Powercells And The Draw Power Spell

[Anaraxes]

Originally Posted by scc

For instance a car with a running engine's cigarette lighter or phone charger can be used but once the engine stops it can't be used?

If you're drawing power from a mechanical engine, that's true. That's what "active" means.

The intent of the spells is pretty clearly to rule out tapping potential energy sources. You can't draw power from gravitational potential of non-moving rocks (the top of a mountain -- or any rock, as it's 4000 miles from the Earth's center just sitting on on the ground, roughly 16 kg of TNT's worth of energy in a 1 kg rock), or latent heat of water in the atmosphere (plenty of energy to drive hurricanes), or the kinetic energy that is heat from anything above absolute zero. The tech spells are meant to tap "machines" in operation. If you could draw magical energy from just anywhere in the environment, especially if it's distributed (no stated size limit on a "machine"!) then you might as well just shrug, call it "mana", and skip all the tech spells.

The problem arises when you zoom in with your physics microscope and want to argue about what a "machine" really is. If you take a hard-science enough approach to your magic, then there is no magic, because physics is just physics.

Electrical power and batteries muddy the issue the most, since they don't have obvious moving parts. Tapping an ICE driveshaft stops when the engine stops. Tapping the alternator's electrical output requires the alternator to be moving, so it stops when the engine stops. Tapping the engine's starter battery doesn't need it to be running. Huh?

Batteries just store chemical energy. But so does sugar, or unburned gasoline or coal, or a living forest, or a vast number of other chemicals that are abundant in the environment. Why can you tap energy from a battery, but not from that guard's body storing ATP and glucose? Aren't humans just biological "machines"? Isn't Draw Power then just an irresistible death spell, as it can suck all the "life force" (in low-tech magical terminology) out of someone, or in more medical terms inducing hypoglycemia, unconsciousness, inability of muscles to operate, and death from lack of neural currents or any operating organs? That's not the intent of the spell, so when you allow these spells you're going to have to live with a fuzzy boundary vaguely defined by the rules and unsatisfyingly defined even if it were. That's what games have GMs.

[malloyd]

Originally Posted by Anthony

It only works on active power sources; a power cell just sitting there is producing 0 power and therefore you can't get any energy from it. Though you could probably hook a power cell up to a simple motor to solve that.

Do you even need a motor? Short the cell with anything with a low enough resistance there is a trickle of current and it'd be an "active" power source.

But the original intent is fairly clearly that you are supposed to be able to Draw Power from power cells, or other deliberate technological energy storage systems, even if that doesn't seem to make sense relative to other things you can't Draw Power from.

I'm rather critical of the entire Tech college myself, but in it's defense if you're expecting spells, even (or perhaps especially) Tech spells, to make physical sense, you're missing a fairly central feature of "magic". The logic of spells, to the extent they have any, is the logic of language, not of physics. You can Draw Power from a power cell, or a power plant, because it's natural name includes the word "power" - maybe the spell would fail to work on a battery (or for that matter a water wheel) simply because people wouldn't use the right word to describe what it does.

[vicky_molokh]

Originally Posted by Anaraxes

Batteries just store chemical energy. But so does sugar, or unburned gasoline or coal, or a living forest, or a vast number of other chemicals that are abundant in the environment. Why can you tap energy from a battery, but not from that guard's body storing ATP and glucose? Aren't humans just biological "machines"? Isn't Draw Power then just an irresistible death spell, as it can suck all the "life force" (in low-tech magical terminology) out of someone, or in more medical terms inducing hypoglycemia, unconsciousness, inability of muscles to operate, and death from lack of neural currents or any operating organs? That's not the intent of the spell, so when you allow these spells you're going to have to live with a fuzzy boundary vaguely defined by the rules and unsatisfyingly defined even if it were. That's what games have GMs.

Humans are not a /TL item. Bioroids, OTOH . . .

Quirk: Susceptible to Draw Power [-1].

[whswhs]

Originally Posted by scc

Apart from being somewhat vague, that means that a large variety of seemingly legitimate sources are unavailable depending upon forces beyond the casters control? For instance a car with a running engine's cigarette lighter or phone charger can be used but once the engine stops it can't be used? Or any other vehicle or installation that has to switch to battery backups?

No. When current is flowing through a circuit, it's providing power, whether it comes from a power line, a local generator, or a battery; and you can tap it magically whether there's a power takeoff or not. It's when the battery is just sitting there, not connected to anything, that there's no power flow, but just stored energy.

[Bruno]

Originally Posted by malloyd

Do you even need a motor? Short the cell with anything with a low enough resistance there is a trickle of current and it'd be an "active" power source.

Sure. Improvise a short on that high TL impossible-energy-density power cell. I dare you.

The concept is sound though - all it takes is a widget designed to have a "handle" for a wizard to connect Draw Power to, which I suspect adds negligible weight and bulk to a cell.

