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  1. #1

    DC to DC Charger & First Lithium Battery

    The issue of dealing with a 32 volt boat and either 12 or 24 volt accessories AND my boat's $$$ conversion to 3 phase by the previous owner have made installing and operating an inverter somewhat interesting.

    I certainly did not wish to change the certified Australian electrician's 3 phase wiring. But the boat did need an inverter for the (now) 240v Australian power points, TVs and low wattage tools. This is because the boat now lives on a swing mooring and goes away for weeks at anchor, rather than day trips from its marina pen. Huge TV's, home appliances and lots of lights are now the go. There is a monster Fisher & Paykel fridge on board. All this great new technology is now available but it has to be powered. We prefer a silent ship, so only run the genset for cooking, aircon, water heating and battery charging.

    So the first step three years ago was to install a 96 cell 57 volt output 300 watt solar panel to the 32 volt (8 x 8 volt batteries in series/parallel) in the port engine room. Then use the original house bank's Newmar 32-12v-20 DC converter connected to a Victron Argofet battery combiner. This had the effect of turning the Newmar converter into a simple battery charger. (Newmar told me how to do this.)

    The Victron Argofet was connected to the original thick 12v cable up to the wheelhouse where a 100AH 12 volt deep cycle AGM battery was installed. A small 1200 watt inverter was connected to the battery and wired into the new Australian dedicated AC circuit breakers providing enough power to run everything except the kettle, vacuum and toaster.

    For the past three years this system has worked flawlessly EXCEPT in humid Sydney summers when the fridge randomly cycles/auto-defrosts and draws up to 60 amps at 12 volts (720 watts) for about 15 minutes. This overloaded the 12v deep cycle battery and the inverter shut down due to low voltage.

    Technology moves on and battery technology has changed.... So I've just purchased my first 120AH Lithium battery to replace the 12 volt AGM deep cycle. This battery will allow up to 100A discharge at 12 volts. But the problem is to charge a lithium battery correctly.

    Finally a new DC-DC charging product that can charge the lithium battery became available AND also acts as a power supply (limited to 20 amps by the Newmar DC-DC converter). This also meant minimal wiring changes, no dedicated inverter house bank and the big solar panel optimised for 32 volts could still be used.

    https://enerdrive.com.au/product/epo...rger-40a-plus/

    There will be an American version somewhere. Maybe US$350.

    DC converter charger.jpg

    DC-DC charger input connected to the old Newmar converter. Output uses original the 12 volt wires up to wheelhouse. Wiring has now been tidied up with loom. The computer fan on the front of the Newmar converter keeps it cooler.


    The updated DC charging system is now installed and working flawlessly. I've seen 95 amps at 12 volts pass through the inverter (tested with the toaster & TVs) and the lithium battery can handle the loads less than 100 amps at 12 volts without the inverter shutting down. This was a test...I don't like the idea of high amps on any wiring and connections. Our average inverter draw is between 7 and 16 amps (<200 watts) at 12 volts.

    The DC-DC charger goes to maximum 20 amps power supply during this period being governed by the maximum 20 amps output of the Newmar converter.

    inverter.jpg

    3 Phase control panel and new circuit breakers for 240 volt AC power points and AC lights. Inverter battery cables have been upgraded to 188 amp 32mm 2B&S size to reduce risk. The inverter has been trouble free 3 years and is small enough to fit. An additional fan blows in the compartment.

    I'm keeping the 12 volt 1200 watt inverter to see how we go over the Christmas period. If we want to boil water for coffee we turn on the genset anyway.

    Its probably not the most technically efficient system, but its quite simple and all wiring is oversized with fuses and circuit breakers.... and I don't have to rewire the boat and panels. This DC to DC charger is a cracking good product.
    Last edited by scottinsydney; 09-30-2019 at 06:14 AM.
    +++
    1984 61MY #353 with 9' cockpit extension.
    Sydney, Australia.

