[SOLVED] UPS for desktop is not working

[BenzT]

Hi,

I am having a UPS for my desktop PC. Suddenly its not working. I removed the covers and measured the voltages..

The battery is a 12V 7.5AH capacity.

I measured the voltage while its charging --> it increased from 1.0 V to 3.2 V slowly in 30 minutes and it stayed there. it did not increase more than 3.2 V.

I removed the charging connection to the battery and measured the voltage at this charging cable from board --> it measured only 0.2 V.

What could be the possible cause of failure..

 

[KlausST]

Hi,

Battery worn out --> replace it.

Klaus

 

[BenzT]

I was expecting around 12v from the output. Since it came as 0.2v, I thought board in trouble.

How you say that battery is worn out.. will it not be problem with PCB?

 

[KlausST]

Hi,

a 12V battery .. with less than 10V (for lead acid batteries) at it´s terminal .. is dead.
If you are sure that your voltage measurement is correct, then don´t waste your time, replace it.



Klaus

 

[Kajunbee]

I was expecting around 12v from the output. Since it came as 0.2v, I thought board in trouble.

How you say that battery is worn out.. will it not be problem with PCB?

Some chargers will not work unless there is a minimum voltage on the battery.

- - - Updated - - -

Therefore you might not measure a voltage across the disconnected charger leads.

 

[BradtheRad]

We had a UPS containing 4 gel cells, each 6V (total 24V). After 3 years it stopped working. I found one gel cell was under-voltage. The instructions said the batteries decline after a few years and need to be replaced whether the unit has had a lot or a little use in blackouts.

I visited (I think) a motorcycle shop or a lawn equipment shop to purchase a single 6V lead-acid battery. Not being an exact replacement for the gel cell it took me me work to hook it up inside the UPS. The unit gave service for a while longer. I had to be careful never to tilt the unit, in case acid might leak out the caps.

All four batteries had to be in place for the charger to work. It refused to charge three 6V batteries even though they totalled 18V.

 

[KlausST]

Hi,

I don't recommend to change only one cell. (This is only useful with an obviously defective cell - not a worn out cell)
The cells are connected in series. And thus the weakest determines the amount of energy that can be drawn from all the batteries.
Example: 6 cells in series, 5 of them can provide 95% of their rated energy, but one only 30%.
Then the total energy is limited the 30%.
Additionally the weakest will be stressed the most. It has the highest charge voltage and the lowest discharge voltage..both reducing lifetime even more.

Klaus

 

[Relayer]

Hello BenzT,

The battery is a 12V 7.5AH capacity.

Is the battery an SLA type?
If so, they cannot be run flat. In fact, there is a specific voltage
they must not go below. Not sure if its around 9~10 Volts. But
once they have gone too low, they'll never be able to be charged
again.

I measured the voltage while its charging --> it increased from 1.0 V to 3.2 V slowly in 30 minutes and it stayed there. it did not increase more than 3.2 V.

As I can see by the quote above, it was drained entirely.
If it is an SLA type, then your only course is to replace it.
Regards,
Relayer

 

[BenzT]

I replaced the battery with another new one.

Now its working good.

Thanks guys.