The rate of power being cycled is directly related to how much the wizard can tap into, however - and also the danger of the device (heat radiation if nothing else).

I like wizards having to draw from an active circuit because that means there's a dramatic brown-out or electric motor failure whenever the wizard does it, and that's awesome.

[Anaraxes]

Originally Posted by whswhs

When current is flowing through a circuit, it's providing power

That'd be the way I'd go in my own mid-TL games, since the TL spells are supposed to work on electrical devices. Requiring mechanical motion works ok as a rule of thumb for medieval tech, but not really well in settings with electricity. Steal Power explicitly takes power from "stored" power sources like batteries, and Conduct Power connects power where it's not connected. So it's not much of a stretch to imagine Draw Power shorting the battery terminals with a little Conductor just to make it "active" enough to Draw Power. Or if you really want to tidy things up, add Steal and Conduct to the prereqs for Draw, or spin off a Steal-prereq version of Draw ("Draw Stored" and "Draw Active). Or conversely, get rid of the distinction between "Steal" and "Draw". Whatever suits; those details aren't central to any game, story, or balance issues.

(Never having actually needed these spells in a game, despite the number of engineering-school graduates involved as players, I'd be disinclined to fuss over them a lot. But your table may vary.)

Originally Posted by vicky_molokh

Humans are not a /TL item.

"Living beings" are an important category in Magic, so it's at least consistent in that sense to except them, and require Stealing/Drawing Power only from "objects". ("Living being" is no more defined than "machine", AFAIK, so you'll still get to argue about robots and golems and zombies :))

[whswhs]

The important distinction for this purpose is not between Conduct Power and Draw Power, both of which tap active power sources, but between Conduct Power, which taps active power sources, and Steal Power, which taps stored power sources. In terms of actual physics, "stored power" seems to be nonsense; power is defined as energy per time, which means the energy has to be in use, or "active," to count as power. But the intent seems to be that "stored power" is energy that's available to be tapped. It's a stock/flow distinction: Steal Power works with energy, which has the unit of joules, but Conduct Power works with power, which has the unit of joules/second, or watts.

A power cell as such is treated as a store of energy, just like a battery, or a wound spring. So what you cast on it is Steal Power. If you want it to be available for Conduct Power, you need to have current flowing from it through a power line of some kind, or maybe have it going into a motor that turns a driveshaft, a system of gears, a belt and pulley setup, or the like. Certainly you could set such a thing up, probably with a Mechanic or Electrician roll; or if you had an uninterruptible power supply and a power line, you could put power cells into it.

I think you're faced with a bit of a boundary case if you have the power supply and the power line, but nothing connected to it. In that case no actual power is flowing. With some mechanical power sources, you can have an "idle" state, where the engine is still turning, without a load; I'm not sure that works for electrical generators—don't they get taken off line if there's no power demand?

In any case, the different spells provide the magical equivalent of physical energy. Draw Power provides a steady stream of so many FP per second to put into casting spells; Steal Power provides a single "charge" of so many FP to restore the mage's FP.

[martinl]

Originally Posted by scc

And the reason I'm asking because I'm kicking around idea for a template/rules for Dungeon Fantasy for people who somehow from a higher TL and can't get back. The potential for magic using characters to be extremely broken under these circumstances. Even at 15% your still looking at 15 energy from a single D cell and that's bad enough for a starting character to have a power item with that much juice, but if he's got multiple? And some way of recharging them? (The concept isn't all that useful/interesting/worth it if it doesn't have an impact beyond the first few adventures/dungeons)

Why not just cost cells they can use once as paut, and any cell they can get recharged (or recharge themselves given a week and $10 per FP) as a power item? You can have the flavor with standard balance then, and ignore the complicated and dangerous to game balance tech magic entirely.

[ericthered]

Originally Posted by martinl

Why not just cost cells they can use once as paut, and any cell they can get recharged (or recharge themselves given a week and $10 per FP) as a power item? You can have the flavor with standard balance then, and ignore the complicated and dangerous to game balance tech magic entirely.

The one concern with that is the player may want to get his 5 points worth of high TL (plus whatever unusual background). But even then, you can make its slightly cheaper for him to do it and everything will work.

[Fred Brackin]

Originally Posted by weby

Indeed, the core books do not have such conversion. The only values given are the actual ones in Infinite Worlds. Though PSI-Tech says that rechargeable cells have four times the power of high tech batteries.



4e power cells apparently go up faster than the 50% in capacity you say above as the REF for exploding power cells is doubled each TL.

<sigh> I do know all these things but it does get more complicated as I also said.

For example, there are energy capcity numbers in IW but they re for batteries of different weight (in spite of using similar names) than the power cells in UT. That's why I didn't bring these matters up. That chart in the 3e Grimoire book was about the only simple source I could name.