I personally strongly believe that 20A is a myth. Even 10A is one. You always have contact and wiring resistances. Look at it like this: 20A over 100mOhms (which is a very low resistance value) causes 2V of drop, i.e. you electronics will instantly go to undervoltage reset. The equilibrium will be reached at a much lower drain, I do not have any data to support where but my informed feeling is that even extreme neopixel builds will not exceed 10A (probably 5A-7A is a better estimate). Therefore 5A seems to me like a safe value for the RC port. Since it's purely a mechanical Switch, I guess A.) it has a huge tolerance B.) worst Thing what can happen is that it will fuse together or slowly wears out (i.e. even with a kill key inserted it will not be fully disconnecting). A thing which in my experience happens anyway after a few years.It's not a myth, it's reality, it's been tested. Measure the current drain my a 20A multimeter, you will see. Here is a tested real current drain with different number of strips powered by a 15A battery, and as you can see we get exactly 9-10 Amps at full brightness White color mix with 2 strips:
There is no disagreement here, only different use cases. Your test results are consistent with the golden reference (see here: https://github.com/Protonerd/DIYino/blob/master/Neopixels_Characterisation_report1.pdf
), which gives credit to your results. As you can see, with 2 stripes 143 each and full whote you can easily reach over 12Amps.
The point is, your setup is based on ideal conditions for the stripes, which is not a realistic use case for a saber. In a saber you will have losses, effectively reducing your voltage supply at the stripes, and with lower voltage the current draw will also decrease.
First of all, you want to have a decoupling with FETs. Even the most common setup with 3 of them in parallel will have an RDson of 100+mOhms, at 10Amps they alone would contribute to a supply loss of 1V. At 2.7V the LEDs have already about half the current draw. As the current of LEDs is not a linear function of voltage, the working point will be reached probably at a slightly higher voltage. Then there are the connectors, adding further, albeit small IR drops.
Plus as in the higher PWM ranges the current draw increases not in proportion to brightness gain, saber boards usually do not drive the LEDs fully, not to waste energy unnecessarily.
So it all adds up to a lower current.
Plus a full 1m blade is a kind of rare thing, most people tend to use 120 or less pixels in a blade with 80-90cm. White color is also a rare main blade color, it is mostly used for clash flash, which takes a couple of ms, therefore can be considered a pulse load, for which often other ratings apply.
In my humble experience, I never managed to trip the 10Amps, although I had a couple of saber builds with 3 stripes.
Jason is planning on supplying the community with more precise measurements, so let's wait for his results, with his many awesome builds he accomulated a lot of experience with pixel blades.