Removing bolts on B- and C- on JBD BMS without tearing it apart?

[ZeeMox]

This thread concerns the bolts/nuts holding the thick black/blue cables on my JBD 200A BMS. These are 4 AWG cables, and using the information in this thread I established that for my battery, it would be wise to replace this with 2/0 cable. Problem is, these nuts are so tight that there is no safe way for me to get leverage without potentially exploding the BMS due to the amount of torque applied. It really seems as if they did not intend anyone ever remove these... ever.

Cliffnotes from the other thread, this is a 24 volt battery using 8 280ah blue eye eves, and i intend to use it with a roughly 3000 watt inverter. I'm hoping someone here either:
A) might have swapped these cables themselves and knows a trick or two, or
B) can tell me this is a fool's errand and i don't need to be doing this at all.

Appreciate any help y'all can offer. Insulation on the stock 4awg cables is rated for 200c. It's important to note that these cables are both part of the circuit and are not splitting their load.

 

[Samsonite801]

If it were me, I would hold it by the lug and not by the BMS body when I was applying the breaking torque. Maybe a vise-grip carefully clamped to the cable lug on the one side, and clamped to the copper plate lug on the other side. And if twisting force of a ratchet or wrench didn't 'feel' good like it would break free decently easy, then I would try zapping it lightly with an impact gun (like a smaller nut driver gun or 3/8" drive impact). The impact should jolt with hammering torque and make it pop loose with out feeling much twist on the unit as a whole... Impact always breaks loose a tight bolt, where consistent turning torque doesn't feel right (make sure the direction is set correctly first, righty-tighty, lefty-loosey).

 

[42OhmsPA]

As Samsonite801 mentioned, use an impact. If I ever have to loosen mine I'll grab my 3/8 Fuel and give the trigger one quick tap. If I didn't have the impact I'd try a hex driver. If I didn't have either I'd figure a way to secure the BMS and give a wrench a hard blow with a hammer.

 

[ZeeMox]

Thank you guys so much. Don't know why I didn't think of the impact gun. Even with it, it took a lot of work to get B- off. They appear to have used some thread sealant on it. That was my last hiccup and now I have my first working DIY battery assembled and functional