You do not have to put main beam on, side lights are ok.
Driving lights do not put much draw on the battery, hence you have to turn the side lights on.
Split charge relays trickle charge the battery as previously posted. So if you do not do much driving, you will take more out of the battery while you work than you will be putting back in while driving.
In which case you will have to top up the battery with a charger. CTEK chargers we have always found the best.