Lithium Battery Upgrade V: Gone to the Island

After much shifting of plans, The Sun King, newly equipped with a semi-massive Lithium Iron Phosphate (LFP) battery stack, cast off in search of adventure and battery performance info.

For review, Sun King was the next progression in my quest for electric boating.  Knightmare, my first effort, was successful, but limited in range.   No solar.  My goal was to be able to do sonar mapping of the river in quest of archaeological sites, but the 16′ Knightmare was a daytripper.  Sun King was for expeditions.  After I began construction 9 or 10 years ago, starting with a $100 Lugar Leeward hull, I began hearing of some pretty interesting waterways, one of which was near me.  So, 8 years ago I set out to circumnavigate Mississippi.  Yep, Mississippi, with bits of other states, is pretty much an island.  Up the Tenn-Tom at Mobile to Paducah.  Down the Ohio to Cairo.  Down the Mississippi to Nawlins.  Back to Pensacola and the Escambia.

Sun King was not just a boat, it was a travelling power plant, similar to a system you might put in a cabin or as a backup for your house…but with a motor added to move it around.  Originally, there were six 270 watt Suntec solar modules forming an overhead canopy.  One was mounted on a computer drive slide (from the days when hard drives weighed as much as you do) so the low-slung boat could be accessed at high docks.  The panels, connected as pairs to 3  maximum power point Tracking (MPPT) charge controllers charged two banks of GC8 golf car batteries wired for 24 volts.  The 12 volt system for lights and horns and such was fed by two 24/12 buck converters.  Finally, a 5kw inverter provided power for the galley.  A man’s got to eat and make coffee.

See?  A complete solar power system with redundancies.  In the case of the failure of a battery, there were two banks.  12v converters…2x.  The  extra  charge controllers could keep me going if one failed.  You don’t necessarily need all that redundancy in your home system, but a little won’t hurt.  On the boat and 900 miles from home, it is a good idea.

For boaters, the motor was custom built from the Minn-Kota parts catalog.  This was never a trolling motor, it was born a cruising motor after trying a dozen stock units.  Because I had once thought I might need two motors, my control panel contained 2 controllers.  I finally went with one motor and retained the 2nd controller.  Good things, because my testing had been done in winter and the summer heat got to one of them before I got a fan. The motor itself can make around 2 horsepower.  I generally cruise at under one hp and have the breaker set fairly low and have rarely tripped it.   A Kipawa prop gives better performance than standard weed whacker props.  It was aft mounted in a bow mounting system.  Steering is via cables and pushrods from an old airplane steering wheel.  The hull is a displacement type and when I stretched it 4 feet I used every trick I knew to make it efficient.  There is enough excess power to rescue stranded boaters.

Performance-wise, I could not have hoped for a better combination.  I could cast off at the first hint of daylight and by 9am all of the motor power was from solar.  By midday, there was as much going into the battery as was going into the motor.  There was only one cloudy stretch of 4 days where I finally decided to pull over and go beachcombing while the battery tried to catch up.  One day I managed to travel a brutal 100 miles down the Mississippi. (The Big Muddy is not for wimps)  Another day I ran across the Gulf of Mexico from 5 am to midnight and still had power to make supper and breakfast.

1920 miles in 44 days without buying a drop of gas.  At Kentucky Lake, the onboard cameras caught the harbormaster and a cruiser talking about how expensive all that solar on my boat must have been.  Ha!  Less expensive than a new outboard and less expensive than the gas to put in an outboard.  That, and all I heard was the rippling of water as I made way.

So if it was all that great, why change it?  I guess because I can!  First off, with 6 panels all in a row, it was ugly.  Blocky.  And a bit top heavy.  Given all the lead in the batteries there was not much chance of tipping over, but it sure was wobbly with its round bottom and no keel to dampen the rocking.  For aesthetic purposes I removed the forward module and the two aft ones, replacing them with wooden frames covered in canvas.  My long term travels would have to be at a more leisurely pace.

After the big trip, there were few small ones.  The boat got blocked in the shed for several years.  Batteries were replaced because one of my farm buggies needed the hand me downs.  Somehow the new batteries came to be 8 years old, but still good.  First Mate and I took a trip down to Pensacola and they got us back just fine, but…

Several things happened.  I had the urge for longer trips.  One of the farm buggies was slowing down.  A friend was selling some big lithium cells on ebay at no-reserve auction.  I ended up with them and now was presented with the opportunity to get some lithium battery experience.  I have long thought I would go to lithium batteries in the Solar Yacht project because of safety issues.  Unlike Sun King, Sunflower and Gopher 2 have closed cabins where you can build up explosive hydrogen gas from lead batteries.  Keep ventilation in mind when siting batteries.  On the other hand, Lithium batteries weigh less and I had removed all of the lead and most of the keels on the yachts, so the lighter weight of lithium batteries will affect stability.  I can fill the keels with concrete and the new 475 watt panels, as huge as they are, apparently weigh the same as the old 270s on Sun King.

So how did Sun King perform with the new lithium batteries?  Pretty darn well!  There were a few glitches not related to the batteries and I am still learning battery behavior.

The day was partly cloudy.  The route would ultimately take us about 29 miles, round trip.  Destination was the Swamp House Marina at Highway 90 in Pensacola.  Departure point was Quintette Landing.  We had hoped to depart from Molino Fairgrounds, but the river was up.  There are many snags below Molino.  These are easily avoided when the water is low, but you can’t see them when it is up, usually resulting in crunching noises and abrubt jolts.

A battery box aboard Sun King.
Sun King’s battery compartments double as galley benches. It looks just the same with lithium as it did with lead batteries. Extra space with the smaller battery bank is filled with flotation foam. Just in case.

