UPS Battery Maintenance Checklist
What a UPS Battery PM Visit Checks
The UPS passed its self-test last month. Then the power went out, and the string held for seconds instead of fifteen minutes.
We get that call three to five times a week, and the self-test was never going to catch it.
Why the self-test misses a weak jar
A self-test puts a light load on the string for a few seconds. A weak jar passes that all day. What the self-test can't show is whether the string holds voltage under a real load for real minutes.
The second problem is the string itself. A string is one circuit, and it performs to its weakest jar. One jar going down takes the whole string with it, because it can't hold the load and it can't give the inverter the voltage it needs to see. The self-test reports on the string. The failure lives in one jar inside it.
Catching that early takes someone standing in front of the rack with a meter, at least once a year.
The eight checks in a standard UPS battery PM
Our standard preventative maintenance visit is an eight-point check. Here's all of it, and what each item is for.
1. Record float voltage on the string and on every jar.
We record float voltage on every jar, next to the string total the UPS shows you. It's the first thing we measure on site and often the most telling. Differences between jars point straight at charge acceptance, and a jar that's slipping usually shows here before it shows anywhere else.
2. Test conductance or resistance on every jar against its published spec.
We compare each jar against what the manufacturer published for that make and model, so the research happens before the technician arrives. You don't need a history of readings for the numbers to mean something. The first set tells you plenty on its own.
3. Take the temperature at every negative post.
Every post gets a reading from an infrared thermometer, so nobody has to guess which one runs hot. Heat is the largest single factor in service life, and the pattern matters as much as the number. If every jar reads hot, we check the string's age first, then the charger, then the room. If one jar reads hot and the rest don't, that jar has a problem and it gets a closer look.
4. Measure resistance across every intercell connection.
A high-resistance connection heats up under load and takes the string down with it.
5. Retorque every connection.
Connections loosen over time. Every discharge and recharge heats the joint and lets it cool again, and that expansion and contraction slowly works the clamping force out of the bolt. Lead is soft, and it gives a little under pressure too. A connection that has loosened runs hotter, which loosens it faster. Measuring a connection tells you its condition; retorquing it is the fix. Both happen, as two separate jobs.
6. Inspect every jar.
Cracking, leaking, swelling. Where there's corrosion there has been acid, and where there has been acid there's a leak. Swelling is the one worth knowing about: a single swollen jar suggests a dead short, present or imminent. If every jar in the rack is swollen, we check the age first. On a string far past its service life, that's expected. If the string is younger than that, we look at the charger next, and then the room.
7. Spot-check rack torque and clean up.
The rack is part of the installation. We spot-check its torque values and leave the batteries and the rack clean.
8. Check the charger's float voltage and equalize settings.
This is the one most people leave off, and it's the one we'd keep if we could only keep one. A charger holding the wrong float voltage, or set for a different chemistry than the one in the rack, shortens the life of every jar in the string, steadily and without an alarm. The batteries get blamed. The charger did it.
What you get back
You get every reading we take on site, as a spreadsheet on a USB drive or by email, handed to whoever owns the equipment.
Two reasons that matters. The readings are yours, so the next visit has something to compare against. And you hold a dated record of the whole string, in a form you can send to a manufacturer if a battery ever fails inside its term.
Standard and Major: which one you need
A standard PM is the eight checks above. It's an inspection and a measurement exercise, and nothing gets replaced.
A major PM includes all of that and adds the work: complete housekeeping and corrosion cleaning, filling, replacing cables, busbars and intercell connectors where resistance or damage calls for it, and inspecting and replacing spill containment bags. The labor for that work is in the major PM price. Consumables are priced by count.
Which one you need depends on what the last visit found, and on whether you're running sealed VRLA or flooded cells. Major PM tends to suit the sites where downtime isn't survivable, which in practice means financial services, healthcare, manufacturing, data centers and telecom providers.
How often a UPS battery PM is due
Annually is our baseline. Sites where the load is more critical get a shorter interval when we quote.
If the string has never had one, the first visit is the useful one. It tells you where the string is today, whatever its age suggests.
Warranty claims, and one thing a PM visit is not
We handle warranty replacements regularly, and the dated readings from a PM visit are what we work from when we do. Warranty is a term in years. Design life is a longer engineering figure. We label both on every quote, and the lifespan article walks through the difference.
A PM visit does not include a load test, a discharge test or a capacity test. Neither the standard nor the major visit performs one. If you need one, for a claim or for your own planning, that's separate work, and we'll quote it separately so you never assume it's covered. We'd rather say that twice than have you find out during an outage that the test you assumed happened never did.
Getting a visit quoted
Send the string size, the jar part number off the label, and the site ZIP code. Pricing depends on the number of jars, the location, and whether the work runs in business hours or around the clock. Visits are sold individually or as an annual contract, and the contract is priced better.
We cover a four-hour drive from Willoughby, Ohio. If you're outside that, send the details anyway and we'll either find someone or tell you we can't.
Your UPS will pass its self-test again next month. That tells you the inverter works. It says nothing about the jars behind it.
Written quote in 24 to 48 hours.