The Gates of Delirium (Dec 06 2012)

A good charger will charge the battery at the appropriate rate so as not to produce any hydrogen.

Which is why adding a car battery to a UPS is wrong. The charger isn't designed to charge a car battery.

I've read that telephone offices used to be required to have a UPS that could keep everything essential in that office running for three days. You might ask telephone offices if they have one they can donate. Warning - expect it to fill an entire room; I've seen one. It had a large rack of 2 volt cells, made with lead and something other than the usual acid.

The UPS for each of my desktops has a connection to that desktop that allows it to tell that desktop that it is running low on power, and that desktop should use the rest for going into sleep mode (suspending nearly all programs, then writing the contents of the entire memory to a hard drive, then adjusting the boot procedure to reload memory from that hard drive file instead of a normal boot, then turning off the power). Are your servers capable of that? The software I've seen for this is for Windows only.

The UPS for each of my desktops has a connection to that desktop that allows it to tell that desktop that it is running low on power, and that desktop should use the rest for going into sleep mode (suspending nearly all programs, then writing the contents of the entire memory to a hard drive, then adjusting the boot procedure to reload memory from that hard drive file instead of a normal boot, then turning off the power). Are your servers capable of that?

A UPS is an emergency-use item, one that will sit unattended for long periods but when you want it, it has to work first time every time or it is worthless, and you wasted the money you spent. That's why it's a false economy to buy a cheap one.

Large installations perform regular disaster recovery tests to ensure, amongst may other things, that the UPS's are working as they should. Few home users do that. I wonder if the University has any policy on disaster recovery testing?

The principal cost is batteries. Battery technology is still waiting for its next breakthrough in terms of storage capacity, charge speed and reliability - we're still using wet cell technology which is more than 200 years old, only the chemicals have changed. Buying cheap batteries for a UPS is particularly pointless, as they will fail early and require replacement more frequently: you end up spending more, and with a less-reliable UPS.

Telephone exchanges used to have very large 48V batteries, massive numbers of wet cells, which powered the remote equipment directly. Not a UPS as such - there was no inverter to produce AC mains power from the battery.
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I've read that telephone offices used to be required to have a UPS that could keep everything essential in that office running for three days. You might ask telephone offices if they have one they can donate. Warning - expect it to fill an entire room; I've seen one. It had a large rack of 2 volt cells, made with lead and something other than the usual acid.

I kinda think they might just be a bit too large!:-) Also they supplied 50V

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That is an accurate picture of a UK telephone exchange battery room as I used to work in telephone exchanges. I think that most nowadays have diesel generators