I am am putting together a NG lithium bank of 4-200 AH Batteries. I was planning to use the LYNX Distribution and LYNX BMS. How do I determine the cable and fuse side from the batteries to the LYNX Distributor and from the BMS to load bus. Is there a percentage of the possible load I should use size to largest single load. I don’t need to scrimp on cost or performance just the ability to fit larger cable in the battery locker.
Local regulations play a part but this is some general info.
I have made some specs up here to make life easy.
What is the max from the battery if this is eg 200A just work with this but i would recommend sizing this way all dc loads by adding up recommended fused for them as a 3000va multiplus at 48v uses around 60 amp but needs a 125 amp fuse for peak use. so in this case dc load would be 125 amp and i would go up a fuse size to 150 amp. Add up charging using a similar method 40 amps for a 30 amp charger based of the reccomended fuse size and lets say 30 amp multiplus charging but ill go up a fuse size although it has the 125 amp fuse That would be 80 amp charging so the battery cable and battery has to handle whatever one is larger as the inverter cancels out charging current ect. You can add them and that is better but you need it the smallest. and go up one cable size from what is needed.
I do not mean going up an actual fuse size but it is a nice margin of saftey in the calculations i can work out from your specs
I hope this makes any sense
The battery fuse sole job is to protect the cable so you don’t start a fire. Battery side fuse sizing must not exceed your battery wiring ampacity rating or the battery max current rating. If you have wired the system to only accomodate the current of the largest single load and not the max rated battery current, then you need to fuse to protect the wire ampacity. The battery side fuse MUST be a class-T type.
Wire ampacity is the maximum amps a wire/cable is rated to pass, regardless of length. You need to follow the ratings for the wire you are using. Different manufacturers have different ratings for the same size cable so you must know the rating to determine the ampacity. If your wire doesn’t have a rating stamped on the wire itself or any specification info you probably bought ■■■■ wire so need to be extra conservative so as not to start a fire (which will make the savings of ■■■■ wire evaporate).
You didn’t provide enough info about your planned system to recommend specifics. Knowing the system voltage and battery configuration (like series/parallel, 12v 1s4p), specific battery model. I’m inferring from your post info of “200ah” and “tight battery locker” that this is a 12v system likely used in a van/rv/boat. This is would result in very different recommendations for cabling and fuses compared to 4 x 200Ah 12v in series to make a 48v system. In a 12v system with 4 batteries in parallel, each battery should be individually fused but you can also use a smaller gauge compared to a single battery, since the current draw will be distributed. While a single 12v battery supporting a multiplus-ii 3kva inverter would require a 400A class-T fuse and 4/0 wire to accomodate the peak load, 4x12v in parallel spreading the load could be fused/cabled as low as 125A class-T and 4awg wire (in my head I’m assuming Ancor brand wiring and lugs:)
You need to do a power budget and estimate peak current demand. Then size the wiring by ampacity to exceed the max demand, then fuse below the ampacity rating with a class-T fuse on each battery.
Thank you for the info, I solved it and now know the correct sizes. I don’t have the time right now to give the details. Thanks again.
R