Embodiments of the invention provide medication dispensing carts and methods. Each DC to DC converter unit includes a power section, a controller and a standard universal interface connecting the power section to the controller such that the power section can be changed to accommodate different input voltages, output voltages and current loads without making significant hardware changes in the controller. The second surface 142 is provided with a second electrode electrically connected directly with the second conductor 120. Particular compositions include at least one of iron or magnesium. The patch may be the same material or a liquid silicone rubber, but at least has similar material properties such as elastic modulus, durometer and elongation.