Yes, it is possible to directly charge a battery from a solar panel if compatible ports are available on the solar panels. For example, Anker Solar Panel 625 features a USB-C and a USB-A output port to directly charge 2 devices at the same time. However, a charge controller or inverter is better to be used for this process to regulate the amount of voltage and current going into the battery and ensure that the battery charges properly and doesn't get damaged.  

When detecting that the battery is full, the solar panel charger for batteries automatically switches to a maintenance mode known as float or trickle charging. In this mode, the charger maintains the battery's charge at a steady level by sending small amounts of current as needed to offset any natural discharge. This helps to prolong the life of the battery by preventing overcharging or undercharging, which can cause damage.

No, quality solar panels do not drain batteries at night. During the day, solar panels generate electricity from sunlight and charge the batteries or portable power stations. At night or in low light conditions, the solar panels stop producing electricity, and the batteries or portable power stations supply power to the devices or systems.

Solar panels and batteries can work in a complementary way, with the latter providing stored energy when the solar panels are not actively generating power. This allows for a continuous power supply, even during nighttime or when sunlight is limited.

The size of the solar panel you need for a battery charger depends on several factors such as the capacity of the battery, the desired charging time, and the available sunlight. As a general guideline, a solar panel with a wattage rating equivalent to or slightly higher than the battery's capacity is recommended. For example, if you have a 100Ah battery, a 100-120W solar panel should suffice. However, a higher wattage battery charger solar panel like the 200w Anker 531 Solar Panel can ensure you faster charging during the same conditions.

The lifespan of a solar panel battery depends on several factors, including the type of battery, usage patterns, maintenance, and environmental conditions. On average, solar panel batteries like those used with solar generators can last anywhere from 5 to 15 years. However, proper care and maintenance such as keeping the battery charged within recommended levels and avoiding extreme temperatures can help maximize its lifespan.