Batteries and storage: sizes, charging, discharging, a transformer in between

Every base on solar power needs storage for the night. Every base with a generator needs a buffer so the generator does not run all the time. Batteries do both – if they are connected correctly.

The unit "W" first#

The power system calculates in ticks of 0.5 seconds. What the game shows as "W" are joules per tick. A consumer with 1,000 W therefore takes 1,000 J from the battery every tick, 2,000 J per second.

That gives the most important formula of this article:

Runtime in seconds = content in J ÷ load in W · 0.5

A Station Battery with 3,600,000 J therefore carries 1,000 W for 3,600 ticks, which is 1,800 s or 30 minutes – not one hour. The Power calculator calculates the same way.

Storage at a glance#

The cells sit inside devices – in the Area Power Control, in tools or in a charger. The station batteries stand on the network as devices of their own.

Self-discharge: According to the game code the Station Battery and the Station Battery (Large) lose energy every tick, depending on the air at their location:

• Air pressure below 6.3 kPa (vacuum, but also the outside air on Mars): 50 J per tick.
• Otherwise 10 J per tick. More in very cold air: up to 50 J · (1 − temperature ÷ 273.15 K), so at 1 atm only below about 219 K (−55 °C) more than 10 J.

Over a game day of 1,200 s (2,400 ticks) that is 24,000 J, in vacuum 120,000 J. The lost energy ends up as heat in the room air. For a full battery it hardly matters, for an almost empty one it does. The rocket batteries Auxiliary Rocket Battery and Battery (Medium) do not self-discharge according to the code.

Reading the charge level#

Station batteries show their level through these logic values:

• Ratio: fill level from 0 to 1 – the most precise value for switching thresholds.
• Charge and Maximum: content and size in joules.
• Mode: level from 0 to 6 (Empty, Critical, VeryLow, Low, Medium, High, Full).
• PowerPotential and PowerActual: what the battery offers and what is flowing right now.

On switches the battery, Lock locks the controls on the device.

Connecting correctly#

A station battery has an input, an output and a data port of its own. Input and output sit on two different networks: generators on the input side, consumers on the output side.

What matters is how batteries negotiate with the network: at the input they request their whole free capacity, at the output they offer their whole content. The network carries the smaller of offer and demand. For the cables that means:

• Input side: The battery's demand is huge, so everything the generators deliver flows. The cable has to carry the full generation.
• Output side: The offer is huge, so exactly the consumers' demand flows. The cable has to carry the full load.
• Output to input: Offer and demand are both huge. The flow is in the millions – that burns out any cable.

Several batteries side by side (all inputs on the generator network, all outputs on the consumer network) are therefore no problem. Batteries in series need a transformer in between.

Charging cells#

You charge battery cells in a charger or in the area power control:

An example: an empty large cell (288,000 J) needs 288,000 ÷ 500 = 576 ticks in the large charger, just under 5 minutes. A nuclear cell needs 4,608 ticks there, about 38 minutes. Five empty cells at once draw up to 5 · 500 + 10 = 2,510 W – plan that into the network.

Worked example: a night on the Moon#

The station needs 600 W at night, and the night lasts about 650 s.

1. Energy: 600 · 650 ÷ 0.5 = 780,000 J.
2. Storage: one station battery (3,600,000 J) covers it four times over.
3. Vacuum: if the battery stands outside (below 6.3 kPa), it loses 50 J per tick. A lunar day has about 2,594 ticks, that is roughly 130,000 J – about a sixth of what the night needs.
4. Charging: with 1,500 W of surplus during the day, the night's energy is back after 780,000 ÷ 1,500 = 520 ticks (260 s). The lunar day is long enough.

IC10: showing the remaining runtime#

The program shows on the IC housing how many minutes the batteries can still carry the current load – calculated as if nothing comes in. The demand comes from a Cable Analyzer on the consumer network. For that, the IC housing, the analyzer and the batteries' data ports sit on the consumer network.

# --- Remaining battery runtime in minutes ---
define BATTERY -400115994      # Station Battery (StructureBattery)
define ANALYZER 1036015121     # Cable Analyzer (StructureCableAnalysizer)
define NBATT HASH("Base Battery")    # name of the batteries
define NGRID HASH("Consumers")       # name of the analyzer
define COUNT 2                 # this many batteries carry the name
define MINLOAD 1               # W: protects against division by 0
define TICKSMIN 120            # 120 ticks of 0.5 s = 1 minute
alias content r0
alias demand r1
alias minutes r2

start:
yield
# --- 1. Measure ---
lbn content BATTERY NBATT Charge 0
bnan content start             # no battery with this name
lbn demand ANALYZER NGRID PowerRequired 0
bnan demand start              # no analyzer with this name
# --- 2. Calculate ---
mul content content COUNT      # average times count = total content
max demand demand MINLOAD
div minutes content demand     # ticks until empty
div minutes minutes TICKSMIN
floor minutes minutes
# --- 3. Display ---
s db Setting minutes
j start

Batch mode 0 returns the average of all batteries with the name. Times COUNT that gives the total content – enter how many batteries you named that way.

Common mistakes#

• Cable between two batteries burns: the transformer is missing.
• Nothing arrives behind the transformer: Setting is still at 0.
• Battery empties faster at night than calculated: "W" is joules per tick, not per second – the load drains the battery twice as fast as real watts would suggest.
• Battery never fills up: too little surplus during the day. A network is only supplied when generation is greater than demand.

Further reading#

• Basics: Power grid basics
• Planning a solar array for the battery: Solar arrays: alignment, tracking, day and night
• Sizing transformers: Sizing cables, fuses and transformers correctly
• Switching by battery level: Backup power and load shedding: separating networks, priorities, IC10
• Recalculate: Power calculator
• IC10 academy: power budget