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How Much Solar and Battery Power Do You Actually Need?



To be sure that your adventure van’s electrical system will meet all your needs and still be safe to operate, it’s best you work with a professional campervan conversion company like 27North Inc. We have a team of qualified electricians capable of designing an electrical system for any type of van or expedition truck.


Start With a Power Audit

Choosing a random solar or battery unit will most likely lead to disappointment in the performance of the system. So, figuring out how much power you’ll use is the first step to determining what size of batteries and solar your camper will need.


Here’s how to perform your power audit.


1. Make a List of All Items You'll be Powering


Create a list of every electrical appliance and gadget you’ll use in your camper. However, note that these devices aren’t the same. There are AC appliances, DC appliances, and DC components concealed as AC components.



  • Alternative Current (AC) Appliances - These are items that you plug into your normal household plug, e.g. a coffee maker, blender, and electric lamp.

  • Direct Current(DC) Appliances - They are wired directly to your DC distribution block. Examples include 12v light strips, 12v fans, water pump, and 12v TV.

  • DC Appliances Concealed as AC - These items are plugged into a normal household plug, but they are actually DC appliances. Some examples are laptops, video game consoles, and printers.

  • Single-Charge Items - They are the items you charge up, then unplug to use. They include phones and camera batteries.

  • Constant Use Items - These are items that will run the whole day, such as a 12v refrigerator, network booster, and hot water heater.


2. Identify the Amps Each Appliance Uses


Ampere(AMP) is the basic unit of measurement for electricity. There's a plate on the device that lets you know the number of amps the item uses. Check the amps for all your appliances and add up the total that you could be using at a time. Some appliances state watts, so you’ll need to divide the watts by 12 volts(if you are using a 12-volt battery) to calculate amps. If you can't find the information on the sticker, look for it online.



3. Estimate for How Long Each Day the Appliance Will be in Use

Figure out the number of minutes or hours you anticipate using each item per day. Now multiply amps by estimated hours of usage to calculate the total amps needed per day for each appliance. Next, add together all amps needed per day to get the total amp hours per day you expect to use. Since you’ll use more power on some days than others, add some contingency. Based on your specific needs, you can add 20%, give or take, to the total amp hours.


What Size Battery Do You Need For Your Camper?


Now that you know the total amp hours, it’s time to figure out how much battery capacity you need in your camper van electrical system. Basically, a campervan has two types of batteries: A chassis battery that starts the rig's engine and a house battery that powers the home part of your van. Here, we will be focusing on the house battery as it’s responsible for powering appliances, interior lights, laptop, phone charger, fan, etc.



Now, how many batteries are needed in a campervan build? It depends. First, note that batteries are measured in amp hours(Ah). This is the amount of current a battery can provide for exactly one hour. Every battery comes with an amp hour rating, and you can use this number to judge how many of your appliances your battery can power.

For instance, a 12-volt battery that has an amp hour rating of 200 means that for an hour, it will support a 12-volt load with 200 amps of current. However, campervan batteries aren’t the same, so AMP hour numbers change depending on the battery type.

For a lead-acid battery (AGM), you should divide the number of amps in half. That means you’ll only get 100 amps of current with a lead acid with a rating of 200. Lithium batteries are about 99% efficient, meaning they will deliver almost 100% of their amp hours.

Calculating Campervan Battery Size With Lithium


Lithium or LiFePO4 batteries are the gold standard for RV batteries. They deliver more power than the others, charge faster, weigh less, don’t need regular maintenance, are the most durable, perform well in all temperatures, and can be discharged without damage. However, they are the most expensive option.

Deciding what size lithium batteries to choose for your power needs is pretty straightforward. Take your expected daily energy usage, double it, then round up to the nearest 100Ah. So, if your total amps needed per day is 70Ah, doubling it will result in 140Ah, while rounding up will give you 200Ah for your ideal lithium battery size. That means you can buy one 12V 200Ah lithium iron or two 12V 100Ah lithium iron batteries to meet your needs.


Calculating Campervan Battery Size With AGM


AGM batteries don’t need regular maintenance, are leakproof, work well in harsh weather, and don’t off-gas. However, you can only discharge them up to 80%. If you opt for a lead acid AGM, the calculations are different since these batteries are only about 80% efficient.

Take the daily energy usage, double it two times, then round up to the nearest 100Ah. So, if your total amps needed per day 70Ah, doubling it will result in 140Ah. Doubling it again will total 280Ah. After rounding up, it will result in 300Ah for your ideal battery size.


Importance of an Extra Battery for Your Campervan Build


While it’s essential to have an appropriately sized battery bank to meet all your energy needs, it’s wise to have an extra battery if your budget encourages it. That’s because when adventuring off-grid, you may go multiple days without being able to charge your batteries properly. For instance, when there’s low light, your solar system may not charge the battery adequately. So, having an additional 100Ah battery will allow you to prolong your energy independence.



How Much Solar Power Do I Need For A Campervan?

For those who want to be completely self-sufficient when camping off-grid, solar panels are a must-have. They harvest energy from the sun and send it down through a charge controller to recharge the batteries in your camper's electrical system. But how much solar do you need for vanlife?


Put simply, the best way to determine the amount of solar you need is after you know the size of your battery bank. Choose a system that can recharge the batteries you have. Now that you know the ideal battery size for your energy needs, you’ll need to also consider the following before selecting solar panels:

  • How much time you plan on spending off-grid or on-grid

  • Other recharging methods

  • The season you will use your campervan

  • The area you’ll travel to

  • Where you park—full sun VS shade

Note that solar panels are measured in watts per hour. So, it’s the total wattage of the entire solar panel array you first need to consider, and not the number or size of the panels. To calculate watts, multiply amps by volts. Let’s say you’ll use 70 amps per day with a 12v battery. Therefore, you need 70 amps x 12 volts = 840 watts of power output by your solar panels each day.

Now, if you need 840 watts per day and we assume you’ll get an average of 4 hours of sunlight per day, you’ll need 840 ÷ 4 = 210w of solar panels. Of course, this number will vary depending on the amount of illumination hitting your panels.




Sizing Your Campervan Inverter

An inverter is a device that connects to your house batteries and converts the 12v DC current to standard household AC current—240v. It’s rated in watts. Choose your inverter based on the maximum load you could be drawing at once. For instance, a 2000 watts inverter can power a 1600 watts hairdryer without tripping. But if you power the same hair dryer with a 1000-watt inverter, the inverter will trip or blow a fuse.

The more powerful the inverter, the more power it draws to run, so don’t go for something that’s excessively powerful to avoid wasting precious energy. Always confirm the wattage of your appliances before shopping for an inverter. It’s also recommended you invest in an inverter that’s a few hundred watts larger than your most powerful appliance.



Get Help Sizing Your Campervan’s Electrical System

Designing a campervan conversion electrical system requires you to take into account a lot of parameters. If you are unsure how to proceed, you can always consult a professional. An expert campervan builder will take every detail into account before accurately calculating the exact battery bank, solar array size, inverter size, and other components required for your campervan electrical system.

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