A plurality of batteries is printed on a flexible substrate, where each battery may output the same voltage, such as about 1.5 volts. Batteries in a first subset are connectable in parallel by controllable switches to control the maximum current that can be delivered to a load. Batteries in a second subset are also connectable in parallel by additional controllable switches to control the maximum current that can be delivered to the load. Another group of switches can either connect the two subsets of batteries in series, to generate 3 volts, or connect the subsets in parallel to increase the maximum current. Additional subsets of batteries and their associated switches may be further connected to increase the voltage and current. The power supply may be standardized and configured by the user for a particular load, such as a sensor for a medical skin patch.