Galaxy 5500 80kVA 400V hissing sound problem

[Anasagha]

greetings 

I have APC Schneider Galaxy 5500 UPS with the battery end-of-life service alarm on, the batteries were installed around 4-5 years ago.

our problem is that after switching ups to bypass mode for 4 minutes and switching it back to normal mode, the ups start making a hissing sound constantly. 

any suggested help pls 

[Teken]

Based on the information you’ve provided if the sound is determined & confirmed to be coming from the batteries - stop!

Battery service life is 3-5 years based on usage, temperature, and environmental variables. 

The hissing sound is coming from the vent caps of the cells because the fluid inside is overheated. The vent cap allows the gas to escape preventing the cell from building up internal pressure and exploding.

It should be easy to identify which cell is bad once it’s removed because it will be very hot! You may also see bulging and deformation of the battery case. 

NOTE: If it’s been confirmed the noise is indeed coming from the batteries. Stop charging the batteries and remove them when safe to do so. Insure the area is well ventilated and wear correct PPE during the removal process. 

The vented gas is extremely toxic and explosive!

[Anasagha]

Thank you for your reply
But I don't think the sound is coming from the batteries
did you watch the attached video? the sound is coming from the UPS Cabinet and it sounds like it's coming from a capacitor or a transformer

[Teken]

If you have removed the batteries and visually confirmed it’s not the cells. It definitely can be from the transformer / inverter system.

On smaller units a similar noise / sound is heard from the transformer / inverter circuit. In the vast majority of the cases this is normal and doesn’t indicate a failure.

If your unit has never made this sound it’s time for an inspection. ☝️