My take on cheapo batteries is to stay away from them.
I own a communication company that provides two way radios, Nextels, and other communication gear to public safety and the military. Almost all of my contracts require OEM batteries where the "battery cells" originate from Japan and not China.
When it comes to voltage you should be fine. I have tried mods on Nicad, Li-ion, and they all work well and last uber long. I can also condition and analyze all my batteries for great performance and capacity.