-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 On 2014-05-06 19:36, James Knott wrote:
Per Jessen wrote:
Depends on how many you have. The typical battery used in large scale UPS's (for bridging whilst the generators get going) is a 24v truck battery. I have no idea how much such a collection can deliver, but when it needs to run cooling, lighting, disks and e.g. 3-4 IBM 3090s of the old kind, it's quite a bit. Usually they're only designed to hold the load for 5-10minutes though.
Batteries used for starting cars & trucks are not suitable for that type of service. Starting batteries are designed for high current, short term loads. Batteries for UPS are designed to be floating on the rectifier output and be ready to take over the load immediately and sustain it for as much time as required.
Car batteries are also floating most of the time. Typically they supply a large and short current for starting, then they get recharged, and after that, they float. The main issue is another: vibration. Or was. The charging of batteries generate hydrogen, which tends to stick on the surface of the plates, diminishing the current flow, and the plate surface is not fully in contact with the electrolyte. Well, car batteries are subject to a lot of vibration, that dislodges the bubbles. Thus they can be compacted further. Batteries for UPS or standby safety lamps, for instance, are not, so they need more space between plates to compensate. However, as current models use gel instead of liquid, and they do not need to be refilled, that is no longer the issue. On the other hand, UPS batteries are designed for deep discharge, but infrequent cycles. Car batteries are seldom fully discharged. Also UPS batteries have to supply a quite heavy and continuous current, a lot, and the clients want them small: thus their life is short. On the other hand, batteries on exchanges last many years. No, the thing for use on heavy duty UPS system is not truck batteries, but heavy duty UPS batteries, which happen to be quite more expensive. Thus they cut corners and use car or truck batteries instead ;-)
Typical UPSs, as used with personal computers only last several minutes.
Because they are undersized and overloaded :-)
They were mounted on steel racks and connected with very large cables.
Which are wonderful as hook cables to start another car, not like those sold on supermarkets ;-) - -- Cheers / Saludos, Carlos E. R. (from 13.1 x86_64 "Bottle" (Minas Tirith)) -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iF4EAREIAAYFAlNpJOMACgkQja8UbcUWM1wTswD/dHW9Z80nq+njYuTg/Wdh0sKp cQ+zaIJKU4fBnRAE7e8A/1cHw18FOVmys9rbr5OnX81jpo9DDLUDCsrSL8wAQZFI =ARR/ -----END PGP SIGNATURE----- -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org