Gameplay Guide - Rjoande/RealBattery GitHub Wiki

Real Battery adds a new layer of immersion by simulating a more realistic approach to electricity management in Kerbal Space Program. This guide gives you a quick overview of how real-world batteries work, and how those principles are translated into gameplay mechanics. You'll also learn about the key battery stats, the in-game interface, and how to optimize your vessel’s electrical systems.

Electricity and Batteries

In stock KSP, electricity is treated like any other physical resource, just like fuel or ore. But in the real world, electricity is a complex and dynamic phenomenon. Simply put, electric current flows from a generator to a consumer, carrying energy along the way.

Because of this, batteries aren’t actually "electricity tanks" (that role fits capacitors more closely). Instead, a battery is a type of generator that produces energy through a chemical reaction. You can think of electrical energy not as something you store and move like a fluid, but as a process (much like the thrust from a rocket engine). It's not a physical object, but the result of a transformation, like the reaction between fuel and oxidizer.

Simulating this in full realism would be far too complex, both in terms of coding and gameplay, and would drift away from KSP’s core focus: running a space program.

So, in this mod, I chose to simulate only the aspects of batteries that are most interesting and meaningful from a gameplay perspective, leaving out others that would be less fun or more confusing. Below, you’ll find an explanation of these features and how they work in-game.

Battery Features

Battery Chemistry

Batteries are essentially containers (or more precisely, “cells”) filled with chemical substances called electrolytes. When these substances react, they release electrical energy. In many cases, this chemical reaction is reversible: when you feed energy back into the battery, it restores the electrolytes and recharges.

Different electrolytes have different properties in terms of how much energy and power they can deliver. The specific mix of electrolytes is called the battery’s chemistry. In Real Battery, you can choose between different chemistries using B9PartSwitch, each with its own pros and cons. You can find a full list of available chemistries here.

In Career or Science mode, any part that originally held Electric Charge will now have a default chemistry assigned, and additional chemistries can be unlocked through the R&D building.

Energy Density

Different battery chemistries can store different amounts of energy. This amount is based on mass, and is called energy density, usually expressed in Wh/kg or kJ/kg (1 Wh = 3.6 kJ). In simple terms, it tells you how much energy can be stored per kilogram of active material.

This means that if you double the mass of a battery, you also double the amount of energy it can hold. Battery capacity can also be expressed in charge: for example, in milliamp-hours (mAh), which is common in commercial batteries. This shows how much current (in milliamps) a battery can supply over one hour.

In Real Battery, energy density is simulated using the resource Stored Charge. Chemistries with higher energy density will provide more Stored Charge for the same battery size, giving you more energy to use during your mission.

Power Density and C-Rate

The main innovation of Real Battery is that it separates energy and power, two concepts that are combined in the stock game under the single resource Electric Charge. In reality, energy is delivered over time, and the rate at which it's delivered is called power. Power is measured in watts (W), or joules per second.

Different battery chemistries provide different levels of power. This is measured as power density (W/kg), meaning “how much power a one-kilogram battery can deliver in one second”. As with energy density, increasing the battery’s mass increases its maximum power output.

However, keep in mind that power density represents the maximum output a battery can handle, not necessarily its optimal or sustainable output. Take a typical lead-acid car battery: it can deliver a high burst of power (about 700 W), but only for a very short time, just enough to start the engine. In Real Battery, this peak power is represented by the Electric Charge resource, which defines how much energy a battery can release in a single second. In this case, that car battery would have 0.7 EC (i.e., 700 W).

For continuous use, most batteries need to operate at lower power levels to avoid overheating or damage. This sustained output is represented by the C-rate, which tells you how quickly a battery can safely discharge. For example, a C-rate of 1C means the battery can discharge its full capacity in one hour. A rate of 2C means it discharges in half an hour, and so on. While these are theoretical values, they give you a useful sense of both power and duration.

In-game, the C-rate for each battery subtype is shown in its description. The actual power output (in EC/s) is displayed in the PAW (right-click menu) and is determined by the battery’s C-rate.

In real life, the C-rate is an operational parameter defined by the manufacturer and often varies between charge and discharge. For example, NiCd batteries typically range from C/10 to 1C. Real Battery simplifies this system for gameplay purposes, but future updates may include a tweakable slider to adjust discharge power (up to the battery’s maximum power density).

Thermal Loss (coming soon)

Whenever current flows through a circuit (including inside a battery) it generates heat. Every battery has intrinsic properties that cause a portion of the electrical energy to be lost as heat. This value is shown in the battery subtype’s description panel.

It’s important to remember that some batteries, like lithium-based ones, may appear thermally efficient but can still produce significant heat. That’s because they also have higher energy and power density, meaning they can deliver more power — and more power means more heat.

