Battery

The battery is an electric device that can store energy and provide power. Energy is stored while there is a surplus on the connected electric grid; the charge capacity is 600 Wd (watt days). Each battery provides an unlimited amount of power if there is a deficit, until discharged. Charging happens at only 50% efficiency, ie. half the power used for charging is lost. Batteries self-discharge at a rate of 5 W, even while disconnected. Batteries need to be operated under a roof, or they will frequently short circuit in rain or snowfall, causing an explosion.

Usage

Batteries are built, moved and stored like other kinds of movable furniture. They will keep their charge while stored ("minified") or disconnected, only discharging at the normal rate of 5 W (self-discharge).

With regards to power production, they behave like the other electric buildings in the game. All power consumers can connect to batteries in the same way as to other power sources: within a 5-tile radius, all consumers can directly connect to a battery (or array of batteries), without any power conduits in between.

In order to charge a battery, it has to be directly connected to a power grid with excess power. It is not possible to connect to batteries "through" power consumers (this is because consumers can not be connected to more than one power grid at the same time).

Just like the other power producing buildings, a battery acts as a power conduit on the 2 tiles it covers.

Installed batteries can not be switched off manually. As long as at least one consumer is connected, the battery will provide power during a deficit, and also be vulnerable to the short-circuit event.

Installed batteries need to be kept dry. If outdoors, a roof has to be built over the tiles occupied by the battery. If a battery becomes wet (either due to rain or snowfall), there is a very high chance of a short circuit, causing and explosion and fire damage (possibly spreading to adjacent batteries and connected devices).

Damage to a battery does not change it other properties and does not lose charge (eg. a 1 hitpoint battery has the same capacity and wattage as a 100 hitpoint battery).

The batteries in this setup connect directly to the wind turbine and the attached coolers, without any power conduits. This completely avoids the random short circuit event ("Zztt...") in this power network.

Batteries as power providers

As a power provider, the battery behaves just like any other power source in the game (eg. generators or solar panels), but each battery will deliver an unlimited amount of power. This means that any wattage can be delivered until the battery is completely discharged. It makes the battery not only convenient as buffers for wind turbines and solar panels, but also to cover arbitrary spikes in power usage, usually caused by turret arrays and other heavy power consumers that are only brought on-line sporadically.

If more than one battery is on the same power grid, all batteries with remaining charge will share the power load evenly.

The maximum amount of charge provided is 600 Wd (watt-days). Discharge time only depends on the power that is drawn. Eg. if exactly 595 W were drawn, a single battery would last exactly 1 in-game day (5 W of self-discharge have to be added). If only 295 W are drawn, it lasts for 2 days, etc. The maximum power draw is unlimited, so it is – theoretically – possible to empty a full battery in 1 tick of game time (instantly).

A disconnected battery will discharge at a rate of 5 W. This means that a fully charged battery can be stored for 120 days (1 in-game year) until depleted.

Charging

A battery will automatically keep charging while it is connected to a power grid with excess power available. Selecting the battery will show the current charge status in the information window.

All batteries in a power grid will evenly share the excess power for charging, but can only use half of it. This means that the charging efficiency is 50%; in other words, to fully charge an empty battery, 1200 Wd of energy have to be provided, as well as 5 W extra to cover the self-discharge.

As an example, connecting an empty battery to a power grid with exactly 1205 W of available power will charge it to full in exactly 1 in-game day. If more power were available, charging would complete more quickly. 5 W of charging power would keep the battery at exactly the present charge level.

Constructing, moving and storing

Batteries behave exactly like other furniture items in the game: they have to be constructed on solid terrain, using the construction skill. It takes 14 work units to build, and can be done even at construction level 0.

After construction, they can be uninstalled like furniture, and then moved to storage, taken to a character's inventory or on a caravan. Uninstalling and reinstalling does not cause additional charge loss, beyond the 5 W of self-discharge that always applies.

It is possible to take charged batteries on caravans as a power source for camps and newly founded colonies.

