top of page

How to Determine the Number of Lithium Batteries for Your RV:

Updated: Apr 12

Are you gearing up for an exciting weekend getaway in your RV? The anticipation of hitting the road and exploring new horizons can be exhilarating. However, nothing dampens the spirit more than running out of battery power halfway through your trip. To ensure you have a seamless and uninterrupted experience, it's crucial to understand how many lithium batteries your RV needs. In this guide, we'll break down the process step by step, using insights from the following video.

Understanding the Basics

Before you Determine the Number of Lithium Batteries for Your RV, let's establish a foundation of understanding. Your RV's battery serves as stored energy, measured in terms of amp hours (Ah). For instance, a typical lead-acid battery supplied with RVs might be labeled as having 100 Ah, but you can safely use around 50 Ah due to potential damage from over-discharge. This is your supply, the energy reservoir you have at your disposal.

When you convert the battery's 12-volt DC (direct current) power to 120-volt AC (alternating current) power, typically using an inverter, there's a significant change in the voltage. While this conversion allows you to run appliances designed for standard household outlets, it also has implications for the energy you'll be consuming.

The conversion from 12V to 120V doesn't alter the laws of physics. In fact, it abides by a fundamental principle: power remains constant. The power consumed by an appliance, measured in watts, doesn't change during this conversion. However, the current, measured in amps, does.

Here's where the misconception can arise. When converting 12V power to 120V power, the current required (amps) on the 12V side increases proportionally to the voltage conversion. In simple terms, for every 10-fold increase in voltage (from 12V to 120V), you'll need roughly 10 times the current to maintain the same power level. This phenomenon is a consequence of the relationship between power (watts), voltage (volts), and current (amps), as defined by the equation: power = voltage × current.

Battery Capacity: "Big Beard Battery"

  • Voltage: 12 volts

  • Amperage: 280 amps

Multiplying voltage by amperage gives you the battery's potential power in watts:

Power (Watts) = Voltage (Volts) × Current (Amps) Power = 12 V × 280 A = 3360 watts

For safety reasons, you're only using 3000 watts of this potential power to avoid fully discharging the battery. This practice helps prolong the battery's lifespan. This leaves you with a 10% depth of discharge (DoD), which is a common practice to maintain battery health.

Supply and Demand: Now, you have a supply of 3000 watts available from the battery. To understand how long this supply can meet the demand of different devices, let's consider an example: Your air conditioner's power consumption can range between 1400 watts per hour and 2000 watts per hour, depending on factors like its size and the outside temperature.

Calculating Runtime: Given your battery's supply of 3000 watts and an air conditioner demand of 1600 watts per hour, you can calculate how long the battery will be able to power the air conditioner:

Runtime (hours) = Battery Supply (watts) / Device Demand (watts per hour) Runtime = 3000 watts / 1600 watts per hour ≈ 1.875 hours

To be conservative and account for variables such as inefficiencies and potential fluctuations in demand or supply, it's a good practice to round down slightly. In this case, you could expect the battery to power the air conditioner for about 1.5 hours.

Keep in mind that the actual runtime might vary due to factors like temperature, battery age, and efficiency losses. Also, if you're running multiple devices simultaneously, you'd need to factor in their combined power consumption to determine the overall runtime the battery can provide.

Practical Implications:

Let's say you're using an appliance that consumes 120 watts of power at 120 volts. On the 120V side, this would mean a current of 1 amp (120 watts ÷ 120 volts = 1 amp). However, when you convert this power back to 12V, you would need around 10 amps (120 watts ÷ 12 volts = 10 amps).

This means that when you're running appliances using an inverter to convert 12V battery power to 120V, the current draw on the 12V side is significantly higher than what you might intuitively expect based on the appliance's wattage

Assessing Your Demand

The next step is to evaluate your energy consumption, or demand. Take into account the various appliances and devices you'll be using during your trip. This could include LED lights, fans, refrigerators, and potentially even air conditioners. Each of these devices draws a certain number of amps per hour.

  1. LED Lights and Fans: LED lights are relatively energy-efficient, drawing around 1 to 2 amps per hour. Fans, depending on their size, might draw 2 to 3 amps per hour.

