Solar panels are ok, most only combat battery drain, for example on a boat where a fully charged battery may be left for mouths it will stop it from discharging due to cold conditions, but won’t actively charge the battery. Tested one my friend had and it only outputted 12v? Which is useless? Should be 12.6 – 12.8 for a holding charge.
What I would do. Buy a good battery with a 5 year guarantee, top tip check the voltage of the battery before you buy it, as some company’s don’t maintain batteries correctly... 12.6 V +