Tuesday, May 23, 2017

Ultra-Tech Quickie: Batteries, Recharged!

A few months ago I did an article covering how much energy power cells hold in real world units and included a few hypothetical suggestion for different kinds of power plants. I also took a shot a handling batteries to give players some more long term storage options at the price of having a lower power output.

Behold, the power of the future!
The stats I posted for them were based on work done by laser wunderkind Luke Campbell since his work match my own research as well as the fact he had more knowledge on the subject then I do. They do their job fine and are about as realistic as you can get, well as well as you can with predicting the future. However they just were kinda.... kinda off with how GURPS does things.

While I'm not afraid to stray into house rule territory if I have to, I try to stay as RAW as possible since I know how some GM's can get. Some just don't like veering off of what's published so if my rules at lest line up with that it increases the chance that my stuff will get the okay.

Well, I've been doing some diving into what info I could get on the early versions of Ultra-Tech to see if I can find any nuggets I could use. While I have yet to find a smoking gun, I have found enough things that seem to point to the fact that originally there were going to be both power cells and batteries in the book (and in fact this makes sense since some of the things listed don't make sense having the duration they do with just normal power cells).

Now granted that's useful and all but... there was no data on how these batteries would work. Then it hit me. A lot of Ultra-Tech was inspired by what was done in Transhuman Space and that setting had both batteries (confusingly called power cells) and power cells (called power packs). So I took a look at these settings assumptions and it clicked!

So here's my second, more GURPSy attempt at stating batteries.

In general Ultra-Tech Batteries hold 10× as much energy as a the same sized power cell of the same TL. For example a TL9 C power cell holds 90kJ of energy so a TL9 C battery would hold 900kJ.

Of course the down side to batteries is that they have a limited ability to discharge that energy as power. Divide the batteries kilo Joules of storage by 900 to see how many kilo Watts it can discharge at. For example since a C battery holds 900kJ it can discharged it at a rate of 900kJ/900 or 1kW. If the item you are trying to power has a greater kilo Watt requirement then a given battery can provide then use a bigger or more batteries till it that requirement is met.

Note that realistically that at TL11, energy density gets as high as it can probably get without super science. The TL12 examples  shown below would need hyperdense materials to be practical.

Battery type  TL9                      TL10                       TL11                           TL12
AA                    0.0001kW/0.9 kJ          0.0004kW/0.36 kJ        0.0016kW/14.4 kJ             0.0064kW/57.6 kJ
A                       0.001kW/9 kJ               0.004kW/3.6 kJ            0.016kW/144 kJ                0.064kW/576 kJ
B                       0.01kW/90 kJ               0.04kW/360 kJ             0.16kW/1,440 kJ               0.64kW/5,760 kJ
C                      1kW/900 kJ                   4kW/3,600kJ                16kW/14,400 kJ                64kW/57,600 kJ 
D                      10kW/9,000 kJ              40kW/36,000kJ            160kW/144,000 kJ            640kW/576,000 kJ 
E                      100kW/90,000 kJ          400kW/360,000kJ        1,600kW/1,440,000 kJ       6,400kW/5,760,000 kJ
F                      1,000kW/900,000 kJ     4,000kW/3,600,000kJ  16,000kW/14,400,000 kJ    64,000kW/57,600,000 kJ 

The number before the slash is the batteries output in kilo Watts and the number after the slash in the batteries energy storage in kilo Joules. Divide the listed energy storage by 3,600 to get how many kilo Watt-hours the battery will provide.


  1. Good stuff; may get some use out of this for something before too long!

  2. So I did some digging of my own. My first run came to similar numbers as yours, but with the second run, I looked at GURPS Spaceships. If you take their kilojoule numbers, those translate directly to kilowatt seconds, and you can build a weapon using the beam weapon creation rules to match the weapons in GURPS spaceships, then check to see how many shots they would get our of a power-cell, and when I did, I came to about 200 kilojoules in a TL 11 C-cell. Maybe we should compare notes if you have time (I think there are likely multiple "correct" values you can get, depending on what assumptions you go with)

    1. My numbers are based on the assumptions that David used for Ultra-Tech, however his number have changed since then so that stands to reason why we came up with different numbers heh.