Calculating out what size leisure battery you need for your camper van conversion is a critical step to building the electrics system. If you underestimate your battery needs, you risk running out of power. This is a more common problem than you might think among the van life community.
In this post, we provide a step-by-step method to help you quickly determine how much battery your camper will require. By the end of this post, you will be able to correct size your battery bank, whether you are using AGM or lithium batteries.
IMPORTANT! This post works best if you download our free battery size calculator spreadsheet. Simply fill out the GREEN color cells and the battery size recommendation will be auto-generated for you. You can download this calculator by clicking the buttons below.
The camper battery calculator spreadsheet looks like the image below.
There are 4 steps (each column shaded in green) you are required to do to determine your ideal battery size.
- Write down each device name.
- Enter each device’s operating wattage.
- Decide the quantity of each device in your camper.
- Determine how many hours each day the device will be used.
Once finished, the calculator will do the rest of the work and recommend you the minimum battery size for your camper van.
If you’re still unsure how to proceed, this post will help you accomplish each of the 4 steps.
So if you’re ready, let’s get to it!
Step 1:
Save Spreadsheet To Your Computer/Cloud
Once you’ve download either the Google Docs or Microsoft Excel spreadsheet, you need to save the document to your cloud account or onto your computer directly. If you are using the Google Docs version, you must also delete the pink text box to begin.
Once downloaded, scroll down to Step 2:
Step 2:
Add Electric Devices To The Spreadsheet
In column A of the spreadsheet, add all the electric devices you plan to have in your camper van. We’ve listed some of the common devices found in campers already in the image above, but add and delete from this list to match 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 10 rows of 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 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.
For Example: If you visit the Amazon page for these LED lights, you can find that the wattage is 3W per light.
If you’re having trouble finding this information, we list the operating wattages of several of the electrical products we use in our camper van. You can view these wattage estimates in the image above and use these figures in your own calculations.
Once you’ve entered the operating wattage for each device, scroll down to Step 4.
Step 4:
Enter Quantity Of Each Device
In Column C, review each of your electrical devices and determine how many of them you will have in your camper van. This should be easy because you will only have 1 of most items, like “Inverter” or “Fridge” or “Blender”. But if you intend to charge more than one laptop or smartphone, so you will need to enter the appropriate quantity for each device.
For Example: We have 12 LED lights in our camper van, so we entered "12" in cell C3.
Step 5:
Enter Each Device's Daily Usage Time (In Hours)
Lastly in Column D, enter the estimated hours used per day that you intend to use each device. If you’re not really sure how long you intend to use each device, err on the side of caution and overestimate.
For Example: We intend to use our LED lights for roughly 8.5 hours each day, between from 6-8AM and from 5-11:30PM. So we enter 8.5 in cell D3.
This can be tricky for devices that you use only for a short amount of time, like a Blender or Water Pump. In cases like these, we estimate the number of minutes we plan to use those devices per day and enter the following formula into the appropriate cell:
=minutes/60
For 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 Battery Calculator Do The Rest
Once you’ve entered all the required information from Column A-D, the battery calculator will determine the Watt-hours (Wh) and Amp-hours (Ah) produced by each electrical device.
Then, the calculator will add up all the individual Amp-hours and we call this your ‘Daily Energy Usage”. You can see the daily energy usage for our example spreadsheet in cell F19.
And from this daily energy usage, the calculator will recommend your minimum battery size in the next step.
Step 7:
Get Your Battery Size Recommendation
With all the information entered correctly, the battery calculator will recommend a minimum battery size for your camper van. All you need to do now is decide whether you will be using AGM or lithium batteries.
Our Opinion: Unless you’re on a tight budget, go for lithium batteries. In most situations, they are worth the extra upfront cost. Read our post to learn why.
In the spreadsheet with our pre-filled data, the battery calculator recommends 463Ah (for AGM batteries) and 231Ah (for Lithium batteries). This is the recommended minimum amount, so it’s a good idea to at least round up to the next battery size.
For example, you can round up to 500Ah (for AGM) and 300Ah (for Lithium).
If you haven’t already, be sure to download our battery calculator spreadsheet below:
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Real World Data:
Comparing Our Calculation To Reality
For 4 days, we disconnected our solar panels from our van’s electric system and we 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.
| Day (@ 10pm) | Power Consumed |
| Jan 15, 2021 | Start |
| Jan 16, 2021 | 72 Ah |
| Jan 17, 2021 | 65.34 Ah |
| Jan 18, 2021 | 83.28 Ah |
| Jan 19, 2021 | 62.33 Ah |
From the above data, it looks like our calculation was moderately close to our real-world energy usage. We estimated that we would be using 116Ah per day of battery capacity and in reality, we used an average of 71Ah per day. A ~40% difference.
The biggest reason for this difference is that we ended up using our Instant Pot, laptops, and hair dryer much less often than we anticipated. But the most important thing is that even on our most heavy usage days, we never used more power than we estimated using the spreadsheet calculator. And this means we should almost never run out of power during van life (since we also used the calculator to determine our solar wattage size).
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Conclusion: Size Your Camper Van Electrical System In Advance
We hope this article has helped inform and inspire you to begin building your own camper van electrical system.
Once you have properly sized your battery bank, you may be wondering how many watts of solar panels you need to help keep your batteries regularly and sufficiently charged.
We discuss this in our next post: Determining 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!
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