Electrical Drain

2 new batteries. Charged with a trickle charger. I am losing approx 1 volt every night. I have triple checked nothing is left on. Stereo quick connect is diconnected. It is a cuddy cabin carburated 502 1997 Mercruiser bravo I. I have chenged the switches that were corroded for example the docking lights. What is the most common item that could be causing this? I have a nice fluke meter but dont know how to check for amp draw with it. Any ideas? Thanks for reading and all the help I have got here.

Re: Electrical Drain

Do you have a battery switch? How are the two batteries hooked up between the house and engine electrical systems.

http://forums.iboats.com/electrical...how-tos-other-helpful-information-583533.html

Re: Electrical Drain

dwelf said:

2 new batteries. Charged with a trickle charger. I am losing approx 1 volt every night. I have triple checked nothing is left on. Stereo quick connect is diconnected. It is a cuddy cabin carburated 502 1997 Mercruiser bravo I. I have chenged the switches that were corroded for example the docking lights. What is the most common item that could be causing this? I have a nice fluke meter but dont know how to check for amp draw with it. Any ideas? Thanks for reading and all the help I have got here.

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Ayuh,.... Put it between a battery terminal, 'n it's connector,...

Re: Electrical Drain

dwelf said:

[The batteries lose approximately 1-Volt] every night.

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It is normal that a fully charged battery, taken off charge, will dissipate the surface charge, and the battery terminal voltage will decrease. It takes an hour or two for this to occur. Maybe you are just observing that phenomenon.

In deducing state-of-charge from battery terminal voltage, a drop of 1-Volt represents an enormous drain, from about 1-percent DISCHARGED state at 12.9-Volts to 70-percent DISCHARGED at 11.9-Volts. In order for your bank of two batteries to be discharged 70-percent in eight hours ("overnight") you must have a very substantial parasitic current discharging them. It should be easy to find a current that large.

Also, disconnect everything from the batteries. Charge them, and test them for loss of voltage. Some batteries just won't hold a charge well.

Re: Electrical Drain

To clarify, the batteries are not dual. Just both are brand new. One is a spare.i will follow the procedure in the link don provided and report back. Thank you

Re: Electrical Drain

OK, was out of town and followed some of these procedures. I have 2 positive cables...
One is the main
two is the trim pump and deck lid... i can conform there is no drain drom number two.
the main however is draining 3 amps at all time. here is other steps i performed.. i took out all fuses for accessories.. still had a 3 amp drain.
i checked each removed fuse seperately and obviously found nothing draining across the empty fuse capsuls. there were 6 of them.

So what is next? the starter maybe? not sure how that would be draining. Thanks for all your replies. def not natural phenomenon. I also have an ignition kill switch that wont let the boat fire when trying to start.. So im assuming it is not the ignition draining me as it does not fire when that switch is off and i keep it off when not running i.e. while doing the amp tests. thanks in advance

Re: Electrical Drain

disconnect battery then unhook the alternator and either make the cables safe or tape the ends up with electrical tape then retest.

Re: Electrical Drain

Glenn you may be right in your thinking. i checked all fused accessories again with no luck, i turned my attention to the engine compartment and the alternator is warm! i am wondering if 1 of the connections back there are partially grounded as there seems to be some frayed wires... Its too dark and too tired but i will get back on it in the morning. no way the alt should be warm, have not started the engine at all or turned over the starter

Re: Electrical Drain

Blown diodes in the alternator.

Re: Electrical Drain

if a diode has failed in the alt then the ............ oh hell i just had a brain fart and i have no idea. either way if the alt is the problem take it to a rebuild shop and they can replace the diode and fix the problem (its not that uncommon)

Re: Electrical Drain

glenn property of pam said:

if a diode has failed in the alt then the ............ oh hell i just had a brain fart and i have no idea. either way if the alt is the problem take it to a rebuild shop and they can replace the diode and fix the problem (its not that uncommon)

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If a diode has failed in the alt then the ............ Alternator will not be charging the battery when the engine is running.
Easy enough to confirm; With the engine running (Don't forget the water!) The battery should be over 14 volts after a few minutes.
If it isn't, you're NOT Charging.

Re: Electrical Drain

If my gauges are right then I don't believe it is charging, I will confirm with my meter tomorrow... This would also cause my 2-3 amp drain I am assuming? I'm pretty sure it's not charging but was assuming the gauge wasntnright the only time I have been out.thanks guys will post back tomorrow

Re: Electrical Drain

NYBo said:

Blown diodes in the alternator.

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A very good suggestion.

