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Emulate Lead battery with capacitors, how?

  • 10-01-2024 03:51PM
    #1
    sebastiannielsen
    Registered Users, Registered Users 2 Posts: 3 ✭


    I have a security alarm system, which I have connected to a separate power supply (UPS) with batteries.

    Its an Vanderbilt SPC 4320.


    The problem here is that the alarm system expects a local battery, and I really don't want it (as there multiple systems in sync with the UPS and I want all systems to die simultaniously or in close proximity to each other) (so at power-back all systems start from a known power-off state if the UPS battery went empty).

    I however, noticed on my Vanderbilt SPC 4320, that the AUX voltage drops each 2 seconds. After a bit of troubleshooting, I found out that its the alarm board actually disconnecting the AUX supply (which also is the battery charging voltage) to test the battery voltage, even tough battery is isolated in Engineer menu, then battery have to supply AUX voltage during that half of an second.

    So to resolve this, I took a bunch of capacitors and connected them in parallel so I got a capacitance of 2200uF. Then connected this as a "Battery" to the alarm system. Checked with a multimeter and capacitor bank gets charged to 13.8V correctly. However, alarm system refuses to recongnize this as a battery, nor does it help with the AUX dips.

    I guess I need other components to "fool" the alarm that a battery is connected, so it uses this for AUX power during the 0.5 second dips.

    The "battery" only need to hold for a second or 2, it really doesn't need to be much.


    So how can I build a proper "battery" circuit with capacitor, to make a 1-2 second "lead battery", just to make the alarm system happy?



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