What are you guys using to charge your spare battery? (link)

[Justin311]

Sprint sent me an extra battery when they replaced my TP (nice of them lol) but I need a way to charge it....looking around I see a huge range of prices, from $5-$45. This is one of the cheaper but OK looking ones on ebay ($8 shipped):

http://cgi.ebay.com/BATTERY-CHARGER-...1%7C240%3A1318

Whereas Expansys sells theirs for $40 + shipping:

http://www.expansys-usa.com/p.aspx?i=172160

Can anybody give me a recommendation? Don't want to fry the battery. I searched but everybody seems to be getting a charger when they buy their aftermarket spare battery so that doesn't help me.

Thanks!