Comments on: How do I make a battery backup for a circuit? http://www.batterybackupguide.com/blog/how-do-i-make-a-battery-backup-for-a-circuit/ Thu, 17 May 2012 21:55:20 +0000 http://wordpress.org/?v=2.7 hourly 1 By: Mez http://www.batterybackupguide.com/blog/how-do-i-make-a-battery-backup-for-a-circuit/comment-page-1/#comment-2591 Mez Sat, 06 Mar 2010 01:18:52 +0000 http://www.batterybackupguide.com/blog/how-do-i-make-a-battery-backup-for-a-circuit/#comment-2591 Hi Daniel, Well, all you should need is a power diode (and the battery, of course). The purpose of the diode is to block the 12 Volt power supply from charging the battery. Connect the anode of the diode to the positive terminal of the battery, and the cathode of the diode to the 12 Volt power supply positive terminal. The negative terminal of the battery can be connected directly to the negative terminal of the 12 Volt power supply. There are a few precautions here. 1. Make sure that the battery voltage does not exceed the 12 Volt power supply voltage. A 9 volt battery can usually provide enough energy for a short-term backup. 2. There will be a voltage drop across the diode when the battery is supplying current (about 1 volt), so be sure the battery voltage is at least 1 Volt higher than the minimum voltage required to drive the circuit. 3. Be sure that the power diode is rated to safely carry the current necessary to drive the circuit. The 12 volt power supply should have a high output impedence, so a blocking diode for the power supply should not be required. I will leave the rechargeable circuit for another day! Good luck.<a href="http://www.currencyexchangemarket.com/world-currency-exchange-rate.htm"> Mez</a> Hi Daniel, Well, all you should need is a power diode (and the battery, of course).

The purpose of the diode is to block the 12 Volt power supply from charging the battery.

Connect the anode of the diode to the positive terminal of the battery, and the cathode of the diode to the 12 Volt power supply positive terminal.

The negative terminal of the battery can be connected directly to the negative terminal of the 12 Volt power supply.

There are a few precautions here.

1. Make sure that the battery voltage does not exceed the 12 Volt power supply voltage. A 9 volt battery can usually provide enough energy for a short-term backup.

2. There will be a voltage drop across the diode when the battery is supplying current (about 1 volt), so be sure the battery voltage is at least 1 Volt higher than the minimum voltage required to drive the circuit.

3. Be sure that the power diode is rated to safely carry the current necessary to drive the circuit.

The 12 volt power supply should have a high output impedence, so a blocking diode for the power supply should not be required.

I will leave the rechargeable circuit for another day!

Good luck. Mez

]]> By: Roger http://www.batterybackupguide.com/blog/how-do-i-make-a-battery-backup-for-a-circuit/comment-page-1/#comment-2590 Roger Tue, 02 Mar 2010 19:21:48 +0000 http://www.batterybackupguide.com/blog/how-do-i-make-a-battery-backup-for-a-circuit/#comment-2590 Ground both the negative side of both the power supply and backup battery. The positive terminal of battery is connected to the anode of a diode 1 and the cathode of the diode is connected to the load. Connect the positive side of the power supply to the anode of a second diode, the cathode of the second diode also connects to the load. As long as the power supply puts out more voltage than the battery, the power supply will cause the battery diode to be reversed biased. When the power supply turns off the battery diode will become forward biased and the battery will power the load. If you want the power supply to recharge the battery a third diode along with a series resistor can be used to charge the battery. The resistor value is calculated by (Vpower supply -0.6 volts - 12.6 volts) /(battery charge current in amps) = resistance in ohms. Calculate the wattage of the resistor by : Resistor wattage >(V power supply - 12 volts)(battery current)<a href="http://www.medicalsupplyservices.com/medical-equipment.htm"> Roger</a> Ground both the negative side of both the power supply and backup battery. The positive terminal of battery is connected to the anode of a diode 1 and the cathode of the diode is connected to the load. Connect the positive side of the power supply to the anode of a second diode, the cathode of the second diode also connects to the load. As long as the power supply puts out more voltage than the battery, the power supply will cause the battery diode to be reversed biased. When the power supply turns off the battery diode will become forward biased and the battery will power the load.
If you want the power supply to recharge the battery a third diode along with a series resistor can be used to charge the battery. The resistor value is calculated by (Vpower supply -0.6 volts - 12.6 volts) /(battery charge current in amps) = resistance in ohms. Calculate the wattage of the resistor by :
Resistor wattage >(V power supply - 12 volts)(battery current) Roger

]]> By: lee26loo http://www.batterybackupguide.com/blog/how-do-i-make-a-battery-backup-for-a-circuit/comment-page-1/#comment-2589 lee26loo Mon, 01 Mar 2010 22:05:45 +0000 http://www.batterybackupguide.com/blog/how-do-i-make-a-battery-backup-for-a-circuit/#comment-2589 You need only one relay to do the automatic back up power circuit. Get a 12 volts relay ,series the the Normal close contact between the battery positive and the +12 volts power supply. Relay coil connects to the 12 volts power source. And modify the power ON-OFF swtich to be inserted after the +12 v.<a href="http://www.telescopebuyingguide.com/telescope-eyepiece.htm"> lee26loo</a> You need only one relay to do the automatic back up power circuit. Get a 12 volts relay ,series the the Normal close contact between the battery positive and the +12 volts power supply. Relay coil connects to the 12 volts power source. And modify the power ON-OFF swtich to be inserted after the +12 v. lee26loo

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