  2. #2

    Re: DC to DC Charger & First Lithium Battery

    Maximum solar input 45 volts. It looks like you could remove the Newmar and use the solar input directly from 32 volts.
    1977 Hatteras 58' MY, Hull No. 304, 4-stateroom galley up model with 8V71TIs in Knoxville, Tennessee

  3. #3

    Re: DC to DC Charger & First Lithium Battery

    Existing solar keeps port house bank full and DC-DC charger feeds off that bank via Newmar converter. The DC charger only takes max 45 volts solar, not existing 57 volts.

    I'd prefer a 24 volt inverter system, but but have to get Newmar 32 to 24 volts converter to do this.
    +++
    1984 61MY #353 with 9' cockpit extension.
    Sydney, Australia.

  4. #4

    Re: DC to DC Charger & First Lithium Battery

    Seems like there have been too many fire issues with lithium batteries in auto, aviation, electronics and, now, marine applications. I sure would consider going another route until these batteries are as safe as the conventional options.

    https://gcaptain.com/fire-and-gas-ex...power-warning/
    Semper Siesta
    Robert Clarkson
    ASLAN, 1983 55C #343
    Charleston, SC

  5. #5

    Re: DC to DC Charger & First Lithium Battery

    Robert,

    Thanks for sharing that.

    'Thermal Runaway' with lithium ion batteries.

    That's interesting.

    Jon
    Jonathan Brein
    1982 43' DCFB #550
    "Paragon"
    Chesapeake, Virginia

  6. #6

    Re: DC to DC Charger & First Lithium Battery

    Note the difference between lithium ion and lithium iron. The battery in the pic above is lithium iron, which is said to have greater thermal stability and to be much safer than lithium ion. The linked article seems to be referencing lithium ion. I'm no authority but I've been reading up as I consider a separate 12 or 24 volt house bank and inverter set up myself. Based on what I've researched, I will most likely go with lithium iron.

  7. #7

    Re: DC to DC Charger & First Lithium Battery

    Very important note: the manufacturer of your battery refers to "pre-installed internal technology" which is essentially an integrated Battery Management System (BMS).

    In order to avoid safety issues wisely mentioned by others, individual cells (you have 4) are protected from overcharging, overcurrent, and temperature by the BMS.

    Those considering drop-in replacements need to become familiar with this stuff, or do as you have and obtain sophisticated solutions like from BattleBorn.

    I have eight such units but will design my own BMS and charging system. Mine are also LiPO4 which is more stable than other chemistries like standard lithium.

    But DO NOT EVER buy basic lithium and connect to a lead-acid charger without a BMS being involved!

    DAN

  8. #8

    Re: DC to DC Charger & First Lithium Battery

    Six weeks into my experiment using the single LifePO4 battery that is charged by the 32-12 volt DC-DC converter and then DC-DC battery charger/ power supply...

    Its fantastic.

    The DC-DC charger shuts down when there is no draw and lithium 12 volt battery is full. My lead acid portside house batteries remain fully charged. When the fridge cycles to defrost and draws 70 amps at 12 volts the inverter continues to run.

    I've seen the lithium battery draw 100 amps for 5 minutes boiling water with a mini 900 travel kettle. Didn't hurt it at all.

    I've decided to keep the 1200 watt inverter as its well sized for most of our needs.

    Will continue use genset for normal kettle, vacuum, toaster and power tools.
    Last edited by scottinsydney; 11-05-2019 at 12:02 AM.
    +++
    1984 61MY #353 with 9' cockpit extension.
    Sydney, Australia.

  9. #9

    Re: DC to DC Charger & First Lithium Battery

    Quote Originally Posted by polpaul View Post
    Note the difference between lithium ion and lithium iron. The battery in the pic above is lithium iron, which is said to have greater thermal stability and to be much safer than lithium ion. The linked article seems to be referencing lithium ion. I'm no authority but I've been reading up as I consider a separate 12 or 24 volt house bank and inverter set up myself. Based on what I've researched, I will most likely go with lithium iron.
    I myself have a 1200W Transfer switch inverter, Over all holds up well untill i kick in a 2000w heater :O Working on updating to Main AC and Heat / AC on seperate feeds and inverters and banks. Weighing options on the battery banks, but currently sticking with the tried and true batteries.

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