Given the rate at which lithium battery prices are falling, we don’t expect this post to be relevant much longer. Still, here it is:
When to replace your generator’s starting battery: 99% of the generators we see have standard flooded lead-acid batteries, the same as you would find in a car or truck. Life-safety code that governs hospitals recommends these batteries be changed every 24 to 30 months. Residential generator batteries are often pushed to twice that, as it is common to see batteries five years old or more. It has been our experience that these standard batteries often get weak or fail completely after four or five years. The failure curve is almost logarithmic, with failures before three years being very rare but becoming common after 4-5 years.
Unlike in a car, where you can hear the starter struggle when the battery begins to fail, in a generator there is often no warning before a battery fails completely simply because no one is listening when the generator starts. As we’re only on site once per year at most sites, we want to be sure that the condition in which we leave the generator will be good for one full year. As such, we recommend battery replacement as early as every two years but no less frequently than every five years.