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Discussion Starter #1
Today I noticed (according to the Xantrex battery monitor) that the batteries were being drained at a rate of -40A. The Xantrex also said the batteries were at 37% of charge, and at -275Ah (for 4 Trojan T125s). Normal high draw rate is -10 to -15A.

These are new batteries, installed 2 weeks ago. They were charged to 75% yesterday. I shut off ALL power (refrigeration, bilge fuse, main breaker, battery switch) and still the drain was -40 A. I started the engine, which normally shows that +40 A is going into the batteries. Xantrex showed -8A, and battery percentage and Ah still dropping. That then changed to -40A with engine still running.

I turned off the engine, and the voltage was 13.0, the voltage draw was -74A!!!! And battery at 17% charge. And this is with everything turned off.

The battery ground to engine looks fine. The bilge pump fuse was pulled. Refrigeration turned off. Still -40A to -74A drain. :eek:

Any ideas of what to check next? Maybe the Xantrex is wrong? It has been flashing "Charge Battery Full" all of the time, full or not, since batteries were replaced.

Meantime I have disconnected the batteries to keep them from draining. But this is not ideal, as I am a live aboard.

Thanks
 

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Can you test the voltage of the batteries with a tester when the Xantrex tells you they are at 17%? The voltage would be expected to be very low if that is the case. I suspect you are going to find that the batteries are fine and there is a problem with the Xantrex. Check documentation for Xantrex to see if there are any error codes. Maybe reset it and see if that corrects it?

Tod
 

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Discussion Starter #5
I put a meter to the batteries and they read .10 amps lower than the Xantrex reads. I disconnected the batteries overnight, reconnected them this morning, and the unusually large voltage draw is gone. I have yet to reconnect the starting battery. There had been water in the bilge, but that is now dry. Could a small gauge bilge pump wire short have drawn -40 amps? Did resetting the Xantrex solve the problem, or is there something else?
 

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Bombay Explorer 44
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Just because the batteries are new does not mean you can not have one with a failed cell. I would check them individually.

The symptoms you give fit that scenario.
 

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Chedk the bateries one at a time with a meter. If they are not dead your monitor is lying to you. If they are dead look for a fried wire. 40A melts insulation.
 

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Discussion Starter #8 (Edited)
I did check the batteries individually, they each read 6.22, they are 6 volt batteries. They are hooked together in a series. Would I check the individual cells with a hydrometer?
 

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the pointy end is the bow
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Is your house bank combined with your starting battery? If the voltage in your new house bank is higher than an old starting battery, the juice is going to run downhill into your starting battery and show a decrease in your housebank amp hr. reading.
 

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You can check the specific gravity of each cell if you have a hydrometer small enough to use the limited electrolyte volume of your Trojan batteries. The sp. gr. of each cell should be within about 5 points of the average (.05).

Wire gauge as small as 16 can carry 40A without damage. Wire insulation damage may not be evident.

You should be looking for a place that a very low resistance to ground has developed…40A at 12V is 0.375 ohms equivalent resistance. You isolated loads and still had the current flowing and that indicates a near-short circuit to ground somewhere.

The best way to isolate something of this nature is to split your distribution system with switches or breakers or fuses while monitoring your instruments until the condition clears…then split the offending half again…and again…until you find the culprit. Near the end you may have to lift leads to isolate the fault.

Good luck.
 

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Discussion Starter #11 (Edited)
Thanks Fryewe

How would I split the distribution system? With all breakers off there was still a drain, so what would I do? And after disconnecting the batteries overnight, and draining 1.5 feet of water from the small bilge area and letting it dry out, the problem is gone, for now. Maybe the short was in a wet wire in the bilge (even though the only wires there were to bilge pump, which I de-fused to no avail)? Or maybe the Xantrex needed to be reset?

AND, will it be hard to find the problem now that the voltage drain is gone? Maybe I should let bilge fill with same amount of water and see if the same problem develops?

Erps - Thanks, but the starting Batt is new also.
 

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Filling the bilge to try to recreate the problem may be your best course of action since you can't troubleshoot a problem that isn't there. An intermittent ground is a difficult problem to solve.

If the high current recurs when you refill the bilge then you know the problem is wetted wiring and you can lift leads at the terminal boards (both positive and negative) for the bilge pump (if that is the only load with wiring in the bilge). If there are others lift the leads for each load…one load at a time…until the condition clears.

If the high current doesn't recur when you refill the bilge I would suggest that you study the wiring diagram for your boat (if you don't have one then you need to build one by tracing systems - if you can) so that you have a plan for splitting the system when the problem recurs (as it likely will at the most opportune time).

Because the problem continued when you opened all breakers then I would make my prime suspects those things whose power doesn't go through the breaker panel. The bilge pump is one load that is not normally powered through either the main power switch or a breaker. You may have others (I don't have any others that aren't powered through the main power switch but I have a few that don't have breakers but are fused…the autopilot/Furuno GPS/depth sounder. You need to know which loads don't have breakers and where the fuses for these loads are…and have spare fuses at hand for them if a fuse blows).

