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
Sure. As a guide. There are a couple of factors that must considered.
- 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 ?
- 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?)
- 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
And
- The fuse rating should be at least 1.25 times the maximum continuous current to avoid heating the fuse.
yes true. well said