My first adventure with flying with batteries was a trip to Germany. I constructed a home made battery for my Netbook computer to extend the run time to many hours. It consisted of 10 “D” size Nickel Cadmium batteries that were soldered in series with small wire. (That way the wire would keep the current low and dissipate the energy slowly.) The batteries were in a common Radio Shack plastic box with zip cord powering the computer. I was able to use the computer for most of the flight to Germany. What I hadn’t prepared for was the German security folks demanding I disassemble the battery before they would let me board my flight. From then on I didn’t try to carry anything homemade on a commercial flight. It it necessary that I carry 200WH of battery when traveling to third world countries where the power was unreliable. The obvious choice was a couple 8AH 12V Sealed Lead Acid batteries. (They were the safest battery I could carry that had sufficient power for my needs.) According to TSA all I had to do was keep the terminals from shorting out and I could fly with them. The safest place on a commercial aircraft is in the cabin, packing batteries in checked luggage is not preferred by the airline. As time went by it became increasingly troublesome to have these two batteries in my bags and I would get delayed trying to explain them to TSA check point. My final flight with them was when a female TSA supervisor insisted that I check the batteries and not carry them aboard the aircraft. (I was unable to sway her decision so I checked them on that trip.) I wasn’t comfortable carrying two 100WH lithium battery packs in my luggage so I bought 24 individual lithium cells that were about 10WH each. I bought six USB battery boxes that could safely carry four individual cells each. Believe it or not, I never had anyone question me about the USB battery packs or the 24 lithium batteries I was carrying, even when returning from a foreign country. I was confident that if a single cell went awry that it wouldn’t heat the adjacent cell sufficiently to cause it to fail. I was pretty sure I (Or flight attendant) could safely pull an overheating cell from the USB case in flight. I found bicycle battery packs that I put the cells into once I got to my hotel room. I still travel with them to this day.