Battery fuse depends on your max potential battery load. Guessing it's a 12v system, 200A will be enough for load of 2600W or so. if your max realistic load is less than that, then reduce that fuse down accordingly. E.g for a 1000W inverter that might get max loaded at 1500W, so fuse becomes 1500/13=120ATheOldHObbit wrote: ↑Sat Oct 15, 2022 9:03 pmI hope I have done enough for the fuses, I have a 200amp at the battery and an inline fuse from the PV panels of 30amp 1000v. When I have the stuff mounted on the board, and the battery where I want it, I will order pre-made heavy duty cables at the right length. This is all new to me and electrics are certainly not my strong point, but hopefully I have judged it about right. My run from the panels to the controller is about 5m so I have ordered 6mm for the job. Thank you all for your responses........Yorkshire Andy wrote: ↑Fri Oct 14, 2022 9:42 pm Just remember fuse it fuse it and fusebox everything ..
When you see how hot a big battery can get wires you'll get why it needs fusing
Also make sure that inverter cables are crimped properly
In reality, I'd suggest a lower value than load might dictate. In that case maybe 80A. Fuses can carry a bit more current than their rating. Besides a short circuit that can blow 100A would make a big bang at the weakest point. I dread to think whether your short circuit necklace would evaporate before your 200A fuse blew. I've seen what a car battery and a careless spanner and wedding ring can do.
As to fusing the panels... Someone will shoot me down here, but why bother??? If they can deliver a max of 30A, you will have provisioned cable able to carry 30A and short circuit condition could only get 30A. AIUI, Panels don't get damaged by short circuits.
As I discovered, Inverter cables need to be fat and low resistance, not just because of the heat they waste, but because if they can drop a volt each, even without getting warm, they can trip the inverter under voltage protection (10V in my case). Personally, I provisioned these generously, to allow for expansion. There are all sorts of loss/metre calculations and stats and its a trade off between the price of copper and the energy loss you can afford to make. Plus you don't want them to overheat.
YorkshireAndy's the go to guy for the details of fusing, but watch him. He makes you buy stuff
As Yorkshire Andy indicated, the quality of the crimping is as important as the cable itself. Also, get your custom battery cables with the right sized holes. Many are 10mm where you should have 8mm. I like to use split washers under any connecting nuts especially the ones on the inverter.