Re: Electrical Drain

(edit ignore this piece corrected below)when a diode shorts the alternator can power up its exciter coil causing a magnetic field that normally happens when power is supplyed to the ignition terminal. A alternator requires a small ammount of power to make power which is why you have the ignition and sense wire connection on the alternator. Even a self exciting one wire alternator requires the same but it draws the from a capacator to start a magnetic field in the exciter coil. Now no one realy cares about this except you have to understand that the alternator when spinning may test good. So checking battery voltage when the engine is running may not give you the answer and may lead to more confussion.
If the ignition wire on the boat side is 0v when the key is turned off (unplug from alternator to test) then the alternator internals are the problem causing a drain and the reason the alternator fells warm is the exciter coil is using the amps to produce a magnetic field. (normally drains around 2-2.5 amps)
The only test that realy shows this problem is to unhook the alternator and check for amp bleed as the alternator output may still work fine as the alternator only requires the alterator to be spinning with a excited winding to make power (depending on the diodes and the voltage regulator the output may be lower-higher or unstable as the exciter field voltage is no longer stable as its not being directly feed from the ignition circuit)

edit: i had a friend just point out that the above post is wrong. Inside the alternator is 3 additional diodes that allow a backfeed from the output coils to power the voltage regulator which in turn powers the exciter when the alternator is around 1.5-2k rpm (alternator not engine) this is to reduce the load on the ignition switch and also to allow the alt warning light to work (if the internal supply of the alternator drops below the voltage at the ignition then light lamps indicating the voltage diffrence which is why they some times flicker when the engine is at low rmp as the alt is no longer at 1.5-2k rpm). when one of the diodes shorts then the power is no longer going from the output coils to the exciter coils but is coming from the battery to one of the main coils causing it to have a magnetic field when the alterator is not turning thus causing it to warm up. The reason the alternator may bench test correctly is that 2 of the 3 coils may still be working correctly if only one diode failed.

If theres voltage on the ignition side of boat with key turned off then the problem is not the alterator but somewhere on the boat side.

Re: Electrical Drain

Thank you all so much for the help. I believe I found the issue. I have 5 wires on the back of my alternator. The 2 with quick connects I believe we're hooked up backwards. I switched them around and my electrical drain went from 2.7 amps down to .005 amps. As long as it charges it should be good to go, if not means the alt is bad. I am assuming the wires were hooked up backwards since I know this engine was taken out by the marina where I bought it. Believe me this is not the only mistake they made. I am hoping this is all that I run in to

Re: Electrical Drain

if they wired the battery wire into the ignition terminal then that would cause a drain as the exciter would be powered. Only the ignition should power the ignition terminal. well spotted and i hope thats the end to your problem (no one though of this as most alternator plugs are idiot proof to stop you plugging them in the wrong way around :facepalm

Re: Electrical Drain

Not really sure what is going on. Now my key wont turn the boat off but the key does turn on the gauges and start the boat. There is a separate kill switch next to my key that does kill the boat though. Maybe there is a diode shorted in the alt after all or maybe the short is in my key ignition module. Either way it is better the way it is right now as its not draining my boat electric and I still have the extra kill switch to kill the engine. To be more specific, now when I turn my key off, all the gauges stop working on the dash but the engine still runs until I turn off the sep kill switch.

Re: Electrical Drain

lol yep the alt is bad so when you switched the wires you are now back feeding the ignition key so it will carry on running

Re: Electrical Drain

dwelf said:

...I believe I found the issue. ... The 2 with quick connects I believe we're hooked up backwards. I switched them around and my electrical drain went from 2.7 amps down to .005 amps. As long as it charges it should be good to go, if not means the alt is bad. I am assuming the wires were hooked up backwards since I know this engine was taken out by the marina where I bought it. Believe me this is not the only mistake they made. I am hoping this is all that I run in to...

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dwelf said:

... Now my key wont turn the boat off but the key does turn on the gauges and start the boat. ...Maybe there is a diode shorted in the alt after all or maybe the short is in my key ignition module. Either way it is better the way it is right now as its not draining my boat electric and I still have the extra kill switch to kill the engine. To be more specific, now when I turn my key off, all the gauges stop working on the dash but the engine still runs until I turn off the separate kill switch.

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There is to much "I Believe" going on here and not enough "I Know, and can prove".
What indicated to you that the wires were reverse? Just a Hunch?
What wires were they?
Is sounds like they are NOW Backwards.

If the Engine stays running, the ignition is still powered. You still have a drain.
If the motor happens to come to a stop with the points open, you will not see it.
If it stops with the points closed, the Ignition coil will remain energized and drain the battery.
Do not make assumptions that are not substantiated.
After you switched two "unidentified" wires at the Alternator, The ignition switch would not shut off the engine.
This indicated the wires were not wrong to begin with, NOT that the Ignition switch "Coincidently" went bad.
Put the wires back to where they were while you can still remember.
Trouble shoot the problem properly or you will be creating a wiring disaster that no one will be able to figure out.

Re: Electrical Drain

It was indeed the alternator, got the new one in and put on Saturday, battery charging beautifully for the 1st time and the electrical drain is gone, thanks for all the help