Batteries that are not installed can be stored in the open, also in rain or snowfall, as they can not short circuit. Like other furniture, they are not subject to decay.

Hazards

Batteries are very likely to explode in rain and snowfall. This can be completely avoided by keeping installed batteries under a roof; keeping them indoors is not necessary. The resulting explosion will not cause any discharge, but it will heavily damage the battery, and possibly surrounding structures as well, also causing a fire.

Batteries make the short circuit event ("Zztt...") more dangerous: all affected batteries will instantly discharge, causing an explosion in addition to the fire that is normally caused by the event. The more batteries are connected, the large the explosion. Note that the event is unrelated to batteries – it can still happen if no batteries are connected, but will then only cause a small fire and no explosion. Empty batteries will not affect the event.

To mitigate the hazard from the short circuit event, batteries can be intermittently disconnected from the grid, and only brought online on demand. Note that for this measure to be effective, not a single power conduit must be on the disconnected power grid. The short circuit event is related to the power conduits – if no powered conduits are on a network, the event can not occur on this network. So in order to effectively protect the batteries, a power switch must be placed directly adjacent to the battery array, with no other power conduits directly connecting to the batteries. It is also possible to place the batteries adjacent to a power generator, and then decouple the generator with a switch – again, no power conduits can be behind the switch.

Battery performance is not affected by temperature, but like many other structures they are highly flammable and may catch fire if the surrounding temperature is very high.

Strategy

Batteries are useful in most colonies, even if the colony does not rely on unstable power sources like solar panels and wind turbines.

If only renewable energy is used, at least one battery is mandatory, because sufficient power supply can never be guaranteed. Solar panels produce no power during the night and during an eclipse, and wind turbines are completely unreliable. If the colony has no other backup power source, it is highly recommended to keep some additional batteries behind a power switch on a separate network (see Hazards above), so they can be brought online in the case of a short circuit event.

Alternatively, some batteries can also be stored in a warehouse, and then placed down anywhere on the power grid on demand. This makes switches unnecessary.

When you calculate the battery capacity that is necessary when using renewable energy, keep in mind that charge efficiency is only 50%. That is, only half of any excess energy will be effectively usable. This is particularly relevant when planning a greenhouse setup, of hydroponics basins and a sun lamp. The sun lamp will draw 2900 W during the day, and 0 W during the night, for an average demand of 1450 W. However, it is not sufficient to generate only 1450 W at all times, hoping that a 3-battery array will even out the difference in power draw. This is because during the night, only half of the extra 1450 W will effectively charge the batteries, storing 8,700 Wh of energy (~360 Wd). This will only be enough to power the sun-lamp for 6 hours during the day. For the remaining 6 hours, the missing 1450 W will have to be provided by other means (usually a solar panel). Simply adding more batteries will not change this. Two batteries will provide enough buffering in this scenario.

The example setup, including 24 hydroponics basins, can be fully powered by a single geothermal generator plus a single solar panel, connected to a single battery to buffer the solar energy. This will not take into account heaters and a possible disruption from an eclipse event.

Even in colonies that do not use wind or solar energy, batteries are useful to cover spikes in power usage, usually caused by turret arrays and devices like crematoriums, smelters and mineral scanners that are only brought online intermittently. A battery can cover arbitrarily high power needs, the size of the array only changes for how long that is possible.

As an example, an array of 20 mini-turrets and 4 autocannon turrets draws 3200 W of power. Instead of building another geothermal generator that would cover this, even a single charged battery can power this entire setup for more than 4 in-game hours. An array of 5 batteries can power the defenses for an entire in-game day. The battery array should be isolated with two power switches from the security grid and main power grid. This makes it then also very easy to power the entire setup with a single switch, as well as keep the batteries safe from the short circuit event.

Architect

Power: Power conduit (Waterproof) • Power switch • Wood-fired generator • Chemfuel powered generator • Wind turbine
(research): Battery • Geothermal generator • Solar generator • Watermill generator • Toxifier generator
(uncraftable): Vanometric power cell • Unstable power cell
Related: Ship reactor