Thread: Solution for fish finder draining cranking battery?

I was having the same problem as you and changed my battery system all around. My cranking battery is only for that. The deep cycle battery at the rear handled both sonar units and the trolling motor. This caused interference on the sonar units and drained the battery quickly. I put a whole new battery system up front for the trolling motor. This leaves the rear battery just for sonar units but still have outlet for trolling motor in case of an emergency. The two rear batteries are on a Pro Mar 2 bank charger and the front battery is on a single bank Pro Mar charger. The front box I built houses the deep cycle battery, charger, 60 amp breaker and a trolling motor outlet. This also adds some weight up front to balanced the load a little better. Always playing with something to try to make it work better. The old definition of a boat, " a hole in the water to pour money into"!!!

Originally Posted by davebrown42

Instead of jumper cables, I added a three way switch in the battery compartment that lets me add 1 of the trolling batteries to the cranking battery or switch to both trolling batteries to start the engine. Works every time so far with less hassle.

that is awesome....wish I could drive there and let you do that to my boat...then we could fish....dream on.Jk. I wish I had your know how.

Thanks for all of the great advice. I'll try to answer all the questions at once. I probably do need to check my battery age, but I do fully charge before going (onboard charger charges all batteries). I have a Tracker 175txw so I don't really have much space for any more batteries - I barely fit three into my existing battery compartment, and all my other storage stays pretty full. My fish finders are Humminbird 859ci HD DI and 899ci HD SI. I'll definitely have to get a set of jumper cables in the boat, and I'm gonna have to look into the switch idea as that seems like a good idea. Not sure why you would need the 3-way, though, as it seems that since I'm running two in parallel, if I just hooked the switch across both, it would be just as good and have the max draw. Any reason you need the option to use just one rather than both?

Originally Posted by davebrown42

Instead of jumper cables, I added a three way switch in the battery compartment that lets me add 1 of the trolling batteries to the cranking battery or switch to both trolling batteries to start the engine. Works every time so far with less hassle.

Also, what kind of switch did you use for this? Is there some other product that works fairly well as is, or did you have to build it from scratch?

"frog" .... I do hope you meant you put your batteries on the charger AS SOON AS YOU GOT BACK HOME from fishing, and not that you just charged them up the day/night before going !!

Leaving them in a state of discharge for any length of time, before charging them up, can lessen the life span of the battery. Also ... you should add distilled water AFTER the battery is fully charged, if the water level is low. And if the water level is below the tops of the lead plates, add only enough distilled water to cover the plates ... fully charge the battery ... then top off with distilled water. It's also not a good idea to top off all the way to the bottom of the fill holes !!

... cp

Originally Posted by CrappiePappy

"frog" .... I do hope you meant you put your batteries on the charger AS SOON AS YOU GOT BACK HOME from fishing, and not that you just charged them up the day/night before going !!

Leaving them in a state of discharge for any length of time, before charging them up, can lessen the life span of the battery. Also ... you should add distilled water AFTER the battery is fully charged, if the water level is low. And if the water level is below the tops of the lead plates, add only enough distilled water to cover the plates ... fully charge the battery ... then top off with distilled water. It's also not a good idea to top off all the way to the bottom of the fill holes !!

... cp

Wow, thanks Pappy. Actually I didn't know much of any of that (other than to use distilled water). Great info. I've never really spent much time researching battery maintenance...I just use them and replace them as needed. I guess I should give it a bit more thought. I guess I'm too busy trying to figure out all the new toys I "need"!

Originally Posted by knox_frog

Also, what kind of switch did you use for this? Is there some other product that works fairly well as is, or did you have to build it from scratch?

You need to be careful with the switch idea. It will work and can be very handy, but there can be gotchas with doing it. The big one is with US2 trolling motors. There is also the possibility of electrolysis on metal parts that touch the water. Nothing insurmountable, just things that may not be obvious to somebody not familiar with boat wiring.

The three way switch generally lets you use either the cranking battery alone, a trolling battery alone or both in parallel.

Definitely start with the batteries. You may have two in parallel, but if one is bad or just a bad cell, the bad battery will almost immediately pull the other battery to it's state. When running two batteries in parallel, always be sure they are "like" batteries and close to same age. And (I know some will argue this), whenever you replace one, replace both to be sure!! As other's have said, you should be able to run all day (normal, non windy, TM not on high) with two batteries in parallel. Do as others have said, and one other thing, ensure your charger is actually charging to full!