Estimating Your Electrical Needs… How much for how long?

Just some food for thought.  If you are doing much camping, you will need power if you want to be happy.  Whether watching TV, reading a book, or cooking a bite to eat, you will want some juice to power a few creature comforts.

Choosing the batteries, inverter, and charger (if you are charging independently from the alternator) is no small task.  I’ve settled on AGM batteries for longevity and resilience.  I always figured bigger is better to some degree.  But knowing what you really need helps you to work realistically and look for what you can afford…

I put together a worksheet to show how I planned consumptions for a worst case (no shore power) scenario.  For the way I plan to run my wiring, when I have shore power, I will unplug all the wiring and plug it in to the shore power panel while also running my charger to replenish the batteries.  The inverter will not be present.  The numbers you see below assume I am in the boonies and running only on my own stored power until I found a drink of 120V juice…



As you can see, I listed each item, the 12V current to run it, and then doubled the number.  Remember, we don’t want to run AGM batteries less than 50% charged so doubling each estimate will help us over-estimate what we need.  In this case, I summed it all up and came up with 130 amp hours needed for each day.

A 400 amp hour bank of batteries will get me three days worth of power.  Add in shore power, a generator, or a solar panel and there you go… more freedom yet because you will be able to replenish.  I plan to keep a long drop cord in the van and when I am eating out, hanging out at a gas station, etc., the batteries can get a little boost!
I like the 3 day capacity idea.  One day is a breath or two from having no CPAP machine (for sleep apnea).  You would be potentially depleting the AGM  batteries and thus shortening their lives.  2 days leaves a little to spare.  3 days is just about right in terms of cost, weight, and space.  I figure if I can’t get to a power source for more than three days then I am probably lying dead somewhere already…

This sheet helped me immensely.  When the walls are done, the lights will come on shortly thereafter!  Just because I am anal, I plan to have an override switch for an emergency tie-in to the van battery should I lose the house batteries for some reason.  I might even buy a cute little 60AH AGM for just that reason.  It could be topped off all the time with solar…Those who use CPAP know how vital it is.  Gotta plan ahead.

Have fun.  I hope this simple sheet helps you plan ahead for your off-the-grid living.  It will be easier when you know your battery capacity needs.  🙂

About VanTrekker

I am a former vandweller in Eastern Iowa who, for several years (off and on), lived in a 2007 Chevy cargo van. I still travel around Iowa with my tortoise shell cat, Jennifer Stefanie. Our favorite place to explore is the Country Heritage Community, the four far northeastern counties of Iowa (Clayton, Winneshiek, Allamakee, and Fayette). Ride along as we fish in pristine trout streams, enjoy fine home cooked camping meals, and meet new people. It's all possible on a shoestring budget. Happy travels always! --- Brad, the "Van Trekker"
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