Yep! Lot of power! What about shorting the secondary and measuring the current with a current sensor like this:

http://www.allegromicro.com/en/Produ...Cs/ACS712.aspx

on a breakout board:

http://www.dx.com/p/acs712-5a-curren...7#.VLRjedKG_CY

[Board Admin: I'm sorry for the ad , I'm sorry! I'm sorry!]