Could it be the Robotech RPG books or possibly Robotech Art 1. You mention Battletech, so was it one of FASA's old BT books? Sorry I can't be of more help (need more info)
Welcome aboard, Roberto! Hope to see you around here again soon. Feel free to make yourself at home here -- we RRers are a friendly bunch. We primarily talk about RT, but any topic is welcome. And sorry for taking so long in replying to your message. I've been rather distracted as of late. Anyway, concerning your inquiry...
Based on the description of the book(s) you're looking for, I think you're talking about the old Battletech Technical Manuals, in particular the first couple volumes. (In total, I think there were around six, maybe more, released.) If you are, then you've got quite a hunt ahead of you since those early Technical Manuals are LONG out of print. Your best bet to find them is to probably check eBay from time to time and/or some of the on-line gaming stores. Good luck!
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Could it be the Robotech RPG books or possibly Robotech Art 1. You mention Battletech, so was it one of FASA's old BT books? Sorry I can't be of more help (need more info)