Choosing the right battery size for your RV/boat

Auswahl der richtigen Batteriegröße für Ihr Wohnmobil/Boot

For electronic devices, battery size plays a crucial role in how long your device can operate without recharging. Whether you are using a smartphone, laptop, or other portable device, it is important to know the size of the battery to maximize usage and efficiency.

In this article, we delve deeper into the world of battery sizes and advise you on choosing the right battery size for your device.

How battery size affects battery capacity and performance

How the size of a battery affects its capacity and performance is a key consideration when selecting the right battery for a particular application. Here are the most important factors to consider:


In general, larger battery size corresponds to higher storage capacity. The size of the battery is directly proportional to its ability to store energy. Capacity is typically measured in amp-hours (Ah) or watt-hours (Wh), and larger batteries usually have a higher capacity rating.


Battery size can affect performance, particularly in terms of current output. Larger batteries can deliver higher performance, which is critical for high-power applications such as electric vehicles or powerful electronic devices. Additionally, larger batteries may offer longer lifespan and a greater number of charge-discharge cycles before their performance degrades.

Physical size and portability

It is important to note that the size of a battery not only determines its energy density, which measures the amount of energy stored relative to its weight or volume. Some battery technologies, such as lithium-ion batteries, can offer high energy density and significant capacity in a compact size. This is particularly beneficial for portable devices such as cell phones and laptops, where a balance between storage capacity and physical size is sought.

When selecting a battery for a specific application, it is crucial to consider power requirements and find the right balance between physical size, capacity and desired performance.

Different sizes depending on application

Depending on the intended use, different battery sizes are used. The physical size of a battery is not usually specified in terms of length or volume, but is determined by its energy storage capacity, which is measured in units such as kilowatt-hours (kWh) or megawatt-hours (MWh). However, the dimensions and weight of batteries may vary depending on the manufacturer, model and technology.

Battery for off-grid solar system

In photovoltaic solar systems, the size of the batteries can vary depending on energy storage needs and solar generation capacity. For small applications such as portable solar arrays, solar street lights, or small device charging systems, recommended batteries typically have capacities from a few watt-hours (Wh) to around 100 Wh.

Residential systems use batteries to store excess solar energy generated during the day and use it during times of low solar production or at night. The size of these batteries can vary significantly, but are generally in the kilowatt-hour (kWh) range, ranging from a few kWh to around 20 kWh or more, depending on the household's energy load and autonomy requirements.

Batteries for larger applications such as schools, commercial buildings or solar farms are even larger because they require more power.

Battery size for electric vehicles

The battery size in electric vehicles is typically larger than the fuel tanks in conventional diesel or gasoline vehicles. For compact and small cars, the battery capacities are between 20 kWh and 40 kWh. For mid-range cars and SUVs they vary between 40 kWh and 100 kWh. Luxury and premium vehicles tend to have even larger battery capacities, exceeding 100 kWh and sometimes reaching up to 200 kWh, resulting in a corresponding increase in size.

Standardization of battery sizes

Battery sizes have evolved over time and are standardized to facilitate compatibility and convenience. The International Electrotechnical Commission (IEC) has established several standards for battery sizes to ensure uniformity in the market. Here are some commonly used standardized battery sizes:

1.AA (LR6): The AA size battery is cylindrical and has a diameter of about 14.5mm and a length of 50.5mm. It is widely used in various applications such as remote controls, flashlights, toys and many portable electronic devices.

2. AAA (LR03): The AAA size battery is smaller than the AA battery and measures about 10.5 mm in diameter and 44.5 mm in length. It is often used in devices that require smaller batteries, such as: b Computer mice, remote controls and some small electronic devices.

3. C (LR14): The C size battery is larger than the AA battery and measures about 26.2mm in diameter and 50mm in length. It is commonly used in portable radios, flashlights and various household appliances.

4. D (LR20): The D battery is larger than the C battery and measures approximately 34.2mm in diameter and 61.5mm in length. It finds application in high-power devices such as large flashlights, boomboxes, and some industrial equipment.

5. 9V (6LR61): The 9V battery, also known as PP3 in Europe, is a rectangular battery with a thickness of approximately 9mm, a width of 48.5mm and a length of 26.5mm. It is mainly used in devices such as smoke detectors, guitar effect pedals and various audio devices.

By introducing standardized battery sizes, manufacturers can develop devices that take these sizes into account, making it easier for consumers to find compatible batteries. Additionally, standardization promotes interoperability and allows consumers to use batteries interchangeably in different devices.

Shapes of battery cells

Various forms of battery cells are available on the market. Here are some common forms:


This is the most common shape for batteries. Examples include AA, AAA, C and D batteries. These cylindrical cells have positive and negative electrodes stacked in a metal housing.

Button or coin

These batteries are round and flat and resemble a button or coin. They are typically used in small devices such as watches, calculators and hearing aids. Examples include CR2032 and LR44 batteries.


Prismatic batteries have rectangular or square shapes. They are commonly used in portable electronic devices such as smartphones, tablets and laptops. Prismatic cells are flat and thin, making them suitable for slim designs.


Pouch cells are flexible and thin and are commonly used in devices such as smartphones, tablets and portable power banks. They are lightweight and offer higher energy density compared to other battery types.

What is the battery group size?

In North America, the Battery Council International (BCI) defines standard group sizes for rechargeable batteries used in vehicles such as cars, boats and RVs. These group sizes determine the physical dimensions of the battery and not its capacity. In general, larger batteries tend to have higher capacity, but this is not always the case.

The following table lists some commonly used battery sizes:

Timeusb battery sizes explained

12V and 24V batteries

The most commonly used voltage for deep cycle batteries is 12 volts, which is also the primary voltage offered by Timeusb. In addition to the 12 volt options, Timeusb also offers a 24 volt, 50Ah alternative.

100 Ah LiFePO4 lithium batteries

Timeusb's 100Ah deep-cycle drop-in replacement battery is in high demand among customers. This battery is specifically designed to seamlessly replace Group 27 and 31 lead-acid batteries.

Below is the table showing the Timeusb LiFePO4 battery size in relation to the lead acid group size.



L*W*H in mm

Group Size

12V 50Ah



Group 26 battery

12V 100Ah



Group 31 Battery

12V 410Ah



Group 8D battery


I hope this article can help you find the best size for you.