Another method of finding the high current that is sometimes successful is to simply touch the 12V wiring inside/behind the breaker panel (wherever accessible) and on terminal boards to see if you can find any wiring that is very warm or hot. Be careful that you don't touch any 115V from shorepower/generator/inverter that may be in the vicinity.

Good luck with this. High current draw in unwanted places can cause a fire (imagine the same effect as the 12V cigarette/cigar lighter in an automobile…it's simply a wound wire resistor with a relatively low value that allows high current to flow in the wire…heating it until it glows red).
 
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There is another thread on this about four years ago. I am not sure that it provided all the answers though. One point that was mentioned was resetting the unit by disconnecting the power at say the two fuses for 30 minutes.
What you don't know for sure is if that amp flow is actually occurring. The batteries appear fully charged so they are not discharging.
Sometimes it might be a loose or wrongly connected wire.
I developed much the same problem over our winter. It was showing 8 amps discharge on the start battery so quickly calculating that it was discharged when it was not. There is a solar panel.
However it still showed that rate when the two wires for that battery from the shunt were disconnected. In my case I suspect a short within the unit has occurred and I will see if I can spot it nothing else seems apparent.
 

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bell ringer
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With start battery disconnected, what is its' voltage?

If you really had a 40 amp draw you aren't looking for a small wire problem as you would have had a fire! And if you still had the draw with all breakers off the load is something not on a circuit on the panel. So you should be thinking battery problem or something big like a windlass shorted.
 

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Have you had a look at the calibration of the Xantrex? With a new battery bank it is highly possible that the Xantrex has to be reset to suit the new batteries.

If you don't have the handbook, they are available on line. Get one and go through the calibration routine.

An easy quick check is to loosen one of the positive terminals and lift it off the post. If you are really drawing 40 amps, you should get a spark that will scare you ever so slightly. No big fat spark, no big fat current draw
 

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Is your Xantrex an inverter/charger? I've occasionally (not recently) left the "invert" switch on, which does nothing while on shore power, but in effect turns my Freedom 2500 and battery bank into a big UPS - running whatever laptop chargers etc were plugged in when the shore cord is disconnected.

One time it was the water heater still switched on; luckily I noticed the "-120A" display before it went on for very long!
 

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Discussion Starter #17 (Edited)
QUESTION - the bottom of the bronze (?) raw water filter was touching bilge water. The raw water filter is hooked up to a grounding system (runs to V-drive and, I think, to the engine. Batteries are grounded to the engine). Could this have been setting up a -40A draw from the house batteries?

Also, there are only four wires that run into bilge - 2 go to pump, 2 go to float switch. If I pull the bilge pump fuse (located at the manual/auto/off switch) would that shut off power to all four wires, or would it just depend on how its wired?

Thank you everyone for the great ideas.

To address some of the questions - I have no windlass, the Xantrex is not also an inverter. I did check the voltage on just the starting battery, it was around 12.5.

The problem has not reoccurred. Seems my best bet is to let a little water back into the bilge via raw water strainer and see if the same problem occurs.
 

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bell ringer
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QUESTION - the bottom of the bronze (?) raw water filter was touching bilge water. The raw water filter is hoked up to a grounding system (runs to V-drive and, I think, to the engine. Batteries are grounded to the engine). Could this have been setting up a -40A draw from the house batteries? [COLOR="Red"[/COLOR]

The problem has not reoccurred. Seems my best bet is to let a little water back into the bilge via raw water strainer and see if the same problem occurs.
I just don't feel any small wire to a bilge pump etc would have survived 40 amps. Maybe the reason the problem went away is that the wire burned out and is now open. You could well have had a short somewhere, but if so you need to find this as it doesn't sound as it was protected by a fuse/breaker as it should have been. I wouldn't assume that filling the bilge with water and the current doesn't happen as you having fixed anything.

You are heading for a fire!
 

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If you're going to play an electrical Sherlock Holmes then you need a proper magnifying glass.

You should have -- ALL boats should have -- an AC/DC clamp-on ammeter. Decent ones are cheap these days (around $60), and they'll save you hundreds of dollars of grief.

Wondering if you have a current leak? Just use the clamp-on ammeter to prove that you do (or don't), and to accurately measure the magnitude of the leak.

Did you really have a 40A current draw with all breakers off, or was the Xantrex lying to you?

No more will you have to say, "I think I have.....". With proper use of a clamp-on ammeter, you'll KNOW you have, or don't have....

You can also know very accurately:

- how much amperage you alternator is actually putting out
- how much amperage your battery charger is actually putting out
- how much amperage your solar panels are putting into the MPPT controller
- how much amperage your MPPT controller is putting into the batteries
- how much amperage your bilge pump draws
- how much amperage just about anything on your boat draws
- how much amperage is being drawn from your batteries
etc., etc.

You get the picture.

Sorry for the mini-rant. It just drives me crazy to watch the antics of folks trying to troubleshoot relatively simple electrical problems on their boats without having even the rudimentary tools required.

Bill
 

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the pointy end is the bow
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I just don't feel any small wire to a bilge pump etc would have survived 40 amps.
The battery monitor gives three readings: Volts, Amps and Amp/hrs. I think in this case, it was a loss of 40 amp hrs that was experienced.
 
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