Electrical Redesign – More Battery

As of the last revision of my camper’s electrical system, I had two battery banks with the ability to charge both and switch between them as needed. Under normal use, the AGM battery bank would barely last one night, and only if it were fully charged late in the afternoon. To balance the utilization between banks, I’d normally run from the AGM battery bank until it was partially depleted, usually about bedtime, then flip a switch and run from the lithium battery overnight. This worked OK up to a point.

Other than having to manually switch banks, the biggest issue was that even with both battery banks (100Ah lithium & 220Ah AGM) we were limited on how many days we could camp without either having decent sunlight or running either the van engine or generator to recharge the batteries. Hence my quest for more battery – preferably lithium. I’m constrained by both space and $money. I needed something that I could cram into a cranny somewhere without giving up storage space & something that had a rational price tag. Adding another 100Ah Battleborn was the obvious option and would work if I were willing to wedge it under the galley next to the Truma. Or I could find another use for the Battleborn and start fresh.

Because it gets down to -25F in our corner of Minnesota and because lithium’s don’t like the cold, I’ve wanted to be able to remove the lithium battery in extreme weather and still have a functional camper. After three years without camping in extreme cold and after experimenting and observing the Battleborn battery and never removing it in winter anyway, I’ve decided to bite the bullet and make the lithium battery the only power source for the camper. That allows me to make the system much simpler.

I wanted a battery with built-in heat, and I wanted access to the battery internals via Bluetooth or serial in case I want to monitor and/or troubleshoot the battery.

After watching the battery market and technology for a year, I concluded that my options were:

  1. Add a heated Battleborn 100Ah battery, (200Ah total): $1100 & change, no Bluetooth.
  2. Build a DIY battery, buying Chinese cells and BMS from either China or a US reseller & assembling and testing it myself, 270-300Ah: $1000-$1200, Bluetooth BMS, DIY case and heat.
  3. Complete battery, Various low-end vendors, 200Ah: $1000-$1700, probably with Bluetooth and heat.
  4. High-end battery, Lithonics brand, 270Ah: $4500 with Bluetooth and heat.
  5. Trade in the campervan on a new van with AWD and factory-installed lithium batteries: $100,000 plus my old van.

Number 5!

Just kidding … the van market is still insane.

A few weeks ago I ran across a new company (Sunfunkits) that makes DIY kits – case, wires, battery management system (BMS), sells matched and balanced LiFePo4 cells and will assemble them for a small fee. Their 300Ah battery will fit in the space where my 100Ah Battleborn currently is housed (with 1/8″ to spare!), has Bluetooth and heat, and cost just over $1500 shipped. This gets the cost down close to DIY without me having to manually match and balance raw cells & figure out details such as internal heating and Bluetooth.

Worth a try.

There is a fair bit of risk running with a product from a startup whose product warranty is five times as long as they’ve been in business, but I figured I’d mitigate that risk somewhat because the battery is made of user-replaceable off-the-shelf parts. Unknown is whether or not their internal heat will be good enough for Minnesota winters. The battery is next to the Truma furnace, and one of the heat ducts runs directly under the battery, so I think it’ll be OK. Worst case would be to set the Truma furnace to 40F on nights below -0F.

It’s larger than the old Battleborn – meaning I had to move a bunch of components to make room. Because I decided to run entirely from lithium and could simplify the electrical quite a bit, I figured it would be best to remove and re-wire most of what I’ve done over the last few years. That meant ripping out pretty much everything and starting over with new locations for the various components, a significant amount of rewiring and a bit of reprogramming and reconfiguring of my battery monitoring, IoT app & touch screen stuff. Nothing that a forty-hour week of kneeling on the floor in a hot-as-heck campervan couldn’t solve.

The end result is two cabinets full of battery and electronics and 300Ah of lithium battery that hopefully sticks around for a few years.

It’s up and working, but I still have a few loose ends to tie up. I need a bigger fuse block & better ground bus, I’m using paired 6 gauge wires in a few places instead of 2 or 4 gauge, and other odds & ends.

I’ve updated the Campervan Electrical page with the as-built-as-of-today components and diagrams.

The old AGM batteries are left in place under the chassis for now. It’s pretty difficult to start a generator from lithium batteries and even though we never use the (noisy) generator, I haven’t decided to get rid of it yet, so the AGM’s stay put.

I think this makes for ‘Campervan Electrical Version 5’?

I lost track.

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