Electric winches cause voltage drop alarm - Deep vs. Starting

[donradcliffe]

There are a lot of unknowns in your setup, so its hard to diagnose online. A qualified marine electrician could look at your particular boat, diagnose your problem, and recommend a solution in less than an hour. The preferred alternative is for you to learn to be your own electrician, because there may be times when an electrician is not available.

That being said, give us a few more details about your boat so we can predict what voltage drop would be expected. Is the boat using one bank to run both the winches and the distribution panel? What is the size of the battery bank? How are the batteries in the bank connected(cable size/length/switches)? Is there a separate cable running from the bank to the winch circuit breaker, or does the winch power cable come from the distribution panel? Same questions for the ground side--cable size/length/is there a ground bus?

Excessive voltage sag can come from a number of sources--insufficient battery size, insufficient charging, insufficient wire size, bad connections, bad switches, and excessive load. To find the murderer, you have to interview all the suspects. Your tools are the digital voltmeter, a clamp-on ammeter, your temperature sensing fingers, and a good history of what changed and when.

The interview usually starts by measuring the voltage at the battery terminals (the post itself, not the clamp or wire on the post) before and during the winch operation. The voltage should be at least 12.4 volts before and 11.8 volts during operation. Run the winch for at least 30 seconds and see how fast the voltage drops. When you are done with the test, put your finger around each terminal and see if you feel any warm spots from bad connections.

The next step is to measure the voltage across the winch motor terminals. You should get zero volts before, and at least 11 during operation (the actual voltage will vary with winch load, and may drop to below 10 as the winch stalls).

If you are losing more than a volt between the battery and motor terminals, the next step would be to run a separate light wire between the battery and the motor area to extend the length of your voltmeter probe, and measure the voltage drop (difference) between the two positive terminals and the voltage difference between the two negative terminals, while under load. The voltage differences should be less than half a volt on each side, and this test can eliminate half the suspects.

If the voltage drop on one side is excessive, take one end of your probe wire and start looking at the voltage drop at intermediate points along that side--every connector and switch. Use your fingers as well to look for hot spots.

The clamp-on ammeter is a valuable tool to see how much amperage the winches are drawing--the typical 1000 watt winch motor should draw 100 amps at full load, and probably30-40 amps with no load. Anything over 120 amps would indicate a motor problem, but in your case since both winches exhibit the same symptoms it is very unlikely that both motors are bad.

Have fun, and report back. I'll be looking at a very similar problem soon on the YC Whaler--one of the big outboards is sometimes very hard to start--problem has existed for years and new batteries didn't fix it, so they have called in Dr Wattson.

[Maine Sail]

#1 Take your volt meter and set it to peak capture for volts.

#2 Now take a long extension wire of perhaps 12 GA with alligator clips on either end (test lead) and connect one end to the winch negative terminal and the other to the negative DVM test lead now place the positive DVM test lead on the battery negative terminal.

#3 Crank the winch under load and go check the captured peak voltage reading.
.
#4 The captured reading is the loaded voltage drop or sag in the negative side of the circuit between the battery and the negative winch terminal. Write it down.

#5 Reapeat the identical test on the positive side of the circuit. If both sides of the circuit match, and the cables are same size etc. then likely not a high resistance point just undersized cable.

#6 If one side has a higher voltage drop reading that is the side of the circuit to start inspecting more closely.

#7 Also test your battery voltage sag under load using peak low voltage capture/hold...

Here is an image depicting what I am describing. Note the test leads are measuring the voltage drop across the fuse holder from point A to point B.

The reading on the DVM is the voltage drop across that portion of the circuit. That 5A fuse, its holder and terminals drops 0.111V at a 5A load.....

Your point A's are the battery terminals and point B's are the winch terminals. Test both sides....


BTW We still need an accurate drawing of your wiring layout....

[GordMay]

Originally Posted by svlamorocha

The resistance of cables does not depend on load. That is the merit of Ohm´s 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.

