Low voltage warnings

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#1
I've seen several threads with this topic but mine's slightly different. We just made our first trip to Catalina Island to fish, while there we dropped anchor several times. I recently installed three new Northstar AGM batteries (from West Marine) and had the battery selector switches on "Both". When raising the anchor with the engines running, I'd get a "low voltage 11.5 volts" message on the Garmin 7610, not through any of the GW gauges. Since the batteries were fully charged, I'm guessing that this may be an issue where I just need to change the low voltage parameters on the Garmin. I don't remember offhand the brand of the windlass but I think it's the standard one on a Sailfish. Anyone else run into this?
 

SmokyMtnGrady

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#2
Sounds like a ground issue to me. I would get the low voltage issue on my 192 and it wound up being a loose ground connection. It would happen when I used the trim on the motor.
 
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#3
Could be a wiring issue, but depending on the winch you are using and the weight of your anchor, it could be normal. The voltage meters on fishfinders are notoriously inaccurate. Try bringing your rpm up to 1500 or so and see if the problem goes away. At dead idle speed, you have both the winch and the engine's electrical system drawing on the batteries.

It's always a good idea to clean all of your connection in any case. Electrical winches can be a PITA and need to be well maintained. They draw so much current when under load that the connections can overheat if not perfectly clean.
 
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SmokyMtnGrady

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#4
Could be a wiring issue, but depending on the winch you are using and the weight of your anchor, it could be normal. The voltage meters on fishfinders are notoriously inaccurate. Try bringing your rpm up to 1500 or so and see if the problem goes away. At dead idle speed, you have both the winch and the engine's electrical system drawing on the batteries.

It's always a good idea to clean all of your connection in any case. Electrical winches can be a PITA and need to be well maintained. They draw so much current when under load that the connections can overheat if not perfectly clean.
Doc, I was just going after the low hanging fruit and target the simple things first seeing how they are new batteries. I don't know the current draw and voltage of the windlass, but there has to be a good load when the windlass is first started.
 

SkunkBoat

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#5
I had similar problem with Garmin volt alarm on my 265. I'm just going to layout some things in no particular order or priority...

Repeated Garmin alarms. Changed Garmin setting to lower threshold to stop nuisance while I figured it out...
The volts on the Garmin were always lower than the volts on the Yamaha gauge.
The Yamaha is fed from the motor connection. The Garmin is fed from the HOUSE thru a 40A breaker, 10 gauge wire and then a terminal panel in the dash.
Cleaned a "green" 12v pin on Garmin...improved but still always lower than Yamaha.
Had all House power go out, at night, in Toms Canyon 90 miles out...o_O While messing with 40A breaker, with flashlight found loose connection on breaker...after that, Garmin matched yamaha.

Later troubleshooting also revealed that one motor was not charging the batteries and needed a new stator.

Bad connections, either loose or verdigris, have resistance and will cause a voltage drop across them. The connection can be either the pos or neg.
Corroded or partially broken wire (some strands broken) will drop a voltage across it.
We think of wire as having zero resistance but long wires drop voltage especially when they carry a lot of current.
The wire size charts that you may have seen describe the sized wire needed for 3% and 10% voltage drop for a given length of wire and current draw.
10% of 12.8v is 1.28v which drops it to 11.5V.

A windlass draws a lot of current.
Ideally it will be fed from the battery not from the the House terminal block and it will have very heavy wire because its the farthest thing from the batteries and draws more current than anything else.
 

seasick

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#6
If the only thing that changed is the replacement of the batteries and the alarms didn't occur before that I would suspect that something isn't right with the install. Perhaps a bad cable , clamp, etc. Skunkboat's voltage calcs are correct p but the piece that doesn't fit is the fact that the motors were running. In that case the voltage at the batteries should have been greater than 12.5, more like 13+ volts.
If possible, it would be helpful to measure the actual battery voltage at rest (nothing on), then with motors running , followed by motors running and windlass operating, and finally motors off and windlass operating. Knowing these voltages will help determine where in the electrical system the excessive drop may be or definitely isn't in which case, measurements have to be taken further upstream of the batteries.
Another option that I have used in the past is to disable the low voltage alarm:)
 

SkunkBoat

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#7
Another option that I have used in the past is to disable the low voltage alarm:)
yah that would seem to help ....but that Garmin is telling you something. It could be just the garmin connection, it could be effecting everything on your house panel.
I wouldn't ignore it. Physics and math don't lie... You can have a running motor with 13+ volts at the battery and still only have 11 volts at loads on your panel. And the more you turn on, the worse it gets...
Iv'e been in electronics all my life but its been a while since I have drawn schematics. I hope this diagram explains it... (and yes I noticed I put the switches on the neg side, which isn't standard practice...sorry)

