The lifespan of a home battery

Two clocks tick at the same time. The first counts charge cycles: one cycle is charging fully and discharging again, and partial cycles count proportionally. A battery running on solar surplus makes roughly one cycle per day, so about 365 per year. The second clock is calendar ageing: even a battery that is rarely used slowly ages over the years.

Which of the two matters first depends on your use. If the battery only stores your own solar power, you rarely reach the maximum cycle count in practice; if you actively trade on power prices, you make more cycles per day and reach that number sooner. The cycle count of a specific system is in the manufacturer's datasheet.

Worn out sounds like the battery fails one day, but that is not how it works. The capacity declines gradually: a battery that stored 10 kWh when new stores somewhat less after years of use. You notice it because the battery runs empty sooner, not because it stops. The system keeps working, just with less storage.

Many factory warranties therefore promise not only a term but also something about the remaining capacity at the end of that term. What exactly differs per manufacturer and is in the warranty conditions. When buying, that is a more useful question than the number of years alone: a long warranty without a capacity promise says less than it seems.

The biggest influence you have yourself is the location. Heat speeds up the ageing of lithium batteries, so a cool, dry and ventilated space is not only the fire safety advice but also good for lifespan. Which spots work and which fall off is covered in where to place a home battery.

The system does the rest itself. The battery management system guards the charge limits and the temperature, so the battery does not discharge harmfully deep or overcharge. If you choose to trade actively on a dynamic contract, you make more cycles and the battery wears somewhat faster; extra earnings stand against that. That is not right or wrong, but a trade-off you make deliberately.

For the buying decision one sum matters in the end: the battery must pay for itself well within its lifespan. What that sum looks like and which savings count is covered under what a home battery costs.

We give a ten-year factory warranty on the HYXi Power home battery. During the site survey we also tell you what the datasheet promises about cycles and remaining capacity, so you do not have to rely on a brochure claim. Curious what that means for your situation? Request a no-obligation quote via our home battery page.