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Old 03-03-2013, 09:50 AM
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Kweisner Kweisner is offline
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Starting Battery Keeps Dying: Need Advice

I recently added a second battery and Borg Warner isolator relay per the "Official Dual Battery Thread" and now I have an issue where my starting battery is draining to empty while sitting. I double-checked my wiring, but have noted it again here, in case I missed something key:

Added a cable from the negative post of START Battery to HOUSE Battery (point-to-point connection).
Added a cable from the positive post of the START Battery to the ISOLATOR relay.
Added a cable from the ISOLATOR relay to the positive post of the HOUSE battery.
Wired the relay to the ignition key (closes when the key is in the "ON" position--opens all other position).

Then, I moved the power supply cables from my Clarion head unit AND Infinity Basslink sub to the HOUSE battery.

I do have a ProSport battery charger/maintainer attached the HOUSE battery only and this shows charged/ready.

Now, yesterday, I turned the key to the ON position and nothing. Also tried blower with same result, indicating dead starting battery. I could not even turn on the radio, since the head unit is still tied to the key being in the ACC position.

I put a separate charger on the start battery and it started taking a charge. I was able to run the blower, turn on radio, lights, etc.

So this battery situation started since I installed the second battery/relay. Seems like it could be just an unlucky coincidence that my start battery is failing, but that just doesn't seem very likely IMHO.

Assuming the relay is good (I checked it--it is), does anyone have another idea of what could be happening here or how I might diagnose?

Thanks in advance--I appreciate all the help.
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Old 03-03-2013, 12:00 PM
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Quote:
Originally Posted by Kweisner View Post
I recently added a second battery and Borg Warner isolator relay per the "Official Dual Battery Thread" and now I have an issue where my starting battery is draining to empty while sitting. I double-checked my wiring, but have noted it again here, in case I missed something key:

Added a cable from the negative post of START Battery to HOUSE Battery (point-to-point connection).
Added a cable from the positive post of the START Battery to the ISOLATOR relay.
Added a cable from the ISOLATOR relay to the positive post of the HOUSE battery.
Wired the relay to the ignition key (closes when the key is in the "ON" position--opens all other position).

Then, I moved the power supply cables from my Clarion head unit AND Infinity Basslink sub to the HOUSE battery.

I do have a ProSport battery charger/maintainer attached the HOUSE battery only and this shows charged/ready.

Now, yesterday, I turned the key to the ON position and nothing. Also tried blower with same result, indicating dead starting battery. I could not even turn on the radio, since the head unit is still tied to the key being in the ACC position.

I put a separate charger on the start battery and it started taking a charge. I was able to run the blower, turn on radio, lights, etc.

So this battery situation started since I installed the second battery/relay. Seems like it could be just an unlucky coincidence that my start battery is failing, but that just doesn't seem very likely IMHO.

Assuming the relay is good (I checked it--it is), does anyone have another idea of what could be happening here or how I might diagnose?

Thanks in advance--I appreciate all the help.
In checking some other possibilities, I disconnected one of the ground cables from the START battery (the one that goes over to the dash area) and heard a "whirring" sound from the rear of the boat which lasted for !3 seconds. As I suspected, this sound was coming from the fuel pump. I reconnected the ground and then turned the key to the "ON" position--as expected, I heard the same whirring sound from the fuel pump--several seconds and then it stopped. However, when I returned to the key to the OFF position, I did not hear the sound, so I disconnected the ground again, and the sound returned.

This makes me think that perhaps the fuel pump is remaining in some kind of powered state when it should not be (key OFF), and that unless i fully interrupt the power, then there some current draw happening that should not be.

While I had the ground cable off the battery, I did put a DVOM between the battery post and the cable and measured less than 1mA, so I don't think there's a phantom leak elsewhere.

Again, all suggestions are welcome!
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Last edited by Kweisner; 03-03-2013 at 03:20 PM.
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Old 03-04-2013, 12:32 AM
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mtajpa mtajpa is offline
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Had a similar problem and I moved the head unit to the house battery using a spare ACC switch and a isolation relay. This way when you turn the ACC switch (cranking batt source) on it picks up the relay and the head unit is then turned on from the house battery. I have an Alpine head set and it was causing the cranking battery to discharge until I moved it to the house battery. Also head unit doesn't shut off when you start the engine up.

You can put a test light in series with the cranking battery to see if there is a drain on your battery also. If the test light lights then disconnect the head set. If the head set is causing the draw the test light should go out. Bad diodes in the alternator can also cause a drain on the battery.

Hope this helps.
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Old 03-04-2013, 06:41 AM
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Quote:
Originally Posted by mtajpa View Post
Had a similar problem and I moved the head unit to the house battery using a spare ACC switch and a isolation relay. This way when you turn the ACC switch (cranking batt source) on it picks up the relay and the head unit is then turned on from the house battery. I have an Alpine head set and it was causing the cranking battery to discharge until I moved it to the house battery. Also head unit doesn't shut off when you start the engine up.

You can put a test light in series with the cranking battery to see if there is a drain on your battery also. If the test light lights then disconnect the head set. If the head set is causing the draw the test light should go out. Bad diodes in the alternator can also cause a drain on the battery.

Hope this helps.
Thanks for the advice. I do have the head unit powered off the house batt, but still have the trigger signal tied onto the main ACC bus/crank battery, so I will move that as well just to eliminate it as a variable. I also disconnected all my wiring between the house and crank battery and am going to let that sit for a few days. If the house batt drains again, then It's likely the battery is failing, (or the alternator)?

