Trickle charging means charging a fully charged battery under no-load at a rate equal to its self-discharge rate, thus enabling the battery to remain at its fully charged level. A battery under continuous float voltage charging is said to be under float-charging.
For lead-acid batteries under no-load float charging, trickle charging is achieved naturally at the end-of-charge, when the lead-acid battery takes in a trickle charge to keep itself fully charged. The lead acid batteries are used to convert the solar DC power to AC power.