planetary supplies ?!

Planets get their supplies from Resupply Depots - a level 1 resupply depot produces 5000 or so supplies per turn, and can distribute up to 1000 of those to other ships (and maybe planets) in the system.

Planets have inherent supply storage - take a look at the PlanetSizes.txt data file for details. Basically, larger planets store more supplies, but if they're domed they store less - same as cargo, facilities, and population. You can however build Cargo Facilities which store additional cargo and supplies - at least in Balance Mod; not sure if Cargo Facilities store supplies in stock...

Also, planets do not consume supplies when their weapons platforms fire in space combat. No idea why this was introduced...

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The power of the ancients is now yours to command. You are truly the Master... of the obvious

You can't increase the supply above the basic level the planet holds. (cargo facilities only increase the cargo (ie. weps platforms etc.) the planet can hold, not supplies) Best to build spaceyards on larger planets. You can build satelites and other orbiting vessels (bases) or supply ships that will allow you to transfer supplies to your new ships.

I believe you can put multiple Resupply Depots on a single planet.

When you retro fit a ship it takes the supplies from the supply pool of the empire right? And i always upgrade my supply tech to increase the storage amounts of my ore, food, and refining facility's. I didn't think it mattered for the planet its self, just enough resources, and the proper facility's to do the refit.

Yes you can build more then 1 resupply depot on a planet, i always try to build 2 on atleast 1 planet in every system i control.

Supplies != resources

Supplies are produced by resupply depots, solar collectors, etc. and are stored locally to a ship or planet. They are used to provide power to a ship's engines, weapons, and several other devices.

Resources are produced by mineral miners, robo-miners, etc. nad are stored in a global empire pool but require spaceports to get there unless you're a Natural Merchant. They are used to pay construction, retrofit, and maintenance costs.

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The power of the ancients is now yours to command. You are truly the Master... of the obvious

When you build a ship it takes the supplies from the pool. When you retrofit a ship it takes the supplies from the planet. If you build a yard on a small planet with only 5000 supplies and the ship needs 10000, it can only fill the ship 1/2 full before it runs out. The next ship to retrofit immediately afterward is left empty. Build large satellites or bases containing only supplies containers and solar collectors to resupply them.

If your retrofit will upgrade engines, just transfer the supplies off the ship before retrofitting. Yes it's a pain and it would be great if it happened automatically, but it doesn't.

If your retrofit doesn't upgrade your engines, you shouldn't lose the supplies.