UPS battery testing and replacement
A float voltage reading tells you a failing cell is fine. A discharge test tells you the truth. We measure delivered capacity and give you the number.
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- Steps in the process
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- Equipment types covered
- Any make
- Not only ours
- Same day
- Pune & PCMC response
What this covers, and why it is done this way
Batteries are the single most common cause of UPS failure, by a wide margin, and almost always because nobody measured them properly. A VRLA cell that has lost 40% of its capacity still reads a perfectly healthy 13.5 V on float. You only discover the loss when the mains fails and the bank collapses in ninety seconds.
Two measurements matter. Internal impedance, taken cell by cell, which trends upward as a cell degrades and identifies the weak one in a string. And a timed discharge test at rated load, which gives you delivered capacity as a percentage of rated — the only number that answers "how long will it actually hold".
Industry practice is to replace a bank when measured capacity falls below 80% of rated, because degradation accelerates sharply past that point. We give you the measured figure and the trend, and you decide.
Step by step
- 1
Visual and physical check
Case swelling, terminal corrosion, electrolyte leakage, rack condition, ambient temperature logging.
- 2
Cell-by-cell readings
Open-circuit voltage, float voltage and internal impedance for every cell, recorded against cell position.
- 3
Discharge test
Timed discharge at rated load with voltage logged per cell. Delivered capacity is reported as a percentage of rated capacity.
- 4
Report and recommendation
Written report with the capacity figure, the weak cells identified by position, and a replacement forecast in months.
- 5
Replacement
Full bank replacement — never partial. Mixing new cells with aged ones drags the new ones down to the old bank’s state within months.
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Disposal
Old bank collected and routed to an authorised recycler, with the disposal documentation handed to you.
UPS Battery Testing & Replacement — questions we get asked
Anything not covered here, call us — most of it is faster to answer on the phone.
How often should UPS batteries be replaced?
Design life for an SMF VRLA battery is three to five years at 25 °C ambient, and that halves for roughly every 8–10 °C above it. A bank in an unventilated Pune server room can be finished in two and a half years. Test annually rather than replacing on a calendar — the measurement is cheaper than either a premature replacement or a failure.
Can I replace just the failed batteries in a string?
You can, and you should not. In a series string the weakest cell limits the whole bank, and a new cell placed alongside aged ones is charged and discharged to suit the old ones — it degrades to match them within a few months. Replace the full string. The only exception is a bank under six months old with a single manufacturing failure.
What is a battery impedance test?
A small AC signal is injected across each cell and the internal resistance is measured. Impedance rises as the plates sulphate and the internal structure degrades, so a cell reading well above its baseline is failing even while its voltage looks normal. It is quick and non-invasive, which is why it belongs in every quarterly visit — but it complements a discharge test rather than replacing it.
Should we move to lithium?
Above roughly 20–40 kVA it is increasingly the better answer: three to four times the cycle life, about a third of the footprint, tolerance of higher ambient temperatures, and real state-of-charge telemetry from the BMS. Below that, the up-front premium often does not pay back within the equipment’s life. We will run the ten-year cost both ways for your bank rather than pushing one.
Do you take away the old batteries?
Yes, and it is included in a replacement job. Lead-acid batteries are hazardous waste under the Battery Waste Management Rules, so they go to an authorised recycler and you get the documentation for your records.
Where we attend
Everything is built at our Pune works and delivered, installed and commissioned across the city and the industrial belt around it.
Outside these areas we contract individually against distance, and we will tell you honestly if the response time you need is not one we can hold to. All areas served
Other services
UPS Annual Maintenance Contract
Quarterly preventive visits, an annual battery load test rather than a voltage check, and a breakdown line that answers. Any make — not only ours.
UPS Installation & Commissioning
From the site survey and cable schedule through battery rack assembly to a witnessed load-bank test and a signed commissioning certificate.
UPS Repair & Overhauling
Component-level diagnosis, not board swapping. On site where we can, at the works where the job needs a bench and a load bank.
Talk to someone who has done this before
Tell us the make, rating and age of the equipment and we will tell you what is realistic — including when the honest answer is that it is not worth doing.