If your uninterruptible power supply for a computer after several years has ceased to hold the load after turning off the power, then most likely it has a damaged battery. This is the most common failure of UPS. Repair is extremely simple: replace the battery and forget about the problem for a few more years.
These types of batteries are not cheap. I suggest trying to restore the battery in a very simple way.
Why is the battery losing capacity and not holding a charge? One of the reasons for the failure of batteries of this type is the drying of the cans. Therefore, we will just need to add a little distilled water to each compartment.
I do not want to falsely reassure you, but the method is not one hundred percent, since the battery may have lost its capacity not because of drying out. Although any recovery does not have a 100% guarantee. Therefore, we will give the battery only a chance that is definitely worth using, since it will not require solid efforts from you, and even if the restoration yields results, it will save you good money.
We disassemble the uninterruptible power supply and remove the battery from it. We measure the voltage with a multimeter. If it is below 10 V, then the chances of restoring the battery are negligible, but still they are.
With a dry battery, the voltage usually fluctuates around 13 V, and when the load is connected, it drops almost immediately.
In my case, everything is bad - 8 in all.
These batteries are non-separable and are not intended for maintenance. Therefore, the compartments of the cans are sealed with a plastic pad, which must be pry off with a sharp knife.
A bit of dexterity and if you go to the edge along the perimeter, the plate leaves.
Under it are six rubber caps for each compartment. These are kind of valves.
They are simply removed manually. We remove them all and remove them to the side.
Next, we need to find about 200 ml. distilled water. It can be bought at an auto store or very simply obtained at home without special equipment - how to do this, read this article.
You also need a syringe with 20 cubes. And if there is none, take any that is available.
Now everything is simple: add 15-20 ml to each compartment. distilled water. It is difficult to say the exact amount, so we pour it into the compartment and look at the flashlight so that it is almost to the top.
We go around all the banks.
If you wait a little, the water level will gradually decrease, as the water is absorbed into the filler, which is located between the lead electrodes.
We close the holes with rubber plugs. We connect the charger and try to charge. Of course, the battery can be immediately installed in the UPS, but who knows whether it will be charged there or not.
After an hour, turn off and check the voltage. It has grown to almost 11 V. So the battery is recovering.
We put the torn off plastic overlay on the glue applied on those places where it was earlier factory.
The battery is assembled.
We continue to charge another 3 hours. And repeated measurement shows that the battery is charging.
This battery was about 5 years old. Of course, she did not immediately stop holding the charge, but gradually subsided. Now it is brought back to life and has 80% of its original capacity. I think it will last a couple of years without problems, although who knows ...
Here is such a simple method that will help bring the old battery back to life. Try it yourself, and you will always have time to throw out the battery.