Battery constant current charging circuit

In battery charging circuits , autotransformers and varistors are currently widely used to regulate charging current . The disadvantage is that the current must be constantly monitored
and regulated. The figure shows a circuit that can automatically maintain the charging current at a given value. It adopts the method of connecting capacitors in series in the primary winding of the transformer
, so that during the charging process, the voltage between the capacitor and the winding is constantly redistributed, thus keeping the charging current at a given value.
    In order to keep the charging current at about 5. 5A, the transformer should be selected with a power greater than 170W. The no-load voltage of each half winding on the secondary side is approximately 27V
. Switch S2 can be used to select the capacitance to control the charging current. When closed, the charging current is about 5.5A.