Fuse need to no what size MRBF fuse to fit to 12v 105 lifepo4 battery

DIY
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1

can someone help me please i want to fit a MRBF fuse to my 12v 105ah lifepo4 battery but dont no what size rateing to fit… things i run off the battery are 6 cieling spot lights …12v tv …12v fridge…the odd 5v usb …battery gets its charge from 2x100w solar panels and DC to DC charger

2

Sure. As a guide. There are a couple of factors that must considered.

  1. The fuse fault rating must be met ( this is to ensure the fuse and holder dont explode when trying to clear a fault. See manufacturers details of battery prospective short circuit current or calculate it if you have internal resistance(datasheet) and voltage ( V=IR ). Some companies expect you to rely on the BMS but would you trust electronics to protect your system ?
  2. The fuse rating (trip current) needs to be such that it wont blow when the battery is charging ( ie check what your charging current will be. ( or what the current will be if limited by the charging device) and also allow your loads to run without tripping ( do a maximum demand calc. what current will you draw?)
  3. The fuse rating must also be less than the derated current carrying capacity of your cable. So you need to size the cable first ( to allow it to carry your load current/charging current, be able to handle the heating effects of potential short circuit ( see k rating in AS 3008) and also satisfy voltage drop. So without detail, its an open ended question. I hope that gives you a start
3

And

  1. The fuse rating should be at least 1.25 times the maximum continuous current to avoid heating the fuse.
4

yes true. well said