Thread: 2018 Merc 150hp voltage

No clue but I’m intrigued as to what could be going on.

If you have a separate starting battery and deep cycle battery for bowmount and or downriggers, it might be best to connect the fishfinder to the deep cycle battery.
What is happening is the voltage "at" the fishfinder is dropping below the threshold required to run it. There are several possible things that can be causing the problem. It can also be a combination of causes.

1) Weak battery. If it is not at full charge, or not able to hold a full charge due to age and/or internal fault, when you start the motor it will draw the voltage lower while starting.

2) Too many things running off the same battery while the motor is not running and/or the motor charging system may not have enough charging power to bring the battery to full charge during the time it is running.
3) If charging system of motor is not charging the battery when it is running.

4) Drop in voltage between the battery and the fish finder. This can be caused by poor (or corroded) connections between the battery and the fish finder. It can be fuse connections, battery connections, crimp connections of wires to terminals, switches and/or connectors. Inadequate wire size, possibly in combinations with length of wire and what other accessories are connected to the same wire.

I would check it out in the following order.
1) Make sure the battery is fully charged and the water level in all of the cells is full. If not, top off with distilled water. Then check the condition of all the cells with a hydrometer. They are inexpensive at an auto parts store. Moderate to poor indication on any of the cells indicates the battery should be replaced.

2) Measure the voltage on the battery with everything off and engine not running (it should be about12.5 to 13 volts). Then measure it with the motor running. It should be a volt or two higher, which will indicate that the motor charging system is working.

3) If no problems are found from 1 and 2 above, check and clean all connections between battery and fishfinder. Make sure all connections are tight. Clean metal surfaces with scotch brite pad, emery cloth, or sand paper. This includes fuse contacts. Shiny metal is clean. You can use contact cleaner or WD 40 for connectors you cannot manually clean. Any connectors that are questionable, should be replaced. When installing new connectors to wires, make sure the wire is not oxidized or dull looking.

Hope this give you a start point for checking…

Thanks for response, but check my post out again. Units are shutting off when lithium reaches 100%. There is no low voltage threshhold being met. Seems I am getting high voltage and alternator is not backing off when battery is fully charged.

Sent from my LM-V600 using Crappie.com Fishing mobile app

Check your regulator.

Yep. That’s my thought as well.

I agree with a voltage regulation problem.

Three sets of Voltages I looked at.
Garmin shows power input of 9 to 18VDC for ultra series, GPS Maps and Live scope box show 10to 32V
Helix shows power input of 10.8 to 20VDC
Ionics recommends charging at 14.6 VDC

Given the above I suspect that the Garmins will all accept 10 to 32 VDC, and are less sensitive to voltage spikes than the Helix. It would seem to be more cost effect to have all the same power regulators across all lines, but who knows if that is true. I would not be willing to consistently run a Garmin Ultra above 18VDC.

The ionic as well as all Lithium batteries, should have a Battery Management Systems built into the battery, this is a safety feature to keep from overcharging the battery. Once it is close to fully charged I suspect it is limiting the amount of voltage used to charge the battery. This maybe ( a big maybe) changing the load that the alternator/voltage regulator is sensing quicker than it can adjust to causing voltage spikes.
The voltage spikes could be causing the Helix to turn off as an overvoltage protection, as said above I suspect the Garmin is less sensitive to spikes.

The only suggestion I have to test the theory would be to put a switch between the hot coming off the motor and the positive of the cranking battery. You would then have manual control over when the battery is being charged.

Have you turned on the voltage reading display on the Helixes? If you do, you can see what voltage they are receiving and know if it's their over voltage protection feature turning them off. I suspect you have a hidden loose connection in the supply or ground of the units (@fuse box or buss bar?) and the vibration/wave action going down the lake at 4K rpm's temporarily shakes/breaks the connection. That loose connection could also explain the voltage spikes you see on Bluetooth as the loose connection adds and removes load from the components tied to it. Just my $.02 but what I'd check if it were mine.

Chris

Your problem is likely that the battery BMS is shutting the battery down for excess current, disconnecting the battery from the system. Since the battery load plays a big part in the operation of regulating the alternator output, his results in the charging system losing regulation and high voltage. This is why Mercury has recommended against lithium-ion cranking batteries for most motors until recently when they issued a service bulletin with battery parameters and a list of engines that can work with lithium-ion batteries.