Powering devices without flattening car battery

[NiceCupOfTea]

Hi folks,

I generally run a dashcam and a GPS tracker on my cars, both run from a permanent live cig lighter.

I have found that the permanent parasitic draw is ruining the car batteries. They are constantly going flat when I don't use them for a couple of days. The dashcam has a parking mode but it sts off after 6 hours so as not to toast the battery. I had assumed that a tiny GPS tracker with a battery in wouldn't pull much.

Anyway, before I buy a new battery I was wondering if anybody has any bright ideas. I am thinking of some kind of charging system with a secondary battery. Would using some mobile phone powerbank do the job, wired to charge only from switched ignition. I don't know if they are designed to charge rather than run things?

Would rather not pay too much as inevitably I'll want to fit the same solution to 3 cars!

[NiceCupOfTea]

Thanks, yes I'd seen that but more than I want to spend.

Interesting looking at the solar chargers on Amazon - I wonder whether one of those paired with some kind of overcharge protection like this:
https://www.amazon.co.uk/Anself-Controller-Regulat...

might do the job?

Ideally I want to fit and forget, I suppose a small solar panel that I could sucker to the rear window or something would be ideal, but don't want anything very obvious...