You can't because they will cross charge, even if they are not rechargeable batteries. You could connect each battery through a diode to what you want to drive to avoid this, but you will loose 0.7V using this technique.
You can't because they will cross charge, even if they are not rechargeable batteries. You could connect each battery through a diode to what you want to drive to avoid this, but you will loose 0.7V using this technique.