Lithium Battery upgrade installation

[james2034]

Has anyone with wiring similar to a 2005 Hunter 41 converted to lithium house batteries? I'm having a hard time deciding how to separate the House (lithium) and start (AGM) and power the inverter and windless from the house batteries . If I connect the windless and inverter to the house side thru the House Battery Switch, when the battery switch is in "Off" position , current is still directed to the inverter and windless while the engine is running through the "combiner". I believe the problem here is that the current will also flow into the house lithium batteries from the engine and charge them outside the lithium charging parameters.
I have tried connecting the windless to the "Start Battery" switch from the house side of the combiner. This leaves the house batteries separate with now current when the engine is running. However, the windless is only drawing current from the "Start Battery". I definitely don't want to kill my start battery. I would prefer to keep the windless on the house side, but don't want to charge the lithium batteries from the engine. I have a DC-DC charger for that.
I am charging my lithium batteries mainly with 400watts solar and a 40 Amp DC-DC charger. Also have an AC charger if needed.
Any suggestions appreciated.
Battery panel wiring attached.

 

[Davidasailor26]

I wouldn’t worry about running the windlass off the start bank. The windlass is a pretty significant load but only for a short duration. Even if it draws 200 amps and you spend 3 minutes running it (which should be enough to pull at least a couple feet of rode) you’ve still only taken 10 amp hours from your battery. Add onto that the fact that the windlass generally only runs when the engine is running (some manufacturers even wire it so only that is possible) and the actual pull from the battery should be minimal. By running the windlass off the start bank you also avoid any concerns about the maximum current through your lithium BMS.

The rest of your issues with battery isolation might be specific to your model or production run, or specific to your individual boat if a previous owner changed anything, so tracing of wires may be needed.

 

[dlochner]

There are a number of issues here. First, get rid of the combiner. You are correct the alternator is probably charging the LFP batteries incorrectly which will damage the LFP batteries.

@Davidasailor26 is correct, it is fine to run the windlass off of the start battery because you should be running the engine when the windlass is under load.

Forget trying to use a 1-2-Both battery switch, it only complicates the wiring. The LFP and AGM batteries should be completely isolated from each other. Pick one to be the recipient of all charging sources and charge the other one with a DC to DC charger. It will be a simpler system and less prone to human error.

Here is a simple schematic of a mixed LFP and AGM system. For your installation, the windlass should be connected to the Start battery, preferably through a DC buss and not on the battery terminal.

 

[jssailem]

I wouldn’t worry about running the windlass off the start bank. The windlass is a pretty significant load but only for a short duration.

Add onto that the fact that the windlass generally only runs when the engine is running

I am a +1 for wiring to the start battery. That’s the plan on my boat. I’m adding three 100 amp hr LiFePO4 to be my house circuit.

I’ll have 3 135amp hr FLA on the start circuit ( these are already on the boat.)

 

[Davidasailor26]

I’ll have 3 135amp hr FLA on the start circuit ( these are already on the boat.)

That’s a pretty serious start bank. Any reason you’re not cutting that back to 1 battery?

 

[Rich 35.5]

On our Hunter Legend 35.5, separating the start bank was easy. Just take the battery cable that's on the common pole of the battery switch, that runs directly to the starter, and connect it to the start battery. All the alternators charging goes thru that one cable.

 

[james2034]

I wouldn’t worry about running the windlass off the start bank. The windlass is a pretty significant load but only for a short duration. Even if it draws 200 amps and you spend 3 minutes running it (which should be enough to pull at least a couple feet of rode) you’ve still only taken 10 amp hours from your battery. Add onto that the fact that the windlass generally only runs when the engine is running (some manufacturers even wire it so only that is possible) and the actual pull from the battery should be minimal. By running the windlass off the start bank you also avoid any concerns about the maximum current through your lithium BMS.

The rest of your issues with battery isolation might be specific to your model or production run, or specific to your individual boat if a previous owner changed anything, so tracing of wires may be needed.

Thank you.
I only carry 1 start battery at this time. Maybe add an additional battery to the bank. Both "Starter" and "house " are now isolated---probably the best way to go. I still have my inverter on the "house " side. The "house " is charged continuously by my solar panels. The "starter'" is charged by the engine, generator and shore power. It should work.

 

[james2034]

On our Hunter Legend 35. 5, separating the start bank was easy. Just take the battery cable that's on the common pole of the battery switch, that runs directly to the starter, and connect it to the start battery. All the alternators charging goes thru that one cable.

Thanks.
I owned a 1995 35.5 for around 15yrs. Had many wonderful cruises around Fl and Bahamas.
She's a much simpler electrical system and battery switching as you can see.
I essentially done the same thing.

 

[james2034]

I am a +1 for wiring to the start battery. That’s the plan on my boat. I’m adding three 100 amp hr LiFePO4 to be my house circuit.

I’ll have 3 135amp hr FLA on the start circuit ( these are already on the boat.)

Thank you.
Always great advice from you

 

[Scott B]

This is a very good article for what you're doing. I also favour leaving the windlass on the start battery. You'll only use it while the engine is running and constantly charging that battery.

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