If your uninterruptible power supply for your computer after several years has ceased to support the load after a power outage, then most likely its battery has failed. This is the most common breakdown of uninterruptible power supplies. The 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.
Theory
Why does the battery lose capacity and not hold a charge? One of the reasons for the failure of batteries of this type is the drying out of the cans. Therefore, we will just need to add a little distilled water to each compartment.
Battery recovery
I don’t want to give you false hope, but the method is not one hundred percent effective, since perhaps the battery has lost capacity not due to drying out. Although any recovery is not 100% guaranteed. Therefore, we will only give the battery a chance, which is definitely worth using, since it will not require significant effort from you, and if the restoration brings results, it will save you good money.
Diagnostics
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 they still exist.
For a dry battery, the voltage usually fluctuates around 13 V, and when a load is connected, it drops almost immediately.
In my case, everything is bad - 8 V in total.
Recovery process
These batteries are non-removable and are not intended for maintenance. Therefore, the compartments of the cans are sealed with a plastic lining, which must be pryed off with a sharp knife.
With a little skill, if you walk the tip around the perimeter, the plate will come off.
Underneath you can see six rubber caps for each compartment. These are kind of valves.
They are simply removed by hand. We remove them all and put them aside.
Next we need to find approximately 200 ml. distilled water. You can buy it at an auto store or very easily get it at home without special equipment - how to do it, read this article.
You will also need a syringe for 20 cc. And if there is no such thing, take any that is available.
Now everything is simple: add 15-20 ml to each compartment. distilled water. It’s difficult to say the exact amount, so we pour it into the compartment and look with a flashlight so that it’s 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.
Close the holes with rubber plugs. We connect the charger and try to charge it. Of course, the battery can be immediately installed in the UPS, but who will know whether it will be charged there or not.
After an hour, turn it off and check the voltage. It has grown to almost 11 V. This means the battery is being restored.
We place the torn plastic cover on glue applied to the same places where the factory one was previously.
The battery is assembled.
We continue charging for another 3 hours. And a second measurement shows that the battery is charging.
This battery was about 5 years old. Of course, it didn’t immediately stop holding a charge, but sagged gradually. Now it has been brought back to life and has 80% of its original capacity. I think it will last a couple more years without problems, but who knows...
Here is the simplest method that will help bring an old battery back to life. Try it yourself, and you will always have time to throw out the battery.
