Consistent 5V - external power

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Many threads in this forum show how the 3.3V-4.2V tiny batteries are not powerful enough to run many stacked boards on battery supply.

I have similar experiences. The code works fine on USB souce with 5V but when I switch to the tiny 290mAh 3.7v battery the green light just barely runs and wireless transmission etc breaks down etc.

So here is my question, how can we get a more consistent 5V / 500mA (or whatever is required) power supply to the tinydinos?

The tinydino processor board description states the following:
>>External power supported with a 0.1″ power connection holes. Supports automatic switching between +5V USB and vbatt

One option is to solder a external power supply to the processor board - can someone explain me in simple terms how to do this or point me to a tutorial please? E.g. how would I solder a powerboost 500c board to the tinydino processor board?
 https://www.adafruit.com/product/1944
Thanks for any help

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I think I found the answer myself - I just solder wires to the + - on the other side of the battery jack and solder these wires to a 2Pin block on the powerboost.
Or I connect a usb cable from the powerboost to the tinydino.

Still a question: Why do the tiny batteries not provide enough power for stacking lots of boards? Would be a much cleaner solution.

Any suggestions?