How To Calculate Your Camper Van Battery Size

Calculating your leisure battery size for your camper van conversion is critical to building your electrics system. If you underestimate your battery size, you risk running out of power. This is a common problem among the van life community.

In our 4+ years of experience, most camper van electric systems are powered with a single 12V 100Ah AGM battery. This single battery, however, is not enough to power today’s modern equipment, which usually includes a diesel heater, a fridge, a couple of laptops, and even electric kettles. What usually ends up happening is that this single battery is often over-discharged daily and ends up dying prematurely less than a year after it was purchased.

Don’t Know Anything About Camper Van Batteries? Read our leisure battery guide to get a basic understanding of camper batteries. This will help you before reading this comparison post.

The good news is that this scenario can easily be avoided with proper planning and simple battery size calculations. In this post, we provide two different ways to help you determine what size battery your camper will require.

Disclosure: As an Amazon Associate, this site earns from qualifying purchases. Though we may earn a commission, the price you pay always remains the same.

1. Simple Online Battery Calculator

Below is a simple way to determine what size leisure battery you need for your camper van conversion. This is for people who want a quick answer without cumbersome wattage calculations. Rather than calculating the power requirements of every single electric device in your van, you can simply:

1. Select whether you are budget or quality-focused.
2. Select your approximate daily energy usage amount from the drop-down menu.

Note: Unless your daily energy usage is ‘very low,’ we always recommend using lithium (LiFePO4) batteries instead of traditional AGMs. Lithium batteries have longer lifespans, can be discharged to lower levels more frequently, and are not nearly as expensive as they used to be.

Unsure which battery to get? Read our Li Time vs. Redodo lithium battery review to see which brand we recommend and why.

2. Detailed Spreadsheet Battery Calculator

Download our free battery size calculator spreadsheet by clicking the buttons below for a more nuanced leisure battery size calculation. One is a Google Docs file, and the other is a Microsoft Excel file (the Google version is better). Fill out the GREEN-shaded cells, and the battery size recommendation will be auto-generated.

The leisure battery size calculator spreadsheet looks like the image below. You will see that most of the cells are shaded in green and yellow. The cells shaded in green are for you to fill out. Do not enter any information in the yellow-shaded cells.

You are required to do four steps to determine your ideal battery size. The individual steps are:

1. Enter each device’s name. (Column A)
2. Enter the operating wattage of each device (Column B)
3. Decide the quantity of each device in your camper. (Column C)
4. Determine how many hours each day the device will be used. (Column D)

Once finished, the calculator will do the rest of the work and recommend the minimum battery size to adequately handle the electrical load in your camper van. For step-by-step guidance on how to use this spreadsheet calculator, keep reading the following chapters below.

Step 1: Save Spreadsheet To Your Computer/Cloud

When you open the battery size calculator, you will see a pink box superimposed over the spreadsheet. This dialogue box instructs you to save the file to your cloud drive or computer. When completed, delete the pink box to start editing the spreadsheet.

Note: You cannot edit the document until you save a copy of the spreadsheet calculator to your computer/cloud.

Once you have your own saved copy of the spreadsheet, scroll down to step 2:

Step 2: Add Electric Devices To The Spreadsheet

In column A of the spreadsheet, under the heading “Device Name,” add all the electric devices you plan to have in your camper van. This is an excellent time to sit down and carefully think about which devices you want to power. The more comprehensive you are with this step, the more accurate the battery calculator will be.

We have already listed several electrical devices commonly found in camper vans in the screenshot below. Still, you can add and delete them from this list to match the electronics you plan to have in your van conversion.

Each row should only have a single type of device, like “LED lights.” If you plan to have multiple LED lights, do not create multiple rows of single LED lights. In step 4, we will include the total quantity of each device in your van.

Once you’ve entered each device, scroll down to step 3.

Step 3: Enter The Operating Wattage For Each Device

In column B, under the heading “Power (W),” enter the operating wattage for each device. You can find the wattage information on the product’s packaging box, manual, or even on the product’s Amazon page.

Example: If you visit the Amazon page for the LED lights we list below, you can find that the wattage is 3W per light. These are the same lights we use in our camper van.

If you are having trouble finding this information, we list the operating wattages of several electrical products in our camper van. You can view these wattage estimates and use these figures in your calculations.

Once you’ve entered the operating wattage for each device, scroll down to step 4.

Step 4: Enter the Quantity Of Each Device

In column C, under the heading “Device Quantity,” review your electrical devices and determine how many of each you will have in your camper van. This should be easy because you will only have one of most items, like “Inverter,” “Fridge,” or “Blender.” But if you intend to charge more than one laptop or smartphone, enter the appropriate quantity for those devices.

