It also doesnt help when you have a very low starting voltage.. the fact the chips CAN boost say from 5 top 20V doesnt mean they will be efficient at such setting... I use MT3608 powered from 1S lithium batteries... whith fully charged battery and output at 5-9V there is no problem drawing 1A (chip is spec'ed up to 2A)... doing the same at 12 V is trickier, chip starts heating up ... over 12V efficiency drops further and you can draw 200-500mA up to 15V maybe but its best not to stress it so far... I think at 24V (from 4.2V) you can draw as much as 50-100mA continuously but its still hot... I am not an expert per se, just sharing my experience!