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UPS Repaired

By on June 15, 2015
ups repaired







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.

ups repair

Do you want to know what I saw inside once the cover opened? Look at the photo below.

ups repairs

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.

ups repairing

The new battery could not be connected directly, why? Because the connectors were fully corroded and with no use.

ups repairings

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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  1. Rex Makun

    June 15, 2015 at 11:13 am

    really intresting i really enjoy it really help and guide me on how to repair electronics board and component.

    • Humberto

      June 15, 2015 at 8:11 pm

      Thanks Rex Makun

  2. vince

    June 15, 2015 at 2:07 pm

    you had got no 1/4 spade terminal's and soldered straight to battery that's poor for a technician
    I would never solder to a battery
    and terminal's can be got at any car parts store
    its an every day consumable I have boxes of them all sizes and types
    rings spades male and female

    • Robert Calk

      June 15, 2015 at 8:07 pm

      Hi Vince,
      You should try to be more understanding. Soldering to batteries isn't that big of a deal if you know what you're doing. If you lived in Cuba like Humberto does, I doubt that you would have boxes of stuff.
      But since the US is talking about lifting sanctions against Humberto's country, I'm sure that components and test equipment will become easier for him to acquire. You just have to remember that people in some countries do not have the same availability to things as we do; and sometimes they have to make do with what they have at hand.

      • Humberto

        June 15, 2015 at 11:34 pm

        Thanks a lot Robert, you are always welcome.
        Please, vince, do not get upset with Robert, he is only trying to explain the reality of my country.

        • Robert Calk

          June 16, 2015 at 10:07 pm

          You are welcome, Humberto. Thanks for sharing your repair with us.

    • Humberto

      June 15, 2015 at 8:45 pm

      It's a pity vince, but I've exhausted my terminals collection, and they are very hard to get where I live. Thanks anyway.

  3. Albert

    June 15, 2015 at 3:37 pm

    Good fix Humberto! On UPS repairs it always is the Battery, the connectors or other bad contacts. In situations were you want to prevent corrosion I've seen pcb's and connectors that were completely Vernished. My old Boss worked with Controller boards full with Op-Amps. And to prevent any bad working Board they were Vernished. Those Controller Panels were mostly used in Farm Air Regulators outside Pigstables and sort. (In our country Cars bought from Coastal Areas are Cheaper because Corrosion from the Sea Salt is likely to make them more Rust. One friend of mine repaired the 100 year old mechanicle clock on one of the Netherlands Antil Islands because it was corroded by the Salt of the Sea.)

    • Humberto

      June 15, 2015 at 8:33 pm

      Hi Albert, thanks for your comment.
      By the way, here in my city we are strongly attacked by the Sea salt too, and our weather here in the tropic is very wet: moisture attacks too much electronic circuits. And near my city, in Varadero Beach and Santa Martha the petroleum gases corrode the PCBs and they are imposible to mend,it's the pity but it's a real phenomenon.
      I remember some russian electronic equipments had the PCBs fully vernished to avoid the corrosion.

  4. Yogesh Panchal

    June 15, 2015 at 3:53 pm


    Congratulations! for this fix.

    • Humberto

      June 15, 2015 at 8:13 pm

      Thanks Yogesh Panchal

  5. thiru

    June 16, 2015 at 6:09 pm


    Good work & appreciated.
    How to solve 36V battery 40Ah charger fault,in which it doesn't charge battery ?

  6. Leo

    May 20, 2017 at 12:45 am

    Hello Roberto,
    Thanks for your comment, it is this type of batteries what little I have seen.
    I wanted to ask you, because I can not open my battery (work) and I want to manage the purchase of a new battery replacement for this UPS-SL650, according to your photo, the original is 6v 7A and replace it with a 12v 7A is so, there is to do some adaptation or just mount, I can order the conventional Panasonic 12v / 7A?
    Thank you. Greetings, Leo.


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