For those of you with useful answers thanks for the input I expect I will get a fan based pad for normal use and I might lash out and spend another $35 and get the non fan based to see how it works for any long distance travel I do with out power.
Most of them are powered by USB. A fan or two doesn't draw much power. It's more the size that is a pain for travel. Good ones act as a USB hub too, which is nice. So you can leave a kb/mouse/etc. plugged into the dock and just pull out one usb cable when you move it around. I did that for a few years when a laptop was my only computer, and it's so convenient.
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