Dumb Girl Question about Power Usage For New Depth Finder

[Nancy]

OK guys,  I have worked hard at trying to ask my dumb girl questions to you guys, but today is your lucky day. I was having some issues with our depth finder and after another discussion here someone mentioned about the Garmins being so great. Cabelas was having a great sale on this unit and I later discovered that they were discontinuing it. I think it will serve me well.

https://buy.garmin.com/en-US/US/p/529879

We had a low end Lowrance unit , not the big screen like this one. More like a 4 to 5 inch square. I would have to run out to the boat to find out the exact model if need be.

But my question is: John had the old unit hooked up to the battery that runs everything else on the boat. With the larger screen, will it suck more power and run the battery down? Most of our (my) fishing involves drifting and jigging so there aren't a lot of times spent running the boat to recharge the battery.

[WillageD]

Same deal as your smaller unit Nancy. Hook it to your 12V cranking battery for your engine. You'll be fine- if drifting for a long period of time and you become a bit paranoid, just fire the engine up and run it for a few minutes, but I doubt thats even necessary.

[RHYBAK]

I have the GARMIN 93
You will love it.
More functions than you can imagine.

Just make sure it has the Canadian maps included in the mapping
If not, oh well. You know your fishing areas.

It also takes a blank memory card and you can do your own mapping while running the unit.

Hook it up to the boat battery the same way the other one was.
I run two fishfinders, the radio and the live wells at the same time and the battery is fine.

[crackers42]

Nancy,

I 100% disagree with the statement "hook it your boat or crank battery".

Electronics are meant to be ran off separate deep cycle battery. 

Depending on your budget I would suggest a gel cell battery but you have to find out how many amps it draws.

Ie. If you get a 18 ah (amp hour) and it draws an amp an hour it will run for a couple days no problem.

Do not run it off your crank battery, if for some reason the unit drains the battery you will not be able to turn the engine over.

[Nancy]

Thank you @WillageD and @RHYBAK . Just the answer I was hoping for. And, Rhybak, it doesn't have Canadian maps. I did notice that when I bought it. There are a couple lakes down here that I may start fishing with a little help, and if those maps are charted, that will be a huge help.

So @crackers42 , even though we are running off a deep cycle battery, you recommend having a separate battery dedicated to the electronics?

I have had the boat out twice by myself this year so far. I was pretty concerned about launching and recovering by myself. But everything went smooth as silk.

[Jay Thomas]

Hi Nancy,

I concur with crackers42. I noticed that you have a 20 HP Honda on your boat. I've had a 15 HP Honda since 2007 and I certainly didn't want to depend on it to recharge my battery - insufficient recharging capability. On the other hand, I'm guessing RHYBAK has a minimum 90 HP Merc on the back of his Lund Impact - different kettle of fish to my mind. I'd suggest you use something like a deep cycle 30 amphour battery to run your new sonar unit for a week's worth of fishing. Just my opinion.

Jay

[RHYBAK]

Nancy

Does your motor have an alternator that keeps your battery charged or do you have to keep charging it up

(LUND boat  powered by 115H.P.)

[Nancy]

@RHYBAK, The only time we have ever put the battery charger on the battery in the boat was once in the spring to get everything fully charged. That is all. We replaced the battery in the boat last year so it is a little less than a year old. John always wanted things in as good of working order as possible before we went to Canada.

This is what it has on it 12-Amp (151 watt) alternator with voltage regulator.

[crackers42]

Nancy,

All it takes is one outing where either your charging system fails and or battery fails

For larger setups such as a 18 foot Lund with say 150hp would recommend three to four bank system (depends what you do with it). 

One for the electronic trolling motor one for crank and at least one for rest of electronics

Just my opinion but you shouldn’t run a deep cycle to crank an engine hard on the battery

[CaptainCrappie]

Regarding batteries, this is how I have my pontoon wired.  I keep it docked at a marina on a lake about 4 miles from my house.  I have a starting battery. It is just like your car battery, and when the motor is running it is recharging that starting battery. My 9.9 hp 4 stroke generates 5 amps of regulated DC at about 14 volts. That starting battwery also powers an on board charger, which recharges my deep cycle battery. The onboard charger generates 4.5 amps. That deep cycle battery powers a radio, trolling motor, two locators, running lights and water pump for a live well.  Of course not all things are running at the same time.  The biggest current draw is the trolling motor. I also have a solar cell which generates about 20 volts of unregulated DC power, when there is light. and that solar cell is also trickle charging my deep cycle battery. Those of you out there thinking (why don't you just let the motor charge both batteries?) Believe me when I tell you it is not as efficient. Also you would have the starting and deep cycle battery connected in parallel and the battery manufacturers do not recommend it.  The on board charger acts as sort of a buffer between batteries. What does this all mean?   It means that all season I never have to disconnect those batteries which is a pain in the rear, and take em back home to recharge them.  And even when I'm not at the lake that solar cell is working it's butt off keeping that deep cycle battery ready for my next fishing trip. On windy days if the trolling motor tells me that the deep cycle is about 50% charged which is pretty rare, I just crank up the motor and troll for those saugeyes and muskies and in an hour,  I'm back to full power. Just don't run out of gas!

C.C.

[Canuckbass]

Nancy,

All valid input.
I’m very experienced with batteries and setting up electronics.
100% run it off your cranking battery.

On your Garmin unit it should be able to display your battery voltage on screen, add it to your main screen and have a look at voltage level every half hour. It will indicate for you if battery drops to low to fire boat motor up. If it starts getting below 12v start motor for a bit.

Many outboards do not charge battery unless running 2000 rpm or higher.
So you may have to idle faster back to start your drift over.

[Canuckbass]

Also, do not run any sonar unit to same battery as trolling motor, they can cause interference that’ll make you pull your hair out trying to figure out why sonar is not reading properly.

[RHYBAK]

Nancy,

All valid input.
I’m very experienced with batteries and setting up electronics.
100% run it off your cranking battery.

On your Garmin unit it should be able to display your battery voltage on screen, add it to your main screen and have a look at voltage level every half hour. It will indicate for you if battery drops to low to fire boat motor up. If it starts getting below 12v start motor for a bit.

Many outboards do not charge battery unless running 2000 rpm or higher.
So you may have to idle faster back to start your drift over.

Good call on the GARMIN screen display.
I do have that on mine and I do make note of it frequently.
Nancy.
A wise man once told me to keep it simple and attaching your fishfinder to your cranking battery is as simple as it gets.
In 35 years of running fishfinders on my boats, they have always been hooked up to the Cranking battery.
I'm sure you never sit in one spot for more than an hour before you pack up and boot to the next spot.

If john had it hooked up that way previously with no affect then this will not be any different.
These new units are made better than the older units and probably draw less power .
you will love the new GARMIN if you actually buy it.

[Nancy]

Thank you everyone for some very sound pieces of wisdom. I am getting it installed tomorrow. This evening I will go over some of the videos that I have been watching on the unit to refresh my memory. Thanks again.

[crackers42]

I don’t understand why most would take the chance with one battery?

Draining a crank battery down and recharging it is very hard on the battery and will vastly shorten its life until one day it won’t recharge.  There is a reason they make deep cycle or gel cell units.

Nancy if you are going out on your own I would highly recommend at least a double bank system