Lithium Upgrade

I alluded to this project in an earlier post back in March, but it's finally completed and fully tested and I'm really happy with how it turned out.  When I first bought the boat I thought I would keep things simple and stick with lead acid for the house and starter batteries with a magnetic latch combiner for charging (came with boat), but the price of reliable Lithium Phosphate Iron (LiFePO4) kept going down and after a lot of research I made the decision to upgrade back in February.  

The battery bank was one of the last pieces of the puzzle for getting the engine going and testing all the systems I installed and it wasn't until 2 weeks ago that everything finally came together and got it all installed.  The heart of the system is a WattCycle 300aH LiFePO4 battery that would be responsible for powering all the house loads while I kept a sealed lead acid battery to power the engine.  As a general rule, you don't want Lithium batteries managing the engine because if the battery management system (BMS) has a fault, it can disconnect the battery from the engine and fry the diodes in the alternator.  So the Lithium and lead acid batteries are effectively isolated from each other.

The problem with this is that if the batteries are isolated, how do you get the alternator (or other charging source like solar or shore power) to charge the lithium bank?  The answer is a DC-DC charger.  I chose a Victron Orion 50 amp DC-DC charger that connects the 2 banks together and detects when the lead acid is being charged.  When it does, it starts charging the Lithium bank with a proper charging profile and manages the state of charge.  This way if the Lithium bank's BMS decides to shut the battery down, the lead acid battery will continue to take a charge from whatever source is charging and will protect the alternator.

The first step was to figure out how to fit all the components into the battery compartment underneath the quarter berth.  It needed to house both the Lithium and lead acid batteries plus the bus bars and fusing to support all the incoming connections and the DC-DC charger. I also added a Victron Smart Shunt that has a bluetooth protocol and accompanying phone app so you can see the state of the system from my phone.  It shows all the current loads, state of both batteries and the DC-DC charger reports if and how much charge is incoming.

After some careful measurements I built the entire system in my office with all the fuses and bus bars mounted to a piece of plywood to make sure it worked.  This all happened back in early March and at that point it was still too cold to actually install anything so the project was put on hold until warmer temps showed up in NH.  

When the temps finally warmed up I was able to move the whole contraption over to the boat.  I mounted the plywood board with all the bus bars and switches to wood cleats in the compartment and started hooking up incoming wires.  It's sad that even though I labeled everything really well, I didn't quite trust myself and retraced all the wires back to their respective sources to make sure the labels were correct.  This consumed way more time than was probably necessary, but I wanted to make sure I got it right and didn't fry something because I was being stupid.  I also added additional ventilation to the compartment with some passive holes and a temperature controlled fan that turns on at 104 degrees F.

After I got everything installed, I re-labeled everything with proper tags and made a laminated diagram that sits in the compartment for future me, because I will forget everything and when it comes time to troubleshoot something I will be confused.  I hope this will help me.  After the installation, I was able to test every single circuit in the boat including the shore power and last week, I fired up the engine for the first time since it was reinstalled late last summer and I was able to confirm that the alternator started charging through the DC-DC charger.  

In other news, I contracted with a hauling company and the plan is to pick the boat up on June 24th and deliver it to Mattapoisett Boatyard.  After that I have a day or so in the yard to get the mast stepped and then the boat will be launched.  So the clock is ticking.  I have a huge backlog of projects that I've been working on and hope to get those posted in the next few days.