How to
Make a Small Battery Backup
Part 1: Introduction
A 12v Batteries can be used to make a battery backup for small or low voltage devices, such as laptop, router, toys and so forth. On this site, we’ll show you how to make one such battery backup for yourself with ease. With power outages occurring throughout the world, people moving outdoors and the ever increasing number of low power high productivity devices such as the netbooks and cell phones, the need for small battery backups is increasing.
To make yourself a 12v battery backup, you will need the following tools in order to make this project.
- Screwdriver
- Digital Multi Meter
- Wire Stripper
- Tape
- Soldering Iron
- Acrylic or a Metal box (If you want to make a box out of it).
Above all you’ll need some peace of mind, a clear table so that it doesn’t become messy and some motivation to start and ultimately to finish this 12 volt battery backup project.
Part 2: Components
So before you sit on the table and hurt yourself with those tools above, get some components to use those tools on. Here’s the list.
- 12V Battery (solid state, Li-Po, Ni-Cd, but sealed lead acid battery is preferred)
- An adapter or a transformer
- 1-5 Ampere Fuse
- LED
- Charge board
The charge board is easily available in the market. It is usually found in those cheap rechargeable torches, flash lights or emergency lights for charging. If you have one of those lights lying around your house and you are sure that you don’t need the light, you can get it from there. I’ll be writing another How-To guide for making that charging circuit otherwise Google is your best friend.
Part 3: Battery
For this project, we will use 12v rechargeable batteries. We can also directly plug-in the battery into the router or whatever the intended device for the application is but that wouldn’t be an intelligent solution. We’d have to remove the battery once the electricity is back and also recharge the battery, hence making the full circuit.
Coming to the choices, there 12v lead acid batteries which are usually found in cars and trucks and usually come in 12v 5ah battery packs, that 12 volt battery will be too much for this application and besides lead acid battery is a tad difficult to handle. A better option is the sealed lead acid battery which is hassle free, compact, though heavy. One could also go for the Li-Po battery or the Lithium Polymer Battery, an expensive but very light weight option; it is a very compact battery. Make sure that you get rechargeable batteries. This project can very well be made with a 9V battery, if you do not intend or want to use a voltage regulator, which are also available in the non-rechargeable form but those will be expensive in the long run.
Do check out the battery ratings before you buy the battery. A 12 Volt 5 Ah (Ampere-Hour) battery rating means 5 Amperes of current can be supplied for a maximum of one hour. If your router is rated at 12V and 1A, then your router can work non-stop for five hours using this 12 volt battery. Simple!
Another issue of important is the 12v battery charge management. In fact, it is important for any battery regardless of its rating and especially if it is a lead acid battery. A lead acid battery should always be maintained in a good state of charge; 50% or more is better. If it is kept in a poor state of charge for a prolonged period of time, the lead terminals of the battery cells may get sulfated and hence destroyed. It is also pertinent that a lead acid battery should never be completely discharged or there will be risk of permanent damage.
For a reference, the voltage levels given below show the state of charge of the battery.
12.68v . . . . . . . . . . 100%
12.45v . . . . . . . . . . 75%
12.24v . . . . . . . . . . 50%
12.06v . . . . . . . . . . 25%
11.89v . . . . . . . . . . 0%
These are approximate values but a Digital Multimeter (or a Volt meter) will give a near enough value. It advisable that the battery should always be connected to a charger but in case it is less than 50%, you should immediately charge it before the sealed lead acid battery is gone for good.
Some of the 12v rechargeable batteries that we recommend for this project are 12v 5ah battery, 12v lead acid batteries and Panasonic lead acid battery.
Part 4: The Method
This 12 volt battery project is going to be pretty simple; it'll just involve the development of 12v battery charging mechanism. In fact if you just want a quick and dirty solution, just your 12v battery to your router and you are good to go provided you keep your battery in a good state of charge. But as I said that’s the quick and dirty solution. What we want here is a permanent fix. To that quick and dirty fix we will just add a simple charging circuit along with some minor adjustments to make a fully functional and independent 12 volt lead acid battery backup.
Part 5: Connect it all together and voila!!
Connect all the components including
the 12ah lead acid
battery together, using the following flow diagram.
Device to Power -----diode----12V Battery----------Charger Circuit-------AC Mains
What I’ve done is I’ve connected the 12v rechargeable lead acid to the router or whatever device you plan to use through a diode of high current rating. A diode is used in order that there is no backwards flow of current. That can happen when there is a power outage and battery is disconnected from the AC mains; when that happens, the current from the battery flows to the AC mains, diode blocks this backward flow.
That’s it folks, more tutorials will follow. Thanks to instructables.com for providing some help in this tutorial.