The thing about data centers is just how much power they use.  This one in Cardiff, Wales uses about 20MW of power and has huge strings of batteries storing power to drive the UPS units.  The batteries are kept in dedicated battery rooms that are air conditioned to keep the cells cool and maintain a life expectancy of about 5 years.

Everything in a data centre needs maintenance, regular visual and physical inspections all as part of a planned schedule. The guys in Cardiff shared these photographs with me last year (2007) when a single lead acid battery failed due to a manufacturing defect.

The distortion of the cell cases is quite obvious in the picture above. This was caused by the batteries cooking because of excess current flowing through them.  The lead plates and acid got very hot to the point that the plastic casing started to buckle.

Note another case of extreme distortion of the battery casing caused by overheating.  This one looks like it was ready to start running down the shelving and onto the floor.

You can see from the battery cover that these units reached a very high temperature.  The cover shows quite severe scorching and blackening.

A manufacturing fault in a single battery caused over current in a whole rack causing overheating and distortion.

If you look carefully you can see bulging in many of the cells. All need to be replaced to ensure that the rack of cells have a similar lifetime.

A picture of a lead acid cell removed from the data centre UPS battery centre. The cell has obviously overheated as can be seen from the distorted case.  Normally lead acid cells last for 3 - 5 years depending on ambient temperature in the battery room.  High temperature dramatically reduces cell life.