LiFEPO4 without solar on a boat

[ekhar]

Very new to the topic.

I was hoping someone could

a) tell me if I am thinking correctly

b) draw a general diagram and components of how to put together a system.

Here is the rest of the story

I have been putting sweat, blood and tears into my somewhat aging but great sailboat. Just replaced an engine and fixing many things that aged over time.
I currently use 2 Lifeline 105AH Deep Cycle batteries with A/B Switch. This is how I bought the boat 25 years ago.
I added Xantrex Prosine 2.0 many after purchase.

In the summer live and work on the boat for weeks at a time. And I am doing a bit more cruising now. As a result want to upgrade batteries and charging systems. In stages however.

My needs are laptop (via inverter) and second monitor (12v DC), fridge and microwave occasionally when my family is on the boat.

First stage batteries - and may be a small removable solar panel to top off batteries when not using the boat.

Second stage - permanent solar panel - although that is not immediate. I have too many other projects to accomplish first.

I learned that I cannot connect alternator from the engine to Lithium for a fear that if BMS cuts off the alternator will burn out.
I was hoping to replace 1 Lifeline with 300AH lithium and keep the other AGM in place. That ought to handle all my current needs (I am used to living with less)

So the charging would be from the engine/shore power when available and from the solar panel as a backup. I understand that Prosine charger cannot charge Lithium battery so I would need a second charger. And here is where I pause for lack of knowledge and understanding and ask for guidance from the forum.


Thank you
Gene

​

 

[Rocketman]

Look at a DC-DC charger - that way it will recharge when the alternator is running.

As far as a diagram, probably the best thing is for you to make a diagram of what you currently have. There are so many different ways to set-up systems - having a good starting place is vital. You will also know what you need to replace.

 

[MV semi-retired]

Is all your dc 12v? And I agree with Rocketman! DC to DC is awesome. Or a buck boost

 

[Mightymach]

I'm the noob here and I'm researching this for my boat as well. Inknow enough to be dangerous, so take whatever I say with a grain of salt.

Having said that, I don't understand why people are so in love with a DC to DC charger. Maybe, I don't understand what the dc to DC charger is, but I'm guessing it's a voltage sensing relay such as these: https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A/FAQ ???

If so, you're essentially daisy chaining your batteries charging potential and giving up a key benefit of LiFePo4 batteries--their ability to to take huge amounts of current and charge quickly. The better option, in my dangerous opinion, is to use an external regulator (Balmar mc614 is what I have) set to a LiFePo4 charge profile. Hook your alternators to an isolator and connect the regulator to the BMS so that it shuts down the regulator (and alternators).

Now, your primary charge is based on your LiFePo4 profile and your starter batteries (mine are lead acid) will be along for the ride.

If the AGM wants more voltage than the LiFePo4 does and the regulator is set to a lower voltage profile, the AGM will never get to full charge, yet you're giving the lifepo4 all they want. When the BMS shuts down, the agms quit receiving charge, but the beauty is, they're cranking batteries And were never really depleted anyways.

That's my thoughts anyways.... and like I said, I'm dangerous enough to be dangerous

 

[ekhar]

I'm the noob here and I'm researching this for my boat as well. Inknow enough to be dangerous, so take whatever I say with a grain of salt.

Having said that, I don't understand why people are so in love with a DC to DC charger. Maybe, I don't understand what the dc to DC charger is, but I'm guessing it's a voltage sensing relay such as these: https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A/FAQ ???

If so, you're essentially daisy chaining your batteries charging potential and giving up a key benefit of LiFePo4 batteries--their ability to to take huge amounts of current and charge quickly. The better option, in my dangerous opinion, is to use an external regulator (Balmar mc614 is what I have) set to a LiFePo4 charge profile. Hook your alternators to an isolator and connect the regulator to the BMS so that it shuts down the regulator (and alternators).

Now, your primary charge is based on your LiFePo4 profile and your starter batteries (mine are lead acid) will be along for the ride.