Excessive heat not only risks damaging the battery (or even causing it to explode), but can also overwhelm your spacecraft’s cooling systems. On top of that, high temperatures will reduce the battery’s lifespan (see below).

Self-Discharge (coming soon)

As mentioned earlier, an electric battery is properly an electrochemical generator. The chemical reactions that produce electricity can happen spontaneously, especially when the battery is not in use, causing it to slowly lose stored energy over time. This is known as self-discharge.

In real life, self-discharge is usually measured as a percentage of total capacity lost per month, and this loss happens regardless of the battery’s current charge level. For example, a 1000 mAh battery with a 10% monthly self-discharge rate will lose 100 mAh per month whether it’s fully charged or nearly empty.

Since KSP doesn’t have canonical months, Real Battery recalculates these rates as % per in-game day, except for nuclear batteries, which follow a much slower decay rate (about 4.5% per in-game year).

Different battery chemistries have different self-discharge rates. While it’s always possible to recharge your batteries to counter this effect, keep in mind that doing so contributes to battery aging (see below).

Durability

As batteries operate, they gradually degrade over time due to internal heat and other physical and chemical processes. This wear and tear is mostly linked to how many times the battery is charged and discharged.

This is typically measured in full charge cycles: one full cycle equals a complete discharge from 100% to 0% followed by a full recharge back to 100%. However, partial cycles also count: for example, a battery rated for 100 full cycles could handle 200 half-cycles (e.g., charging and discharging from 50% to 100%).

A battery’s actual lifespan is also affected by operating temperature and C-rate. High temperatures and faster discharge rates tend to shorten battery life.

When a battery reaches its rated number of cycles, it doesn't stop working, but its output capacity drops to about 80% of its original performance. After that point, degradation accelerates.

This also means that primary (non-rechargeable) batteries, which have CycleDurability = 1, will approach ~80% efficiency just before they're fully drained.

How Batteries Work in the Game

Choosing the Right Battery

Real Battery modifies every part that originally used Electric Charge, making them compatible with the mod’s mechanics. Each of these parts now includes Stored Charge resource, and a built-in converter that handles the transfer between Stored Charge (energy) and Electric Charge (power).

Depending on the part, you’ll have access to different battery chemistries, selectable via B9PartSwitch subtypes. Standalone batteries usually offer a wider range of options.

In Career and Science modes, most parts start with just one basic chemistry, usually low-performing. As you unlock more tech nodes in the R&D building, additional subtypes become available. These can offer better energy density, higher power output, longer lifespan, or other advantages, but often come with trade-offs like higher mass or cost.

So it's important to choose the battery type that fits your mission needs: do you need something cheap, lightweight, high-capacity, long-lasting, or powerful?

You can find a summary of each subtype’s key traits and pros/cons in its info panel. In the editor, the part's right-click menu (PAW) will show estimated charge and discharge rates for that subtype. In flight, you'll see the battery’s current status and conversion rate (more in-flight info may be added in future updates).

Discharge, Recharge, and Power Spikes

When a part needs Electric Charge — like a light, a reaction wheel, or an antenna — it draws from the ship’s shared EC pool. The drain is usually distributed evenly across all connected parts.

If the total EC level of the vessel drops below 90%, batteries will begin converting Stored Charge into Electric Charge to compensate. The conversion script will try to prioritize higher-performance batteries, and the output will scale to match demand, up to the limit defined by each battery’s C-rate.

If the total power demand exceeds the batteries’ combined output capacity, the EC level will keep dropping until it runs out. In gameplay terms, this simulates a power spike: a sudden surge in demand. Batteries can handle brief spikes, but if they last too long, they’ll cause a power shortfall or brownout, just like in real systems.

On the flip side, when Electric Charge is being generated — from solar panels, fuel cells, alternators, etc. — it will first refill the EC pool. Once the shipwide EC level exceeds 95%, batteries will begin recharging, converting EC into Stored Charge at the maximum rate possible. This recharge speed depends on both the available EC and each battery’s internal characteristics.

Final thoughts and tips

Real Battery adds a deeper and more realistic electrical system, but with a bit of practice, it remains easy to use. Just keep a few key points in mind:

• Stored Charge is your total available energy; Electric Charge is how much power you can deliver at any given moment.
• Choose the right battery chemistry for your mission: some are more durable, others are lighter or provide more peak power.
• Watch your C-rate and power spikes: every battery has limits.
• If something seems off (slow recharging, sudden drops, battery not working), check the Troubleshooting & FAQ section for common issues and helpful tips.

The goal is to make energy management a meaningful part of ship design: strategic, not tedious. Experiment, rebalance, and enjoy building smarter and more capable spacecraft.