Charge car battery via power station?

Hello dear community,

Unfortunately, I have the problem that my battery never gets fully charged despite long journeys and now of course I'm always worried that the auxiliary heating will switch off if it runs for too long.

I drive for 30 minutes and usually only heat for 15 minutes out of fear that another battery alarm will come on. The battery is a year old.

Since I obviously want to use the auxiliary heater until the car is free of ice, I thought about adding a trickle charger (e.g., from Ctek) and running it via a power station I already have. The battery is in the trunk anyway, so I could lock the car and still charge it.

Charging once a week should help.

The only question now is, can I connect the charger to the battery in the trunk, or do I have to use the charging terminals in the engine compartment? Perhaps it's better to take this to a garage for this task?

The car model is an Astra K ST 1.6 CDTI.

Thanks in advance for tips and help