Shape: Battery Switch, Isolators & Integrator
Ship Shape II: Battery Switch, Isolators & Integrator
Systems How To
battery switch, isolator (isolators) and integrator (integrators)
systems are worth their weight in gold when it
comes to dual (multiple) battery management. No boat owner should be
Learn how to keep batteries aboard
your boat from leaving you stranded!
It is, therefore, the foolish one
who sees it as impractical having dual anything aboard a vessel, until left
in a predicament. So while two is generally accepted as better than one, it
can well be said that one may be no better than two, if the latter is
For example, let's say you've been on
an overnight fishing trip. Floodlights, bilge pump, aerator, spotlights,
etc. have all been in active use the whole night. You have no electric
generator for you are cleverly equipped with dual 12 volt batteries and
Unfortunately, upon trying to crank the engine, you discover both batteries
are dead due to the battery switch having been left in the "all" position,
draining both batteries dead. This is the dilemma many find themselves
in when managing their batteries with a battery switch alone. Also, if the battery switch
was left in the "1" position (main cranking battery) while the
"#2" (aux. battery) was drained from use, how will it
be recharged by the alternator if the battery switch is not moved to either
the "2" or "all" position?
Another problem with utilizing a battery switch alone for dual battery systems
is that when the boat is not in use for an extended period of time and the
battery switch is left in the "all" position, the weaker of the
two batteries can drain the the stronger one. An even more serious problem,
which can ruin the alternator, is placing the battery switch to the
"off" position while the boat's engine is running.
The simple fact is, dual battery switches alone leave too much to chance – like always having to remember when to
switch to the proper setting for battery charging.
simple solution to these common problems is to install a battery isolator
(isolation diode or isolator or diode divider) to charge the batteries and
utilize the battery switch for
starter cranking (activating the starter cranking circuit only). When properly wired, this
charge both batteries no matter what positions the battery switch is in.
However, when using a battery isolator in conjunction with a battery switch,
leave the battery switch in the "1" position (for starter cranking battery) unless it becomes
dead for cranking, then switch temporarily to #2 house battery for
accessories (see wiring diagram below).
Furthermore, you will no longer risk blowing the
alternator in the event the battery switch is inadvertently put in the
"off " position while the engine is running. The reason being is that
the charging circuit (alternator output circuit) is not wired to the battery
switch, but to the battery isolator which distributes the charging current to both batteries
through a diode (a one-way electrical valve).
come with the battery isolator, along with various drawings as how to wire it
with a battery switch.
As aforementioned, since
the isolator is an electrical one-way valve, the alternator current goes to
both batteries without allowing current to backup through the isolator ─engine running or not. The center lug of the isolator is where the
alternator output wire is attached and the terminals marked "1"
and "2" on either side of the center lug is where you wire each
battery for charging.
isolator will also prevent batteries from draining in the event an
internal alternator diode problem develops, which can cause a voltage draw on the
batteries even with the ignition key in the off' position.
auxiliary battery can be wired for the boat's main
accessories/ignition feed wire and add-on items such an aerator and
floodlights, etc.; while the other battery can be used exclusively for starter cranking
only. Both battery positive terminals are wired to connect to the #1 and #2
isolator lugs according to the designated location on the isolator for charging purposes.
A boat's wiring diagram can aid in the specific location of the alternator
charge wire (wire that charges the battery) and the accessories/ignition wire (wire that feeds the boat's fuse
panel and accessories). Typically, these are located at the positive lug on the starter solenoid.
After identifying the accessory/ignition feed wire, it should be
disconnected and wired to the the #2 positive terminal (battery for
accessories or house battery) with at least the same size gauge electrical
wire. Then from the #1 isolator lug, run another wire to the #1 positive battery
terminal (battery for engine start/cranking).
identifying the alternator charge wire, it should be disconnected from the
alt. and wired
with at least the same size gauge electrical wire (#10 min.) to the center
lug (alt. lug) on the isolator. The number #2 lug at the isolator is wired form the isolator to the #2 battery
positive terminal house battery.
