![]() That will depends on your thermal budget for the cells, which will of course be heating themselves at 135/270 A. If you are happy for the batteries to absorb some heat from the connecting wires, then this will increase your rating of the ampacity of the wires. Note that short wires are effectively heat-sunk by the battery tags/faces. 'Short wires for battery packs' are specifically mentioned, in that you should do your own tradeoffs for that application. You are told the ratings are conservative, so it sounds like you could get away with some stretching. It's not even clear what the single strand rating really means in your context. Double the mass of the wires, double the heat that can be absorbed.īut as the description says, those are guidelines. If it's based on a very short term adiabatic (no time for heat from the wires to diffuse into the environment) pulse, then yes. As the thermal heatsinking capacity has not doubled, the ampacity rating will not double. Both heat-producing wires are sharing the same thermal environment, heating the same air-space, heating the same battery faces. If it's based on the long term temperature rise, then no. Will it be 2x the rating? It depends on what the 'rating' is based on. Two parallel strands of wire will have a higher rating than a single strand. Contact your local electrician to find out what is legal! NOTE: For installations that need to conform to the National Electrical Code, you must use their guidelines. For short lengths of wire, such as is used in battery packs you should trade off the resistance and load with size, weight, and flexibility. The Maximum Amps for Chassis Wiring is also a conservative rating, but is meant for wiring in air, and not in a bundle. The Maximum Amps for Power Transmission uses the 700 circular mils per amp rule, which is very very conservative. In careful engineering the voltage drop, insulation temperature limit, thickness, thermal conductivity, and air convection and temperature should all be taken into account. As you might guess, the rated ampacities are just a rule of thumb. In other words, how many amps can it transmit? The following chart is a guideline of ampacity or copper wire current carrying capacity following the Handbook of Electronic Tables and Formulas for American Wire Gauge. Larger cables may be necessary if the distance from the inverter to the battery is greater than 10 feet (not recommended).From the chart you linked to, I'll reproduce the definition of ampacity, with my own highlightsĭefinition: ampacity is the current carrying capability of a wire. The table below will help you choose your cable size and fuse or breaker size for a common inverter. Recommended Inverter Cable and Overcurrent Protection * The overcurrent protection device may not exceed 30A for 10 AWG wire, 20A for 12 AWG wire and 15A for 14 AWG wire.įor ambient temperatures above 86☏ (30☌), multiply the approved ampacities from the table above by the correction factor listed under the insulation temperature below. Circuit length is 50’, circuit type is ‘non-critical’, and correct wire size is 4 AWG. The NEC code allows rounding up cable ampacity to the next standard fuse or breaker size. The table below displays approved ampacities of wires in conduit, raceway, cable or directly buried, based on an ambient temperature of 86☏ (30☌).
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