Spaceships series: Electrical Batteries module?

[Flyndaran]

Has anyone made such a module? It wouldn't just be good for ultra tech and overly optimistic battery tech. But also to make realistic things like diesel subs that ran silent on batteries while under water.

[vierasmarius]

I've considered it before. For designs that are intended to use batteries, I've usually substituted in Fuel Cells and called it close enough. However, batteries would have the advantage of being chargeable, and potentially being able to provide quite a high output for a short time. Unfortunately, the Spaceship system modules are, shall we say, "opaque". I wouldn't even know where to start in making a realistic battery module.

EDIT: Well, I suppose we could start at the Chemical Energy Power Plants (Fuel Cell and MHD from SS1, Internal Combustion and Gas Turbine from Pyramid 3/34). Since they're all available at TL9 we'll compare them there, using a SM+7 module as the basis. Each module is 15 tons.

Fuel Cell: 11.25 tons, provides 1 PP for 12 hours per 3.75 tons fuel (48 hours per fuel tank)
MHD: 11.25 tons, provides 2 PP for 6 hours per 3.75 tons fuel (24 hours per fuel tank)
ICE: 12.5 tons, provides 1 PP for 10 hours per 2.5 tons fuel (60 hours per fuel tank)
Gas Turbine: 12.5 tons, provides 2 PP for 4 hours per 2.5 tons fuel (24 hours per fuel tank)

Surprisingly, the TL8 ICE comes out on top, with an "energy density" of 60 PPh (Power Point Hours) per fuel tank. The others are all at 48 PPh. A quick Wikipedia search puts the energy density of Gasoline at 47 MJ/kg, and the best batteries almost two orders of magnitude less (0.3-0.7). In other words, a realistic battery module would provide about 0.5 PPh capacity, or 30 PPm. This is probably why realistic batteries are not included among the ship systems. =P

For a cinematic battery, I could see it providing, say, 6 PPh per module, or 30 PPh for a blatanly Superscience version. Its advantage is that it could provide that all at once if needed (eg 6 PP for 1 hour) and be recharged afterward.

[Tzeentch]

-- This has come up before. IIRC the reason there are no battery modules is because of the variable turn length in Spaceships. Yeah, I generally replace batteries with MHD or Fuel Cells (this is how batteries were handled for the Transhuman Space conversions).

[Flyndaran]

So while batteries would be a bit more useful that fuel cells, it doesn't rise to level of SS granularity?
Ok, I can see that.

Still, batteries could conceivably give a few PP only with a very short duration. That would be very useful for some small vehicles like mecha.

[vierasmarius]

Okay, check my previous post. Did some back-of-the-napkin calculations, very rough but they might be helpful.

[vicky_molokh]

Originally Posted by Tzeentch

-- This has come up before. IIRC the reason there are no battery modules is because of the variable turn length in Spaceships. Yeah, I generally replace batteries with MHD or Fuel Cells (this is how batteries were handled for the Transhuman Space conversions).

Actually, this isn't a problem. 3 PP×hours can be either 3 PP for six 10-minute turns, or for sixty 1-minute turns. Or 30 PP for six 1-minute turns (assuming the capacitor has a maximum output rate of at least 30 PP). After all, a PP is a unit of power, not energy.

[Kax]

Part of it, I think, was a hidden handwave based on the original weapon modules--the Vehicles weapon designs had a speed rating that couldn't be slower that 1 shot per 2 sec. This gives a ridiculous damage output in a 20-min combat round.
The combat rules for ships was based on 1 or a few shots per round due to movement and so on.

Now, a 1 space/dton battery pack would allow, given the written designs, a pocket battle-ship's output from a pirate's converted trader for 1 or two rounds--quite enough if you aren't facing a military ship.
It's rather expensive--but if I were a pirate (or making defensive Q-ships) I'd be stupid not to make the investment.

So they don't exist due to handwaving the original designs to under a 10th the original RoF.

For Q-ships (and pirates with backers) they would still have a use, though.

On the design: the modules are not monolithic, so the battery pack segments can be spread amongst the power systems and/or split between the weapon turrets.

[Flyndaran]

Originally Posted by vierasmarius

Okay, check my previous post. Did some back-of-the-napkin calculations, very rough but they might be helpful.

Cool. That means THS 1 kWh / lb batteries equates to 10 PPH and $900k for SM+7 vehicles. Even better for the 1/3, times 3 scaling.

[Peter Knutsen]

Originally Posted by vierasmarius

Fuel Cell: 11.25 tons, provides 1 PP for 12 hours per 3.75 tons fuel (48 hours per fuel tank)
MHD: 11.25 tons, provides 2 PP for 6 hours per 3.75 tons fuel (24 hours per fuel tank)
ICE: 12.5 tons, provides 1 PP for 10 hours per 2.5 tons fuel (60 hours per fuel tank)
Gas Turbine: 12.5 tons, provides 2 PP for 4 hours per 2.5 tons fuel (24 hours per fuel tank)

Surprisingly, the TL8 ICE comes out on top, with an "energy density" of 60 PPh (Power Point Hours) per fuel tank.

Are some of these systems dependent on external oxygen?

[Flyndaran]

Originally Posted by Peter Knutsen

Are some of these systems dependent on external oxygen?

The bottom three are. Fuel cells include all necessary ingredients, I believe.