Wire gauge for diy 48v 280ah battery cells to bms.

Been trying to get my head around this one for my shepherd's hut build and I keep going round in circles, so thought I'd throw it out here.

I'm putting together a 48v pack using 280Ah cells (EVE, ordered through Fogstar) with a Daly BMS rated at 150A continuous. My question is really about the wire runs between the cells themselves and then out to the BMS — are people using the same gauge throughout, or sizing differently for the cell interconnects vs the main terminals?

I've seen some builds online (mostly American, mind) recommending 2/0 AWG for everything, but AWG sizing doesn't translate cleanly to the metric cable we can actually buy over here. I'm thinking 70mm² for the main positive and negative runs to the BMS, but is that overkill for a hut that'll realistically pull maybe 60-70A peak?

Also — are the busbars between cells a separate consideration entirely? Some builds seem to use the supplied copper busbars and only upsize the terminal cables. Is that the right approach or should I be looking at beefing up the cell-to-cell connections too?

Would love to hear from anyone who's done a similar 48v DIY build, especially if you've used a Daly or JK BMS. What cable did you end up going with and did you use a proper crimp tool or ring terminals from somewhere like BES or Wirecare?

For a 48v 280Ah pack you're looking at potentially massive discharge currents, so don't skimp here. Rule of thumb: work out your max continuous amps from the BMS, then size wire accordingly.

Most folk running similar setups use 50mm² welding cable between cells and BMS — it's flexible, cheap, and handles serious current. Anything less and you're just building a heater rather than a battery 🔥

Check your BMS spec sheet for its continuous rating. A JK or Daly 150A BMS needs properly rated cable or you'll get voltage drop and heat.

Also — keep your busbars as short as humanly possible. Did the same build in my static van last year and the difference proper short runs made to internal resistance was noticeable on the Victron readings.

What BMS are you going with @CornishBoater?

@DustyCaptain covered the theory but forgot to mention that your BMS rating dictates everything — no point running 95mm² cable to a 100A BMS that'll throttle you anyway, which is exactly the expensive lesson my Renogy setup taught me in the shepherd's hut last winter.

@Renogy_Nerd makes a solid point re: BMS dictating the run. Worth adding — keep those cell-to-cell interconnects as short and equal length as possible too. Unequal lengths = unequal resistance = cells not sharing current properly. Learned that the hard way on my cabin build with 16x EVE 280Ah cells. Also use proper lugs, crimped not soldered, and torque the terminals to spec (usually around 4Nm for EVE). Fuse as close to the positive terminal as you can manage — ANL fuse holder does the job nicely.

@CornishBoater this is almost exactly what I did for my shepherd's hut build, so hopefully this is useful.

One thing nobody's mentioned yet — don't treat all your cable runs the same length. Your cell-to-BMS sense wires are low current and can be thin, but your main busbars between cell groups and the BMS B- terminal need to be rated for your full continuous discharge current, not just peak.

For my 16S EVE 280Ah pack I used 50mm² welding cable (more flexible than automotive, cheaper than marine grade) for the main runs, which handles the ~100A continuous my Daly 200A BMS is actually spec'd to deliver reliably rather than its rated maximum.

Welding cable from a local supplier beat anything on Amazon for price — worth checking trade electrical merchants rather than buying "battery cable" branded stuff with a markup.