Electric Power on the Shearwater II,

Updates in July 2001and January 2004

Everyone who cruises in the summer in warmer climates struggles with the management of electric power unless you make the decision to “primitive camp” on the water.  Our home has a water maker, air conditioning, a refrigerator and separate freezer, a microwave, and a   washer/dryer combination.  If forced to choose what we would give up to save power, many of these would be kept before our navigation lights and VHF when all the votes were counted.

Our power is generated, stored and delivered by a DC/Inverter system assembled from common components.  This section describes our experience with parts of that system after about eight months of heavy use.

First, the important stuff:

Batteries

Voyage delivered the Shearwater II with 8 6-volt 225 Amp hour absorbed glass batteries (AGM) connected in a series/parallel arrangement. 

These replaced our original gel cell batteries that were intended to be maintenance free but they used nearly two gallons of distilled water since commissioning them in 2000. 

In May, 2003, one of the serious potential failures with large battery banks occurred.  One cell of one original 6-volt gel cell batteries internally shorted - reducing that battery's voltage to about 4 volts.  The remaining three sets of 12-volt batteries (formed by placing two 6-volt batteries in series) tried to charged the failed cell.  The resultant heat, boiling acid, and smoked charred both battery boxes, filled one cabin with acidic gas and could have been very serious had it continued. 

Fortunately, we turned the master "A"-"B" switch OFF, disconnected the offending battery and assessed the damage.  400 Ah of our total 800 Ah was damaged beyond salvation.  We were in Havana at the time.

We sailed to Galveston and replaced the 800 Ah of Gel Cells with 900 Ah of AGM batteries.  The new AGMs used the same space as the old Gel Cells but, unfortunately, were not delivered with the terminals we ordered.  We had requested bolt-thru "L" type terminals and were delivered batteries with holes tapped for 1/4-20 bolts.  Short copper bolts were also delivered making it quite hard to bolt on the wires required by our installation.  Because of the lead length in a catamaran - up to 40' round trip - and the limited sizes of the wire chases, two red and two black wires were run from each bank of two sets of 6-volt batteries to the master "a"-"b" switch.  An additional set of red and black "00" batteries (lower right) were run to the engine closest to that portion of the bank - a run of about 12 feet round trip.  Finally, the two sets of 6-volt batteries were joined into a 12-volt battery with a 1/4" by 1" strip of copper bus bar.  We used this rather than wire to limit the height of the stack so the battery box door would close. and required significant re-work before placing them in full service.

Alternators

Voyage delivered the Shearwater II with two 55 Amp alternators, one on each engine.  We use these primarily for charging the dedicated starting batteries, again one for each engine.

We have added a Balmar 95-210 210 Amp alternator to each Yanmar 3GM (27 HP) engine.  These alternators each were intended to generate sufficient current to operate an air conditioner (via an inverter) and slightly charge the house battery bank.

The only significant change to the original charging circuit is the installation of a wire from the engine control circuit to supply power (exciter power) the regulator of the new alternator.  This circuit demands a maximum of about 8 amps for all regulator functions - thus is unlikely to significantly effect the charging operation of the engine battery.

Field current, a maximum of about six Amps, is drawn from the engine start battery to a new regulator and then to the new alternator.  A Balmar 95-210 Amp large frame Alternator is attached.  A heavy-duty double belt drive system is used to transfer about 8hp (maximum) from the engine.  We find that Carquest Green Striped grove belts last about 1000 hours in normal operation and require adjusting about every 50 hours or so.

Power to the new regulator is supplied by the "key" on each engine.  When starting the engine cold, I normally crack the throttle a hair, engage the starter, and turn the key off after the engine starts so the engine can warm up with no load.  Once the engine has warmed sufficiently (about 2 minutes), I turn on the key and activate both the factory original and new alternators - the original alternator recharges the starting battery and supplies a small amount of current to the new regulator while new alternator supplies power to the house bus and the house battery.

We use two Balmar 612 alternator controllers (voltage regulators), one on each engine.  These regulators permit a setting of initial delay to permit warm-up of the engine before engaging the new alternator.  This delay starts after the key is turned on - so in our case, the original alternator is engaged and 45 (adjustable) seconds later the new, larger, alternator load is applied to the engine.

Each new alternator is connected to 1/2 the battery bank (about 450 Ah) by a set of "00" marine grade cables.  The cables are fused at 250 Amps, and there are no switches in the charging link.  There is about 12 feet of cable in the round trip between the house alternator and the half of the house bank charged by that alternator.

