How Many Batteries are needed in a DIY Camper Van Electrical System

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This blog post is going to be a step-by-step guide on how to perform a power audit so you can ACCURATELY size your camper solar system based on YOUR own power consumption to determine how many batteries you need for your camper van electrical system.

Quick note before we get started.  This is just one part of a overarching “How to Install a DIY Camper Van Electrical System” series.  If you’ve just stumbled on this article directly without seeing that, there are likely some things we’ve already covered.  If you want to check out that step by step guide, you can do that here: https://www.explorist.life/diy-campervan-solar

Also, we have interactive solar wiring diagrams that are a complete, A to Z solution for teaching you exactly what parts go where, what size wires to use, fuse size recommendations, wire lug sizes, and all kind of other stuff to help save you time and frustration.  You can check that out here: https://www.explorist.life/solarwiringdiagrams/

How to Size Your Camper Van Electrical System

You NEED to know how much power you use on a daily basis to determine the size of solar system you’ll need to power your camper.

Sure, you can buy a random solar kit and go for it, but more often than not, that tends to lead to disappointment in the performance of the system.

Be warned: This is an involved process. You’ll need to gather the items that you will be using (or look up their power usage) and put some numbers into the following spreadsheet you’ll need to download. After you’ve followed the step-by-step guide in this blog post, you’ll have a highly educated estimate of how much power you anticipate using throughout the day. This will give you a great baseline to determining how big of a camper solar setup you’ll need.

Step-by-Step Power Audit

What Appliances Will you be Powering?

You will need to gather as many of the items you will be powering.  If you don’t physically have the items yet, you will need to look up their power consumption rates (or use the ones I have pre-filled in for you).

Not all Appliances are the Same

There are AC appliances, DC appliances, and DC components disguised as AC components.  Confusing, I know. Hang with me, I’ll break it down.

AC Appliances

These are items that you plug into your normal household plug.  These will be items like a Coffee Maker, Instant Pot, Blender, Induction Cooktop, and a Vitamix.

TAKE ACTION: Gather all of these items into one pile and put a sticky note with “Table 1.1” next to them.

AC Appliances go in pile “Table 1.1”

*But wait…there is a catch…*

DC Appliances disguised as AC Appliances

There are imposters in your ‘AC Appliances’ pile.  There are likely items that plug into a normal household plug, that are actually DC appliances.  These items are like Computers, video game consoles (xbox), Cricut Die Cut machine, and printers.

A computer is a DC appliance disguised as an AC appliance.

How to Identify these imposters:  These items will have a ‘Wall Wart’ or an inline power supply AC/DC power adapter.

TAKE ACTION: Segregate these items into their own pile and label with a “Table 1.2” sticky note.

Inline power supply adapter commonly found on laptops
A wall wart converts 110v AC power to something usually in the 5v-20v range

DC Appliances

These items will be wired directly to your DC Distribution block (Fuse Block).  These will be items like 12v light strips, 12v puck lights, 12v fans, Maxxair Fans, Water Pump, and 12v TV.

TAKE ACTION: All of these items get their own special pile.  Label it with “Table 1.3”. “Table 1.3”.

DC Appliances power supplied by a 12v distribution block

Single Charge Items

These will be items like Phones, Camera Batteries, Drone Batteries, External Charger Packs, Etc.. Basically, anything you charge up, then unplug to use.

TAKE ACTION: Put these items in a pile and sticky-note it “Table 1.4”

Single charge items with replaceable like cameras and drones

Full Day / Per Day use Items

These are items you will let run ‘all day’.  12v refrigerator that cycles off and on, Weboost 4g booster, hot water heater are a few examples.

*Note, The list is pre-populated with a few items for you to use as benchmarks, but if these items have already been accounted for in a previous table, there is no need to add them here.

*Note, The refrigerator listed in the pre-populated list is the ARB 65qt and most top loading 12v refrigerators will have similar electrical demands.

*Note, the hot water heater is a delicate calculation.  The figure pre-input into the spreadsheet is for a 4 gallon Bosch hot water heater unit.  It uses about 65 Amp hours to heat up, then it holds that heat for 12 hours-ish.  The “Quantity” on that would be for “How many times do you plan on heating up 4 gallons of water”.  Use this as a benchmark, but not a rule*

TAKE ACTION: These items go into yet another pile. Label it “Table 1.5”.

Performing a Step by Step Solar Power Audit

Now you have your 5 separate piles labeled with Tables 1.1 – 1.5, we are going to go through them, pile by pile, item by item and input the ACTUAL numbers to get you as close as you can get to a PROPER educated guess that will tell you how much solar power you will need based on how much power you use every day.

For all of these items you will need either watts and volts *OR* amps, *AND* a rough approximation of how many minutes per day you anticipate using the device.

