Lithium batteries

[greenaub]

Anyone switched over the whole bank from AGM to Lithium?

[penneyma]

Zombie thread but I'm in the middle of doing this right now on my house bank (1995 3500 Express). Replacing the four house batteries the PO had in, which were inexplicably group 27 starter batteries, with three 100 amp hour 12v LFP (aka LiFePO4) batteries from WattCycle.

You don't want to rely on the batteries' on board BMS, so I've done the following:
1. Install a Victron 12/12-18a DC-DC converter between the 100 amp alternator and the first in parallel battery. Victron has a setting for LFP batteries, which is 14.2 volts. You can go higher on the amperage, but I'm paranoid about frying the batteries. You also want to be able to turn off the charging function if you don't need the batteries charged.
2. Run a second hot to the house bank panel switch. On my boat it's mounted on the aft engine room wall.
3. Install a dedicated battery charger to the battery pack because they require 14.6v to charge and have finicky float charge requirements.

I strongly recommend making sure every component is Bluetooth enabled so you can monitor the charging situation in real time.

I took out around 240 pounds worth of lead batteries and replaced it with only 75 pounds that gives me higher amp hour storage. It's pretty cool. My goal is to install an inverter that should be able to run my new forward 6k BTU AC.

[hiccup]

It's going to take a long time to charge that bank at 18A. Hopefully your dedicated charger has a lot more output than that. 100A would be a good size for that bank.

Make sure you have proper overcurrent protection and if you're reusing the battery cables, carefully inspect the terminals as they're 30 years old. Done correctly an LFP house bank is amazing!

[penneyma]

I have also hardwired a 40 amp charger to run from shore power. I don't spend more than an afternoon on the hook at a time, so I figure there wasn't a huge need to go bigger on the DC-DC charger since those costs increase quickly based on capacity.