Second battery charging via cigarette ignitor

Good day ahead, am new here Does someone have a solution proposal for the following more special idea: I want to charge a small 12v 6-10Ah battery “somehow” via the cigarette lighter. Speed doesn’t matter. The Ziga slot has ~12v 10/15A max or? The main idea is that a device needs permanent power supply (so 12V min. 50/60Watt) and therefore the battery should not supply power when the car is off –> so the Ziga slot does not supply power, the supply is taken over from the battery When switching on, the battery should be recharged again (how fast does not play a role, especially the safety will survive) but the main feed should be taken over directly from the Ziga slot. If this does not work with the change between directly from the Ziga slot and the battery, can the load also go directly to the battery? Just thought it would be more gentle for the battery. Is there an all-in-one device (battery charger, if fully then off If not, then maybe from 2-3 components. I attachment is so the idea in a device, instead of the solar panel would be there the Ziga-Slot Best Thanks & Sorry if the description is not understandable