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.

Easy LiFePo4 Conversion - Marine How To

Easy LiFePo4 Conversion Before reading this article please read the 101 article on Drop-In's: Drop-In Batteries Be An Educated Consumer Hardly a day goes by where we don't see or hear

marinehowto.com

 

[marcham]

Yes.

Remove that solenoid combiner from your system! Dc dc chargers are very inefficient for charging a lithium battery and expensive to get high charging current (more than 60 amps).

You have some badly oxidized lugs that require immediate attention ( cut them off, ensure wire is not corroded inside). Electrical fires are the worst!

Some wires appear to show discoloration due to overheating (difficult to tell with a photo).

To get the max bang for your buck, you need to completely rebuild the dc distribution system. Doing it piece meal will take longer, cost more, and cause problems along the way.

1. Lifepo4 house batt can charge quickly and hold voltage under load. Your alternator must therefore charge this battery. Also connected to inverter and windlass. If you don't do this, your alternator is only working at 25 pct capacity.
2. Charge the start from the house with a small dc dc charger, wired to only operate when the engine is running (victrons can do this).
3. At the dock, your start battery is charged by your victron inverter (they have a 4 Amp secondary charging circuit) or a 10 Amp charger.
4. Get a modern alternator regulator (wakespeed, emax) etc...set your alternator field to not go above 80 pct alternator output and set the t lim on the regulator to 85 deg C. Ws500 and Arco Zeus are currently supported.
5. Seperate your distribution busses and switches. Setup a charging bus (alternator, mppt, etc...) and a load bus (dc panel, windlass, etc...). Inverter gets its own dc disconnect switch. Bilge pump gets it's own breaker, before any battery switch.
6. Get an epoch or sok battery that has can-bms for victron so that it can regulate the charging sources through the cerbo gx.
7. Setup a engine start battery switch, either on-off or 1-2- off. With the 1 2 off, you can start the engine with the lifepo4 if you have to (not a 1 2 all, never parallel your agm to lifepo4).
8. Setup a house on-off switch so that the charging loads and inverter are still connected with the switch off. This means the switch feeds the dc panel and windlass only.
9. Don't forget a class t fuse within 8 inches of each lifepo4.

Voila. Modern dc setup. If you need the inverter, cerbo gx, shunts, alternator regulator and 600Ah epoch or sok battery, then figure about $6000-$8000 if you diy and about 50-60 hrs of work.

https://www.pysystems.ca/resources/diagrams/inverter/

https://www.pysystems.ca/resources/diagrams/dc-overview/

https://www.pysystems.ca/resources/videos/

Py systems do over the phone consults, we'll worth the money. (I'm not affiliated).

 

[MFD]

I am in the process of finishing up a house bank conversion for a 2009 41DS.
Your DC main panel looks the same as mine, and depending whether any prior owners did much, matches Hunter's original wiring diagrams and other documentation. I have read through the docs a bunch of times, and tested/traced wiring as needed to validate things.

I retained the AGM start battery to reduce both the overall cost & labor effort right now for my upgrade. I am still just using the stock Hitachi 80amp alternator and did not want to deal with all of that right now.

For the combiner solenoid that parallels the batteries when the key is on... There is a pair of switchable 150amp breakers that connect each battery bank to that. I turned those breakers off and left the combiner solenoid as-is and still active.

For your as-built charging system... If you have the Mangum inverter/charger, then you will probably not have anything connected to the 50amp push button breakers on the main panel that are labeled 'battery charger'. That is how mine was.
EDIT: Looking again, I see in your pic, you have cabling on those (orange). You will also have a Guest battery isolator that goes from the house bank to the start battery (with I believe a 0.6v drop from the diodes). The isolator was connected to the battery side of those 150 amp breakers up by the combiner solenoid. If you have the '100 amp alternator' option, which I don't know about, then that may also go to the Guest isolator. In my case, the isolator just had 'in' from the house bank, and 'out' to the start battery. The other 'out' unused.

As-built, the engine alternator will only charge the start battery, and start+house when that combiner solenoid is enabled from the engine key (with the circuit breakers also turned on obviously).

Given my new hybrid battery setup, and in the interests of minimizing changes while also remaining safe.

My charging sources are:
A1. 600w solar => MPPT => house bank.
A2.100w solar => MPPT => house bank.
B. Magnum Inverter/Charger => house bank.
C. Engine alternator => start battery.
D. Start battery => Victron DC-DC charger => house bank, rate limited at 40 amps after voltage high enough. I used the unused 50 amp 'battery charger' push button fuses in the main DC panel for this since they were already there.

For now, I will have no float on the start battery. In a way, given the 0.6v drop from that guest isolator, there never really was any float anyway? I am a live aboard so no problems with the engine getting used enough to top up the start battery from sitting in 'storage' as needed. AGMs are supposed to have a very low voltage loss just sitting and I have bluetooth monitoring on it. I thought about putting some kind of tiny float charger on it, but didn't want the extra complexity. Obviously when motoring for a long time, the Hitachi alternator is not great for it either, but that's how the boat has been for 15 years and a project for another day.

It remains unclear to me if it is a valid emergency plan to flip those two breakers on the combiner solenoid ('Parallel Start/Charger Circuit') if the start battery is dead. The potential huge current from the LifePo4 to a deeply discharged 75amp AGM.

I installed two Epoch 460AH batteries with a Victron Lynx battery combiner with a pair 250amp Class-T fuses in it. A new Victron 500amp shunt. Upgraded the battery wiring to 4/0, including to the negative bus bar and also from the Lynx to the existing 300amp Class-T fuse. After that Class-T fuse, the existing 3/0 wire goes to the main DC panel as it always has. Of note, I had the bow thruster option, and that has an entirely separate battery switch off a (70amp?) MBRF fuse directly from the existing Class T fuse, and the Magnum inverter charger is connected on that (Class T fuse) post as well. That's how it came originally.

At some point, if/when I or a future owner upgrades the alternator, then that would charge the house battery. Everything would be charging the house battery, and the DC=>DC charger would be reversed to charge the start battery.

 

[MFD]

Also, around page 10 of the attached shows the factory wiring options on that main DC panel.