Orlando,
I don't have a rc4wd hoe, but the batteries sound like it runs a 3s 11.1v lipo - which come in many sizes, capacities and current ratings...
See
http://www.rchelicopterfun.com/rc-lipo-batteries.html for more info around lipo batteries... They do need a little bit more talc than nicads(nimh)....
For initial setup you might run a 7.4v(2s) battery to slow the pump down whilst you get the bubbles out of the hydraulics...
They should have some initial start up guides with the hoe as well... I am sure someone here will help with any questions as well.
Cheers,
AP.
P.s. Congrats on the purchase