Wiring in a second accessory battery

[ZachDean]

Hey guy just had a question about something I'm wanting to do before boating season. I'm wanting to put a second battery in to just run my radio, depth finder, etc. I'm thinking about just wiring two batteries in parralell with a continuous duty solenoid between the negative posts and the switch terminal on the solenoid connected to the accessory terminal on my key. This way when I'm running the boat it will turn on the solenoid and charge both batteries but when I'm just swimming and whatnot I can play my radio without it running my starting battery down. Will this simple set up work?

Thank for any help y'all may have!
Zach

 

[Fireman431]

Re: Wiring in a second accessory battery

+1 for what Bubba said. Wire it like this:

 

[Silvertip]

Re: Wiring in a second accessory battery

Starter solenoids draw a bunch of power and are not intended for continuous duty. Use the switch. Cheap, effective, and versatile. Doesn't get any simpler than this. You can start from either or both batteries, charge either or both batteries, and run everything on the boat from either or both batteries.

 

[ZachDean]

Re: Wiring in a second accessory battery

I see what you mean by the perko switch. I'm just trying to get away with not having to manually switch something. The solenoid I'm using isn't a traditional starter solenoid. It's a continuos duty solenoid like one that is used to run a winch or a hydraulic pump. I guess I'm just being lazy my engineer is coming out in me haha.

 

[Silvertip]

Re: Wiring in a second accessory battery

Then as an engineer use of the Perko (or other) switch should not be a mystery. You don't have to constantly fiddle with it and it provides much more versatility than the solenoid. 1) your engine can be started many doezens of times before the battery needs charging. In the good old days electric start outboards didn't even have a charging system. 2) The switch also allows you to KILL all electronics on the boat when you are not in it. 3) It allows you to start the engine from the house battery if you ever need to. Unless you have a mega-watt stereo with an amp you should be able to run the radio all day with no issues. It all depends on the size and health of the battery. So perhaps an ACR is a better choice and probably better suited than the solenoid plus it is a heck of a lot smarter. The acr has the starting battery as the primary. It will always be charged first until the cutover threshold is reached which is a little over 13 volts. The house battery then gets charged. When the key is off the two batteries are isolated from each other. My preference, for what it's worth is still the switch because of its versatility and away from the boat power disconnect safety. But it's your boat -- you don't need our blessing and besides, we have no idea what the specs are for your solenod so only you can determine if it will work. Lastly, how well the second battery is charged depends on the alternator output. Why charge both of them all the time when it is likely the house battery that needs the juice. Why not give it everything the alternator can supply. That's the beauty of the switch -- YOU determne where the power goes and when.

EDIT: There is one other condition you may want to check carefully. The "A" terminal on the igntion switch is intended to supply power to the console and not every accessory on the boat. So make sure that solenoid is not pulling more current than the ignition switch can handle.

 

[ZachDean]

Re: Wiring in a second accessory battery

Thank for the ideas. I think I'll go with a perko switch. I like the multiple options it provides. I had never heard of on before now so it wasn't an option but now it is. Any ideas where to get one?

 

[bruceb58]

Re: Wiring in a second accessory battery

Put in a battery switch and an ACR.

http://bluesea.com/category/78/1/productline/overview/329

 

[Fireman431]

Re: Wiring in a second accessory battery

Thank for the ideas. I think I'll go with a perko switch. I like the multiple options it provides. I had never heard of on before now so it wasn't an option but now it is. Any ideas where to get one?

They are available at any marine store, right here on iBoats, and I believe the local WalMart should cary it (at least the do around here).