Low voltage mistaken alarm

[boaterdude1]

Whenever I disconnect shore power, and start boat, or run heavy electrical equipment like bow thruster, or windlass, the low voltage alarm comes on and voltage meter shows about 11.3 volts. If run boat for a while the voltage gauge will read 12.2 volts and the alarm silences. After use and the volt meter shows 11.3 volts, if I put a meter on the actual batteries they read a great 12.6 volts, almost fully charged. Any ideas what is causing the low voltage to show at the helm gauges?

[markcouz]

You should be taking battery/alarm voltage from (as close as possible) the battery terminals and not at a remote location which would include voltage drop on cabling to that location.

[GordMay]

Originally Posted by markcouz

You should be taking battery/alarm voltage from (as close as possible) the battery terminals and not at a remote location which would include voltage drop on cabling to that location.

Indeed. ➥ https://www.cruisersforum.com/forums....html#post1256

[thomm225]

You may need to clean all your connections from the batteries to each load.

[jmschmidt]

I get a GPS "low voltage" warning which I think the manufacturer sets at about 10.5vdc, but my electrical panel will show 12vdc or higher underway.

[surazo]

Probably the voltmeter is reading the voltage in the net and not the voltage of the batts .Remember the start peak energy consume .It worse if you have a batt regulator with differents batt banks

[Madehn]

if it is a new problem then i strongly suspect that it is corroded connections somewhere not a voltage drop by wiring size problem-- go through and loosen every connection you can find both positive and negative and spray some corrosion blocking spray on them and i am betting your issue will go away- replace anything that looks suspect with a new heat shrink terminal as you go. start simple- then work up to more complex solutions-- "when you hear hoofbeats think horses not zebras"

[SV__Grace]

Our low voltage alarm was going off because of one bad battery in the bank.

To measure the voltage of your batteries accurately-

- disconnect each battery completely from each other and the boat (a pain, but has to be done)
-let them sit a few hours
- test and record voltage of each
- ideally, test again after 24 hours or so as one indicator of a bad battery is loss of energy while sitting, while a good battery shouldn't change at all after 24 hours

If one battery is bad, I'm told that you have to replace the whole bank. Ouch!

So I disconnected the battery pair (6v mastervolt AGMs) from the bank and went from 1200ah to 800ah and haven't had trouble since.