Seperate battery for depth finders?

[settnhooks]

I am building up a 14' alum. jon. I have a new 12v everstart marine battery I use for my trolling motor. I just got 2 small $100 humminbird depth finders and read somewhere that I could experiance interferance hooking up both depth finders and the trolling motor to the same battery. I am buying battery powered LED NAV lights so that isnt an issue. Can someone let me know if this is true and if so what kind of small battery should I get for the depth finders? Also the guage of depth finder power wire, annnd it says to install an inline fuse between batt and sonar... I have a 50 amp breaker I was going to use between trolling motor and batt. will that work in place of the fuse if I am able to use one battery for all? Thanks

 

[TerryMSU]

Re: Seperate battery for depth finders?

Generally it is strongly recommended not to use the Trolling motor battery for the Fishfinder. You could try to use the TM battery, as it won't damage anything, but if you need to open up the boat to route wires, I would only do it once. The breaker for the TM is intended to protect very large diameter wire. You will be routing the FF with smaller wire. You should use a seperate fuse or breaker for just the fishfinders. Make sure it is the right size for your power wires for the FF. Look up what the FFs draw and add the two numbers together. Make sure you wire size will handle that and then pick a fuse/breaker that will handle your FFs and still trip before your wire gets damaged.

TerryMSU

 

[bassman284]

Re: Seperate battery for depth finders?

Usually depthfinders come with an inline fuse holder on the red wire like the one shown in this link to iboats store:

http://www.iboats.com/Water-Tight-M...2283700--**********.079300367--view_id.191238

If not, you need to get one for each and connect it to the positive wire. 16 gauge wire is probably heavier than you need and the 10 amp fuse is definitely too heavy. My Lowrances have 3 amp fuses. Also, I'm powering my front depthfinder from the trolling motor battery and have had no issues, but some do so YMMV.

 

[cyclops2]

Re: Seperate battery for depth finders?

A word of caution.

I would like a $100 bill for every time I left the fishfinder.......ON........After fishing. Lots of times. Most people call me if they hear it beeping on low battery.
Had the battery so low, the auto bilge pump stopped & had 3" of water.......My 9.9 starts easily with a pull. Does not take too long to wear down a size 24 battery.

#16 wire is more than enough for current. ....But the real problem is vibration. For that reason I make ALL wires #14 gauge.
It is thick enough to not have too many strands cut while stripping the insulation off.
It is thick enough to also not have the strands of smaller gauges cut or squashed to nothing by a crimper.

 

[cyclops2]

Re: Seperate battery for depth finders?

I did a carefull & neat job of running all the bow, lights, horn, & anchor wires in the tubular top rail. I drilled a 1/2 " diameter hole under the corner Aluminum plates. I moved the drill to a rearward angle to make a longer oval hole. both ends of the boat. That allowed me to use auto rubber hose as a chaffing protector. Been good for +20 years.
I used THHN electrical wire from a local electrican. Tough & thin insulation.
Neat & never gets stepped on. That is on a 16' Lowe v hull.
The electrican loaned me his " wire snake ". Piece of cake.

Remember to drill CAREFULLY into the top rail if needed.

 

[Silvertip]

Re: Seperate battery for depth finders?

Leving a fish finder ON is not going to be solved by installing another switch. The locator already has one. Installing a MASTER switch that kills everything makes sense since you have only ONE switch to remember. Some locators do indeed experience interference from the trolling motor and some do not. Before you install a separate battery, temporarily hook it to the troller battery and try it. If it works fine, no other battery is needed. If a problem arises, a spearate battery is needed. Household wiring THHN is not recommended for a boat because it is stiff. 14 gauge is also overkill. 16 gauge marine wire (duplex) is perfectly fine for nearly every circuit on a boat including the locators. Fuses are to protect the wire, not the device it feeds. The owners manual for the locators tells you what side fuse is needed and that number will be for each locator. Any of the small sealed batteries 12 AH or bigger will work for the locators. Charge the battery immediately after each use. A 17 ah battery is the same as those found in most jump start boxes.

 

[cyclops2]

Re: Seperate battery for depth finders?

Last check of USCG wire types was found that they allowed any type of NEC ...National Electrical Code....coded wires.

 

[settnhooks]

Re: Seperate battery for depth finders?

Thanks for all the responses. I will deff make sure each FF has its own fuse, the instruction manual says to do this anyway. Just wasnt sure what guage wire to use, sounding like 16 guage is the way to go despite the FFwires being like 20 or 22. I will be buying all my wires, connectors, lugs and all from a Marine dist. just for longevity of the end result. I think a speperate battery for the FF's is the way to go too, I dont want to realize my first trip out this spring that I have interferance and need a seperate batt.
So now my question is which battery, sorry but Im not exactly sure what the 12 AH or 17 ah means? Amp hours I would guess. But still needs to be a 12volt, will a motorcycle, atv, or lawnmower battery work? Thanks again, great info here.

 

[Silvertip]

Re: Seperate battery for depth finders?

The wires on the fish finder need to carry very low current so they can be much smaller. That small a wire however is not intended as a "feed", such as running from the battery to a fuse panel. It is simply not heavy enough to use for "distribution". 16 gauge wire will safely carry 10 amps over long spans. Other than the trolling motor you have nothing that draws anywhere near that amount of current. All of the batteries you mentioned will work but none of them are deep cycle and all are lead acid types which means if you tip them over they are likely to spill. A lawn mower battery will work best as it will have the most capacity (Amp/hour) rating. A 17 AHr battery will provide 17 amps for one hour our 1 amp for 17 hours. A lawn mower battery will have about three or four times that capacity.

 

[cyclops2]

Re: Seperate battery for depth finders?

Leave it to Federal agencies to do nothing but create unenforced regulations. Wire sizes of equipment being installed are ridiculous. # 16 & # 18 are the minimum. HMMMM. Lots of add ons are much smaller. HMMMM Pure Copper wire also.
They are pushing to allowable voltage drop to the limit WITH A FULLY CHARGED battery.

Cheap cheap cheap. I have had F F wires & night light wires break or corrode many times in 5 to 10 years. I just do checks every 3 or 4 now to stop problems. The Perko ? red & green bow light wires are cute.

 

[cyclops2]

Re: Seperate battery for depth finders?

You could E MAIL your fish Finder companies. They can tell you how to avoid interference. It used to be if you ran them at 2 different frequencies, there would be no problem. Shallow water & a deep water units in the same boat.

A rock solid connection of the F F NEGATIVE LEADS to the - battery post did knock out a lot of the F F / motor problems. We did use the terminal black rubber coatings on both F F ringed lugs that went directly to the - battery post.

Todays motors SHOULD have excellent supression to prevent those problems.