13/01/2013
Maintaining Your UPS
Make sure the UPS keeps in contact with its electrical ground at all times. Don't overload it. If it shows signs of misbehavior or malfunction, yank it until it's repaired, or replace it.
Your UPS has a battery inside it. Usually it is a lead-acid type (those are the least expensive for the manufacturer), but both lithium and gel-cel batteries are sometimes used.
The battery is by far the most vulnerable and failure-prone part of your UPS. If you have your UPS long enough, you will probably have battery problems. Once every six months to a year or so you should recalibrate your UPS's battery sensor, and once every several years you will have to replace the batteries.
5.1. Service contracts
Some consumer-grade UPSes, and all UPSes designed for serious data-center use, can be bought with vendor service contracts. These don't make sense for low-end units that can be replaced cheaply from a local electronics store. If you're an IT shop with a bunch of UPSes scattered over a campus, a service contract might make sense, depending on circumstances. If you have a larger UPS in the 5-10 KVA range, a service contract may be a valuable hedge against extended downtime.
5.2. Extending battery life
To extend your battery life, (a) avoid deep discharges, and (b) don't expose them to extremes of heat, cold, or humidity. Unfortunately there is not much you can do to avoid deep-discharging your UPS other than living in an area where power outages are few and short.
5.3. Recalibrating Your UPS
Your UPS's dwell-time calibration will lose accuracy over the life of the battery. The usual symptom of this problem is that the UPS overestimates the dwell time it has remaining during outages, but occasionally it can also lead to an actual bad-battery condition going undetected and very odd symptoms as a result.
UPSes have a recalibration procedure built into their firmware. It generally involves deep-discharching and recharging the battery while the UPS is in a special test mode. Your recipe for triggering such a recalibration will vary according to your UPS software.
You always need to do this when you install new batteries (see below). It is a good idea to do it once every six to twelve months as routine maintenance, but no more often than that; as we noted previously, deep discharges shorten your battery life.
5.4. Replacing Your Batteries
All modern UPSes have a low-battery alarm and run a periodic self-test; they will alert you when replacement is needed. Usually they both flash an indicator and make an alarm sound. If you have a monitoring daemon set up, they will alert it and you will probably get warning mail. If you ignore the alarm it will time out, but be repeated at intervals.
You will occasionally get a false alarm. It's a good idea, if you get an alarm, to explicitly trigger a UPS self-test the next day and see if the alarm goes away (the procedure for doing this varies depending on your UPS software). If the alarm is persistent, you need to replace the batteries.
It has been reported that bad batteries can also produce symptoms that mimic inverter failures or wonky control electronics. Even if your UPS is displaying epileptic symptoms like repeating alarms and flashing panel lights, a bad battery is the first thing to suspect.
UPS manufacturers would of course prefer that you replace your entire UPS when the batteries die, since they make more money that way. But in fact there is nothing unique or magic about UPS batteries. They are standard types also used for other applications such as powering marine electronics, with standard connectors. You can buy them from sources other than the UPS manufacturer, and sometimes replace them with equivalents that are better and less expensive.
It's best to wait until the low battery alarm before ordering a replacement; keeping batteries on the shelf reduces their life unless you keep them fully charged.
Do not throw old batteries in your regular trash! They contain toxic metals and acids. Be kind to your environment and hand them to a qualified party for recycling. Most battery dealers will cheerfully do this for you. If not, your local garbage company or waste-disposal authority can explain to you how and where to turn them in safely.
Many UPS models use gel-cel batteries in standard formats like 12.0 V, 7.2Ah (151x64x94 mm). Warning: Many manufactors sell two or three different types: standard use, cyclic use and high-current use. UPSes require high-current and some UPS don't work well with batteries for standard use, because the voltage goes low too early under high load (the UPS turns off too fast or the output voltage drops so that the computer turns off). Standard batteries are for alarm devices, emergency lights or things like that. For instance Panasonic sells the "LCR127R2PG1" (standard), and "UPRW1245P1" (high current), Fiamm the "FG20271" (standard) and "FGH20902" (high current), CSB the "GP1272" (standard) and "HR 1234W" (high current).
Below, you will find some suggestions for buying replacement batteries. One important note of caution: at least one user purchased one of the aftermarket batteries noted below and found out that they would not fit into his unit. This required cutting and soldering and other very undesirable things, so be extremely careful in measuring your batteries — including every millimeter of the terminal connections, which can cause problems.
Although you can do a hot swap of your batteries while the computer is running, it may not be very satisfactory, because the unit will not know that the batteries have been swapped and your monitor daemon will continue to show a low-battery indication. To correct this situation, you must do a discharge and recharge of the battery. At that point the battery should be calibrated better.
It may take several discharges and recharges of new batteries before they reach full capacity and the dwell-time calibration is accurate. If your UPS contains two or more battery units and your monitoring software reports separate voltage levels for them, one way to tell is to watch the divergence in voltage levels. As the cells reach nominal full capacity, their voltages should converge.
