UPS Earth Fault

[Ethnan]

We have several number of UPS systems in my large facility. The UPS systems are of SAFT and use Ni-Cd alkaline batteries which are all arranged in standard insulated racks.
We have experienced a common problem across these UPS systems, and that is earth fault. This was traced to the battery electrolyte evaporating over time and condensing on the body
of the batteries and the battery racks, thereby forming a closed conductive path between the positive, negative terminals of the batteries and the earth. Note that the racks are
earthed. When the batteries are disconnected and washed with plenty of soap or vinegar, and then reinstalled, the earth fault clears. But this will only last for about two years,
before the earth fault returns again.

The task of dismantling the batteries, washing them and reinstalling is quite laborious, takes time with its attendant risks, plus the risk of losing the vital loads in the event of a primary power outage.
I would be grateful if anyone who has experienced this could share a better solution to solving this perennial problem without having to dismantle and wash the batteries. Thank You!

Kind Regards

 

[RRaghunath]

NiCd batteries are known to require very little maintenance but it doesn't mean you don't conduct periodic visual checks and maintain them clean.
Why the alkali should be coming out and forming a conducting path to the earthed rack needs to be looked in to, as it is not normal!
It could mean
* the batteries are being overcharged or
* the batteries are being topped up in a wrong way.

 

[Ethnan]

So you are saying there is no reason the alkali should evaporate and condense on the battery casings and racks? This is a very tropical region of average daily temperature of 32 degrees.

 

[RRaghunath]

The vent plugs are designed in such a way the fluid that evaporates condenses and falls back (most of it) in to the battery cell.
Please refer the maintenance instruction manual and speak to the manufacturer for better clarity.

 

[Ethnan]

Thanks for this. I will check out in details the maintenance manual.

I appreciate your time.

Kind Regards