12 Volt Sealed Lead Acid battery

Also called the SLA.

Very similar to the flooded battery except the acid has had a gel added to it to make it more or less solid and the pressure release lids are no longer needed.

A wide variety of capacities.


Update there is a thory that a SLA battery can be reconditioned by charging and then discharging (fast) about 10 times.

I have tried this technique with a few 6 Volt batteries with variable success, some batteries recharge and then begin to hold charge others are simply to damaged internally.


This became relevant for me as i recently found a large capacity 12 volt SLA and I’m attempting to recondition it using a battery charger and a 50W halogen bulb for discharging and I’m currently at the second discharge cycle.


So with a 50W bulb how much current will I be using?

P= V x I

50W = 12 V x ?A

50/ 12 = ?A

4.16 = A

Wires rated for 10A so no problem.



<pictures of SLA and cross section diagram>

A more portable version of the car battery weighing in at 1.5 Kg for a 7.2 amp hour battery.

Cost $25 for 7.2 Amp hour battery


Resource Challenge, Car

We will be having a series of challenges based on a given real word resource.

The challenge is finding as many alternative uses for it and how many resources can be extracted from it.

Abandoned car, ran out of petrol, otherwise in working order.

I’ll list as many things a I can think of and challenge other readers to think of others.

I’ll look at sudden collapse first:

Add fuel and drive away.

A home for the night or maybe longer.

A source of fuel:It may be possible to siphon out the last remaining fuel.

use a copper spike (non sparking) to puncture the bottom of the tank and extract fuel from underneath.

fluids in a car:

detergent in window wiper containers. oil in sump, brake/hydraulic fluid, water/ ethylene glycol in radiator.

useful engine parts: engine bay

battery, alternator, radiator: can be use as heat exchanger, rubber belts, electrical wiring, electric motors and pumps, engine controller electronics.

car interior:

seat belts, cloth from ceiling, screws from holding plastic moldings together, springs from seats.

Cleaning yourself

Such a mundane but essential thing. You probably had a shower recently, you probably didn’t even think about it much until you read this.

How long were you in the shower?

How long did it take to get get clean and how long was just being a little self indulgent?

How much water do you think you used?

Consider yourself in a water and water heating limited situation.

How fast could you get yourself clean and what’s the least amount of water you could use?

Could you do it in 2 minutes?

Could you do it with less than 20 /10/ 5 liters of water?

What are you going to do with all the black(?) water you just created?

Have you tested your own home made soaps?

$5 Fingernail sized computer

micro SD card, finger nail size, with SD card adapter.


Put a live USB for Linux Ubuntu LTS 12.04 on a bootable 4Gb micro SD card and you’ll realize it’s not impossible.




<need make bootable and loader links>

In fact I’m using it right now. And I bought the card (4Gb with SD card adapter for $5) just weeks ago.

O.K, it’s not a whole computer, is a whole operating system and saved files , but as soon as you find PC with with a flash card adapter or a USB port, you’ll quickly be able to have your familiar environment and files on screen.

You can get all the software for free, you may need to hunt down someone a little computer savvy to help you set it up.

Once set up, it is a small as you are going to get your files, and it contains a system to view and alter them, connect to the Internet, the whole thing.

To use this you will  possibly need to alter the host PC BIOS to accept boot from USB and probably press a key on restart to enable this to happen*.

micro SD card with USB adapter

*guide coming soon

You could of course use a USB stick but its not quite as compact. The extremely small size of the micro SD give its the ability to be hidden if necessary. Something that small can be hidden in so many places the mind boggles, even more so for a person trying to find it.

If you find yourself in a an emergency or sudden collapse scenario, you can take all of your important data with you as a very small item and very fast. Any one searching your computer would not be aware for quite some time that you took this essential component with you. leaving behind a computer with a copy of windows or apple OS with nothing particularly interesting/identifying/incriminating on it. It can really change the game.

You may be traveling for a long time in a sudden collapse scenario and the ability to periodically access a computer and have everything you want on it ( exactly the way you left it last) would be very useful.

Imagine you have been on the road for  a week and find an abandoned house.In the house there is a desktop computer with the side of the case missing,clearly the hard drives are missing. The house still has some power from whats left of a solar PV and inverter setup. They left in a hurry, and as it is, the PC wont work .Those plants you saw 2 kilometers back, are they edible? Load up your tiny fingernail computer and compare them to the edible plants data you have. Are there any WI-fi signals here?  What dose my map tell me? All these things become possible with this tiny investment you made when you saw a post on the Internet about a $5 fingernail sized computer.

Cost $5 or less, might save your life.

Ubuntu Logo. Ubuntu is a popular variant of Linux, a free and open source computer operating system.

12 Volt DC charger for laptops and other devices

This device will allow you to charge devices in the 15 -24 volt range at around 3 Amps.

12 V DC-DC charger with adapters for laptops and other devices 15-24 volts

This is a much more efficient way to convert stored energy in a battery to stored energy in you laptop( or to run another device) rather  than through an inverter.

When looking for one of these adapters  (which there are many designs)  look at the adapter tips to make sure they will fit the devices you intend to use it to power.

Make sure the voltage is switchable and matches the voltage you need for your devices.