Now, you’ll need the spreadsheet your downloaded earlier. (It was toward the top of this blog post)

Table 1.1 | 110v Appliances

Look for a plate on the device that tells you how many watts the appliance uses.

  1. Change the name of the Item as Necessary
  2. Input the Watts into column 2.
  3. Input the number of minutes you anticipate using the item per day.

Your spreadsheet has been pre-populated for popular appliances and power outputs.  If your needs vary, alter as necessary by altering the GREEN columns. If you anticipate NOT using an item, you can delete the values in all of the GREEN columns, or simply input ‘0’ into the ‘Minutes Used Per Day’ Column.

Example:

Input 110v Watts and Minutes used per day into Table 1.1

Table 1.2 | AC/DC Adapter Appliances

Look for a sticker on the wall wart or AC/DC Converter that tells you how many amps and volts the is on the Output side of the cord. It’ll look something like this: 

Input DC power values into table 1.2


Your spreadsheet has been pre-populated for popular appliances and power outputs.  If your needs vary, alter as necessary by altering the GREEN columns. If you anticipate NOT using an item, you can delete the values in all of the GREEN columns, or simply input ‘0’ into the ‘Minutes Used Per Day’ Column.

Table 1.3 | DC Appliances

DC powered appliances typically hide their power usage for some reason.  If you look for a label or sticker with no success, usually looking online is the best option. You’ll be looking for the wattage of the device to insert it into column 2. If you find the amps and volts of the device instead, no worries!  Table 1.3 has a built in Amps to Watts calculator. Input your amps and volts into their appropriate spot in table 1.3, look at the resulting wattage reading, and insert that wattage reading into Table 1.3, column 2 under ‘Watts”.  Change column 5 to represent how many minutes you plan on using this device.

Input watts & quantity of DC appliances into Table 1.3

Your Spreadsheet has been pre-populated for popular appliances and power outputs.  If your needs vary, alter as necessary by altering the GREEN columns. If you anticipate NOT using an item, you can delete the values in all of the GREEN columns, or simply input ‘0’ into the ‘Minutes Used Per Day’ Column.

Table 1.4 | Single Charge Items

For Table 1.4, you will:

  1. Change Column 1 to the Device Name.
  2. Change Column 2 to the Battery Size of the Device.
  3. Change Column 3 to the number of times you plan to charge the device per day.
If given Wh (Watt Hours) input into Table 1.4a
If given mAh (Milliamp Hours) input into Table 1.4b


Your Spreadsheet has been pre-populated for popular appliances and power outputs.  If your needs vary, alter as necessary by altering the GREEN columns. If you anticipate NOT using an item, you can delete the values in all of the GREEN columns, or simply input ‘0’ into the ‘Minutes Used Per Day’ Column.

Table 1.5 | Full Day / Per Day Usage

Table 1.5 is for items that get used CONSTANTLY.  You’ll have to take a constant measurement of your items over the course of 24 hours.  This is good for things that cycle off and on like a refrigerator. The pre-populated ‘Refrigerator’ option is based on a top loading ARB 50qt 12v Refrigerator.

TOTAL: How Much Solar Power Do I need?

Now that you have filled in ALL the blanks with the electrical items you anticipate using throughout your normal day, check out ‘Table 1.6’.  This is how many Amp Hours you will PERSONALLY consume per day according to all of your inputs as well as a recommendation for battery bank size, solar array size and a few other goodies:

Your Camper Solar Results

The numbers you see are just general recommendations. Want to spend more time in cloudy environments? Maybe you should consider sizing up a bit. Budget can’t handle your recommended components? Perhaps size down (but PLAN for expansion). These are all just general recommendations that I feel confident in recommending. Any more is better. Any less is on you.

Now that you know how much battery capacity you need in your camper van electrical system, now it’s time to decide if you want to play the short or long game and go with AGM batteries or Lithium Batteries.  Check out our comparison here: https://www.explorist.life/choosing-a-solar-battery-bank-for-a-camper/

Everything that you are learning here is put to use in our FREE Interactive Solar Wiring Diagrams.  If you haven’t yet, check them out as they are a complete solution for a camper van electrical system.  Check them out here: https://www.explorist.life/solarwiringdiagrams/

Remember, this is just one part of a full camper van electrical educational series.  To see all of the individual guides, click here: https://www.explorist.life/diy-campervan-solar

Finally, If you found this guide helpful, It’d truly mean the world to us if you’d share it with somebody who can use it, pin it to pinterest for later reference, or share it to a facebook group when somebody has a question about this subject.  Click the bubble in the lower right corner to subscribe to be notified of future updates and as always, leave any questions you’ve got in the comments below.

