I have the SG550, and I use the low discharge AA rechargables. It's very important that you get the low discharge ones since the regular NiMH lose their charge within a month. I ran my SG550 for 4 months on 8 low-discharge AA batteries, and it was still going strong when I brought it in to recharge!

I have the Imedion's and I got them here:

http://www.thomasdistributingshop.co...ies_c_199.html