Not every possible voltage is supplied, common voltages are:  15 16 18 19 20 22 24

Many devices are voltage tolerant to some extent, if need be 1 or 2 extra volts work, if you cannot supply the exact voltage.

Make sure the power rating of the adapter is more than the power rating of the the device.

Check the polarity of the device and charger, usually the outside shaft of the adapter is negative (-) whereas the tip or inside is positive(+). Some adapters allow polarity changes on the tips.

The rating for the adapter can be between 80 and 150 watts.

The easy way to determine the power rating is to look at the AC adapter of the device and multiply the DC voltage and current together and that will be the power rating.

Cost 80W  $25

Cost 150W $120

Cost of an obscure tip $3, time to find one, up to 6 months (be warned).

The sensation of success after a long determined hunt, priceless?

Car battery 12V lead acid flooded

You probably didn’t realize just how specific you must be to define what type of battery you are talking about.

12 Volt car battery with cutaway showing lead plates and cell connections

12Volt : This is the voltage, some batteries similar in appearance are 24V (common in trucks for example).

Lead acid: (sulfuric) is the internal chemistry of the battery, sometimes this term is chemistry or battery chemistry.

Flooded: means the acid is liquid rather than as a gel or an electrolyte in a solid or granular substance.

Capacity: Generally has  a capacity of 42 amp hours. batteries will discharge most efficiently if discharged at a rate less that one tenth (1/10) of the amp hour rating. This is also called the C10 rating

CCA: Cold Crank Amps, the level of current the battery can produce at 32F (0C) for 30 seconds. An older term popular in north America and Canada where cold starting is critical.

Converting Cold Crank Amps (CCA) into Amp hours

Amp hours = (CCA /10) +16


Reserve capacity (RC): This is sometimes listed as well as or instead of CCA.

RC ≈ CCA / 5

≈ means approximately equal to.


So for a battery listed as having 330 CCA.

Amp Hours = (330 / 10) +16

Amp Hours = 33 +16

Amp hours = 49


Danger! This battery produces enough current to kill a human. Do not touch both terminal at the same time. Do not allow a metal or conductive object to touch both terminals at the same time. If the battery came with a plastic cap to cover one of the terminals, use this cap when the battery is not is use for safety purposes.

This design of battery is very old ( from 1913) almost 100 years old as I write this. Prior to car batteries being used in cars the driver was required to actually hand crank the car to make it start. You many have seen this in very old films.


The battery is made from pure lead plates suspended in (30% by volume) sulfuric acid mixed with distilled water. Tap water  river water or boiled water cannot be used. if the wrong type of water is used or hard water salts (calcium) enter the battery it will cease to charge or hold charge. the outer case is acid resistant plastic.

This battery or one very similar will be in almost every car on the road, so know about how it work would be good an in the future there will be less cars and a lot of these batteries, at least for a while.


<need a charging/ discharging chart for lead acid>

There are many option for charging a car battery, an AC charger, a solar panel with or without charge controller, or the most obvious, a car alternator that is turning, rectified and charging (may or may not be part of a working car).

Having more than 40 Amp hours of capacity means in most cases they don’t need a charge controller for charging from 12 Volt solar PV. If you are able to measure the actual voltage of the battery you should be advised that 12 volts is a misnomer. The battery is fully charged at 13.8 volts when the battery is at 12 volts its actually getting quite flat. Most 12 Volt inverters will shut down if running from 11 volts. If using Solar PV it is actually possible to charge the battery to a float voltage of 14.4 volts but this voltage is not able to be stored long term, its effectively floating on top of the 13.8 volts and drains away quite quickly under load.

The small screw top lids on the battery (there will normally be 6, 2 for every volt a battery produces) are for releasing pressure that might  occur as the battery charges and for adding distilled water if the acid dries out too much. This pressure is caused by the release of Hydrogen gas (H2) and is explosive. So while a battery is charging you should treat it as explosive. Never use a cigarette lighter to look in side a battery. If you leave the lids on a battery as it charges it may swell dangerously and even fracture the casing, destroying the battery and spilling toxic and acid contents everywhere. The production of hydrogen gas is usually a sign or result of overcharging, charging too fast or calcium/scale buildup on the plates.

12 Volt car battery diagram with cutaway and labeled components

It is possible to recondition a battery from calcium build up which requires the use of washing soda and fresh or cleaned sulfuric acid.

1) Discharge the battery. Take the pressure release lids off and empty the fluids from the battery, attempt to estimate the volume of fluids removed. Make note of this volume.

2) Make a solution of washing soda (NaHCO3) in distilled water and pour this into the battery.

3) Wait at least 48 hours. The battery will make a fizzing or bubbling noise, this is normal and safe, the gas released will be CO2.

4) Empty out he battery again and rinse out with distilled water.

5) Make a up a 30% volume sulfuric acid (H2SO4) solution with distilled water and fill up battery.

6) With lids off, attempt to charge the battery.

Charge a phone virtually anywhere kit.

well you’ll need a power supply like a 12V battery or a solar panel but with this equipment you have a lot of options.

12 Volt car socket from alligator clips.

iLuv USB car adapter

USB with 10 different phone charger connectors. ‘The octopus’

Make sense? I hope so.

so with these 3 items you are able to convert any 12 Volt battery (or 12 Volt solar panel) into a phone charger in a less than a minute.

cost of items about $25,being able to make that call or access that data, priceless?