45 thoughts on “How Many Batteries are needed in a DIY Camper Van Electrical System”

    1. Would you do a favor for me? See the items I labled table 1.2? Like the computer and ‘wall wart’ items? Would you take a picture of the back of all of the numbers on the back of that adapter and send it to me? That would help me out a ton.

        1. Hey Salva! I will be adding a EU version in the near future. I’ll announce it to our newsletter when it goes live or you can just keep an eye on it.

          1. Howdy – Any news on the EU spread sheet? I notice all your DC Amps are divisible by 12 and your Watts are Output volts multiplied by output Amps.

            Do you know what the calculations would need to be for 240v appliances?

    2. Stefan – I don’t think it makes a difference. Just put in the values for your 240v gear into the 110v tables, you’re only putting in watts and time used after all. I can’t see anything in the formulae that would make a difference.

      1. Thanks so much. Just getting started on a new Transit Connect build. Will use solar and inverter generator combination because I will have some air conditioning usage. Lithium batteries are planned. Trying to figure out how to size the inverter/charge controller for charging with the generator. Any help is appreciated

        1. I would do the power audit, but leave the air conditioner out of the power audit. Once you get your final recommended numbers, I’d advise rounding up as necessary. Let me know what kind of numbers you come up with and I’ll make another suggestion.

  1. Nate,

    This is incredible!!! Are you an electrical engineer or contractor by trade? This has been the best breakdown and explanation I have come across in allot of research. I am brand new to full time RV’ing and want to add a solar system to my Bigfoot travel trailer.

    Thank you so much for all the time and effort you put into this!!

    Shane

    1. Hey Shane! Glad it’s helpful!

      My degree is in Fire Science, so nope… not any of that stuff by trade. lol

    2. I only need power to run a maxxair fan overnight which came out to about 93 ah. If I get a 100 ah battery, wouldn’t that discharge it almost completely? Would that harm the battery? Also the recommendation stated 200w solar panel. Is it possible to go less, like just one 100w or something?

  2. I love this! I am currently chomping away at getting all the values needed for the spreadsheet. I am finding though that in Excel 2016, the AGM Battery field gives an error. Can I assume that the AGM requirement is twice the Lithium requirement and use the formula =(ROUNDUP(F87,-2)*2)&” Amp Hours”? Thank you very much for putting this together. I was aiming much higher than I thought. This is helping me realistically plan my trailer conversion. Wish me luck. Happy trails.

    1. Awesome! Glad it’s helping!

      Yeah, the spreadsheet does some weird stuff when it’s imported into Excel rather than using it natively in Google Sheets, but yes, The AGM figure should be, basically, lithium x2.

  3. This is incredible. And for free?! Will definitely be buying from your affiliate links. Thank you for all the time and thought you’ve put into this! You have a knack for breaking things down and explaining it in a way that makes sense (and making lovely spreadsheets and diagrams). Just wanted to say thanks!

  4. Hi Nate, I’m hoping to use a Bosch electric tank-less water heater in our camper-van build and was wondering, wouldn’t the minutes used per day be only when I turn on a hot water tap? Like taking a shower or washing dishes, and if so it would only be about 30-40 minutes per day.

    1. The figures in the spreadsheet are based on a few people who have, and use the unit and what their real life energy usage is for the unit. If you’d rather do your own calculations for what you think you’ll use, just put a zero next to the water heater (or erase it), and follow the steps in the 110v section and add the heater to your calculations that way.

  5. Hey Nate !

    Great tutorial ! Just wondering why do we dimensions our battery to be able to store one day of power ? Why don’t we just need to have batteries that can store the energy needed for the night and the less sunny part of the day ? I know it is to be sure not to run out of power but isn’t it a bit overkill?

  6. Ran the Calculator says i need 100ah worth of batteries but the spreadsheet doesn’t seem to factor current draw. If i have an appliance that wants to run at 1500 watts AC for 10 minutes that seems to exceed the maximum draw from the Battle Born Batteries right? that would be 150amp DC. So i would need (2) 50AH batteries right? except the 50ah batteries seem to only allow 60Amps continuous so does that mean i’d need 3 batteries?

    1. That’s a good point and you are correct that the calculator doesn’t take that into account. I’ll put that on the schedule to add that feature. In the meantime, you’ll really be looking at 2x100Ah Battle Born Batteries as each battery has a continuous discharge rating of 100 Amps, so 2 x 100Ah Batteries would double that to a continuous discharge rate of 200 Amps.

  7. Hi Nate,

    I love your work. The page on wiring solar panels as Series or Parallel is stellar. I’ve never seen anyone make the case for Series to maximize battery charging for less that ideal sun input (not in your control). Awesome.

