Battery connector and wire ampacity

Question

I’m considering using a JST ACH connector with my LiPo, but I don’t understand whether the current rating on the data sheet is for aggregate or for each wire individually (which is my guess since they won’t all connect the same direction). The current rating doesn’t seem to line up with the wire gauges though, based on the ampacity charts I’ve been able to find. I’ll lay out my requirements, then my questions.

I’m using a standard 3.7V LiPo, with 1-4” of wiring. I’d like the wires to support up to 1A of current. The wires will be stranded (for flexibility), though I’m not sure how many strands or whether it is copper or aluminum (maybe assume aluminum for a margin of error, since it carries the lesser current of the two). Currently, the wire I use is 30AWG. The wires will be inside a housing with the rest of the project but will not necessarily be bundled or shrink wrapped together.

Questions:

• Most ampacity charts show only single-stranded copper ratings, with only tips regarding wire variations. Do these charts apply as much for such short lengths of wire, or are they really intended for use when running long lengths of wire?
• How can the connector support such a high current for so small a wire gauge (28-32AWG)? Note that this product page states:

  These connectors have a 2.0 A current rating for both two and three circuits using 28 AWG wire.

• Am I just being paranoid? I really don’t want wire burning up near a LiPo. I’m considering selling the project on Tindie, so would like it to be safe.

Answer 1

There are a lot of factors to take into account when dealing with power transfer and heat dissipation.

Almost always, conductor and connector datasheets refer their current limits based on the tolerated heat before the insulation start to fail (usually with quite a margin to ensure not only the integrity of the insulation but also to guarantee its longevity)

But, the connector/conductor can most likely tolerate more in some circumstances:

1. If the average current is bellow (if you only have bursts), and the periodicity of the burts is big enough to let everything cool down
2. If you implement some sort of forced cooling of your system so the temperature stays bellow the manufacturers recommended operation (+85°C for your choice of connector)

Thus the AWG rating of the conductor or contact resistance of the connector is relevant to extrapolate the elevation in temperature, but the current limit will be determined by the insulator ability to sustain that heat.