Friday, 4 January 2019

Energy Cells

This started out simply as an attempt at creating better tables for the blog. It has turned into a more detailed look at energy cells in Transhuman Space. Most of this is not needed for gameplay but the extra detail does help flesh out the background.

Page 140 of Transhuman Space 3rd edition tells us one pound of batteries stores 1 kilowatt-hour (3.600 kilowatt-seconds or 3.6 MJ) of energy and costs $30. It then gives examples of common standardized energy cell sizes. The sizes are similar, but not identical to, the energy cell sizes given in 3e Ultra-Tech, p.10-11. In Ultra-tech 3e the AA cell is 116" in diameter and 132" thick, 8,000 to the pound. The A cell is ¼" diameter and ⅛" thick, 400 to the pound.

TS 3e also tells us that a pound of battery occupies 0.02 cubic feet. Using this figure gives energy cells that seem far bulkier than seems likely. The AA cell, for example, works out as equivalent to a cube of sides of more than 6.5 mm. This seems impractical for an energy cell that is intended for use in very small items such as the 1/20" (1.27 mm) nanobug (TS 3e p.154). It seems likely the author was thinking of UT 3e AA cells and not aware the figures he gave describe something larger. UT 3e AA cells are still bigger than a nanobot.
I will deal with the subject of energy cells for very small devices presently. I began experimenting with different values for volume. I tried making the AA cell the equivalent of a 3 mm cube, which works out as a volume/lb of 54 cubic centimetres. Interestingly, this is 0.0019 cubic feet. This makes me wonder if the figure of 0.02 was a typo and should have read “0.002”. Not remembering the nanobug description, I decided to make the AA cell a 2.5 mm cube, which seemed a practical shape for such a small object. This gives a volume/lb of 31.25 cubic centimetres. The cell descriptions below are based on this. Dimensions given are approximate, and given in metric since this is more likely to be used in the TS-era.
 

Size

wt (lb)

no./lb

kWh

Dimensions

Cost


0.0005


0.0005

2.5 mm
cube

$0.015

AA2

0.0005

2000

0.0005

1.6 dia.
x 7.8 mm

$0.015

AA1

0.0005

2000

0.0005

4.5 dia. x 1 mm


AA-Flex

0.0005

2000

0.0005

4 mm
square.

$0.015

A1

0.005



7 dia. x
4 mm

$0.15


0.005

200

0.005

12.7
dia.  x 1.2 mm


A-Flex

0.005

200

0.005

25 mm
square

$0.15

B

0.05

20

0.05

12.7
dia.  x 12.7 mm

$1.5

C

0.5

2

0.5

26 dia. x
30 mm

$15

D

5

0.2

5

50 dia. x
80 mm


E

20

0.05

20

90 dia.  x
100 mm

$600

The limited volume of devices likely to use the smallest cells suggested that more than one configuration of some types may be needed. The most common variety of AA cell would be a 2.5 mm cube with rounded corners. These are relatively easy to handle, although it helps to have tweezers. Bulk packs of AA cubes include a pair of plastic tweezers. AA cubes are also know as AA3 or just AA3s. The AA1 configuration is intended for thin devices. AA2 cells are used in the narrowest of devices and are relatively uncommon compared to the other configurations. AA2s are known as “pin cells” or similar names.
A-size is also common in more than one configuration, one being a flat disc and the other a more compact “pill-cell” cylinder. 
B cells are of similar size to a pistol cartridge case. C cells are slightly over an inch in diameter and height. (Actually the size of a modern 3/5 C cell!)
New E cells often include a carrying handle as part of their packaging. Heavy power demands use multiple E cells, individual E cells being easier to handle than a single larger cell. 

Non-rechargeable cells have the same sizes, weight and cost as rechargeable cells but store twice the energy. Thus a non-rechargeable A-flex holds 0.01 kWh.

Ultra-Tech 4e p.19 changes the weight of AA and A cells to reflect those in TS 3e. It also introduces adhesive, flexible energy cells resembling polymer postage stamps. These are used in TS-era clothing, smart labels, smart paper, and flexible, disposable items. AA and A flexible cells are the usual cost; other sizes are 4 times the normal cost and may be much harder to acquire.

TS 3e p.140 tells us AA to E cells are just some of the standardized sizes available. Other size energy cells may be encountered but the range and sizes suggested here should meet most needs. Very small devices that cannot use any of the AA cells proposed here would probably use built-in batteries and utilize wireless recharging systems. Physically changing the batteries in every microbot is not really practical!

(Blogger still screws up tables! A solution!)