mge / eaton evolution battery backup

[cashkennedy]

Below are pictures of 1 of the 2 boards from a mge / eaton evolution 1150va battery backup. The battery backup has no signs of life with fresh batteries. It died after a power failure discharged the batteries. / shows no signs of life, will not turn on. This is a high quality battery backup with avr / full sine wave output.

I'm trying to determine if there is a startup cap / whether it is c53 on the board, please help me with the photos below.

C53, C6 is 50v 10uf
C66, C22, C19, C2 are all 50v 47uf
C5, and C8 are 250v 22uf
c13, c65, and I believe but cant read c64 are 35v 1000uf

The negative on every cap is connected to the negative of the batteries most of the outer edge of board is all negative instead of case ground. There appears to be almost no case ground on this board. Negative on the battery would be 23-26v depending on battery charge. (4 x 6v sla batteries)

The power button logic / usb and what not are on a separate smaller board connected by a ribbon cable, but youd think the batteries probably should charge even if that board is not present, but this doesn't charge the batteries when plugged in.

[cashkennedy]

Re: mge / eaton evolution battery backup

nr1 (8 pin ic) is uc3842B pwm controller (might be made by st, hard to make out logo)
nr2 (8 pin ic) is 431ac precision shunt regulator?

[cashkennedy]

Re: mge / eaton evolution battery backup

C6 appears to be connected with its positive going to pin 7 on the pwm ic (Vi). so I assume c6 is the startup cap.

(edited the initial post, because I had wrong capacitance on c6)

[cashkennedy]

Re: mge / eaton evolution battery backup

with the battery connected I get 25v on both sides of C6 and get 25v at pin 7 (Vi) of the pwm controller. not sure if that means C6 is working fine or what. Not really sure why you even need a startup cap in a battery backup that uses the batteries to initially power the IC's.

[budm]

Re: mge / eaton evolution battery backup

If you disconnect the wires to the batteries and measure the DCV on the wires when the UPS is plugged in, do you get any DCV charging Voltage at all? The charging circuit is always without having to turn the UPS on, it will charge the batteries when incoming AC power is present.

[redwire]

Re: mge / eaton evolution battery backup

I notice E3 (VT1) looks cooked, TO-220 with small heatsink on corner of board.
Tiny fuse F1 on PCB underside feeds it, I would check both.