Ok, I have an Eflite CX2 battery thats been sitting around for a little while. When I put it on the charger, the display says low voltage and wont charge. Is there a way to revive these things? The charger is a Thunder AC6... Thanks!

LIPO batteries cannot be shelved for a long time without being recharged to the storage level charge (70% I believe). You should never store batteries fully charged. if you have a voltage meter, you could check cell levels. If below 3V, then the battery cannot be recharged. Try a balance charge instead of a normal charge, and use a very low charge rate (say .1A) if your charger can handle it.

I have seen other tricks in other forums, but don't remember where...

I'm trying the NiCd low amp trickle, we'll see.

You must be using LIPO batteries with your Cx2. Don't charge with NiCd. You could cause a fire or explosion...

I've read where many people have successfully ressurected LiPo's using a low amp NaCd charge momentarily.. I'm talking .1 amp for 25 seconds or so. Search it.
http://www.rccrawler.com/forum/showthread.php?t=251562