What fuse

[saflyer]

I have two 12v LiFePO4 lithium batteries installed in parallel in place of the original 4 6v batteries in serial/parallel. The original setup had what I believe is one Class T fuse on the positive line from the batteries about 3 feet from them. A few questions. First, I watched a video that said any fuse should be within 7 inches of the power source. Do I need to move the Class T fuse closer to the batteries. If so it will require new cables.

A bigger question, though, is what fuse protection should I use. I’ve read Class T is best with ANL and MRBF fuses are next best in that order. What is more confusing is one person on a forum said I should have a fuse on the positive line making the parallel connection between the batteries and another on the line from battery two to the system. I’ve never seen anything like that. Would they be different size fuses since the second one would have to protect for twice the current of the one between the batteries? Nate Yarborough of explorist.life, a site for learning about van solar installations, has wiring charts that show just one fuse on the main cable connecting the battery bank with the battery cutoff switch.

Regardless of whether it’s one or two fuses can anyone help me with the size of fuse(s)? Like I said, the batteries are 12v. The max continuous discharge rating of each is 100a, peak discharge 200a(3sec) and max charge current is 70a, 40a recommended. I have my charger set for 50a max. Since there are two batteries in parallel should I size the fuse for twice these numbers plus a margin? I’ve heard 120% as this margin. So should the fuse be at least 2x100ax120%=240a fuse or 2x200ax120%=480a fuse for the peak discharge number? 
 

Thanks,          
Ed            
‘05 HR Ambassador