Example: We have 12 LED lights in our camper van, so we entered “12” in cell C3.

Step 5: Enter Daily Usage Time (In Hours) For Each Device

Lastly, in column D, under the heading “Hours Used Per Day,” enter the estimated hours used per day that you intend to use each device. If unsure how long you intend to use each device, err on caution and overestimate.

Example: We intend to use our LED lights for roughly 8.5 hours daily, between 6-8 AM and 5- 11:30 PM. So, we enter 8.5 in cell D3.

This can be tricky for devices that are only used for a short amount of time, like a blender or water pump. In cases like these, estimate the number of minutes you plan to use those devices per day and enter the following formula into the appropriate cell:

=minutes/60

Example: We estimated that we would use a hair dryer for 6 minutes every day. So, we entered the formula =6/60 into cell D13.

Step 6: Let The Spreadsheet Calculate Your Daily Energy Usage

Once you have entered all the required information from column A-D, the battery calculator will determine the Watt-hours (Wh) and Amp-hours (Ah) required by each electrical device daily. This data is displayed in columns E and F.

In cell F19, the calculator will add up all the individual Amp-hours (Ah) incurred by each device. We call this sum your ‘Daily Energy Usage”. The daily total energy usage for our example spreadsheet is 116Ah.

Step 7: Get Your Battery Size Recommendation

Assuming all the information you entered is accurate, the battery size calculator will recommend a minimum battery size for your camper van. All you need to do now is decide whether you will use AGM or lithium batteries. (Hint: You should be using lithium)

Notice that the recommended minimum AGM battery size (463Ah) is double that of the recommended lithium battery size (231Ah). This is because the calculator considers depth-of-discharge (DoD) differences between the two battery chemistries. AGM batteries should ideally only be discharged to a maximum of 50%, while lithium can be discharged well past 80-90% without significantly affecting its battery life.

Round Up! Based on the example in the spreadsheet, round up to a 500Ah bank (for AGM batteries) or round up to 300Ah (for lithium batteries).

Step 8: Select Our Recommended Batteries

If you scroll down in the battery size calculator spreadsheet, you will reach our battery recommendations. We highly recommend the Li Time (Trolling Motor) 100Ah battery if you are on a tight budget. It has a robust battery management system (BMS) and includes the all-important low-temperature cut-off protection. Since the battery is made for marine environments, it also has increased shock absorption and improved sealing to keep out moisture and salty air.

Read our Li Time vs. Redodo lithium battery comparison to learn more about this battery.

The spreadsheet also provides a ‘premium’ lithium battery recommendation, Battle Born batteries. While we use three Battle Born batteries in our camper van, we can’t ignore that the Li Time batteries we recommend come with the same BMS specs at almost 1/3 the price.

Step 9: Download Our Solar Size Calculator

Now that you have a leisure battery size that meets your power requirements, you can move on and size your solar system. You can find a link to download the solar calculator spreadsheet at the bottom of the battery calculator.

For more information, read our solar array wattage calculator to get started.

Building a camper van? Download our free e-books with intuitive electrical, solar, and plumbing diagrams.

Comparing Our Battery Size Calculation To Reality

For four days, we disconnected our solar panels from our van’s electric system and measured the flow of amps out of our batteries using our Victron Battery Monitor. We wanted to see how our real-life energy usage compared to our calculated estimation.

Below is a table showing our results.

From the above data, our real-life daily energy usage was moderately close to our theoretical calculated amount. In the spreadsheet, we estimated that we would be using 116Ah of battery capacity per day, and in reality, we used an average of only 71Ah per day. A ~40% difference.

The biggest reason for this difference is that we used our Instant Pot, laptops, and hair dryer much less often than anticipated. This is fine because using less energy than you initially expected is always better. It also reduces the likelihood of running out of battery during your travels.

Note: Appropriately sized leisure batteries are only half the battle to ensuring you do not run out of battery power. Use our solar calculator to ensure you have the right amount of solar watts.

Conclusion: Size Your Camper Van Electrical System In Advance

We hope this article helped inform and inspire you to begin building your own camper van electrical system.

Once you have adequately sized your leisure battery bank, you may wonder how many watts of solar panels you need to help keep your batteries regularly and sufficiently charged.

We discuss this in our next post: How To Calculate The Size Of Your Solar Array.

If you have any questions or comments after reading this leisure battery sizing post, please let us know in the comments below!

Happy building!