The modern Battery Chargers use switch mode technology and employ 3 or 4  stage characteristics; bulk, absorption, float and storage being the 4th stage.

 

This technology makes the Chargers more compact and lighter when compared with those Chargers using Transformers.

 

As a  general guide when choosing a Charger, it should not be less than 10% of the auxiliary capacity; e.g. a 20 amp charger for a 200 AHR battery capacity.

 

The Chargers have temperature compensation and can be supplied with a dip switch to select for Lead Acid, Gel or AGM.