Something I've completely missed on my first like 4 watches is that EVAs have exterior batteries that attach to their shoulder pylons, but they're only ever used during two scenarios I can recall- the battle with Matariel, in which they have to be discarded along with the rest of Units 00, 01, and 02's stuff because ???, and then again at the end of ep14 [the recap episode/the one where Shinji tries to pilot Unit 00 and recycled animation ensues] when Rei is in Unit 00 carrying the Lance of Longinus through Terminal Dogma to jam it into Lilith's body so she'll stop growing.
So, why the hell weren't these batteries used more often? Even if they add more weight, EVAs are most effective in hand-to-hand combat, so additional operating time would be infinitely more useful than a palette rifle or a prog knife. Shit, if Unit 02 had them during the fight against the Mass Production EVAs, Asuka might have stood more of a chance, taking her time to smash the Cores instead of just disabling each unit like she did. Ep11, during the fight with Matariel, gives us zero reason as to WHY the pilots ejected all their shit before Asuka came up with her plan to fight the Angel, like MAYBE it was so they would all fit in that little alcove in the wall of the shaft? I'm still rewatching the series so I'll keep an eye out if these external batteries get destroyed or we're given a clear reason as to why they can't be used. It's super weird that they're not mentioned on the other Evangelion wiki, and only given a very brief mention at the bottom of the EvaGeeks wiki's page on Power Sources.

That's... a good question actually. I vaguely recall a conversation I had about that ages ago with someone or other, but I don't remember what we concluded, if anything. I'd probably just write it up to it falling under the category of "bit of tech that made for a neat one time gimmick but noone thought about the implications of it"

I know this isn't a Rebuild discussion, but at least in Q they have replaceable battery packs (Mari has to get one for Asuka when she is trying to stop Shinji & Kaworu ).

^Yeah, this definitely felt like part of the original plan for the New Movies, remakes of NGE with some new stuff thrown in or reinterpreted

The external battery packs are large and are attached to the part of the Evangelion that normally interfaces with the launch platform, so maybe it's not physically possible to use the E-M launch system when the battery packs are installed.

That's a good point! However, that does make it out to be a seriously sloppy design, forcing a tactical choice between the EM launch rails and the use of extended battery power.

They can send in new equipment on the fly, new guns and such. Should be able to just as easily send the battery pack after launch, if during launch is a problem.
But if that is how it works, then I guess it isn't as big of a plothole, because you would have to request the pack specifically, meaning, having time and space to retrieve and install it. In the same manner how extra weapons were delivered, these are features hardly used, because battles don't last very long. And during battle its all generally much too chaotic and hectic to even have time for such things.

Think back of the times that battery power was an actual problem and then think if in those occasions if there was enough time to bother with an external battery.

Only thing that really comes to mind is Asuka's final fight against the MP Eva's, when hiding on the bottom of a lake with the intention to hold out there for as long as possible ... it would have been nice to have a few battery packs launched with her.

Both of you make very good points here, never thought of those. Gonna be worthwhile to mull that over for a bit, might be a neat concept for a tech study-type writing project

Asuka not having them in the last fight does make sense. It’s not like they had any reasonable expectation that she would be fighting, they literally put her in the bottom of the lake for safe-keeping (presumably, the power consumed by standby life support systems is negligible compared to the power required for actually syncing with and operating the Eva).

Besides, based on how they’re attached, the batteries don’t look like something that can be easily swapped out on the fly in the field. They’re big and bulky and attached at the back of the shoulders - not somewhere you can easily reach. Based on where they attach, I think it’s actually pretty safe to assume that the existing batteries are installed in the shoulder pylons - batteries take up a fuckton of space, and it’s implied that the Eva under the armor is basically entirely flesh with an entry plug jammed in its spine - you can’t exactly hollow out their chest cavity to put batteries in. It also makes sense why the “prototype” Unit-00 didn’t have shoulder pylons - it wasn’t initially outfitted for combat, and IIRC is never shown operating without an umbilical until after getting refurbished into the pyloned, blue version. It would also make sense why the MP Eva’s, having their own internal limitless power source, also lack pylons.

Sort of a fun fact - on modern nuclear submarines, there is a giant bank of batteries that are kept constantly charged by the reactor. These batteries don’t actually do anything… unless the reactor goes down, in which case they provide power for emergency lighting and life support systems… for a couple of hours, just long enough to troubleshoot and reboot the reactor. We’re talking about a massive bank of a few hundred batteries each weighing a few hundred pounds… all to provide just enough backup power to get your main power source up and running again in case of disaster.

So basically, the Eva’s were not specced for extended fights on a big battlefield. They were designed for fighting large, slow-moving single targets - the 5 minute backup battery is really there to provide just enough time to jump from one umbilical building to the next if the Angel jumps too far away - or to finish the job, because if you haven’t killed it in five minutes, it’s probably killed you.

Eva-00 does run on an umbilical system in Episode 06, the same as any other Eva, and its berserk incident in Episode 05 ends only when its batteries run out of energy. It uses both umbilicals and batteries. These could just as well be mounted in the chest, back or abdomen, under the Eva's armor. Even when Zeruel blows up the armor around Eva-01's chest, there's nothing to show that batteries aren't mounted there.

Also, the fins are quite specifically part of the Eva's restraints. It's why Eva-01 blows off the shoulder and fin armor when she frees her restrains in Episode 19 (going from robot-substitute to Yui Ikari's divine incarnate) and why Adam in Episode 12 has shoulder pylons: they're part of the built-in restraints (like the armor) meant to keep the Eva under Nerv's control and suppress its true power.

Archer wrote:
Sort of a fun fact - on modern nuclear submarines, there is a giant bank of batteries that are kept constantly charged by the reactor. These batteries don’t actually do anything… unless the reactor goes down, in which case they provide power for emergency lighting and life support systems… for a couple of hours, just long enough to troubleshoot and reboot the reactor. We’re talking about a massive bank of a few hundred batteries each weighing a few hundred pounds… all to provide just enough backup power to get your main power source up and running again in case of disaster.

Those batteries also power the "sneak motors" that can keep the submarine going very quietly at very low speed, just enough to maintain depth...or perhaps blow the trim or ballast tanks and get the sub to the surface when the reactor has a genuine emergency. They may be a backup to the reactor, but they're far more useful than you make them out to be.

Not REALLY the right place for it, but submarine batteries (at least on modern US classes, I can’t say anything about foreign navies) literally are only used as emergency backup in the event of reactor failure. Off the top of my head I don’t know if blowing the ballast tanks is part of that emergency functionality (certainly wouldn’t surprise me if it were), but I can say with near certainty that they are NEVER used for propulsion. You’re correct that electric motors are indeed much quieter than a mechanically driven propellor, but even on a boat with a hybrid electrical/mechanical drive the motors are going to be getting power directly from the reactors anyways. On submerged a nuclear submarine, the ONLY time the reactor is off is when something’s gone seriously wrong - as long as the reactor is still running, going on battery power for propulsion isn’t going to do anything to reduce its acoustic signature.