they can be used, but ultimately a sustainable light source and battery must be found. Since LEDs can't be produced locally, it will always be the weakest link.
You will always have wood ash produced as a result of cooking fire and heat. This also means charcoal. Another potential electolyte that is sustainable is urine. It might be possible to concentrate it to produce a stronger electrolyte. Usually normal urine batteries are low amperage and low voltage.
Anyone who can learn how to do this, will be able to create a small business in a SHTF scenario when trade goods when things get more stable again.