Q about marine batteries & charging

[DZink24]

I figured this to be the best forum to post in, as most of you who camp, RV, and enjoy the outdoors can answer this for me.



My 25HP Johnson outboard has electric push start. The battery I have, a deep cycle trolling battery is used to start the motor, run the trolling motor, sonar, and lights.



My question is, is there any way to get the motor to charge the battery as the motor is running? Some type of alternator? My knowledge of electronics and electricity is very limited. TIA

 

[JoeBioDiesel]

Some outboards are made with a charging circuit, and some are not. Get the manual for your and see if it has the capability to recharge the battery. If it doesn't, I don't know of a way to convert it. . but if it's possible someone here will know how.



Joe

 

[EricBu12]

Run a battery cable gauge wire from your battery and the deep cycle and meet in the middle with an Isolator. There is a small terminal for swiched Pos (+) key on that connects and disconnects the 2 batteries. So when the motor is running, it charges bot batteries. When the motor is off, only the deep cycle will drain when trolling, keeping your main battery fresh.



Most RV supply stores have this stuff.

 

[jelag]

Joe has it right here... if the motor has the provision to charge a battery than its a simple thing to connect... if it was designed to never charge a battery... than I'm going to guess that it would be very costly to install and not worth the effort... .

 

[Hoefler]

Most of those little motors are not capable of charging. If the motor will start and run with out the battery, it does not have the ability. What year is it?? I could look it up and check if it had the option.

 

[MChildress]

I know in the past you had to buy a stater kit for charging and a starter if the motor did not come with electric start.

 

[Ramtough]

Most marine alternators do not put out enough power to make much difference. Combine that with the relatively short run times of inland marine engines and my guess is that you are wasting your time and money for the benefit you will get.



For example if your trolling motor uses 20 amps in an hour, it will take a marine alternator putting out 5 amps 5 hours of continuous running to replace what has been consumed.

 

[TowPro]

I had a 7. 5hp Johnson engine on my Sailboat. yes it had a "electric output" system, but it was not designed for charging. It was only designed for running lights, in fact it was even AC. I think it had a 12V zinor diode on it to cap the voltage.



Check your owners manual, the information will be in there. If you don't have an owners manual, go to the manf's website and download one.

 

[EricBu12]

If you are not able to do any of the above and is too costly, you might want to try a portable generator to run a battery charger or get solar panels if you have a roof. . 2, 100 watt panels should put out 7 amps of power all the time. . it is sorta costly though...

 

[TowPro]

If you are not able to do any of the above and is too costly, you might want to try a portable generator to run a battery charger or get solar panels if you have a roof. . 2, 100 watt panels should put out 7 amps of power all the time. . it is sorta costly though...

P=IxE So 2-100 watt panels (200w total) putting out 14. 2 volts = 14 amps

If you use solar panals, you will also need a regulator so you don't over charge your batteries.

 

[EricBu12]

on my Rv, I have a 100 watt and 2, 50 watt. I have a digital readout regulator and on th sunniest day at noon, I see about 7-8 amps because of the angle of the sun to the panels. If I tilted the panels I might see more but don't know. mine are mounted flat and do well for what I have. they charge up 4 deep cycle batteries before the sun goes down.