Wii controllers keep losing connection. What can I do?

It is highly likely that this issue is not the result of interference. Interference is often indicated by erratic or inconsistent behavior rather than disconnection.

It is possible that your battery terminals have become damaged or bent out of position. The act of performing in-game motion controls may be temporarily unseating your batteries, causing the disruption. Rechargeable batteries can sometimes be the cause of this issue due to the fact that some brands differ slightly in size than traditional batteries. Jamming in slightly oversized batteries can bend or push contacts out of alignment. This can result in the oversized batteries working perfectly while any differing brands or types of batteries do not.

My suggestion is to try to use the same batteries or a replacement using the same brand and type to see if this rectifies the problem. It is also possible however that the wii-motes are permanently damaged.