This be battery charger the automatic circuit again interesting circuit. Because of use IC LM324 then make economize. And can charger get both of battery 12V sizes and 6V with the filtration that at S1. Certainly circuit this still base property be when battery have voltage full already, circuit as a result order give Relay RY1 cut the system departs battery immediately. For R1 and R7 use for fine decorate the rapidity of the circuit. The test is as a result easy. Lead the battery that have Full voltage wasp with the circuit fines to decorate R1 and R7 give RY1 work. detail other part see in circuit picture sir.