Just so I'm clear--can bad diodes in the alternator cause the battery to drain while the boat is not in use(sitting in the garage)?

Thanks!
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Old 03-04-2013, 07:54 AM
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Quote:
Originally Posted by Kweisner View Post
Thanks for the advice. I do have the head unit powered off the house batt, but still have the trigger signal tied onto the main ACC bus/crank battery, so I will move that as well just to eliminate it as a variable. I also disconnected all my wiring between the house and crank battery and am going to let that sit for a few days. If the house batt drains again, then It's likely the battery is failing, (or the alternator)?

Just so I'm clear--can bad diodes in the alternator cause the battery to drain while the boat is not in use(sitting in the garage)?

Thanks!
Bad diodes is the main reason a battery drains while sitting, assuming it has been charging when the engine runs. If you didn't upgrade the alternator when you added the second battery, you need to. The added load stresses the alternator, which wasn't sized for this.

You lifted a ground that the ECM needs and when that happens, the circuits will find a ground path anywhere it can. You need to disconnect the accessory battery before the main one to avoid this.

The fuel pump can't operate if its relay doesn't latch. If you disconnect the main battery's negative cable, you'll be able to measure 12VDC on just about every wire in the ECM harness. The engine block was still grounded to the other battery, so the 12V on the fuel pump relay caused it to latch because the relay is grounded to the engine block.
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Old 03-07-2013, 06:33 PM
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Quote:
Originally Posted by JimN View Post
Bad diodes is the main reason a battery drains while sitting, assuming it has been charging when the engine runs. If you didn't upgrade the alternator when you added the second battery, you need to. The added load stresses the alternator, which wasn't sized for this.

You lifted a ground that the ECM needs and when that happens, the circuits will find a ground path anywhere it can. You need to disconnect the accessory battery before the main one to avoid this.

The fuel pump can't operate if its relay doesn't latch. If you disconnect the main battery's negative cable, you'll be able to measure 12VDC on just about every wire in the ECM harness. The engine block was still grounded to the other battery, so the 12V on the fuel pump relay caused it to latch because the relay is grounded to the engine block.
JimN, thank you for the guidance. I "think" I've been able to eliminate the bad diode possibility. Last weekend, I disconnected the leads between the Start and House battery. The Start batt is now wired as it was originally (Pos and Neg leads to the starter/alternator and the accessory bus). It is now holding a full charge--over four days the voltage is steady and I'm able to turn the engine over.

On the point about taxing the alternator, mine is specified as 90 amp output which I thought would be sufficient from reading other threads. Even so, I'm thinking there should not be a time when both batts are dead (once I get this solved). Here's my rationale.

In the garage, the batteries are disconnected on the positive leg by the relay. The house batt is hooked to a charger/maintainer, so when we get to the water, it won't tax the starting battery when they're joined in parallel. Once running, the alt should really only be replenishing the start batt since the house was full.

Conversely, once the motor is off the batteries are separated by the relay and we use the house for the stereo/amp, so even if we drain it, the start batt should remain fully charged. Finally, when we get home, the house batt goes back on charge and maintain.

NOW, that ALL seems logical to me but I'm not an electrical engineer and am open to correction or other ideas.

I need to continue my troubleshooting and find out what's happening once both batteries are wired together (even though the positive leg IS interrupted by the relay). This does make me think there's something going on with the ground which is allowing something to drain the start battery while in storage.
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Last edited by Kweisner; 03-07-2013 at 06:59 PM.
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  #7  
Old 03-08-2013, 05:50 PM
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Kweisner Kweisner is offline
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Chapter 3: It's NOT the Starting Battery
Been a week and the starting battery is holding a charge and able to spin the motor. It's still disconnected from the House battery (new Optima Blue Top).

On that front, I had unplugged the charger/maintainer from the House batt and whaddya know. . .it's dead as can be. But it will take a charge so I've plugged the maintainer back in. Once it's fully charged again, I'll completely disconnect it and see if it loses charge or not. If not, then I think that says I have some draw happening somewhere and I'll just have to chase it. If not, then it's under replacement warranty.

The only things I have wired to the house batt are the clarion stereo and an infinity basslink powered sub and both have been off. The clarion is controlled by the key in the ACC position, but get's its constant power from the house batt. The basslink amp is wired to the clarion's accessory circuit so it's being powered down when the stereo turns off. I believe that rules out the stereo as the current leak, and maybe I just have a bad battery. Looking for any other alternatives or confirmation my conclusions are correct.
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Old 03-08-2013, 08:28 PM
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mtajpa mtajpa is offline
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Its probably from the constant draw from the head unit. Mine was like that. I use an ACC switch that powers up the head unit. You lose the memory in the head set all the time but at least the battery stays charged.
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Old 03-09-2013, 08:52 AM
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Kweisner Kweisner is offline
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Quote:
Originally Posted by mtajpa View Post
Its probably from the constant draw from the head unit. Mine was like that. I use an ACC switch that powers up the head unit. You lose the memory in the head set all the time but at least the battery stays charged.
I will definitely isolate the head unit and see if that's it, although when I was still on a single battery system I never lost a charge. I'm kind of at the point where I think I got a bad battery and just need to get it replaced.
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Old 03-09-2013, 10:07 AM
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If the head unit kills the battery is a few days, something is wrong with it. The memory olny draws a few milli-amps and some head units have non-volatile memory, so it doesn't even lose everything. These still have the red and yellow wires, but the red amounts to only being an ignition enable and the yellow has been the main power lead for a couple of decades.
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