My sonar is hooked up to my starting battery. When I start my big motor my sonar shuts down with a low voltage message on the screen. I have checked the battery and it has the appropiate volts and keeps a full charge according to the battery charger. Connections seem tight and are clean as I have already checked them. Is there soemthing else I am missing?
Neither of those tests mean you have a good battery.
You need to do a load test to verify if you battery is good or not.
What are the specs on your battery?
Is this a new issue?
If this wasn’t an issue last year, i would venture to say that your battery wasn’t maintained properly over the winter and you will fail the load test.
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My sonar is hooked up to my starting battery. When I start my big motor my sonar shuts down with a low voltage message on the screen. I have checked the battery and it has the appropiate volts and keeps a full charge according to the battery charger. Connections seem tight and are clean as I have already checked them. Is there soemthing else I am missing?
It means the battery is not producing enough voltage to run both the starting motor and your electronic unit, during the time you are cranking the engine.
You either need a new battery or a bigger battery.
What it is your sonar set at for low voltage alarm?? Check there
Question…I think my connection for my sonar(s) is off the front trolling motor battery and not the rear starting battery. Is sonar usually connected to the starting battery??? Maybe I am doing it wrong… 
…RR
You could get interference off of the tm batteries.
DT
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Neither of those tests mean you have a good battery.
You need to do a load test to verify if you battery is good or not.
What are the specs on your battery?
Is this a new issue?
If this wasn’t an issue last year, i would venture to say that your battery wasn’t maintained properly over the winter and you will fail the load test.
Agree 100%.
The lead suspect is the battery is going south. Load test it and be ready to buy a new one.
Volts are only one measure of a battery’s health, and not necessarily the most important one. A battery’s ability to deliver the amperage is the real test the (in general) matters most.
How did you store your battery over the winter? Even though it’s a PITA, I found it’s worth the time to store them indoors. I put mine in my workshop and then a couple of times during the winter, I give them a quick top-off charge. IMO, this adds years to their lives on average compared with leaving them in the boats, frozen solid for 4 months.
Grouse
Assuming your sonar is set to the appropriate low voltage setting, it is telling you that your battery is either too small or just about shot. When you crank over the motor it is taking all of the juice from the battery to turn it over, a sign of a weak battery. If the battery is new, then you need one with a bigger CCA rating and a bigger reserve amp rating.
Start with a battery load test (free at any auto store), if ok you have a loose or bad connection from the power block to your graph. Happened to me. Followed the power from the battery to my graph. it made 4 connections before it got to my graph. wired it right to the ACC switch with a direct power from the battery and problem solved.
Exactly what happened when my battery went bad in my old boat that only had 1 battery. Most likely going bad.
Your low voltage is a bad cdi unit on motor you have to test for voltage output.cdi controls voltage output to battery if your motor dies out you will need a tow in.
make sure battery fully charged EVERY time you leave the dock. battery might be bad. I had same problem… turns out battery i got with the new boat was garbage… optimax and new sonars require mucho juice. replaced starting battery with optima D31m… no more problems… put on charge before every trip…
best case sonar should be wired directly to battery, no switchs etc… might also have some corrossion around cheap fuse thing they supply…
Try lowering your low voltage alarm on your graph. This will take care of your alarm. Of its actually shutting down, battery may need replacement.
Simply hard wire the locator directly to the starting battery. That will take care of the locator shutting down when you start the motor. All sonar/locators should be hard wired to the battery with the appropriate fuse installed.
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Simply hard wire the locator directly to the starting battery. That will take care of the locator shutting down when you start the motor. All sonar/locators should be hard wired to the battery with the appropriate fuse installed.
My trolling motor has its own two batteries. My motor and bilge share a battery, and all other electronics are on yet another battery.
If ya got the room for the batteries…. Why risk running your starting battery dead.
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