Hey everyone, I’m looking for some clarification on conductor ampacity ratings as they relate to battery cables. My understanding is that the term ‘free air’ wasn’t actually defined in the NEC until 2020 and that conductors installed in a nipple, wire trough, conduit body, or enclosure don’t qualify as ‘free air.’ That said, I’ve noticed some battery manufacturers and installers seem to be applying Table 310.17 (free air) rather than 310.16 (raceway) when specifying conductor sizes—particularly for battery-to-inverter connections.
For example, a battery manufacturer offers a 48Vdc LFP battery with 10kW continuous output, which would suggest needing a conductor rated for ~245A (safety factor included). However, they provide a wire trough for the battery to inverter connection and provide a 1/0 Cu battery cable. This seems undersized if 310.16 applies. Am I overthinking this, or are these configurations typically tested and listed accordingly? I see similar situations across multiple manufacturers, and while I don’t put too much trust in marketing images, I noticed SimpliPHI using a single 1-1/4” conduit from a stack of 6.6 batteries to a 15kW inverter, which also raises questions. Is there a code-compliant rationale I’m missing, or are manufacturers and installers misapplying Table 310.17? I spoke with one applications engineer that referenced table 310.17 as the “battery cable table”. I get the value of running free aired battery cables with regard to ampacity allowance, but I also see the value in protecting energized conductors in a raceway. Would love to hear your insights! Best, Chris Sparadeo C_802-369-4458
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