This isolator can be purchased for under $65.00 and should be a
marine type only. The isolation diode is generally rated
enough for the standard alternators on most boats, both inboards and outboards.
Some systems have monitoring gauges for each battery which can be
purchased at an additional charge.
even better alternative for battery charging management is a battery
integrator, more often used on outboard motors. Keep in mind that the integrator
and isolator are not used together. You would use one or the other with a
battery switch. The battery integrator device is more costly than the
typical battery isolator, even though it serves a
function similarly to that of a battery isolator or manual battery switch
for charging the batteries.
However, it offers
significant advantages over both of these more traditional methods of
battery bank isolation.
This device incorporates voltage sensing circuitry and a specialized solenoid/contactor to
automatically integrate two separate battery banks whenever a charge voltage
is being applied, then to isolate the banks when charging is not taking
place. This allows charging multiple banks simultaneously from a single
source (boats alternator/generator), yet permits selective discharge
(electrical draw from accessories) of each dedicated bank.
Because the batteries are integrated by direct connection through the
contactor, there is no voltage drop from the charging source to the
batteries as with diode isolators, and because operation is automatic, there
is no need for a manual battery switch to connect and disconnect the batteries
before and after charging. However, a battery switch can be added if wired
for cranking purposes ONLY as previously described when using and isolator.
See diagram above illustrating the incorporation of a battery switch for
cranking (starting) and an integrator for automatic charging of both
batteries regardless of where the battery switch is set to.
The Battery Integrator features a heavy duty marine UL listed contactor and
solid state circuitry. The housing is compact and hook-up is simple. The
standard model accommodates two 12 volt battery banks. It
is most notable to not use an external battery charger to charge the
batteries unless all of the batteries are completely disconnected from
the boat's starting and charging system as this may damage the battery integrator
circuitry. (charge batteries as a stand-alone battery, completely disconnected
from all systems)
The unit may be wired to provide a "start assist" from the
aux./house battery during engine cranking/starting if that battery bank has a higher charge than
the reserve start/cranking bank battery.
An optional contactor is available for integrating a third bank whenever the
other two banks are being charged.
Battery Switch Device: Depicts
connections made internally when selector switch is moved to different
Battery Isolator & Switch: This
device can save you a lot of trouble when it comes to dual battery management.
Battery Integrator, Battery Isolator &
Switch: The battery integrator device is more
costly than the battery isolator, but it has more advantages. Schematic
depicts the typical wiring diagram for each system when employed with a
Enables charging of two separate banks
without voltage drop, yet maintains 100% isolation at all
other times. For systems of three banks or more, an
additional unit may be installed for each additional bank
Heavy duty silver-plated contactor,
continuous duty rated to 100 amps
Voltage sense circuit, epoxy encapsulated
and heavy duty continuous rated solenoid are all designed
for use in marine environments
Easy-to-install: compact size - may be
mounted with any orientation
Easy three-wire hook up for two bank
systems (BATT +, BATT +, GROUND)
Terminal for optional wiring of remote
light indicating when battery banks are integrated
Optional internal connection can be wired
though key starter or manual over ride switch, tying
battery banks together for extra boost during engine start
Duty Cycle: Continuous rating to 50° C Derate linearly to 70%
@ 80° C
Temp. Rise: 95° C at full rated current (mount vertically for
Voltage Drop: At 50% load 0.7V, At full load 0.9V
outside US: contact
Multiple orders of the same item will
require additional shipping fees if not calculated in.
Contact us for shipping fee discount where multiple orders have
improperly calculated fee.
Checks are also accepted upon approval, contact
Questions Call: 504-228-3861 orToll free: 1-888-239-6680
Search term: boat battery
isolators integrators installation how to boat battery wiring
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