From top down you have a battery at 12.8 Volts. You have a resistive load at 12.8 ohms giving you a current(I) of 1 amp and a power of 12.8 Watts. The wires and connections have zero resistance.
below that you have 2 identical switched loads which will draw 1amp each for a total of 2 amps and the voltage drop across both is 12.8v (in an ideal world).
Now below that is where I make my point.
If there is a mere 1 ohm of resistance between the battery and the load(s), we change the total resistance, total current and see a voltage drop across the 1 ohm and reduce the voltage across our loads even though the voltage at the battery is still 12.8 volts. As you go further down you see that turning on the second load makes the voltage drop even further...down to 11.07 volts. The power output of the load has dropped to 11 watts (i.e. the lights dimmed by 9%)

Scan 1.jpeg
 

seasick

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#8
Brings back memories of college classes. Some of those memories are painful:)To me, the first piece of info that is needed to go forward is whether the alarm condition is new since the new batteries were installed or has existed for a while. Perhaps the plotter is new also? I mentioned a similar alarm I had on a Lowrance plotter and that was just due to the low value being too high.That machine didn't have the capability to adjust the alarm voltage limit. In addition, the default setting for the low voltage alarm was ON whereas the default on my Garmin was OFF. The point is that I may have had 'low' voltage conditions on the Garmin for years but never knew it.

One test I didn't mention the first time is to measure the standing voltage at the battery with the battery switch on, normal electronics powered, motors off and compare that to the voltage at the plotter. There will be a difference. That difference should be less than 3% for electronic loads. A 3% drop for a nominal 12v application works out to about 11.6 volts. In that instance a low voltage alarm set at 11.5 wouldn't be activated.

Finding where the excessive drop is coming from is a lot harder. It could be a simple as dirty fuse connections or as complicated as an undersized conductor somewhere or the accumulated effects of added loads like new stereos, extra/new VHF radio, navigation additions, sonar or networking controllers etc.
 
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#9
yah that would seem to help ....but that Garmin is telling you something. It could be just the garmin connection, it could be effecting everything on your house panel.
I wouldn't ignore it. Physics and math don't lie... You can have a running motor with 13+ volts at the battery and still only have 11 volts at loads on your panel. And the more you turn on, the worse it gets...
Iv'e been in electronics all my life but its been a while since I have drawn schematics. I hope this diagram explains it... (and yes I noticed I put the switches on the neg side, which isn't standard practice...sorry)

From top down you have a battery at 12.8 Volts. You have a resistive load at 12.8 ohms giving you a current(I) of 1 amp and a power of 12.8 Watts. The wires and connections have zero resistance.
below that you have 2 identical switched loads which will draw 1amp each for a total of 2 amps and the voltage drop across both is 12.8v (in an ideal world).
Now below that is where I make my point.
If there is a mere 1 ohm of resistance between the battery and the load(s), we change the total resistance, total current and see a voltage drop across the 1 ohm and reduce the voltage across our loads even though the voltage at the battery is still 12.8 volts. As you go further down you see that turning on the second load makes the voltage drop even further...down to 11.07 volts. The power output of the load has dropped to 11 watts (i.e. the lights dimmed by 9%)

View attachment 6676
Great diagram, I'm going to post it on the bathroom wall...
 
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#10
All,
the low voltage alarm occurred before when raising the anchor, one of the three original batteries (I think it was the house) was 8.5 volts at rest so that's why I replaced all three. I bought the boat a year ago in April, the Garmin was installed shortly thereafter.

In another thread I posted that during the Christmas boat parade I used the Halogen spotlight on the hardtop and with the new batteries it triggered a low voltage alarm as well. I'm going to start poking around with the voltage meter this weekend and look for bad grounds.
 

DennisG01

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#11
Compare the voltage on the Garmin to the voltage seen in your Yamaha gauge or dash gauge. Do they match? In other words, let's see if you truly have a low voltage situation, or not. As mentioned, then checking at the battery will help, as well. You could also check at the battery switches and the main bus bar at the dash. The main idea here is to narrow down the variables and get closer to where the problem is. Once you know that, you can figure out if it's a bad battery (yes, even new ones can be bad) or a wiring issue -- loose or corroded connection... or failing wire (corroded internally). Another easy thing to do (and maybe it was already mentioned)... disconnect each battery and read the voltage directly at each battery with a DMM. I'd also suggest load testing each battery as an early step in this diagnosis - otherwise you'll be chasing your tail and pulling your hair out.
 

seasick

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#12
All,
the low voltage alarm occurred before when raising the anchor, one of the three original batteries (I think it was the house) was 8.5 volts at rest so that's why I replaced all three. I bought the boat a year ago in April, the Garmin was installed shortly thereafter.

In another thread I posted that during the Christmas boat parade I used the Halogen spotlight on the hardtop and with the new batteries it triggered a low voltage alarm as well. I'm going to start poking around with the voltage meter this weekend and look for bad grounds.
Reminds me of the story" After my surgery, I couldn't play the piano" Could you play it before??? NO!
I got a laugh in that the original post kinda lead me to suspect something odd about AGMs. Of course with your latest post, it seems the problem wasn't AGM related at all and the info on the halogen lamp tells it all.

Yup, checking voltages is the logical step.

On a separate issue, I am not sure I've seen a battery measure 8.5 volts. At 11 volts it is about as discharged as it could be. 8.5 volts tells me that maybe two cells were shorted

Good luck with your tracing.