This UPS was brought to me for changing the battery, which was in bad state. It has no screws in the external cover, so it means it had been open by another tech. The model is UPS-SL650, and China made.
Do you want to know what I saw inside once the cover opened? Look at the photo below.
It was an old battery I found inside. I had to confess I had not seen something like this before.
It was a 6 volts battery from a Rechargeable Lamp, and UPS use 12 volts batteries. Well, the new battery was given to me too.
The new battery could not be connected directly, why? Because the connectors were fully corroded and with no use.
I do not know why in this model of UPS, when the battery is fully exhausted the terminals from the circuit (negative and positive) deteriorate themselves. As I had no connectors as spare, I had to cut them, and solder the wires directly into the battery.
When the device was turned on, it did not start. So the problem was getting complicated. First thing done was to check the rear fuse, but it was fine. Then I put my magnifier glass on to the PCB and took a close look at the darken area. I saw cold joints and some points will develop cold joints soon-see the photos below:
All the cold solder joints and solders in the dark areas of the PCB were re-soldered. By the way all the pins of the five relays of this device were re-soldered too with fresh tin.
Finally, when the UPS was turned on, it really started fine and supplying a good ac voltage output of 120.9 Vac.
This article was prepared for you by Humberto Rodriguez, one of our ‘Master Authors’ from Cuba.
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