3.5 "Cool down" Magic System

[G.Cube]

Is there a well-tested and balanced alternate magic system that uses some sort of cool down set up? Prefferably something like X spell takes Y rounds before you can cast it again?

[mabriss lethe]

The closest thing to that is the Binder from Tome of Magic. Each vestige a character binds grants a handful of abilities. Usually a few passive abilities, an at-will ability and a "big gun" that can be used once every 5 rounds.

[Psyren]

There is one - the Recharge Magic (http://www.d20srd.org/srd/variant/magic/rechargeMagic.htm) variant from UA.

You will likely have to tweak it a lot to balance it properly however.

[RMS Oceanic]

I dunno about well tested or balanced, but there's a Variant Magic System from Unearth Arcana that appears to do what you want (http://www.d20srd.org/srd/variant/magic/rechargeMagic.htm). Most spell slots come back after a few rounds, but certain spells take 30 minutes/24 hours or something to replenish.

[PrinceOfMadness]

I don't know about 'well-tested' and 'balanced', but there's actually a magic variant in Unearthed Arcana where your spell slots recharge after a random number of rounds. Something like your highest level spell slot takes 1d6+1 rounds to recharge if you're a prepared caster, and 1d4+1 rounds if you're a spontaneous caster, with progressively lower cooldowns depending on what level spell slots you can cast.

Whoa, epic ninja.

[DR27]

Recharge is actually a pretty well balanced way to remove the 15 minute work day - casters can't nova, because they have to wait for their high-level spells to recharge. They can't blast encounters with obscene amounts of power, but can use a little less all day long. Tome of Battle is kind of a must-have with it though, so melee types have reason to be in the game. The recharge-esque nature of ToB really makes sense alongside the recharge magic system. The main caveat is that every encounter starts at max HP/spells available, but that could actually be seen as a boon to a DM who doesn't like having to guess how wrecked PCs will be after each encounter in the day.

I don't particularly like how OP Tier One classes are under the recharge variant, but the difference isn't that major if you realize that they are plenty overpowered under the current system. For me, Tier 3 works particularly well with recharge, allowing high-CR encounters all day.

[Grod_The_Giant]

A few years ago, DonQuixote created an incredible amount of material that basically makes magic work like ToB maneuvers. (http://www.giantitp.com/forums/showthread.php?t=224508)