new fishfinder--puzzling issues

[gajpb]

Installed a new bow mounted Humminbird 565 sonar unit recently, and have it attached to the trolling motor battery. The problem is, when TM is on it's highest setting and I am trolling, the screen constantly reads "Low Voltage Input" until after a while it just shuts off. It does not do this on the low settign at first but if I am out for a while, after a few hours on low, it does the same thing. What does this mean? Should I attach it to the cranking battery? Or should I adda nother battery to my setup?

BTW--the Trolling motor is a 43 lb thrust motor guide and I also have the lights and the dashboard fishfinder attached to it as well. And a bilge pump. And the lights.

[surfer]

Yes.  The easy thing would be to wire it to the cranking battery as you will routinely draw down your trolling battery by trolling.  The low voltage alarm will then warn you if your cranking batery is low.

[gajpb]

Good idea--then, what if the batt runs low and I get stuck? Is that possible? I know the CB recharges, but don't want to risk it.

[Long Mike]

Depths finders do not draw a lot of current, but if you have anything else, e.g. lights, move those to the CB  I'd move the console depth finder to the CB also, because the only time you generally us it is when the big motor is running.  Don't forget, when the big motor is running, the CB is being recharged.  The TM battery isn't.

[surfer]

I have left my fish finder on for an entire weak in my garage by accident.  The cranking battery still cranked the boat Saturday morning.  It must not have much draw.

[Catt]

Have your battery check because a depth finder does not draw that much power; I've ran aluminum boats for years with just 1 battery supplying a trolling motor, depth finder, bilge pump, Q-beam and electric assisted hydraulic trim.

[gajpb]

Wow--that's good to know. I imagine it's a bad battery because it is fairly new. I had no problems with it until I switched it out. Thanks.

[RobDar]

you would have to fish a LONG time to run down a battery with a fish finder.

hey...maybe this is an excuse to give my wife..."I am doing a study dear! cant come home yet!"

You have X amount of stored capacity and current capacity. ramp up the draw and DC current will load up against the biggest draw along the easiest pathway and start dropping out auxiliary loads. The TM is such a large draw so quickly..the battery is trying to supply it, but there is only so much capacity there to the work...so it "steals" from you graph to try and supply the TM.

anyone who has lights that dim when the A/C starts or the fridge kicks over...same deal...

[gajpb]

Very well explained--thank you! And now that I have a free weekend--sunday I mean, saturday is a football-filled, I will give this all a shot and see what happens. Cheers

[Tpayneful]

The Humminbird has a voltage alarm setting. My voltage alarm would ring when I turned on the livewell pump. The alarm was set to 12.5V. I bumped it down to 11.5V and it never has gone off since. The livewell pump was on its last legs and has since been replaced as well.  I have everything on my cranking battey (lights, bilge, livewell, radio, depthfinders) and only the trolling motor on the trolling motor battery.

[gajpb]

That is a lot of stuff on the CB. And it's never died on you? Nice. What kind of battery is it?>

[cart7t]

I seriously doubt there's anything wrong with either your TM battery or you're graph.  Simple ohms law, as the current draw goes up due to the TM drawing more the voltage goes down.

Most electronic devices, especially designed to run on DC won't 0perate correctly under a certain voltage for long.

Disconnect your graph from the TM battery and put it on your cranking battery.