When we first decided we would do a van build, the electrical portion was one I began researching immediately as I knew the least about it.  Let’s start with “no matter how novice you are with electrical concepts, you can learn the basics of a 12V (or higher) system with a bit of patience and research.”

Disclaimer – I’m still very much a novice with all of these concepts.  I mostly pieced together what others had done, shared in their blogs, or what I could find in forums and solar sites.  Many of my formulas are estimates, could be pretty off base, or could be completely wrong (if so, I’d love to hear about it – email me, don’t leave nasty comments as that helps no one)! This is simply the math I did when figuring out our system and so far it has worked well and we haven’t had any fires!

Power Needs

When determining how to build out our electrical system, we first needed to determine our needs.  Our primary needs for power are:

• LED Ceiling Lights
• Refrigerator
• Water pump under sink
• MaxxFan
• 110V elecronics
  • Macbook
  • Macbook Pro
  • camera battery charger
• 12V Electronics
  • Phones
  • bluetooth speaker
  • iPad

Once we tallied all of that up, we needed to determine the power draw (in amps) each item would take on a daily basis.  The calculation for each uses the below formulas:

Watts = Volts x Amps

Amps x Hours used (in 24 hour period) = Amp hours

You can visit my spreadsheet I used for more details here for reference.  I’ve been told organizing spreadsheets isn’t my calling so if you have questions, please reach out.  Ultimately, we found we had about 100Ah of power per day.

System Size

“Do I go with 12V over 24V (or even 36V)? 100Ah, 300Ah, 500Ah?!?! What is a lithium ion battery!?!”

Quite simply, we tried to do things on the cheap and keep it simple.  I know there are perks (such as efficiency) to higher voltage systems but won’t go over these here.  We’re happy with 12V.  Options were plentiful, resources online were unlimited, and it was the most cost effective.

Knowing that we didn’t want to use more than 65% – 70% (see depth of discharge (DOD) for 12V batteries), this meant we needed a battery bank of about 300Ah.  To accomplish this, one can go with any variety of  options (a 300Ah 12V single battery, two 150Ah 12V batteries in parallel, two 300Ah 6V batteries in series, etc.) as long as it results in 300Ah at 12V.   We ended up going with three 100Ah batteries in parallel as Amazon had a steal of a deal when we purchased.

Battery Type

“So we know how much power we want to be stored.  Now, what battery type do I need?” I knew I didn’t want to have to service my batteries – I only wanted to keep them ventilated and I could trust they would function as expected. The batteries used in the battery bank are deep cycle 12V or 6V batteries in most cases. These batteries come in lead acid, AGM, and gel varieties.  I went with sealed lead acid as I didn’t want to be filling it with water on a recurring basis, effective.  To do this, you’ll want to ensure that you double the necessary Ah draw needed as you shouldn’t drain your battery bank system below 50%.

I knew I didn’t want to have to service my batteries – I only wanted to keep them ventilated (some batteries off-gas) and I could trust they would function as expected. The batteries used in a typical van conversion battery bank are deep cycle 12V or 6V batteries.  Deep cycle batteries can be discharged dramatically (down to 40-50% on a regular basis) and still retain a full charge for quite some time.  Start batteries don’t work as they’re really meant for delivering a high amount of power quickly – discharging these too much will damage them.  Deep cycle batteries come in lead acid, AGM, and gel varieties.  I went with sealed lead acid from Amazon and I’m very pleased so far.