I have salvaged a number of ups units that have been thrown away by offices
I would like to modify a Tripp-Lite BCPERS300 UPS, I would like to turn it into a simple 12volt to 110 volt inverter, it currently uses a 12 volt 4ah standby battery and converts it to 110volts whenthere is a A/C power fail, so I just need to figure out how to simulate a ac power fail or manipulate this trigger.
the on board IC chips are : LM339, uln2804A Darrlington array, lm358n op amp, 64T429 3-leg device, PIC16C72A 8-bit cmos microcontroller, I don't know to much about the circuitry yet and have been unable to find a schematic, at this point I am assuming that maybe the microcontroller is
sensing the ac and acfail and activating the inverter can anyone out there help me figure out how to make the inverter switch on without the acor acfail ?

 

i thought of doing the same.


This is my conclusion...

these dc-ac inverter circuits are probably designed to run for 10 minutes without cooking.

 

I guess you just disconnect it from mains and let it do its job. When you hook up a battery to UPS it should immediately start producing 110vac.