The LiFePO4 batteries are a good option for portable radio operation. They are fairly light and pack enough energy to keep you on the air for a couple of hours. Of course, it depends on the power your rig is sucking out of the batteries, so you might be working for shorter periods. With the Yaesu FT857D, operating at around 35W, we could work for more than an hour at around 0 degrees Celsius.

The batteries come in a cylindrical shape, having a diameter of 38 millimeters and a length of 146 mm. We've seen them duct-taped in a pack, but it didn't cut it for us. When portable, especially when activating summits in winter, there's a good chance that sooner or later you're going to slip and fall. Protecting the radio and auxiliary equipment must be a priority, and so we needed some sort of a protective case for the new batteries.

The cylinders were packed in a matrix, side by side, with their ends fastened to two plastic plates (10 by 10 cm squares). The electrical links between the batteries were made from blank copper coated circuit boards (to be improved in the future). To further strengthen the assembly, the plastic plates were fitted at the corners with threaded rods , held together by nuts and washers. The entire assembly was then placed in a plastic box. See the pics below. To protect against short-circuits, another set of plates can be installed on the threaded rods, above the contacts. The entire case weighs about 1.5 kilos, about 3 kilos lighter than our previous (motorcycle) battery.

First, let's talk about the whole radio package that we take on a regular SOTA activation. This is not the ideal set-up by far, but this is what we use and it works. Our equipment is quite heavy, amounting to 8 kilos or so. There are others who successfully activate summits (usually in CW) with gear that weighs less than a kilo. We're only working in SSB.

1) Yaesu FT-857D with a vertical dipole antenna on a 7m fishing rod (for the 20m band) and a 12V & 12Ah SLA battery (from a motorcycle). These items alone weigh about 7 kilos.
2) Baofeng UV-3R+ with stock or aftermarket antenna for 2m and 70cm bands.
3) Motorola GP300 with a dipole for the 2m band

In the future we want to improve on this setup. For example we will make a dipole antenna that we'll use with the FT857 in the bands of 70cm and 2m, thus discarding the handheld transceivers. The battery that we currently use is a 12V from a motorbike and it weighs around 4.5 kilos, but we plan to acquire LiFePO4 cells to considerably reduce on the weight of the entire package (it gets about 3 kilos lighter). The coax cable is to be replaced in the nearby future with one of better quality (H155). Perhaps the 7m fishing rod could too be replaced, with a 5m one, if we decide to work in 21MHz.

Tarp - we use an old tent sheet. We lay it on the ground so we can protect us and the equipment from dirt, snow, etc. It's a dry place to put your stuff and to sit on.
Clipboard, paper and pencils - Logging is easy on a hard surface. Pencils don't freeze, run or stop working unexpectedly.  Even if you break a pencil, you can still make it work (maybe resharpen it against a rock). Additionally, we carry a small notebook and an extra pencil.
Wristwatch (set on UTC) - We always find a way to hang the wristwatch in a visible place, so when the pile-up starts we have one less thing to worry about.
Audio recording equipment - phone or music player - Audio recordings provide good backup for the paper logs. You can always go back and listen to what happened.
Foam mat - Sitting/kneeling protection from rocks and cold. It's a good insulator that provides some cushioning for those long hours spent at the rig.

Avoid cotton clothing! It dries slowly, gets heavier when wet and keeps you cold when wet. Use wool or synthetic fiber materials instead. They dry quicker and keep you warm even when wet, plus they don't get a lot heavier when wet (but synthetics are less skin-friendly). See some recommendations here (bottom of page).

Layered clothing (and depending on season/weather): t-shirt, long sleeved fleece, windproof and waterproof jacket; seamless underwear (prevents chafing), underpants (if cold), pants, over-trousers (in case of rain or wind); good pair of socks (pack an extra pair); gaiters (for snow and mud); gloves (fleece for mild winters, can operate with them; heavier duty gloves for colder temperatures); winter hat (also useful on cold summer nights); buff (can be used to protect face, neck, ears, etc. from cold - very useful); sun-hat in summer; light trekking shoes in summer and for easy trails, boots in winter or for tougher trails.

Extra stuff: sunglasses (whenever sunny, regardless of season); sunscreen; waterproofing spray or wax for boots and clothing (do it before leaving on the trail); trekking poles (good for a wide range of applications, including keeping dogs at bay and using them as antenna anchors); flashlight (headlamps are pretty good); fire source (matches, lighter, fire steel - you never know when you need a bit of heat); pocket knife; water bottle (with water!); food (energy bars or something small enough to carry around); GPS (with at least the starting and summit points marked); charged phone; map of the area; small pepper spray (for dogs); bear-spray (we don't have this, but it could be useful).

When hiking in remote areas you should tell people where you are going and for how long. Plan ahead, find as much information about your trail and hiking area as possible. Check the weather forecast. Always be prepared for bad weather. Take whatever medicine you might need with you.

At the top we look for the best spot to make camp. The main factor that influences where we set camp is the wind. If there's wind, we look for a spot with some cover, if possible. If there's no wind, then we set up on the best ground available (straight, no rocks, dry, etc). After we picked the spot, we lay down the tent sheet and start unloading the gear. We place the battery, the radio and all the items on the tarp and prepare the antenna. We use a 7m fishing rod which we usually anchor from nearby objects or tent nails with three ropes. Sometimes the snow can hold the antenna without any extra anchoring. After the antenna is in place, we connect it to the transceiver, then lay out the clipboard, pencils, a wristwatch on GMT and then we start calling. If we got cell coverage we also post a spot on sotawatch.org . When the activation is over (too cold, too hot or not enough power in the battery), we pack up (in reverse order) and hit the trails.