Various ones. Some have Smartech, Traxxas, really old Futaba, etc. I will check it out.

Remember that 7.2v and 8.4v are the NOMINAL voltage and not fully charged.  

But he is correct, look up your various esc's and they will be able to tell you.

Depends on the esc if it handles the higher voltage.
Should be fine if it handles 2s lipos.
Also what car & esc is it ? (Should be able to look up specifications on it if you visit the manufacturers page)

Depends on the esc if it handles the higher voltage.
Should be fine if it handles 2s lipos.
Also what car &amp; esc is it ? (Should be able to look up specifications on it if you visit the manufacturers page)

After seeing recently where someone used a 7 cell pack, I started wondering can any car take this? 

How do I know if I can use 8.4v packs instead of 7.2?