Okay, so it's an indeterminate future where power is at a premium. Things happened that reality has not seen, like laser rifles and a Detroit that would make The Old Man from Robocop proud.
So why not assume that batteries sometime became more universal? Rechargeables are more readily available to people than ever, so maybe someone created a new standardized battery that works for multiple objects: small enough to fit goggles and flashlights and off-brand electronics that use removable batteries. The reasons I have for mentioning this are a few:
1. Cut down on resources. Laptops still use those bulky batteries, but it saves on stuff the game has to account for.
2. It makes sense. The military would want a setup that makes things more foolproof, at least in an ideal scenario.
3. It's happening now. Look at digital cameras, where more powerful models use their own power supply, but mid to low end DSLRs can accept regular batteries or options to accept them. Performance is debatable, but it still is common.
4. You can justify energy transferring better. Say they figured out a way to trickle the energy over in an efficient setup.
Off-topic here, but I am also curious about seeing if batteries can be handled like lighters: at 0% they're dead but still usable. Probably more of a pain to program though, right?