Dual Battery Question

[wxfcstr]

My question is this:  When the voltage drops on the starting battery below a certain threshold, does it affect the operation the power trim/tilt? I haven't charged my 1st battery very much when I'm running the motor as most of the time, the alternator is charging the 2nd battery that powers the stereo. I've had a couple of instances where the boat has been running and I go to adjust the outdrive trim the boat dies or almost does. This happened yesterday 3 or 4 times. I switched the battery charging to battery 1 and the issue stopped. Everything was fine.

I'm guessing the voltage got too low on battery1 and when I hit the trim switch the load was too much and it almost killed the motor. Is this a normal type of behavior with a dual battery system? I know not to charge both batteries at once, it's either 1 or 2. Both batteries were new this spring. Battery 1 is a marine starting battery and 2 is a deep cycle to power the stereo. Any information would be appreciated. This is my 1st Rinker that's had dual batteries.

Bob

[alswagg]

Well, your situation all depends if the dual battery's were factory installed or otherwise.  The factory installion is going to include a Dual battery switch, individual circuit breakers, a battery isolator system, and proper sized battery cable. 
Many dealer or owner installed systems only include the Switch assy and usually undersized cables.  many piggy back the ground cables even.
If the system is OEM installed.  The battery isolator will charge either battery in any position.  1-2 or both.
The trim system cables should be connected to battery one, this was the intended design.  If battery one is not being charged and the switch is on battery on, the ecm will soon see a low voltage.  Check for proper voltage at both batterys.  Check the isolator if present.  Al

[wxfcstr]

Al,

I 90% sure this was a factory installed dual battery system. I've seen the separate circuit breakers near each battery. I usually have a solar panel deployed charging the stereo battery (#2) while I'm anchored, but just haven't used it very much this year. So if I read your reply right, you said I can charge both batteries at once??  Given my Faria voltage gauge doesn't go above 13 volts, I assumed there is not enough output from the alternator to charge both batteries at once.

Thanks for the reply.

Bob

[mattie]

Got the same issue on our 276BR. Factory dual batteries. Added shore power/charger later.

Taken a couple runs at the issue. Dealer is going to check the isolator when I drop the boat off for winter storage. That's the last thing to check.

I've replaced the batteries, tested alt, etc.

Temp solution: When running the boat I now have the switch on "both". When anchored I set it to "1". Seems to have resolved the dropping voltage, trim issue, when running. V-meter shows just over 13V when running.

(BTW never change the batt switch with the engine running.....)

Mattie

[alswagg]

Rinker charging systems with battery isolators;
The alternator supplies voltage/amps to the isolator only which disperses voltage/amps to individual batteries.  This is not the way voltage/amps are dispersed on a single battery system.  On an isolator system, your gauges will read battery voltage not necessarily voltage or amps output of the alternator.  A simple change or mod to the wiring will change this.  Mercruiser engines have an ORANGE alternator wire in the wiring harness.  Rinker removes the ORANGE wire from the alternator and installs a 8 gauge RED wire which runs directly to the battery isolator.  The ORANGE wire is usually just cut and taped back into the engine harness near the alternator.  I have boosted all of my customers charging systems by reattaching the ORANGE alternator wire along with still using the RED isolator wire.  This ORANGE wire is run from the alternator to the starter buss.  I have seen some instances where the ORANGE wire was also cut at the starter buss,  You can check very easily by measuring voltage with batteries on at the ORANGE wire near the alternator.  NOTE this ORANGE wire is an 8 gauge also.  If voltage is present, the wire is connected at the starter also, thus you only need to add a 6" extension and an 1/4" eyelet to the end of the ORANGE wire.  Connect the ORANGE wire plus the RED isolator wire to the alternator stud.   If no voltage is present you will also need to reattach near the starter buss.  Doing this simple mod, your gauges will read alternator output, supply higher voltage/amps to the ECM and fuel pumps.  Many causes of fuel pump failure is low voltage,  without this mod, the way Rinker supplies, the voltage at the starter/ECM is 11.8 to 12.2 volts.  With the mod, the voltage is around 12.4 to 13.8.  This is the same as what the voltage would be if no isolator system was installed.  This mod will still charge all other batteries also.  Be careful with live wiring in the bilge area with batteries connected.  Good luck  Al

[mattie]

Very cool Al !!

I'll take good look when I get the boat out for the winter. Sounds like the fix for me....

Sorry to hijack thread.

Mattie

[RobyW1]

Whatever battery is selected when your power trim almost kills the engine then I would have that battery tested. Im betting you have a dead cell. I would also use a battery switch that will allow the selection of both batteries to be run at the same time. this way they can both charge off the engine