There is a power shortage in where I live, so I manage to make a power back-up from some component I've already got and an old car battery.

This is how to make back up power from old car battery.

Old car battery still can store electricity so when my car needs a new battery I keep the old one, until the new battery getting old and need replacement. Of course the old battery is not as good as new one, so we have to charge it periodically.

This way it will make the use of the battery about 2 year long..... or until you have to replace your car battery with the new one...

Step 1: What We Need

- old car battery (of course)
- 24 hour timer
- car battery charger
- power inverter DC to AC

Step 2: Get Connected

1. connect 24 hour timer to power line.
2. set the time for 2 or 3 hours 'on' per day.
3. connect battery charger input(AC) to the timer.
4. connect battery charger output(DC) to the battery.
5. leave the switch on charger in 'on' position.

This way the battery will automatically charge for 2-3 hours per day and it will ready for emergency use.

When there is a black out, this is what you have to do
1. Turn off the charger
2. Disconnect battery from charger
3. Connect inverter input to battery then turn it on.

You may need over length cable to distribute the power.

It's only to power basic needs, like couple of 10watt fluorescent lamps and a small 18watt electric fan...
and also to charge cellphone....
With a single battery we can get about 3-4 hour of power......

Step 3: Other Use (as Power Booster)

Recently I've using this circuit as what I called 'POWER BOOSTER'.

Let say that my household capacity is only 900 watts and I need to power 1000 watts sound system for family gathering. So I'm using this circuit with 2000 watts inverter, that way I can run the sound system for a couple of hours until the battery goes dry.