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Old 21-01-2015, 14:17   #1
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Electric winches cause voltage drop alarm - Deep vs. Starting

When sailing, using the power winches causes the house voltage to drop far enough that our Lowrance plotter goes into alarm mode, and stays there until we manually clear the alarm. Annoying, and not exactly soothing for guests new to sailing.

I'd guess that a starting battery would be better at providing the surge of power than a deep cycle. But I suspect that just replacing one of the batteries with a starting battery in parallel would defeat the purpose.

Any suggestions?
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Old 21-01-2015, 14:24   #2
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Re: Electric winches cause voltage drop alarm - Deep vs. Starting

If the winch is truly causing a house battery bank voltage drop, and not just a drop on the panel circuit containing the plotter, then your house bank is either way undersized or about dead.

Depending on how things are wired, it could also be poor connections, undersized wiring, incorrect wiring, incorrect circuit, etc.

Have you measured the terminal voltage on the house batteries while operating the winch to see what it actually is?

The problem isn't deep cycle vs. starting.

Mark
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Old 21-01-2015, 14:41   #3
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Re: Electric winches cause voltage drop alarm - Deep vs. Starting

As Mark says a healthy house bank, properly wired, on a boat big enough for powered winches should be able to remain above alarm voltage for 12V equipment.. Measure voltage at the battery terminals under winch load then measure the voltage at the plotter under the same winch load. It could be as simple as voltage drop due to how the system is wired.. Could be knackered batteries too.
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Old 21-01-2015, 15:02   #4
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Re: Electric winches cause voltage drop alarm - Deep vs. Starting

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Originally Posted by colemj View Post
Have you measured the terminal voltage on the house batteries while operating the winch to see what it actually is?

The problem isn't deep cycle vs. starting.

Mark
Had not done that test. But will soon. Will also do some tests to determine how the winches are actually wired.

We're not the original owner, and understand that some things, like the solar and fridge, were done after the factory.

Thanks for the wake up call
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Old 21-01-2015, 17:12   #5
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Re: Electric winches cause voltage drop alarm - Deep vs. Starting

As pointed out above, it is most probably a battery or wiring/connection problem.
Do the lights dim when you activate the winch? Is it just one particular winch that causes the v drop. Are you operating more than one at a time ie main sheet and genny winch? It may be worthwhile also checking the start up amp draw of each winch against the specifications as you may have a motor issue ( burnt out insulation?) placing an abnormal load on the batts.
Older electronics are quite sensitive to even quite small voltage drops. Wiring in a capacitor to the Lowrance is one thing to consider. A soft start relay for the winches is another.
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Old 22-01-2015, 09:51   #6
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Re: Electric winches cause voltage drop alarm - Deep vs. Starting

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Originally Posted by dave777 View Post
When sailing, using the power winches causes the house voltage to drop far enough that our Lowrance plotter goes into alarm mode, and stays there until we manually clear the alarm. Annoying, and not exactly soothing for guests new to sailing.

I'd guess that a starting battery would be better at providing the surge of power than a deep cycle. But I suspect that just replacing one of the batteries with a starting battery in parallel would defeat the purpose.

Any suggestions?
Don't even consider paralleling dissimilar batteries. If I read that right?
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Old 22-01-2015, 13:58   #7
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Re: Electric winches cause voltage drop alarm - Deep vs. Starting

what is the alarm setpoint and what was the battery voltage before you used the power winches?
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Old 06-02-2015, 09:00   #8
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How to test battery cables?

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It could be as simple as voltage drop due to how the system is wired.
The battery cables run through a conduit which had standing water in it at one time, from a leak of unknown source. So perhaps those cables are corroded, which would make them have a higher resistance and thus a voltage drop.

How do I test a battery cable?

Will a voltmeter detect the resistance of corroded cables, or would that only appear under a higher load?

More info: The alarm goes off when either winch is used. The batteries were recently replaced, and shore power keeps them charges. Haven't been able to get on the boat for any voltage tests yet.
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Old 06-02-2015, 09:26   #9
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Re: Electric winches cause voltage drop alarm - Deep vs. Starting

Was it working normally before the batteries were replaced? Before the water was found in the conduit? Anything else changed?

I agree the first test should be to check voltage at the battery while the winch is turned on and off.
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Old 06-02-2015, 09:29   #10
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Re: Electric winches cause voltage drop alarm - Deep vs. Starting

Are you running your engine with the RPM run up a bit while running the windlass? If not, try that.

