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What Size Battery You Need For Your Camper – How To Calculate

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Banner image for our post to calulate how much batteries you'll need for your camper van's electrical system

Calculating what leisure battery size 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 common problem among the van life community.

In this post, we provide two different ways to help you determine what size battery bank your camper will require.

  • Simple Online Calculator: For people who want a quick answer without having to do cumbersome wattage calculations.
  • Detailed Spreadsheet Calculator: For people who are interested listing out all their intended devices, their power ratings, and usage times.

Which ever way you choose, you will be able to calculate the correct size battery bank for your van, for both AGM and lithium batteries.

So if you’re ready, let’s get to it!

Best Budget LiFePO4
Li Time "TM" LiFePO4 Lithium Battery

Our top lithium battery recommendation! The Li Time "TM" packs a serious punch in a compact enclosure. Wide-ranging BMS with low-temperature protection. And superior shock resistance.

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09/16/2023 03:33 am GMT

Simple Online Battery Calculator

Below is a simple way to determine what size battery you need for your van conversion. Rather calculating the energy of every single electric item in your van, you can simply:

  • Select whether you are budget or quality focused.
  • Pick from one of the drop-down options.
Battery Size Calculator
  • Very Low: Only the basics. One laptop, one smartphone, a few LED lights, and a vent fan.
  • Low: A couple laptops and smartphones, 12V fridge, vent fan, water pump, 6-10 LED lights, and small appliances, like a blender.
  • Medium: Everything from "Low", but add a diesel heater and occasional use of a hairdryer, coffee machine, electric kettle, and Instant Pot.
  • High: Everything from "Medium", but add more constant use of AC appliances and some use of an induction stove.
  • Very High: Everything from "High", but add a hot water heater, some use of an air-conditioner, and more frequent use of an induction stove.

Battery Bank Size:

100Ah (AGM)

100Ah (Lithium)

200Ah (Lithium)

300Ah (Lithium)

400Ah (Lithium)


One 100Ah AGM Battery

One 100Ah Lithium Battery

One 200Ah Lithium Battery

Two 100Ah Lithium Batteries

Three 100Ah Lithium Batteries

One 270Ah Lithium Battery

Four 100Ah Lithium Batteries

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

Detailed Spreadsheet Battery Calculator

IMPORTANT! Download our free battery size calculator spreadsheet by clicking the buttons below. Simply fill out the GREEN-shaded cells and the battery size recommendation will be auto-generated for you. You can download this calculator by clicking the buttons below. (The Google Docs version is much better than the Excel version)

The camper battery 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.

Camper van battery calculator spreadsheet summary

There are four steps (each column shaded in green) you are required to do to determine your ideal battery size. The individual steps are:

  1. Write down each device name.
  2. Enter each device’s operating wattage.
  3. Decide the quantity of each device in your camper.
  4. 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 that will be able to adequately handle the electrical load in your camper van.

Step 1:

Save Spreadsheet To Your Computer/Cloud

When you open the battery calculator, you will see a pink box that laid over the table. This dialogue box instructs you to make a copy and save the file to you down cloud drive or computer.

You will not be able to edit the document until you save a copy of the battery calculator to you own file.

Once you’ve saved a copy for yourself, 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 the electronics you plan to have in your own 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 [Amazon], 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, estimate the number of minutes you plan to use those devices per day and enter the following formula into the appropriate cell:


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 Spreadsheet Calculate Your Daily Energy Usage

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. This all happens in columns E and F.

At the bottom, on row 19, the calculator will add up all the individual Amp-hours. We call this sum your ‘Daily Energy Usage”. You can see the daily total energy usage for our example spreadsheet in cell F19, which is 116Ah.

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.

In the spreadsheet above, with our pre-filled data, the battery calculator recommends a 463Ah battery bank (for AGM batteries) and 231Ah battery bank (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: Based on the example in the spreadsheet, you can round up to a 500Ah bank (if using AGM batteries) or round up to 300Ah (if using 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.

Step 8:

Select Your Batteries

If you scroll down on the battery calculator file, you’ll reach our battery recommendations. You will see that we STRONGLY recommend going with lithium. This is because prices for lithium batteries have come down dramatically recently and basic, no-frills lithium batteries are now similar in price to AGM batteries. These days, AGMs offer very little competitive advantages over lithium batteries.

In the image above, you can see that the battery calculator recommends two popular lithium batteries. One is a popular budget model and the other is a premium one. So, if after using the calculator, you determine that you need a 200Ah lithium battery bank, you just need to purchase two 100Ah batteries from the list.

You can also find these batteries below:

Great Value Pick
Redodo 12V 100Ah Mini LiFePO4 Lithium Battery

Lithium batteries outperform standard AGM batteries in virtually every category. The 12V Redodo battery is a great option (at a fantastic price) to 'go lithium' without breaking the bank. Pro Tip: Use our battery calculator to size your energy system.

We earn a commission if you make a purchase, at no additional cost to you.
09/16/2023 08:36 am GMT

Step 9:

Download Our Solar Size Calculator

Now that you have an appropriately sized battery bank, you’re ready to move on and size your solar system. At the very bottom of the battery calculator, you can find a link to download the camper van solar calculator.

For more information, read our solar array wattage calculator to get started. The post provides the same step-by-step instruction as this one.

Happy building!

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

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 [Amazon]. 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, 2021Start
Jan 16, 202172 Ah
Jan 17, 202165.34 Ah
Jan 18, 202183.28 Ah
Jan 19, 202162.33 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).

Speed Up Your Electrical Install With Our Free eBook

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: 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!

Go Back: How To Build A DIY Camper Van

Thank You For Reading!

We’re Yuko and Eric! We both grew up in Asia ( Japan & Hong Kong ), we left our jobs and homes in 2018 and started traveling full time from Canada to Argentina in our self-converted camper van since end of May 2019. “Asobo” means “Let’s play” in Japanese. We named our site “Asobolife” because the life is always uncertain and we live only once so it’s important to always keep positive, playful mind and enjoy the moment you are in the present. We also want to use this website to share our road trip and van building experiences to inspire our readers. We hope you enjoy!

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