  2. Refrigerators: Refrigerators can either be absorption style or 12-volt refrigerators. An absorption-style refrigerator uses about 1 amp per hour, while a 12-volt refrigerator could draw 4 to 8 amps per hour.

By totaling the amps drawn by all your devices, you can estimate your daily energy consumption. Keep in mind that for a lead-acid battery with a usable 50 Ah, you have around one day's worth of energy at your disposal. This means if your total consumption exceeds 50 Ah, your battery won't last the entire weekend.

Determining the Number of Batteries

To ensure your RV's battery capacity meets your needs, you need to do some calculations:

Evaluate Your Consumption: Start by listing all the devices and appliances you intend to use during your RV journey. This might include LED lights, fans, air conditioners, refrigerators, microwaves, chargers, entertainment systems, and more. Be comprehensive in capturing both essential and discretionary items. Every device has an energy consumption rating, often measured in watts or amps. These ratings indicate how much energy the device uses while operating. Consult the user manuals, labels, or online resources to find these ratings. Note whether the ratings are given in watts (W) or amps (A).

To estimate your daily energy consumption, follow these steps:

  • Convert Watts to Amps: If your devices' energy ratings are in watts, you'll need to convert them to amps using the formula: Amps = Watts / Volts. In this case, the voltage is typically 12 volts for RV batteries.

  • Calculate Total Amp-Hours: Add up the amp-hour consumption of all devices by multiplying their amp ratings by the number of hours you intend to use them each day. For example, if a fan draws 2 amps per hour and you plan to use it for 4 hours, the fan's contribution to your daily energy consumption is 2 A × 4 hours = 8 Ah.

  • Remember that energy consumption may vary based on factors such as device settings, usage patterns, and environmental conditions. It's advisable to add a buffer to your calculated consumption to accommodate these variations and ensure you have enough energy.

Calculate Daily Consumption: Determining your RV's daily energy consumption is a crucial step in ensuring a smooth and enjoyable trip. By accurately estimating the energy your devices and appliances will use each day, you can plan for an adequate power supply. Additionally, having backup power sources like portable generators or solar panels can provide peace of mind for extended journeys.

Plan for the Weekend: If your trip lasts a weekend (2-3 days), you need to multiply your daily consumption by the number of days to find out the total amp hours required for the trip. Again, having backup power sources like portable generators or solar panels can provide peace of mind for extended journeys.

Choosing Batteries: Choosing the right batteries for your RV is a pivotal decision that directly impacts the success of your off-grid adventures. The selection process involves understanding your energy needs, considering battery types, and relying on expert advice. Big Beard Battery, with its high-output high-storage batteries and dedicated team of experts at, offers a valuable resource for designing and optimizing your RV's power systems.

Lithium Upgrade: Consider switching to lithium batteries if your energy needs are high. Lithium batteries offer higher capacity, faster discharge rates, and more usable energy compared to lead-acid batteries. Enter Big Beard Battery, a reliable source of high-output high-storage batteries designed to meet the demands of modern RV adventurers. These batteries are engineered to provide ample energy for devices like air conditioners, refrigerators, and any off grid appliance.

Factors to Consider: If you intend to run power-hungry devices like air conditioners overnight, lithium batteries might be your best choice due to their ability to deliver higher capacity and faster discharge rates.


Choosing the right number of lithium batteries for your RV requires a thoughtful assessment of your energy consumption and desired comfort level. By following the steps outlined in this guide and understanding the relationship between battery supply and device demand, you can ensure a hassle-free and enjoyable RV experience. Whether you're a casual camper or an avid adventurer, having the right amount of battery power ensures that you can truly embrace the freedom of the open road.

377 views1 comment

1 Comment

Aug 16, 2023

I live in Tennessee and have worked at & owned a AC company from 1981.

In the south we used the AC on average of 8 hours a day. Just fyi when you are figuring your loads.

My RV AC pulls 11 amps so that would require around 900 amps from battery power per day to be off grid and fighting the southern humidity.

Thanks for your time in this matter and have a great weekend anywhere you want to go.

bottom of page