Battery Power

I recently purchased a Tak EM-10 (USD3) Mount and have researched portable battery options available. I am looking for a simple/portable rechargeable setup 12/18 v. What should I look for? Which system is the most reliable? How long do they last on a charge? Any help would be great. I've attached a photo of my setup.

Thanks in advance,
Thom

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i recently went thru the same purchase dilema..i purchased a 17ah sealed battery system(coleman jump start$60), a 350w vector power converter(walmart$45), and the tak 110v/24v converter($129). i use with an em-10 and it works fine for visual use..may need a larger battery if you are heavy power user.. i am able to run the em-10(at temma 250 speed) and laptop with no problems...best wishes...chip