My bike is kept in an underground carpark (no sun light), with no power outlets.
And the bike has a tracker on it.
Sooooo… conventional trickle chargers that plug into a wall socket are no use, or solar either. And removing the bike’s battery - to charge in my flat - means no tracker.
Is there anything I can buy to maintain the battery that uses self contained power?
No idea if this will work, but possibly a high-capacity leisure battery (or 2) either linked via tender to the battery or via an inverter to a trickle charger to your bike.
It should last several months without a charger or being run, even through winter.
And if you are parking over winter it might be easier to just take the battery indoors if you are worried.