Eurovan : adding a Battleborn 100 Ah 12V LiFePO4 house battery

Updated 2020-07-29 : First version.
Updated 2021-05-24 : Version 2.0: Added SunPower 110 Watt flexible solar panel, Victron BMV-712 monitor, Victron IP22-Charger, etc.

Introduction

My 2000 Eurovan Camper had been modified by the PO (previous owner) with dual 6V Trojan T145 lead acid batteries. After killing them, I replaced them with somewhat smaller GC2 6V golf cart batteries. After killing them, I decided it was finally time to upgrade to Lithium.

Why Lithium?

Lead Acid batteries are cheaper, but not necessarily less expensive in the long run. The Trojans cost about $400, and the GC2s were about $200 at Costco, but I only managed to get 3-4 years out of each set. After 10 years with the van, I've spent over $600 on lead acid batteries!
Lithium batteries are expensive (about $1000 per 100 Amp-Hours), but will last 3000+ cycles (which is probably longer than the Van will last).
Advantages: Lithium batteries are better than lead acid in almost every metric.
- The Amp Hour rating of LiFePO4 batteries is 100% usable, whereas Lead Acid batteries can only deliver about 50% of their capacity. Therefore, a single 100Ah lithium battery may perform as well as, or better than, a 200+ Ah lead acid battery.
- Lithium batteries don't suffer the Peukert Effect (in which overall capacity goes down at higher amps)
- Lithium batteries are more efficient when charging (so they charge faster and waste less energy)
- Lithium batteries can be left to sit at a low state of charge (SOC) percent, whereas this will damage (sulfate) lead acid.
- Lithium batteries have a slightly higher voltage (about 13.5 to 12.8 in normal use) which makes all your devices happier.
- Weight: two Trojan T145s weigh 144 lbs. One Battleborn weighs 31 lbs, about 75% less for a savings of 110lbs
- Safety: the LiFePO4 chemistry is quite safe (compared to others such as Lithium Polymer) and unlike Lead Acid, does not outgas hydrogen (boom!) or sulfuric acid fumes (caustic and can rust your van). Although mine is still in a ventilated box, you don't really need to vent them.
Disadvantages:
- The voltage discharge curve of LiFePO4 is quite flat, meaning it's hard to look at the voltage and know the battery SOC (state of charge). Once the battery hits 0%, the Battery Management System (BMS) will cut the power abruptly to protect the battery. This is a different behavior than Lead Acid batteries which gradually fade away as they empty.
- Cold weather: to protect the battery, the BMS will prevent charging when the battery is colder than 25F (about -4 C).

Parts:

Battle Born 100 Ah 12V LiFePO4 Deep Cycle Battery
[Variation] GC2 version The same battery, just in a different size
[Optional] A new battery box? My van was modified with one of these: Dual 6V battery box but there are other brands and sizes.

Tools:

Nothing special needed, just a screwdriver, drill and screws for mounting, wrench for tightening terminals etc.

Step-by-Step:

(click each picture for full size)

BattleBorn LiFePO4 100Ah battery, mounted in box

See notes above about this custom box. (Not shown) I added additional brackets to hold the battery securely in place.