From a gameplay perspective, fusion cores make perfect sense. Power Armor would be overpowered otherwise.

But they aren't mentioned in the other games (IIRC), and I've seen folks sleep in Power Armor before. Is there a lore-reason only the Sole Survivor needs batteries for their armor?

is there a lore reason settlers have infinite grenades?

To me it's just a matter of gameplay and a way to keep the player from basically living in the power armor. I had a tendency to do that in Fallout 3 and New Vegas, however, I have plenty of fusion cores to suit my needs and I've completed most of the game's quests and am at level 52. Come to think of it, this is a short game.

I'm well aware of the gameplay aspect.

It just irks me is all.

It's a retcon, power armor models starting with T-51 originally had batteries that lasted for years - if you want to headcanon it, you can argue that those original batteries have all gone dead after 200 years of sitting around. (let me take this chance to http://www.nexusmods.com/fallout4/mods/8294/? my mod once again =D)

As for why NPCs don't use up Fusion Cores, it's the same reason non-companion NPCs get infinite ammo and unbreakable power armor, and why some of them can't die - gameplay. Plenty of story situations where the NPCs talk about running out of juice, like the Battlefield Holotape in the Lost Patrol or the soldier's log near the crashed vertibird in Concord.

Maybe what is established in Fallout 4 is the lore from now? We finally know what that big wheel on the back of the power armor is for, that's for sure.

In hindsight, it makes the resource scarce Mojave chapter look silly; wasting all those precious fusion cores...

There's not a lore reason for only the Sole Survivor needing fusion cores. That's just a game play mechanic. The same goes for ammo. You can give settlers 1 bullet and they'll have infinite ammo. That's because if you were to try equipping all of your settlers with an actual supply of ammo, you'd go through it like crazy. Making sure that settlers stayed supplied with it would be an incredibly tedious task.

I have enough power armor now that I leave several suits with cores in them in my bigger settlements. There needs to be a core in it for them to use it, but they don't drain them. It'd be a pain in the ass having to go around to all of my settlements and make sure that these suits always have charged cores. The same for companions. Sometimes on a long trip with power armor I'll go through a few fusion cores. If I had to supply companions with them, they'd go quick. They'd either have to put way more lootable fusion cores into the game or they'd have to make the suits way more efficient otherwise.

Power armor in general has gotten pretty thoroughly overhauled in Fallout 4. It's becoming more of a standalone vehicle of sorts now, whereas previously it was more of just a really powerful suit of armor. I think the new power armor system is a huge improvement. I love it.

While can appreciate a person that knows how to code, it seems to me using that mod is a kind of God Mode for power armor.

I have over 700 hours game play. I am currently on my third character. This one i intend to keep. Finding fusion cores is easy. Buying them is even easier. Currently I have somewhere in the area of 300 cores. With probably no more to be found I just buy them. It is the perfect cap sink along with rockets. Even when i only had a few cores, I never came close to running out of power.

I would venture a guess that most people know using God Mode in a game is cheating.

In my opinion using God Mode for Power Armor is a cheat.

Sorry, had to say it.

Fallout 4 is the first fallout game where I went and used Power armor for more than one battle!

In fallout 3 and NV, my power armor just sat in storage as I slay stuff while wearing leather.

Enemies is kinda better positioned to deal harm to me than before. So if I assault an base, like raider base.. I bring power armor and won't die right away just because a raider snuck up on me while fighting few others.

In previous games I generally just stuck to 10mm and 9mm pistols and beat the game with them unless i'm fighting a pretty tough enemy.

But in fallout 4, i'm constantly having to switch weapons depending on what kind of enemies I'm facing. Its quite a novel experience getting to use all kinds of weapons I haven't used before. Like gamma gun, missile launchers, etc. lol

Definitely this, found myself having to use melee for a while because I had no bullets. First time ever in any fallout game using melee and I realize it's much more fun than guns.

It's not a retcon, it's a game mechanic that has nothing to do with the lore of fusion cores.

As far as I'm aware, there's nothing in-game explaining Fusion Cores or the Frame system. My personal headcanon is that both are prototype systems unique to the Commonwealth, both focused on minimizing downtime when a suit needed repairs. Unfortunately, the programs were still in their infancy when the Great War happened, so the systems we see aren't complete solutions; just initial advances that were still having the kinks worked out.

Honestly the frame makes senses. You can't just attach the playing to clothes. You have to wear a recon suit under the frame also.

I agree with fusion cores I have like 20 I just randomly found

There's no real lore justification, just an apparant retcon of "oh, they've always been used."

For people who complain- remember, the original lore stated they were good for a century or two.

It's been two centuries.

Would you rather be using the fusion core system, junk the entire suit after the battery dies down because you simply will not have the facilities or resources to refurbish the power source, or simply have FO4 be the first game without usable Power Armor as all the suits are dead/dying due to the afore-mentioned lack of appropriate facilities and resources? Something's going to have to give at this point, and retconning the lore to have replacable batteries that can last two centuries without use offers more future flexibility for the series than having Fallout 4 potentially be the last game using the iconic armor. And yes, Power Armor is iconic to Fallout, simply because it's the thing plastered all over the box art for all but two installments.

Going back to FO and even to its progenitor, Wasteland, PA always had fusion power. Why fusion? Because it needed to be a power source that never ran out. If PA ever "ran out of gas", it would become just so much inert metal until such time as more fuel was acquired. That would mean recharging stations, battery life expectancy, etc. = Maintenance. Most players do NOT want to do Maintenance; they would prefer to just use something than to "waste" time taking care of it. [One of the things the devs all along -- and even now -- have NOT taken into account is the probable explosion that would occur if the "fusion bottle" gets breached. They allude to that happening with fusion-powered vehicles that get caught in a crossfire, but never if it is PA that had it's fusion bottle cracked.]

Maintenance was introduced with the Repair system in FO3 for weapons and armor. Just skimming these forums, you get the impression that the majority of players were quite glad that the Repair system was removed. EXCEPT for repairing PA pieces + the new addition of fusion cores to power PA. Which, quite honestly, requiring frequent swapouts of fusion cores is kind of ridiculous. Fusion is a process, NOT any kind of battery. It's fission-on-steroids. The appeal of fusion is that once started, it is almost entirely self-sustaining. What is needed in the way of finite power is the "ignition switch". We don't have fusion as a power source in RL because we haven't figured out how energize the internal plasma flux with a REALLY BIG jolt of energy. (And then once started, keeping that much energy safely contained in the fusion bottle.)

As for lore for fusion cores, there is none. It only appeared just now in FO4. And has been suggested, it keeps PA from being too powerful, and gives players cause to crawl out of their shell from time to time.