Maintenance-free lead-acid batteries, as the name suggests, are characterized by "maintenance-free". Compared with lead-acid batteries, the consumption of electrolyte is very small, and there is basically no need to add distilled water during the service life. It also has the characteristics of shock resistance, high temperature resistance, small size and small self-discharge. Of course, its price will be more expensive than lead-acid batteries. As for the service life, the recommended replacement cycle for maintenance-free batteries under normal circumstances is about 3 years, which is equivalent to lead-acid batteries.