You want your alternator to be doing a full charge of current if that is what the system voltage is calling for.

You may also be under gauged with your wire or have a dirty terminal, both of which would limit current causing heating of the wire or wire terminal. You can determine this by measuring for voltage drops across terminals or voltage drops along wire runs....with a load on the windlass at the same time.
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Old 06-02-2015, 09:53   #11
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Re: Electric winches cause voltage drop alarm - Deep vs. Starting

I doesn't surprise me really, I had more than one boat that the electronics went off/restart when I cranked the engine. An electric winch motor isnt terribly different. I would imagine having your electronics on a different battery bank would help?
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Old 06-02-2015, 10:08   #12
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Re: Electric winches cause voltage drop alarm - Deep vs. Starting

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Originally Posted by darylat8750 View Post
Was it working normally before the batteries were replaced? Before the water was found in the conduit? Anything else changed?

I agree the first test should be to check voltage at the battery while the winch is turned on and off.
We had poor battery performance before the battery replacement, why we replaced the batteries. The plotter is a new installation and its monitoring the voltage and alarm is a new function. The older plotter didn't have an alarm, but it would periodically reboot after a long sail, which is worse. We saw water in the conduit when we purchased second hand.

We'll test the voltage at battery before and during winch grinding.

I was just reading David Pascoe's page on battery problems, and he suggests that any water on battery cables is a likely problem cause.
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Old 06-02-2015, 10:18   #13
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Re: Electric winches cause voltage drop alarm - Deep vs. Starting

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Originally Posted by David M View Post
Are you running your engine with the RPM run up a bit while running the windlass?
While under sail, engine off, operating a sheet winch, not a windlass.

The current guess is that corrosion of the battery cables is the issue.

Quote:
Originally Posted by David M View Post
You can determine this by measuring for voltage drops across terminals or voltage drops along wire runs....with a load on the windlass at the same time.
Understood.

What differences in voltage drop under load - measured "at the terminals" versus "along the run" - indicates undersized/impaired cable run?
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Old 06-02-2015, 11:06   #14
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Re: Electric winches cause voltage drop alarm - Deep vs. Starting

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Originally Posted by dave777 View Post
While under sail, engine off, operating a sheet winch, not a windlass.
(snip)

What differences in voltage drop under load - measured "at the terminals" versus "along the run" - indicates undersized/impaired cable run?
I am not sure I understand your last sentence completely, but by definition the standard for "acceptable" voltage drop applies to drop between battery terminals and the load (winch in this case). The battery has (almost) nothing to do with it; it is (mostly) all about the load and the cables/connections.

Some people will be comfortable with 10% drop if it is very expensive to reduce it (as in long windlass cable runs). When those people know what they are doing they make sure that the line that is sized for 10% does not feed things that are sensitive to voltage (usually fed with lines sized for 3% drop).

The instantaneous variation of voltage at the terminals caused by a load (in A) is called "sag", reverses after you stop the winch and it is (almost) all about the battery (its internal resistance) and the load. The cables in the middle do not matter (much). You can reduce sag by getting a bigger battery bank (in Ah), changing battery technology (say AGMs instead of flooded; big difference here), or getting newer batteries.

If you run the engine at mid-to-high rpm AND certain things work OK then you will (almost) eliminate sag in the battery. That said, the only way to be sure is measure proper drop between negative battery terminal and negative load terminal and same with positive.. Then you break the run between battery and load into segments and measure drop in each segment until you find the culprit.

Calderīs book explains this quite clearly if I recall correctly. Ignore what Calder says and you will be in trouble, as usual.

On a related topic, it is always a bad idea to use a plotter (or any other load) as a voltmeter. You want to measure voltage at the battery, not at the plotter that may drop 0.5V just because of the plotterīs own draw. If you cannot afford a voltmeter connected directly to the battery with its exclusive pair of cables then connect it directly to the panel with wires that only feed the voltmeter.
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Old 06-02-2015, 11:11   #15
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Re: How to test battery cables?

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Will a voltmeter detect the resistance of corroded cables, or would that only appear under a higher load?
The resistance of cables does not depend on load. That is the merit of Ohmīs law, which apply to DC cables. If you want to measure resistance a voltmeter is not enough, you need an ohm-meter. A good multimeter will have one. You could also use an ammeter together with a voltmeter but that is probably not ideal for you.
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