We also have a 2017 Thor Aria 3901 and are about to convert to LiFePO4 batteries as well. Been doing tons of prep/research and I generally agree with the other posts thus far. There are several things you will need to consider:
1) If you have the stock Inverter/Charger (which early 2017 Aria's came with the Magnum Energy ME2012 modified sine-wave I/C); I would encourage you to upgrade to an MS series (pure sine-wave) version (i.e.: MS2012 or MS2812) as part of this project. Personally, I upgraded to the Magnum Energy MS2812 pure sine-wave inverter/charger (which gave me a big more wiggle room on wattage output - ~3000w). It also solves a few common problems with the Aria discussed in other threads on this forum.
2) You will need to configure the charger profile on your Inverter/Charger to accommodate the LiFePO4 battery charging requirements. The good news is that most LiFePO4 batteries are 'drop-ins' and have intelligent Battery Management Systems (BMS) that can work with a variety of chargers and configurations usually designed to accommodate FLA or AGM configurations. You can configure the charger profile one of three ways: Option 1) Use a compatible existing charge profile via the Firefly preset battery configurations (i.e.: many LiFePO4 batteries will work with the AGM profile on the Magnum Energy Inverters), Option 2) Use an external Magnum Energy Remote (ME-ARC) and connect directly to the I/C to do a custom charge profile configuration, Option 3) Work with Firefly Integrations to customize your software on your control panel/screen to accommodate custom charging profiles. Option #3 is the path I personally chose for my install (along with an upgrade from the 4.3" B/W screen to the 7" color display)...but it has the highest price tag:
3) Decide on your LiFePO4 battery manufacturer, capacity/configuration. After reviewing several options, I decided on Battle Born LiFePO4 batteries (qty. 6 100 Ah BB10012 for a total usable capacity of 600 Ah). They just arrived and are ready for install:
4) Upgrade your Battery Isolation Manager (BIM) to one that is Li-ion compatible. The Precision Circuits LiFePO4 Li-BIM-225 is a good choice and an easy swap with the original BIM-225. Same physical footprint makes conversion easy.
5) Consider adding a battery monitor capable of measuring your LiFePO4 battery plant's state of charge (SOC). The Firefly control panel will do little for you in measuring the batteries available capacity since it only shows voltage...and voltage is so consistent for a Lithium-based battery. I personally went with the Victron BMW-712 with Bluetooth so that I could get the readings via an app on my phone.
If you have any questions or want to discuss in detail, let me know.
Thanks,
Hunter
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