Planar Battery - Balanced or not?

I've been out of the game for a bit. I could see a card like this being viable, feasible, and usable, but would it be balanced in the modern world? Would a card like this be banned the instant it came out or never played? Even better, if this doesn't sit where you think it should in power level, how would you edit it?

Seriously, treat this post as a complete noob. Do not worry about being too critical.




Thought process assuming 1 land drawn per turn:

Turn 1: have one land, cast it
Turn 2: have 2 lands, exert to add 2
    [Alternative: cast a 1 spell and exert to add 1]
Turn 3: Exerted
Turn 4: 4 lands possible, 2 mana charged, add 4 more.
    [Alternative: 1 charged, exert 1-4 to charge more]
Turn 5: Exerted
Turn 6: 6 mana charged, 6 lands possible, 12 mana total. Charge more or mega cast something.
    [Alternative: 2-5 charged, cast or exert more]
I figure by turn 6 in modern magic, you should be getting towards the end game where this could be viable.
If it is not balanced, what could slow it down or limit it more?
If underbalanced, what could speed it up a bit?

Would this be a better alternative?



[Edited 6/11/2024 23:21 EST for grammar]