If the AGM wants more voltage than the LiFePo4 does and the regulator is set to a lower voltage profile, the AGM will never get to full charge, yet you're giving the lifepo4 all they want. When the BMS shuts down, the agms quit receiving charge, but the beauty is, they're cranking batteries And were never really depleted anyways.

That's my thoughts anyways.... and like I said, I'm dangerous enough to be dangerous

Let me make sure I understand

Are you saying to add an additional dedicated alternator for Li batteries? If so, then I would not have room for it (although engine allows a second alternator)

 

[Rocketman]

There are several different ways of doing things.
Here is an example of a DC-DC Charger:

Orion-Tr Smart DC-DC Charger Non-Isolated - Victron Energy

The Orion-Tr Smart DC-DC charger is a professional DC to DC adaptive 3-stage charger with built-in Bluetooth. For use in dual battery systems in...

www.victronenergy.com

When your motor is running, it then takes whatever voltage it is producing, and adjusts the voltage for what the lithium battery needs.

Stirling(sp) also makes some. They are the easiest to implement. Run wires, make sure it’s not going to overtax the alternator, and program.

Relay switch’s and dedicated alternators are also other ways. They will charge faster, but are more complicated to make sure EVERYTHING is running correctly.

 

[Mightymach]

Let me make sure I understand

Are you saying to add an additional dedicated alternator for Li batteries? If so, then I would not have room for it (although engine allows a second alternator)

No, not at all, but that's the most ideal.

You'll add an isolator, a externally regulated alternator, and a Balmar 614 regulator.


Regulator is programmed to make the alternator charge with a Lifepo4 profile.

Alternator connects to isolator.

Isolator connects to lifepo4and starting batteries and "distributes" charge to battery bank and starting bank. All batteries will receive a Lifepo4 charge profile.

Wire regulator to BMS. When BMS stops pulling a charge, it shuts down the regulator and alternator without damage.

To me, the noob here, LiFePo4 relevant benefits are deep discharge and ability to take a lot of current in order to quickly recharge. In order to achieve this, you need the external regulator and alternator set to a charge profile for the lifepo4 batteries. Working the opposite way (internal regulator, connected to the start battery, with a dcdc charger daisy chained to the lifepo4 bank) will take forever to charge...and your lifepo4 will never achieve full charge. Also remember, your 50 amp stock alternator will probably put out 30 amps at most.


Just my thought my on it. I ordered my batteries and this is the way I plan to wire it. The starting batteries should never need a deep charge, only a top off. The house bank...that will always be taxed while away from the dock.

 

[willo]

Howdy. Being that I keep wanting a sailboat, I'll just live vicariously through yours. mmmkay?

Even if you don't want full solar, I'd put SOME on it. Seriously, anytime you can avoid running an engine to charge a bit, it's a good thing.
So yeah, I'm ignoring the no-solar bit you've indicated.

So, start with this:
1) Approximate power goals/needs. You need to establish a reasonable load estimate and then determine what your goal is for your power needs.
2) How much solar real estate do you have for solar? Are we talking about some on deck? Bimini? This will directly affect how much solar panel capacity you can have.
3) How much space do you have for batteries? The space should be relatively contiguous for optimal power. If you have to separate battery banks, this is ok, but it will affect what you can do.

Once we have that, you can make good decisions about battery sizing: Voltage, Amperage, etc.

Then we can work out the details of: Solar controller, Inverter, DC-DC charger needs, DC-DC converter (if needed), etc.

Some thoughts:
Solar parts can be hard to acquire when traveling. In my RV build, I've used a single controller (for now) that can handle all of my panels. For a boat build, I'd probably use a pair of solar controllers for redundancy and reliability. If you aren't going to use much shore power (or worry about a generator input) I'd look at simple inverters rather than charger/inverter combos. There's also the non-ignition rated stuff that you'll want.

Short list of gear to get you started:
Solar panels
Solar controller
Batteries
BMS (if using lifepo4 cells to diy)
Inverter (if you want 120v power)
Converter - if you use a non 12v build, you need to converter from say 24v to 12v, for example.
DC-DC charge controller (recommended to protect the LifePo4 cells from the alternator)

Gimme some data and I'll help you size your system.
Do you need to power a water maker?