At Quintette, the Escambia River is tidal.  You never know which way it is moving or if it is moving at all.  You might head downstream to find you are actually going upstream, or vice versa.

We got underway with Nic at the helm, her first lesson on handling Sun King.  We were running on the starboard battery.  The left or port battery had not decided to turn on yet.  It had been charged before delivery to a level above where I had it programmed to charge and apparently just didn’t know how to behave.  I did not know how to interpret this behavior, but the starboard battery had done the same thing.   (What, me worry?–Alfred E. Neuman)  Why does this seem peculiar?  If you take two car batteries of different charge levels, the hottest will send current to the other until both are the same, if wired parallel to each other.  These LFP batteries have Battery Management Systems (BMS) and they have their own way of doing business.

swamp lily
Stop and smell the swamp lilies along life’s way.

Somewhere along the way, the port battery decided to help out, but only a little.  there again, with two banks of lead acid, the freshly connected battery would have been providing most of the power.  Okay, whatever.  I’m just here to watch what happens.  Watching what happens is easy with the app and the Bluetooth link to my phone.  I have an Android burner phone that I think may become my dedicated battery monitor, with another for navigation.

We crossed US90 and doubled back under the bridge to go into the marina where, to our dismay. we discovered the marina eatery is closed on Tuesdays.  It was Tuesday.  Drat!  Fortunately, though I had left the microwave oven at home, ship’s stores included some just-add-hot-water meals and I NEVER cast off without my coffeemaker.  We would not starve.  Since we had a little time, we headed out to the mouth of the river where there is an uninhabited island.  We explored and discovered Scarlet Wisteria plants.  I have never seen these before.  They add a nice splash of color.  From there, we took a brief venture into Mackey Cove.  In the late 1700s, during the British occupation of West Florida, there was a colony of French Huguenots living on the cove.  The French all died because the land was swampy and unhealthy.  Today it is lined with megabuck homes.  Go figure.

Solar electric boat Sun King on desert island near Pensacola

An island in the sun.   View of Mackey Point.  Sun King’s center panel/hatch open for egress

We headed back upstream with me at the helm.  Whereas the 810 watt solar array had been providing good current through the charge controller, now not so much.  Huh?  Good explanation: an overlooked detail.  When I went to set the charge controller up for the lithium pack, I could not find the instruction sheet.  I knew exactly where it was, but the Man Cave is so loaded up with Bro’s estate stuff I could not get to it without major effort.  I recognized the problem and realized I needed to put in an effort to get the manual.. Remember, always RTFM.  The controller dutifully went up to the programmed voltage, lower than where it had been set for the lead batteries, and then it had dropped down, owing to the 3 step charging method.  LFP batteries don’t drop the voltage way down when you take off the charge, but the charger was set for lead batteries.  There is no menu item in the setup that specifically names battery types, so you need the manual to select which number to plug in.  Next day I did that, did a power down reset and then all was well.  What I am saying here is that we had only about a half day of solar assist, so there was more effort on the part of the battery.

Now, speaking of battery effort, with 810 watts of solar, you are only looking at 30 amps, tops, when charging.  About the same or less discharging when underway and a little more if preparing food.  At noon, the battery could be neutral with all power coming from the sun.  LFP batteries can handle outrageous charge and discharge rates, but they can get hot when you are pushing them.  The cases can swell, causing damage.  For this reason they are clamped together, though I doubt there would be an issue on Sun King.

We made good time going upriver spotting some nice spider lilies and some pond lilies, nearly running down a gator, but never spotted a water moccasin to catch for John.  When we made it back to the landing, the app showed that one of the batteries had consumed a hair over 1/4 of its power and the other maybe 1%.  So, an all day cruise, with minimum solar assist, only took about 1/8 of total battery capacity.  My friend Courtney, who sold me the batteries, said, “Do you realize at 6000 cycles life and one trip per week it will take 115 years to wear out your packs?”   Well that sounds good.  I only cycled one of the batteries, though, so I can hold out for 230 years before I need batteries.  Maybe I need to take more trips!  As a practical matter, a new set of GC8s would outlast me at my age.

But, that’s not what counts.  I’m having fun and going farther and learning stuff.  One day I will need to replace my house batteries and lithium may be the option I choose.  The best feature of the lithium battery for a home in cloudy weather is that they do not sulfate, lose capacity and need to be equalized.  Yes, they have to be charged, but not a full charge every day.  That is a huge difference.  I have to run the diesel generator with the lead batteries to rejuvenate them several times a year and a barrel of Diesel ain’t cheap.

Other notes?  While I like my charge controller, it is not ideal for boats.  It has a fan and sucks soggy, salty air across the electronics.  The original controllers were sealed and were iffy on running 3 panels in series.  The MPPT I am using is advertised as having 160 volt solar input capacity, meaning 150v, but only at 48v output.  With a 24v battery that drops to 120v.  It so happens that my panels are 60 cell with a 35v output, so we come within spec with 3 panels in series on one controller.  It gets hot, though, and the fan has to run.  Display visibility when mounted low is an issue, too.  I am going to dig up the old controllers and review the specs and ability to run with LFP to see if they can be put back in service.  They have remote displays that I can mount anywhere for good access.

A couple of other issues that came up were normal boat stuff.  Some corroded connections prevented 2 cabin lights from working.  No big deal.

Conclusions?  Better performance (21 vs 7 hours cruising on battery alone).  Lighter weight (100 vs 390 lbs).  Longer life (20x cycles).  Longer range (90 vs 30 miles without charging).  OMG price, but maybe just worth it (It would have been cheaper had I merely matched performance of old batteries).  Will the Solar Yacht have component-built batteries?  Maybe not.  There are some really nice packaged systems coming into the market.  We’ll see.  I’ll update again at the end of summer when I have had more time with them.–Neal

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