Masthead29_Mar2014 - page 12

ith fewexceptions, themarinebattery systems found
onmany recreational power and sailing vesselshave
remainedessentially unchanged for decades. There’s no
shame in familiarity. In fact,
isanaccolade tobe
surewhen it comes toanymarineequipment or design, es-
pecially thoseof anelectrical nature.
As commonas thesearrangementsmaybe there’s still a
variety of designand installationdetails thatmust be con-
sidered tomake them reliable, seaworthy and safe. There
arealsodecisions tobemadeby the installer anduser re-
garding redundancy, versatility and compliancewith com-
monly acceptedguidelines suchas thoseestablishedby the
AmericanBoat andYacht Council (ABYC).While typically
considered voluntary, dependingon the vessel’s useand
fuel source, theseguidelinesmay bemandatedby federal
agencies (gasoline-powered vessels, for instance, are re-
quired tomeet a series of standards under theCodeof Fed-
eral Regulations,many ofwhich relatedirectly tobatteries
andother electrical components) or your insurer.
Whether youare consideringa completeelectrical refit or
you justwant toensurea reliable starter and fully charged
batteries, theprerequisites for proper designanda safe,
compliant installationapply equally.Witha careful inspec-
tionof theexistinggear anda littleplanning, it’snot toodif-
ficult toenvisiona system thatwillmeet your needs.
Traditionally, thebuildersandmaintainers of vesselsusing
more thanonebattery arranged them in suchaway as to
afford theuser somedegreeof redundancy, andwithgood
reason. After all, in the schemeof thingsmarine, few fea-
tures aremore important thanbeingable to start theengine
when youwant to, not tomentionhaving thepeaceofmind
of knowing you cando so.
Themost commonbattery installation involved twoequally
sizedbattery “banks” thatwere connected to theengine via
abattery selector switch that offers [battery] 1, [battery] 2,
BOTH [batteries combinedor paralleled] and [all batteries]
OFF. The switchenabled, nay required, theuser to “manage”
both current leaving thebatteries for startingandother ves-
sel loads aswell as thatwhich returns to thebatteries from
theprimary charge source, theengine-drivenalternator.
Typically, for startingpurposes, the skipper turned themulti-
position switch toBOTH, whichallows theengine’s starter to
receive themaximumamount of crankingamperage from
bothbanks, enabling it, ideally, to start quickly andeasily.
Even if theenginewill start ona singlebank, there’s some
logic to this customof supplyingmore current. If the starter
labors, becausea singlebank isweakor inadequate, or
worse, the cabling is under sizedor compromised, thedrop
in voltagemay beexcessive, which in turn causes an in-
crease in current flow (theyare inverselyproportional for
motor loads suchas starters), and that in turn increases the
heat that is generatedwithin the starter. Over time this in-
creasedheat production, andextended cranking can
shorten the starter’s life.
Once theengine starts thealternator begins charging. If the
selector switch remains in theBOTHposition, charge current
from thealternatorwill bedirected to thebanks simultane-
ously. That’s straightforwardenoughand it’s a system that
has served thousands of boat ownerswell formany years.
It’s thenext stepwhereevents oftengoawry. Once the ves-
sel sets sail and switches theengineoff, or reaches itsdesti-
nationanddrops thehookor driftswhile fishing lines are
put over the side, the vessel’s electrical demand, often re-
ferred toas house loads, lights, VHF radio, fans, bilgepumps
etc, will, because they are connectedas one, drawonboth
battery banksequally. If the skipper forgets to turn the se-
lector switch to1or 2,
batterieswill remain in ready re-
March 2014 Page12
BatterySelector Switch
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