Battery Backup Guide

manerch asked:


I disconnected the positive cable and put a multimeter between the cable and battery post and it was reading 10 volts. What should it read? Should I be testing for volts or ohms?

Matt F asked:


This is a little project I am undertaking for the fun of it. My alarm clock doesn’t have battery backup so I wanted to install a capacitor in the event of short brownouts of a minimum of 3 seconds. I am not sure of the secondary voltage of the alarm clock but it is no more than10 volts as their are other capacitors rated for 10 volts. I measured the amperage during normal operation at .2 amps. So the total resistance should be around 50 ohms. I am thinking I will need a fairly large capacitor like in the milifarad range. Thanks!
This is a little project I am undertaking for the fun of it. My alarm clock doesn’t have battery backup so I wanted to install a capacitor in the event of short brownouts of a minimum of 3 seconds. I am not sure of the secondary voltage of the alarm clock but it is no more than10 volts as their are other capacitors rated for 10 volts. I measured the amperage during normal operation at .02 amps. So the total resistance should be around 50 ohms. I am thinking I will need a fairly large capacitor like in the milifarad range. Thanks!
This is a little project I am undertaking for the fun of it. My alarm clock doesn’t have battery backup so I wanted to install a capacitor in the event of short brownouts of a minimum of 3 seconds. I am not sure of the secondary voltage of the alarm clock but it is no more than10 volts as their are other capacitors rated for 10 volts. I measured the amperage during normal operation at .02 amps. So the total resistance should be around 500 ohms. I am thinking I will need a fairly large capacitor like in the milifarad range. Thanks!
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