I have an application for which I need a relatively high amount of current @5V. I was thinking of connecting four external USB battery packs like these in parallel, as they output a nice regulated 5V and are easy to charge. But I know lithium chemistries are sensitive souls and having "unbalanced" cells connected together is a no-no.
How can I avoid any individual pack with a higher charge accidentally trying to charge another? Is it as simple as putting a Schottky diode in series with the positive lead out of each battery? Do Schottky diodes have an intrinsic voltage drop (like LEDs) which will waste a significant amount of power and/or cause my circuit to see less than 5V? Is there a better approach?