Change batteries from serial to parallel configurations with switches?
I have a 5s4p battery pack. The cells are 3.7 nominal voltage lithium ion cells. In a serial configuration it is 18 volts nominal. If I wire it in parallel it is in a 1s20p configuration and 3.7 volts nominal. I had this awesome idea to use switches to change the configuration from 5s4p to 1s20p. I want to do this because then I could charge whole pack with a 3.7 volt charger. Better yet, I would not a balance charger. Once I got to trying to design the switch configuration I was amazed at how complex it would have to be. The only way I can think of at the moment is to use 4 single throw single pull switches to isolate the cells and then use 5 double pole single throw switches to connect all the pos and negs together.
Does anyone out there know how to make a circuit which could work with with one circuit board and one switch? It could switch between 18 volts serial to 3.7 volt parallel?