    Anyway, regarding the spreadsheet above. I have the Wh and mAh data for my iPhone and iPad. I plugged both into Tables 1.4a and 1.4b as a test and got different results. You need a voltage to make the unit conversion from Wh to mAh – wouldn’t that voltage be different for each device based on the output of the device?

    Keep up the good work,
    Dave

    1. Good catch! Yes, that’s correct. I’ll check it out and adjust it soon. Currently, as it sits, it should be FAIRLY close though.

  8. Well done. It seem that your calculator has a minimum of 200 Watts of solar and 100 AH of battery. I did my calculations and I will be using under 25 Amp Hrs per day. Can I get away with 100 watts in solar and an 80 AH AGM sealed battery?

    1. IMO, you’re in the realm of simply using a Goal Zero unit. It’ll be more cost effective as such a small system.

  9. Hey Nate… What a site!!! I’ve learned a ton and feel confident I could plan and execute a complete build off everything you’ve provided, and I have zero experience in this area.
    Question, for a 120v 3.1cu fridge that I run all day what would you rate the amp hours at per day (conservative # is great)
    Also after inputting all my electrical usage in it came back at under 400ah and my heaviest draw on 110v is from a 1700w item and the spreadsheet still recommends a 3000w inverter… in another part of your blog you recommended using an inverter that exceeds your heaviest drawing daily use item, so would a 2000w inv be enough?
    Thanks a ton

    1. If you want to test the daily usage of your particular refrigerator you need to hook it up to a kill-a-watt meter (https://amzn.to/2KhNBHj) so you can get a real measurement.

      For the inverter: I do build in a bit of buffer. It’s up to you if you want to size down keep the margin.

  10. Four panels 400 wats it’s ok with an inverter/charger 2000 watts I only have one tv ,domestic fridge,lights..that’s it.

    1. Once you finish your solar audit from the instruction provided on this page, recommendations for panels and inverter are made at the bottom of the spreadsheet.

  11. PER GUNDERSEN MELBYE

    Hi there, I am an older norwegian with a young hart living in Mexico, old but new to all this exiting information, dont know if you can helpme out but its worth a try.
    I use oxygen part of the day, Inogen one G3 and want to charge the lithium battery via solar panels and a deep cycle battery, I am looking at a Renergy panel with a Renergy Wanderer controller but I am barely in the beginning of planning my G3 beeing the main problem to solve first.
    I would be happy to hear your point of vieww

  12. Good Morning Nate,

    So, i’m trying to future proof my build, allowing me to add additional panels and also additional batteries to the battery bank after my initial build.

    I was thinking starting off with 2x 160w 12v renogy panels on the roof and one battleborn 100ah lithium.

    Down the road, i would add 2x more of the solar panels, and incrementally add the batteries as i get paid. I know more panels means a faster charge with the battery bank, my concern is the electrical side, is it as simple as adding an addition battery and rewiring the battery bank to accommodate the new batteries or is there more to it?

    I can’t seem to find the answer in all of my google searches. I’m hoping you would know a place to find it, if you don’t know the answer.

    1. Plan the build around the biggest that you plan on making it and simply add as you described. There’s no harm in that. The only issue will be with charging via the alternator. Hold off on charging via the alternator until you get 2 batteries in the system.

  13. Hi Nate, great compliments on the best tutorial I’ve ever seen. With regard to LiFePo4 Batteries I understood that they are very temperature sensitive. Would it work to use a temp controller to monitor the bat temperature and to switch off loading once the temp is going beyond e.g. 5 degrees Celsius? Or are these bats also (unrecoverable) damaged when just exposed to low temperatures ?

  14. Hi Nate, This is fantastic, I have been struggling with this for so long. Thanks very much for the time you have put into this and sharing with us.

  15. Hi Nate,
    I have nailed our consumption at a modest enough 275 Ah. We already have a 100Ah leisure battery so the solar will need to be pumping twice that or more each day to keep up. You recommendation seems to be for about 650 lead acid or 350 Ah Lithium.
    My question is where could I find the space for even 350Ah Lithiums never mind the lead acid pack?
    Our MH is a Swift Ducato Escape 624, not large but just fine for we two.

  16. Hi Nate, thank you so much for all you do on this site! It is so helpful! I’m doing the energy audit but had a question about the overhead AC. If I get one, I anticipate using shore power only to power it. Can I just leave it off the energy audit or are there other considerations? Thank you!

  17. When discount box stores started showing up and running conventional businesses out of town, a knowledgeable sales associate once said to me “People won’t save any money if they buy the wrong stuff.” I would like to add a big heartfelt thank you to Nate for providing this information to those of us just starting out. You have personally saved me from several costly mistakes, and the time lost to backtrack from them. And I am sure I am not alone. Cheers!!!

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