Battery cable ampacity

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Eros

Member
Location
United States
There are charts everywhere showing battery/welding cable ampacities. Where is the most reliable place to find the ampacitiy ratings for the cables from the batteries to the inverter as well as battery to battery. ? Thx
 

480sparky

Senior Member
Location
Iowegia
I'd use the various charts as a guide but not the definitive answer. I would also upsize any cabling a size or two just to cut down on VD. Myself, I can only draw 175 amps on my system, but I used 4/0.
 

Smart $

Esteemed Member
Location
Ohio
For work under NEC purview, terminal temperature limitations will set your maximum ampacity [110.14(C)]. This will typically set your limit at the value for size in the 75°C column of 310.15(B)(16) as noted by ramsy. There is a technique that can get you up to the 90°C value, but for short runs it's not economical.

Not sure what a battery terminal temperature limitation is. Anyone?
 
Location
MD, USA
Occupation
EE
There are charts everywhere showing battery/welding cable ampacities. Where is the most reliable place to find the ampacitiy ratings for the cables from the batteries to the inverter as well as battery to battery. ? Thx

Ampacity for conductors should be obtained from the manufacturer - they'll typically site a particular NEC article/table.

Btw, welding cables are not listed for anything other than welding or temporary installations. They are certainly not listed for running in conduit. My understanding is that heat dissipation for these types of cables are different than typical permanent wiring conductors.

I'm dealing with this situation at the moment where the EC installed welding cables to connect UPS battery cabinets to separate UPS inverter cabinets and ran four current-carrying conductors in conduit. When I started asking Southwire how do you derate welding cables in conduit, they said you can't, since it's not meant for conduit applications. Let's see what the AHJ says.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Ampacity for conductors should be obtained from the manufacturer - they'll typically site a particular NEC article/table.

Btw, welding cables are not listed for anything other than welding or temporary installations. They are certainly not listed for running in conduit. My understanding is that heat dissipation for these types of cables are different than typical permanent wiring conductors.

I'm dealing with this situation at the moment where the EC installed welding cables to connect UPS battery cabinets to separate UPS inverter cabinets and ran four current-carrying conductors in conduit. When I started asking Southwire how do you derate welding cables in conduit, they said you can't, since it's not meant for conduit applications. Let's see what the AHJ says.
Most manufacturers provide an ampacity based on operation at 90°C and in free air. Not an ampacity that can be used for an NEC application.

As far as using welding cable, there is some on the market that is dual rated as both welding cable and RHH or RHW. The dual rated cable can be used for NEC applications. The same applies to DLO cables. In both cases, if it does not have the dual rating, it cannot be used for NEC applications. Also don't forget that those cables are fine stranded cables and need terminations listed for use with finely stranded conductors.
 
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