Friday, September 10, 2021

Out with the Old, in with the New

2019-Cruise-308xOur current practice is to have our bottom cleaned and recoated with anti-fouling paint every two years.  We tend to start a list of other things we want worked on or done at the next haulout as soon as we splash back into the water from the current haul out.

In the 2019 haulout we identified upgrading our house bank of batteries (the source of our electricity when we are not on shore power or running the generator) but upgraded the alternator charging our house bank instead.  We nursed our batteries through the 2020 and 2021 cruising seasons but couldn’t put off an upgrade any longer.  Fortunately, battery technology progressed during the intervening two years.  While still expensive, the cost of the lithium iron phosphate (LiFePO4) batteries were getting to the point that on a per usable kilowatt-hour basis, the lithium batteries were cost competitive with traditional lead batteries.  2021-08-035xThe demonstrated reliability of lithium batteries was also becoming apparent, as well (thank you, first adopters).

One of our criteria was that it had to work with our existing charging system and not require a redesign of the electrical system.  It also had to fit in the space of our old battery bank, four 8D AGM batteries that weight 160 pounds each).  We ended up with ten smaller batteries that weighed 37 pounds each).  The listed amp-hour capacity of the new battery bank is 500 Ah at 24V which is not too dissimilar then the 540 Ah capacity of the old batteries. The real difference is that lithium batteries can be depleted almost completely without harming them while a lead battery ought not be depleted below half its capacity if you want it to last very long.  We expect we’ll be able to 2021-08-036xregularly use 80% of the lithium battery bank capacity,400 Ah.  Our old battery bank had aged to the point that even getting to the 50% point would only give us about 200 Ah.

The other advantage of lithium batteries are their ability to charge rapidly which we tested during our sea trials (below). At our normal cruising RPM, we are able to charge at about 150 amps until the batteries are nearly fully charged. While charging with our generator using the existing charger/inverter and the new standalone charger we are able to also charge at 150 amps until nearly fully charged.  While lead batteries can accept a high charge rate until the 80% level. Past that point the rate of charging diminishes rapidly and the last 20% can take a depressingly long.time.

Out with the New, in with the Old

One thing we also changed while hauled out were our anodes (they protect the metal parts of the boat from galvanic corrosion by offering up a “sacrificial” metal anode). In 2019, we switched from zinc anodes to aluminum anodes.  Aluminum is less toxic to marine life than zinc.  Aluminum is also more reactive than zinc which, apparently, turned out to be a problem for us.

2021-08-008xAs we hung in the slings of the travel-lift after being pulled from the water, the amount of “hard growth” (barnacles and mussels) on our boat was impressive and far greater than normal. In particular the growth on the anodes themselves was an issue. The best explanation offered was the greater reactivity of the aluminum meant the individual anodes were “working" less to supply the necessary galvanic protection. A zinc anode while working will sluff 2021-08-010xmaterial.  Barnacles prefer not to make their home on a surface that is disappearing under them.  The aluminum anodes were apparently not losing as much material and allowed the hard growth to build.

When protecting a boat from galvanic corrosion, a calculation is done (or ought to be done) to determine the approximate location and size of the anodes.  Since our boat had come with zinc anodes we decided that perhaps the switch to aluminum was a failed chemistry experiment. We decided to switch back.

Sea Trials in the San Juans

We splashed back in the water on Tuesday, 8/24, did some testing at the dock then did a quick sea trial in Port Townsend Bay to make sure there were no issues with the preventive maintenance done on the engine.  We stayed the night at the dock to clean things up and put things back after two weeks in the boatyard. The next morning, we left with the ebb tide out of Admiralty Inlet. Our goal for the next two weeks was to spend most of our time at anchor, using the boat normally, watching the battery deplete than periodically recharging them with the genset.

2021-08-059xWe spent the first three nights at Prevost Harbor on Stuart Island, the next three nights in Garrison Bay on San Juan Island, followed by three nights in Echo Bay on Sucia Island, two nights in Fisherman’s Bay on Lopez Island, and two nights in Griffin Bay on San Juan Island.  We had a great time as all of the anchorages offered shore access for us to stretch our legs. 

The batteries and charging system worked exactly as we hoped.  We could usually recharge a day’s worth of battery use with less than one and one-half hours of generator time.  Previously, we had to run the genset for three and one-half hours spread over a morning and evening genset run.  Even then, the old lead batteries were never completely refilled by the charging.  We could also charge the lithium batteries by cruising for only one and one-half hours (about 10 miles of travel). The greater capacity gave us great flexibility as to when to do the genset run.  Our normal consumption is about 9 Ah per hour so we could do a the genset run whenever it was convenient during the day.

Our last night in the San Juans was Mackaye Harbor on Lopez Island where we visited David and Rachel, owners of the Diesel Duck Shearwater.. From there we crossed back across the Strait of Juan de Fuca to Port Townsend to have a couple of items addressed for which parts hadn’t be available before our departure two week earlier.

The next morning, Thursday, 9/9, we scooted through the Port Townsend Canal near Port Hadlock, then down Puget Sound back to the Queen City YC outstation dock in Eagle Harbor where we have winter moorage. Tying up there brought us full circle and finished off the 2021 cruising season.

1 comment:

  1. Was your existing electrical system compatible or did you have to change out some of the system. A post on just the conversion would very interesting. Thanks for the posf