Voltage drop varies according to current flow. Unless you operate the circuit so current flows through it, you can't measure voltage drop.
Because an ohmmeter's battery can't supply the current that normally flows through most circuits, ohmmeter tests usually can't detect restrictions as accurately as a voltage drop test.
Connect a Connect a DVM across part of a circuit under load, and it directly reads the voltage drop across that wire, cable, switch, or connection.

So assuming a tolerable Voltage Drop of 3%, measuring voltage from + battery terminal post to + windlass motor terminal:
With engine/alternator running, a VD of 0.2 V
With a fully charged battery (engine/alt off) a VD of 1.875 V
would be acceptable.
This assumes similar readings on Negative terminals (0.4V & 3.75V drops on entire circuit).
Otherwise, see Main Sail's instructions.

[Cadence]

The simple explanation is probably your winch is sucking down the voltage due to demand. I am not sure I would worry about the alarm as long as everything else works after using the winch? An isolated winch battery would probably be the real answer then we can go back the a thread about charging that battery. As far as the alarm remaining on, it it probably designed to stay on until reset manually.

[dave777]

Originally Posted by svlamorocha

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.

My terminology is bad, I should have said "Sag" and Volt-Ohm meter.

Complicating things is that the battery cables run to various devices: off switches, combiner switch, dedicated circuit breakers for each winch, there is a charger, and the cables pass through a number of blind conduits. There is no relevant documentation.

I'll get the following data points, as well as others suggested here:

Vb Voltage at battery terminals, no load
Vbl Voltage at battery terminals, while winch is running (unsheeted)
Vw Voltage across winch terminals no load
Vwl Voltage across winch terminals , while winch is running (unsheeted)

If I understand correctly:
Sag = Vb - Vbl

Not sure what is most telling: Sag at the winch terminals, or the voltage drop along the path for the winch.

thanks

[dave777]

Thanks for the step by step Maine Sail!

My volt meter doesn't have a capture function. Upside to upgrading is I won't need another person standing around for the testing.

Originally Posted by Maine Sail

BTW We still need an accurate drawing of your wiring layout....

Not as much as I need one!

[Cheechako]

"#2 Now take a long extension wire of perhaps 12 GA with alligator clips on either end (test lead) and connect one end to the winch negative terminal and the other to the negative DVM test lead now place the positive DVM test lead on the battery negative terminal."

Wont this just capture the peak voltage at start rather than the minimum voltage during run?

[Maine Sail]

Originally Posted by Cheechako

"#2 Now take a long extension wire of perhaps 12 GA with alligator clips on either end (test lead) and connect one end to the winch negative terminal and the other to the negative DVM test lead now place the positive DVM test lead on the battery negative terminal."

Wont this just capture the peak voltage at start rather than the minimum voltage during run?

Depends upon your meter and what you have it set to. If you have it set to peak in-rush min it will capture that. If you have it set to peak average it will capture that.. Good meters can capture minimums and maximums and averages.... I use all those tools on my Fluke's with pretty good regularity as they are very, very handy.

Still you are looking for excessive voltage drop and even during in-rush you should not be exceeding more than double design drop... So if you are designed for 200A average at 3% drop and you see 11% on start up you likely have an issue....

[BruM]

Since this is a reworked boat it is quite possible that the instruments in question were wired near the winch motors. The voltage at the motor will drop as the load increases. Try hooking the instruments to the battery terminals directly.

The best solution will be to hook instruments to the house battery not the engine starting battery but that many not be necessary.

[svlamorocha]

Originally Posted by dave777

Not sure what is most telling: Sag at the winch terminals, or the voltage drop along the path for the winch.

thanks

I think you meant to say "Sag at the battery terminals", not at the winch terminals. The critical thing is that you do not mix issues; you need to measure voltage drop separately for negative and positive runs (2 measurements) and you need to measure battery voltage across battery terminals (just one measurement).

If you measure across **winch** terminals then you are mixing two issues, which means your measurement is almost useless when trying to find a root cause.

