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Battery Bank fuse - UPDATED QUESTION END OF THREAD

Kirsty

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Jan 21, 2022
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Could someone please help explain in layman's terms.... Why does this generic diagram of Nate's have a 400amp ANL fuse coming off the battery bank and then also mega fuses in the Lynx Distributor? Isn't this somewhat doubling up fuses. I can understand you need a fuse to prevent arc or whatnot when turning on or off the master shut off, but it's a Blue Sea Systems 300amp m-Series Battery Switch (so has a built in fuse itself?)

Thanks in advance for keeping your answers simple :giggle: I'm still learning :p


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Could someone please help explain in layman's terms.... Why does this generic diagram of Nate's have a 400amp ANL fuse coming off the battery bank and then also mega fuses in the Lynx Distributor? Isn't this somewhat doubling up fuses?

Yes, but it's good to have a fuse as close to the source as possible. It should also be a Class T fuse.

I can understand you need a fuse to prevent arc or whatnot when turning on or off the master shut off, but it's a Blue Sea Systems 300amp m-Series Battery Switch (so has a built in fuse itself?)

No. It doesn't have a fuse, and there will be an arc. They're just built to take it for the most part. You'll still need a pre-charge circuit if you have an inverter in the system.
 
A fuse is to protect the wiring after it. The one by the battery is to protect the large cable coming from the battery to the Lynx. Since the cables coming off of the Lynx mostly are of smaller gauge they also need smaller fuses so that they will blow quicker than the large one coming off of the battery. If you didn't do this the smaller cables would burn up if there was a short and you only had that main big fuse by the battery.
 
Thanks Sunshine_Eggo and Rhino, I understand you both.
I'll make sure to get a Class T fuse. I believe you are referring to a ceramic resistor to pre-charge before connecting inverter and yes I already have a 25w 30 Ohm resistor for that.
Thanks again!!
 
I have x1 CATL 302Ah LiFePO4 and x1 EVE 304ah LiFePO4. And I have x2 Daly 4s 250amp BMS's (and 3000w inverter for running AC in travel trailer). I'm going to configure them in 4s2p like the design below (Thanks FilterGuy for the great resource).

Just to double check: I can put my Blue Sea 400amp Class T fuse after the positive busbar? Each battery doesn't need it's own 400amp fuse now does it :cautious:? Cause the fuse is there to protect the wire and my wire will remain as 4/0 cable??

Also, to save me research and calculation time, what size busbars would you all suggest?

4s2p set up.png
 
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