Boat battery charging

[merc_man]

Was wondering if the charging aystem in a boat is strong enough to charge a second battery up under the dash.

What i wanna do is run a heavy 12 volt wire from main battery switch in back of boat to the battery under the dash but dont wanna strain the charging sytem if it would be too much.

Boat is 17' so wire would run across the stern, through gunnle under dash to battery. Probly about 12- 15 feet of wire. Motor is a 07 optimax 115h.p.

 

[Redfin]

What batts are you trying to charge. Im assuming a high cca for engine and another for trolling?

 

[merc_man]

They could both crank motor if need be and one in under dash would do the front electric anchor or trolling motor. The swith at back gives option for batter 1 or 2 or both.

 

[merc_man]

Ther was two batteries in back but ther is only a spot for one and thought would be a good idea to get a little extra weight out of the back.

 

[Redfin]

As long as they are same type. You should have no charging issues.
Make sure wire gauge is sufficient.

 

[jakethesnake]

Yeah you'll be good You using the motors alternator if you're concerned you could toggle the switch to do one at a time I have the same switch in the back oh my boat. As stated use a good heavy wire your motor will charge both at the same time with ease

 

[merc_man]

Yeah you'll be good You using the motors alternator if you're concerned you could toggle the switch to do one at a time I have the same switch in the back oh my boat. As stated use a good heavy wire your motor will charge both at the same time with ease

Ok thanks. It was charging both while the two batteries were at the back no prob but wasnt shure about charging through the long heavy wire. What guage wire would you suggest 10 guage be heavy enought or go heavyer.

 

[jakethesnake]

I'm a tad bit anal on boats I might go heavier .... Ten would work though honestly. You have ten? If so use it . You can always bypass that battery if it have you trouble . Also use some dielectric grease on those connections I've had good luck with that If you can solder those connection ends I'd recommend it. Again I go a little overboard on electrical on boats but I also run into crappy seas where I live so a simple electrical nuisance can be a real bad thing. The more you can do to insure your connections is what I'd do shrink wrap the whole 9 good idea on the switch and adding a second battery

 

[jakethesnake]

I can check the wire size out on my harness when I get home if that would help? Honestly more than likely it will come right down to the connections if everything is tight and sealed up it should be good

 

[merc_man]

I will go ten if you think i should. Dont mind spending a little to make it write.

If ya brake down on water ya cant just walk home. Mite as well be write.

 

[merc_man]

Probly wouldnt hurt to stick a fuse on the wire too.

 

[jakethesnake]

I just checked I'm running 8 no fuses

 

[jakethesnake]

I fuse all my accessories coming off of the battery but none from my alternator to a battery I'm not sure you would benefit there plus that's another connection

 

[jakethesnake]

My batteries are pulled because I left my radio on for two weeks .. Is this similar to your setup

 

[jakethesnake]

I used 8 I think it is my batteries are pulled because I left a radio on for two weeks My main harness bypasses the toggle switch just in case it were to fail the motor would still crank I wouldn't bother with fusing the main line from the switch to the new battery I don't believe it'll do you any good It's also another connection to deal with

 

[jakethesnake]

Yeah that's weird my posts didn't show up at first so now I've posted the same thing over..

 

[Grimmy]

I wouldn't fuse from your alternator to the second battery. I would but in some sort of isolation and keep the batteries separate. If you need more cranking power, then energize the isolator/contactor (just be sure it's rated high enough) and start. However, if you second battery is really low, I wouldn't charge it with an alternator. Put a charger on it before you go out again. Could you charge with it, yes, but it's hard on it. They aren't made to charge dead batteries. That's what chargers are for.

 

[merc_man]

View attachment 21977 View attachment 21978 My batteries are pulled because I left my radio on for two weeks .. Is this similar to your setup

Yup same kind of switch

 

[merc_man]

I wouldn't fuse from your alternator to the second battery. I would but in some sort of isolation and keep the batteries separate. If you need more cranking power, then energize the isolator/contactor (just be sure it's rated high enough) and start. However, if you second battery is really low, I wouldn't charge it with an alternator. Put a charger on it before you go out again. Could you charge with it, yes, but it's hard on it. They aren't made to charge dead batteries. That's what chargers are for.

all i wanna do is put the battery where ther is a proper spot so it cant roll around. i always like to have two batteries just in case. Wanna hook it up to switch like in pic above. Battery wont get drained. It will just get used to run the anchor up and down a few times. But still want it to get boosted back up when boat starts.

 

[jakethesnake]

That sir will work that's exactly what those switches are for and god forbid a dead battery on the water you then have a spare