We cannot tell you which one is most telling. You have to look at both separately to see whether you have a wiring problem or a battery problem.

You will do well if you follow Gord´s 7-point checklist in post #17.

If you do not know how to set your meter to read peak voltage then just read normal voltage; the results will most likely still help you. Alternatively, get a cheap analog voltmeter with a 2-volt scale and you will be able to see the peaks accurately enough. This peak thing is only important for motors.

[rwidman]

Originally Posted by dave777

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 parallel two different types of batteries. Bad practice.

We have to assume that the plotter and winches are powered by your house battery or bank and that you have a separate starting battery.

Your problem could be a simple as a weak house bank that needs the batteries replaced. Or, it could be undersized wiring or loose or corroded connections.

If it's neither of the above, you could add capacity to the house bank or rewire either the plotter or the winches to the starting bank. The winches are probably a better choice because if you wire the plotter to the starting bank it will probably indicate low voltage or even turn itself off when you start the engine.

If none of the above suits you, it is possible to use an additional battery or a large capacitor and a diode to maintain power to the plotter while the winches are operating. This is a little more complicated.


BTW: The fact that the cables were in a conduit filled with water shouldn't mean anything. While water in a conduit is not something we want, cables with the proper insulation should not be affected by water. Electrical cables spend many years submerged in water in wells with no ill effects. Unless there's a defect in the insulation (rare) or the insulation was damaged during the installation (less rare), the water in the conduit should not be a problem.

[GordMay]

Originally Posted by svlamorocha

... You will do well if you follow Gord´s Main Sail's 7-point checklist in post #17...

Main Sail provided the excellent step by step.

[rwidman]

One other possibility:


Change the low voltage alarm setting on the chart plotter. I had the same issue with mine when I first installed it several years ago. I set the alarm for a lower voltage and it hasn't bothered me since. I had actually forgotten about it.

[donradcliffe]

We haven't heard the results of the OP's tests yet, but I did give the YC whaler some love this week. The boat has twin 115 hp outboards, and two group 24 batteries. The batteries go to a 1-2-ALL switch with #2 wire. After the switch, two #2 red wires ran about 15 feet to two positive buses (one for each engine). From each bus the standard engine maker's #4 wire runs to a positive post and then to the starter. On the negative side, the batteries have a jumper between them, then each had a 15 ft run of #2 wire to a ground bus, which was shared between the 2 engines, and the #4 engine wiring to each engine block.

The setup sounds underwired, and the results showed it. On turning over each engine, the voltage between the battery terminals sagged from 12.4 to 11 volts. The voltage between the starter terminal and the engine block sagged to 6.5 volts! Each starter showed about the same voltage, and the starter current was 130-180 amps. Needless to say, the engines did not turn over very briskly.

A check from a negative battery terminal to each engine block showed about 1.7 volts loss on the ground side during cranking. The same check from the positive battery terminal to the starter post showed 2.5 volts lost. At the positive bus bars near the transom, the loss was over 2 volts, and at the output of the 1-2-ALL switch the loss was only 0.35 volts.

Even though the bus bars and connections had been heavily coated with liquid electrical tape, this area gets direct exposure to salt water spray. Opening up the connections showed significant corrosion on the busses and the ring connectors.

Not only did we clean up the bus connections, we tied all the positive wires onto one bus, making the 15 ft run two parallel #2 wires instead of one. We also found some corrosion on one of the battery terminals, so cleaned up those connections for good measure. Everything was dosed with CorrosionX and the bus area was recoated with liquid electrical tape.

The end result was we cut the voltage drop from the batteries to the busses from 2.5/1.7v down to 0.5v on both positive and negative sides. The starter voltage is now about 9 volts, and so far both engines start when we want them to (however it was sunny and 75 degrees).

The voltage drop still seems excessive, so if I get any more complaints about starting problems I plan to upgrade the long cable runs to 1/0 wire and put new ring connectors on the motor cables. The motor cables go through some seals and narrow places, and upgrading them would be a real chore.