TSE Power

A quick guide to UPS battery monitoring and maintenance


A UPS is a vital line of defence in the event of a power outage. Keep it in optimum condition with these tips for UPS battery maintenance in the UK.

Nearly all business will have a UPS to protect their data and systems in the event of a power outage. These devices are utility mains and battery backed and require maintenance to ensure that they are operating at full capacity should the unexpected happen.

Common issues with UPS battery maintenance in the UK

A myriad of factors influence the health of UPS batteries, but they are all within your control. Ambient temperature is especially important. All batteries come with a recommended operating range, and this should be followed to the letter. Even minor temperature fluctuations can have an extremely detrimental effect on a battery. Many are designed to operate at around 20-25 degrees Celsius (68-77F), so always keep this in mind. Avoid putting the batteries near open windows or radiators, and maintain a steady temperature.

Similarly, other environmental factors like dust and damp can be damaging and batteries should never be installed close to caustic fumes. Many companies will choose to buy additional backup batteries as spares, but it’s important to remember that these can’t simply be put away and forgotten about. They’ll need to be charged at least every six months or they’ll start to degrade. Over or under charging a battery can also have negative and occasionally fatally damaging consequences, so always follow the manufacturer’s instructions. Watch out for float voltage too, which should normally hover between 2.25 and 2.27 per individual cell.

Predicting battery life span might seem like a dark art, but with proper maintenance and monitoring, it can be a science. It’s possible to schedule replacements with a degree of accuracy. A visual inspection often goes a long way. Leaking or swollen batteries should sound alarm bells, and these will need to be replaced as soon as possible.

There’s plenty of commercial battery monitoring systems and software available on the market, many of which are remote. The beauty of these systems is that they’ll send an alert when batteries reach certain thresholds, for example, if internal resistance becomes too high. They’ll also monitor crucial factors including float voltage and temperature. These systems are fantastic for extending battery life by identifying problems early and minimising downtime.

Testing and UPS battery maintenance in the UK

UPS systems are powered by a long string of batteries, which makes them especially vulnerable to failure. If one battery degrades, it can disrupt the whole chain. Failing individual cells are a major cause of outages and downtime, as a single faulty cell places additional strain on other cells in the chain, eventually causing the whole battery string to malfunction. This can be costly to repair, as well as devastating if it occurs at the wrong time, so it’s important to have your UPS battery serviced regularly.

A battery impedance test is usually the procedure of choice, and this is probably the most common method of UPS battery maintenance in the UK. Rather than testing the full string, technicians will examine individual battery blocks. This involves testing a cell’s resistance. If that figure rises above 50% of its base level then the cell is considered to have failed, and will be replaced. It’s difficult to overstate how important this kind of testing is. Identifying small problems in the string early is usually enough to prevent much bigger ones occurring later. Impedance testing is preferred to load testing, which looks at string health as a whole, and won’t identify issues with individual cells.

We recommend conducting one of these tests at least annually. This takes around 1-3 hours but can save you a lot of time (and headaches!) further down the line. Routine voltage assessments are also important, and will help you better understand when batteries are nearing the end of their life. Of course, ensure that you hire a fully qualified engineer with all the appropriate safety training, as there are high voltages involved. Since UPS batteries tend to last between 3-5 years (or 8-10 depending on specification), no amount of testing will negate the need to eventually replace them, but it will ensure that you get maximum lifespan and avoid any nasty surprises.