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DC - DC Charger Placement in Sailboat LFP setup

I was going to try my setup without alternator charging and then broke down and got a Victron Orion just for those times when we DO need some charging while driving at night or rainy weather. I took the isolator solenoid out, no longer needed, the lfp house and fla starter circuits are completely separated now. House gets 600w of solar on a mppt charger, a new converter/charger for genset and shorepower, and soon I'll hook up the Orion for driving. As mentioned, a separate 100w solar panel for the chassis/starter bank for maintaining.

The problem with your two agm banks is self discharge in storage. If the boat spends a lot of time docked, plugged in or not, those batteries will lose their charge and sulfate over time. IMO you need a way to trickle them to keep them up, and either an onboard charger for each for shorepower, or a solar power setup is indicated. I think self discharge is less on AGM's, I've never worked with them, but still something to watch for. Plus any parasitic on the starter side - anything that stays on when the motor is shut off - bilge sniffer, LPG sensor, smoke alarm, etc.

The problem with lifepo4 is they just don't do very well with old FLA charging profiles. They really don't need to 'float', and they don't need to be constantly fully charged. I even put a switched outlet in for my converter/charger unit, so it could be turn off when running the genset for AC, or plugged in to shorepower. Solar controller can also be shut down if not needed, say plugged in for an extended time, like sitting in a RV park long term.

We've looked at the new Beneteaus at the local shows and always liked them. I had a Catalina and an Oday in my former lifetime. ;)

My old sailboat had a Mercedes 180D 4cyl diesel for auxiliary, and a 8D house battery. Mechanical refrigeration run off the motor, also with quite a lot of space for ice storage, and a diesel-fired cook stove with a cast iron top. It was a fun boat, fast too for a full keel, but I spent two summer vacations in a boat yard replacing rotted wooden planks in the hull. It was built in 1958 in Oregon, fir planking on oak frames, galvanized screw fasteners, canvas covered decks. Sold it before moving to California in 1992. Those old boats just don't do well in the dry climate here.

Prior to that I have a Edwin Monk designed cutter, also all wood, built by a shipwright for himself, on Lake Union in Seattle. Cute little boat, all bronze hardware, cedar planking with bronze fasters, teak decks and trim, volvo diesel aux. I restored that one and took it to wooden boat shows and festivals.

I built two other boats from scratch, a pram dingy and a 16' rowing and sailing skiff by Pete Culler. The latter when my oldest daughter was first born, she's 35 now. :oops:

The Mari-Mari on the cover of Nor'Wester magazine in the 60's. I have good pictures of her, but they're color prints - from before the digital age. So this is a picture of a black and white picture LOL.



This is our 'land yacht', and we have a 17' sport fisher with outboard.

 
I'm currently helping my brother-in-law re-do the electrical on their 40' Island Packet. We've settled on a set-up that is similar to what others here have discussed:
  • LFP 560Ah House Battery, charged from a 100A alternator (Blamar, with a Wakespeed regulator), TBD of solar (two charge controllers), and a Victron Multiplus Compact 2000 / 80 when on shore power.
  • A 200Ah Bow Thruster AGM, charged with a 15A DC-to-DC charger
  • A 100Ah Starter AGM, charged with a second 15A DC-to-DC charger
I thought I had convinced him to put the Windlass on the Bow Thruster battery, but I guess it will be on the house battery.

The solar is currently TBD, but should be close to 1kW when everything settles. The boat had 2 x old 150W panels on the Bimini, but he's now convinced that some 24V 60 cell panels (generally ~65" long by ~40" wide) will fit, then he will have a third one of about the same size over the davits in the back. I wanted to do a bifacial over the davits, as it seemed like a perfect spot for bifacial, but all the bifacial panels I can find are very long 72 cell.
 
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Amp-L-Start looks neat - sort of a DCDC charger, but not charging/just passing current from one battery bank to another and acting as an isolator between them (a 'dumb' DCDC charger)?

@Horsefly my setup is very similar to your brother-in-law's, although I have a 'dumb' alternator and am using that to go directly to the Bow Thruster and starter AGMs via the Isolator.

To charge and maintain my bow thruster and house bank, I went with this:


Dual output, so will hook up one 5a output to each AGM Bank.

With the Amp-L-Start and my setup, I think I would end up in charging loop when the engine is on. With engine/alternator going, it would be charging my AGM banks and turn on my Orion DCDC to also charge the house LFP bank. If I had Amp-L-Starts also connected back to the AGMs, then this would then loop charge back from LFP house bank to AGMs.
Would work though where the alternator is charging the LFPs directly.
 
RE the Amp-L-Start, I missed this from the web page:

A new Ignition-Controlled Relay Kit is now available for use with all AMP-L-START™ revisions. It automatically inhibits operation of the AMP-L-START™ whenever your motorhome engine is running - Perfect for applications where a DC-DC power converter is also installed.

I guess this would avoid the 'charging loop' problem I was worried about due to DCDC charger I'm using. Will check this out.
 
jc1409: I'm glad someone else brought the AMP-L-START.

I am planning a retrofit of a sailboat as well. I prefer to keep the it as simple as possible.

My plan is for the alternator to charge the start battery and then use two dc to dc chargers in parallel to charge the LIFEPO house bank.

To ensure the starting battery is properly maintained I plan on using the AMP-L-START.

Its at 12v to 12v charger/maintainer. I like it because there are several on/off voltage settings so you can reduce the SOC of your house battery to get maximum cycle life and still have this provide a trickle to the start battery. It is a cheap and simple solution.

AMP-L-START Starting Battery Charger/Maintainer - Overview Page

15 Amp Starting Battery Charger/Maintainer
www.lslproducts.net

Please let me know if you disagree.
 
I have a 100amp alternator with a sterling alt to battery charger and an alternator saver. The Sterling is set to lifepo4 and charges my 2 x lifepo4 280ah batteries. These do the house and the bow thruster pulling 170amps from the thruster.
I also have a seperate lead acid bank 3 x 110amp for starting and as back up. In addition I have a Panda generator which also charges the batteries and runs the microwave / combi oven and the induction hob. In addition I have solar charging.
 
personally , I would add a small DC DC from the LFP to the thruster /start banks , its always useful to trickle charge these to ensure they are recovered for when needed . its not expensive ( 5A or 10A dc dc ) . Id not have the mains chargers connected to teh low capacity batteries its a waste of resources

id focus my money on making my alternator charge the Li bank directly
 
jc1409: I'm glad someone else brought the AMP-L-START.

I am planning a retrofit of a sailboat as well. I prefer to keep the it as simple as possible.

My plan is for the alternator to charge the start battery and then use two dc to dc chargers in parallel to charge the LIFEPO house bank.

To ensure the starting battery is properly maintained I plan on using the AMP-L-START.

Its at 12v to 12v charger/maintainer. I like it because there are several on/off voltage settings so you can reduce the SOC of your house battery to get maximum cycle life and still have this provide a trickle to the start battery. It is a cheap and simple solution.

AMP-L-START Starting Battery Charger/Maintainer - Overview Page

15 Amp Starting Battery Charger/Maintainer
www.lslproducts.net

Please let me know if you disagree.
Charging the LFP bank is much more efficient. Start there.
 
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