Voyage also augmented the boat's wiring by placing a second set of heavy (about 1 gauge) wire in parallel with the battery wire originally supplied after we determined the original battery wire was undersized for our load..  Out total system voltage drop at worst case (low batteries, one alternator running, and a heavy load such as the washer/dryer) is only about 0.2 volts.  There is no detectable heating on any connection except the radiated heat from the alternator.

Should full engine power be needed in an “emergency”, simply shut off the engine switch withdrawing power to the alternator field.  Actually, both the 55 amp and the new house alternator are shut off, but the original 55 amp alternator normally places only an insignificant load on the engine because the starting battery is usually fully charged and there is minimal equipment on the starting circuit.

During simulated emergency practice with 100 hours on each engine, there was a clearly observed reduction in the engine load but no corresponding increase in boat speed.  I suspect the engine is incapable of being throttled to absolutely full output in our installation and the removal of the alternator load is adjusted automatically by a reduction in the governor’s feed of fuel to the engine.  I’m not sure of this – only that full cruising power, RPM and speed seem to be available even when the alternator is supplying significant power to the battery bank and inverter.

As the engines have aged (about 4000 hours since 2000), the alternators now cause a slight reduction in RPM at cruising speed - from about 3200 RPM to about 3150 RPM when the key is turned on and the 45 second regulator timer expires.  This aging turned out to be the first symptoms of engine failure.

Unfortunately, the Balmar alternators have proven to be unreliable in our environment of heavy use at nearly full power.  While they would probably be quite satisfactory for charging batteries, we demand nearly full power over an extended period when operating our washer/dryer or air conditioning.  The heat and load ages them quickly.

Between 2000 and 2004, we have had 3 rebuilds on each alternator.  Each rebuild cost us between $250 and $550 per rebuild - more than the original cost of the alternator over only a three year life.

See the Zena page for our current charging solution.

Inverter

The next critical part of our system is a 3000-Watt Prosine inverter.  This is a combination battery charger, inverter, and power switching system.  It automatically detects the delivery of shore power from the dock and synchronizes the inverter-generated power before cutting over to shore power.  Thus, our computer and air conditioner usually continue to operate without interruption when plugging in after a sail.  This is a no-switch system.  Arrive at the dock, plug in the shore power cord, have a beer.  Time to go?  Unplug the shore power cord and sail away.

The air conditioner operates between four and six hours on battery depending on  how many minutes of each hour the compressor operates to provide the necessary cooling.  The computer operates about three days on battery power if the engine is not operating and the air conditioning is not on.

One engine at 2500 rpm or more is sufficient to operate the air conditioner indefinitely and maintain a DC bus voltage of about 12.5 Volts.  This “costs” about one liter per hour, maybe one-half a buck at today’s rates.  Not bad for air conditioning in the middle of nowhere by an engine that is so quiet we can hardly hear it above the normal boat noises with the air conditioning running.  Boats sharing our anchorage can hardly hear it from a boat length away.

A few minutes operation of the microwave requires no engine support. 

The washer/dryer requires engine operation when in use away from shore power.  I normally start a second engine at about 1500 rpm if the washer/dryer and air conditioning are both in use.  One engine at about 2500 rpm will carry both loads and maintain about 12.3 Volts on the bus – with the computer running.  This is our normal mode when under way.  Yep – we run one engine, maintain just over five knots, and can support both the washer/dryer and air conditioning – all for about one-half gallon per hour.  The house batteries are not charged in this environment - all the output goes to the inverter.  Two engines at 2500 rpm each get us just over six knots, raises the bus voltage to about 13.8 and will operate everything on board while supplying full power to the props, and charge the house bank.  We always maneuver on two engines.

John Zeitlin, http://www.zrd.com/, supplied the Balmar alternators, regulators, and installation kit that went to South Africa with us when we commissioned the new Shearwater II.  He is also continuing to research our two minor problems that remain.

Balmar Regulator Quirk

We investigated the second problem, called the pulsing problem, with Balmar.  During the process of the investigation, Balmar shipped us a replacement regulator.  The new regulator reduced the problem somewhat and eliminated the severe smoking that took place each time the engine pulsed.  Unfortunately, the reprogrammed second regulator would not take the battery bank to full charge when any load (50 amps or more - we don't worry the small stuff) was present.

We acquired a set of Ample Power regulators in late 2001 and installed them on both engines.  They work flawlessly under high, do not pulse the engines and top the batteries a bit faster under low load.

Balmar has shipped me a third set of alternators that were designed to correct the remaining problem.  The pulsing problem continued with the third set of alternators.

John Zeitlin eventually tracked this problem down for us in 2003.  Apparently under some conditions the temperature sensor on the battery causes the alternator controller (regulator) to behave strangely.  Disconnecting the battery temperature sensor eliminated the problem.