(To make this short, the opening is the only thing that saved this show).
At first, I thought Battery would be another sport anime, following the same path as, almost, every sport story out there, but, all in all, you would still enjoy it.
I was wrong.
While it's nice seeing something different, and exploring a different side of the sport genre, it doesn't mean that it would be a masterpiece, that just because it's different and refreshing it would automatically mean that it will be amazing.
Battery wanted to add all these drama to middle schooler baseball players, it wanted to make it complex: not just kids playing sport for fun and just wanting to win, but it wanted to show the drama 'behind the scenes' of a team, and what it takes to form an actual relationship with your teammates. Even though that was the purpose of it all, it, in lack of better words, sucked at it.
From the start to the very end, everything was too dramatic, too out of their middle schooler sense: non of the character grew throughout the serie, actually, they were all really plain and with annoying traits, while it was understanding that some of them were stubborn (since they are still 'kids'), it got to a level where their behavior didn't justify their actions. Conflicts, as little as they were, didn't reach a conclusion even when the last episode ended, the relationship between the characters (mostly Takumi and Gou, aka our MC) stayed the same, even when 'time already had passed by', where they didn't learn from their past mistakes.
It also falls into the same abyss as most shows: a lot of characters, too little development. Not to mention that, whenever they play, it's not exciting because there's no attachment to any of the players, there's no interest in the game since the show didn't prepare you for it, it doesn't make you feel hopeful for the MCs team, it doesn't make you anxious because you want them to win. Of course, the main idea wasn't the team playing baseball.
You could say that Battery was aiming for something refreshing, but they missed the mark by quite a lot; while it's nice not wanting to fall into the same old clichés as most sport anime, Battery didn't know how to play its cards to make it into an interesting and memorable show.