Battery wiring

Dave065

Cadet
Joined
Sep 18, 2009
Messages
10
Just bought a Key West 17 foot with a two stroke 90 Yamaha outboard which puts out 10 amp charging. The previous owner added a deep cycle battery for the trolling motor and for all the accessories. The deep cycle is not hooked up to the charging systems because he charged it at home before each use. I am going to dry dock the boat and will not be able to charge the deep cycle. How would I hook up the deep cycle to my existing system?? Would I use a Perko selector switch or something like that? Wasn't sure if engine would charge a deep cycle? Thanks for any help.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: Battery wiring

There is no free lunch when it comes to electricity. Your engine outputs 10A which is barely enough to keep the starting battery fully charged and to run any other accessories. Now you want to charge a deep cycle battery that will be deeply discharged by the trolling motor. The average trolling motor draws 46 amps or so every hour it is run. So running it for as little as one hour will draw in excess of 20 amps if run at half speed. More if it is an older motor. So do the math. You would need to run the boat wide open for over two hours (20 amps divided by 10 amp output = 2) to get the battery anywhere near fully charged. That number would also need to be increased because the starting battery also needs charging. See where I'm going with this? You simply don't have enough alternator output to accomplish what you want to do. Removing the battery and charging at home is the only option unless you have access to AC power at the storage facility. If you do, install an on-board charger, plug it in and forget it until next use. These are automatic chargers and are your batteries friend. A dual output can be attached to the starting battery as well so you will be assured both batteries are up to snuff when you want to use the boat.
 

Fl_Richard

Lieutenant
Joined
Jan 21, 2005
Messages
1,428
Re: Battery wiring

Get a high output solar charger and mount it to the boat. I may not completely re-charge the battery in 24 hours but if you use the boat once a week it will probably be perfect.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: Battery wiring

It won't work inside a building and it will also last about a day before it goes walk-about.
 

Dave065

Cadet
Joined
Sep 18, 2009
Messages
10
Re: Battery wiring

Thanks for the input guys. Probably just two regular marine batteries hooked together with a selector switch would be better for me right? So i wouldn't get stuck. Thanks
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: Battery wiring

So which issue are you concerned about. Your original question was about how to charge the trolling motor battery. Your engine can't do that without running wide open for several hours so a switch does nothing for that situation. Now you ask about being stuck. If you don't run the trolling motor from the starting battery why would you be stuck? You would only have a run down trolling battery. Save your money. It won't help you and the options for charging the troller were clearly described.
 
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