I use a 12V deep discharge battery and a wall-wart trinkle
charger.

Buy a cheap digital voltmeter and check the battery voltage while it is charging.

If it goes much above 13.8 Volts and you leave it that way 24/7, it will loose water.

The better trickle chargers regulate to 13.8V or less.

If it is much below 13.5V 24/7 the battery will sulfate.

The float voltage is critical for long shelf life.

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