During a recent storm, I was at a customer’s business. The power flickered, and their PC went dark. I mentioned that we might need to invest in a battery backup to prevent damage to the PC and loss of data in the case of a sudden power event. They replied that they already had one; had been using it for years. It turns out that the battery was weakened enough to not be able to keep power to the attached devices, but no so dead yet that the low battery alarm on the unit had gone off.
A good rule of thumb is that a battery backup only lasts 2 – 3 years. If yours is older, don’t trust it to keep your mission-critical systems running in a low power situation. A dead battery will cost you data, and might let your computer assets get damaged.