I am currently working on a school project that have a stack of 4 (12V 20A) lead acid charged by adapter from wall outlet. With 4 individual batteries, if i put in series, i will have 12V, 24V, 36V, and 48V output. My questions is how can i control the specific individual battery that i want to use and not use the whole stack of battery to step down to a desirable voltage level.
For examples: 4 of the batteries now named #1, #2, #3, and #4
The load is only ask for 15V, so now i only need to use 2 from the stack of 4 batteries. In this case, i will use battery #1 and #2. Then, i step it down from 24V to 15V, while keep the other 2 batteries charging.
When i notice battery #1 and #2 draining out, i can switch my source to battery #3 and #4. Then, charge battery #1 and #2.