Battery Charger?

[PorcupineTree]

I bought myself a '63 V40 D3 manual a couple of weeks ago. When I first got it, there was a message on the dash to say that the battery was low. A long drive home (Kent back to Oxfordshire) seemed to do the trick as the message had gone but looking in the "my car" section of the infotainment systems, it says the auto start/stop is disabled due to low battery charge.

Therefore, I was thinking I would get myself a trickle charger to top it up and then when I next use it, it should be a bit happier and run more efficiently (not having to burn extra fuel to run the alternator on full).

Is this a good idea or should I just give it a few more long drives? Also, is it likely it's just the battery that's dying and a better option would be to just replace it?

And lastly, if I should go ahead with the charger idea, are there any recommendations? Looking into it a lot of them aren't suitable for cars with start/stop and further complicating things there appear to be two batteries - do both need charging?

Any advice you can throw my way would be most appreciated.