I have the above networked together with an LSS-1 Structure scan. After a couple hours of having all of the above on - the "Voltage Alarm" goes off indicating that the supply voltage has dropped to 11 volts or less - however, if I check actual battery voltage, it is always 12+ volts. I have just put a NEW Optima group 27 AGM battery in the boat -problem still exists. Freaks me out, as I expect to go crank up the motor, and have it go "click, click" and not start - never happens.

I have wired the supply voltage to these units through the main "Power" switch on the boat.

Anybody have this happen? Or what could it be?

Wire both graphs directly to your optima battery and bypass the main power switch. This should solve your problem. It is not uncommon to have a voltage drop when wiring through a switch in boats

I had the same problem. There is just too much junk tied into the main power source (and the wiring is too small), do as mentioned above and make a dedicated electronic circuit running to the batteries.

I have Gen 1 HDS 8 and 10. Both are direct to starting battery. I had the same problem with the alerts going off and beeping. This got tiresome because like you, the starting battery is good as indicated by the console voltage gauge and separate voltage reader. I just think the units are sensitive when the start battery is cranked. My remedy was to turn off the alarms and sound to the alarm. Then I set one or two screens on each unit to have the voltage displayed so I can keep an eye on it from time to time, especially if on the water for long periods of time.

All good stuff guys, and thanks. I kind of new that may be the problem. Just have to muster up the energy to get it done. I have the tools to do it (an electrical snake). I'll probably get some 14 gauge, 2 wire SO cord to do it. Or maybe just a good quality extension cord from Home Depot.

14 Gauge wire good enough ya think?

At <12.2 volts measured at battery, you would be over-discharging your cranking battery

1) Best Fix: Use a dedicated House Electronics Battery...end of voltage issues. ( and your cranking battery voltage should never be allowed to fall below about 12.2 volts (50% state of charge) which will sulfate the plates and permanently damages it.)

2) Else, get a larger cranking battery and also find cause of such a large voltage drop in console, rather than just wire around it....better boat builders size their wiring to prevent such issues.

3) Last, if giving up and wiring around the console, and if fishing brackish/salt water, use marine grade wiring directly to the battery and not through any existing breaker.
Don't forget the needed fuse located within inches of the battery.

Hi...i wil suggest If you have just a little bit of bad contact - you can loose voltage.Then check your alternator cables and alternators. Since it only happens when you are running - you might have a defective alternator or a bad ground connection to the engine.Then check your cables are the right size
Then check your ground circuit. A little bit of corrosion can really FU your voltages.

Agree. Additionally, if you don't want graph connectors powered up continuously, you can add a dedicated switch for each graph. I did and have no issues running 2 HDS 12's/Ethernet linked.

I doubt he is still having this problem lol. The original post is over three years old