Suggestions on battery booster.

So I’ve been thinking about getting a battery booster since I often ride with just a few other people, and sometimes alone a good ways out (yeah I know not brilliant). My buddy killed his battery on his new X3 RS a month ago on the trails and this would have saved his day. Question is, if I get one big enough to start my 6.7 is it too much to use on the X3? I’m assuming the booster is smart enough to limit the power on a small battery/machine. Electrical is not my thing. Any input on a decent unit? Looking at the Yesper below after watching the Project Farm YT review of several. Don’t want to spend 200 bucks on one, but will if I have to.