Wiring a guest 2 battery switch

[Fishing Junky]

Hello all. I'd like to add a battery switch in my boat so I can charge my single battery up front when no electricity is available. I would get a guest battery switch. (for two batteries) Can anyone set me straight on how I would wire this up? Thank you. Junky..............

[Northlander]

Junky Im not sure I follow you. Do you mean something that would run off your main motor? I dont know if there is such a thing but there sure could be I guess.

[Fishing Junky]

Hopefully I can explain. I have a group 27 up in the front compartment of my boat. Like for a bowmount trolling motor. I have a group 27 in the back for starting and running acc. I would like to put in a battery switch, that would allow me to start the motor and run acc. off of the front battery and would charge it while the motor was running. Then when that battery was charged, I could reswitch it to the rear battery. This will help me when I'm up on Sag with no power to use a charger to charge the front battery. Thanks for any help. Junky....

[marine_man]

You would connect your motor cables and accessory cables to the feed side of the switch, and connect up your two batteries to their respective location (B1 and B2), and you should be set. Be sure to leave a inline fuse in between your accessories and the feed connection to protect them adequately.

Good luck!

marine_man

[Wish-I-Were-Fishn]

Check out this related thread:

Aux. battery charging

[Fishing Junky]

 Originally Posted By: marine_man

You would connect your motor cables and accessory cables to the feed side of the switch, and connect up your two batteries to their respective location (B1 and B2), and you should be set. Be sure to leave a inline fuse in between your accessories and the feed connection to protect them adequately.

Good luck!

marine_man

I'm a real electrician wizard here. How do you wire the negative sides of the batteries. He He He. Thanks for the help and link, MM and WIWF. Junky.....

[marine_man]

Sorry about that...

You will still need to run the negative cable from your engine to your starting battery. Now I'm wondering if you'll need to connect the grounds between the trollilng motor and starting batteries as well... I'm thinking you will...

But, let's back off of that for a minute... what size is your engine? Don't you have a 30hp Honda engine? If you electric trim & tilt your alternator puts out 10 amps, if you don't have electric trim & tilt your alternator puts out 4 amps - all of these at wide open throttle.

If you have the 4 amp version I would not install this switch with the hopes that it will charge your batteries while you're running. The 10 amp verison is also questionable, but it's up to you in the end.

marine_man

[Fishing Junky]

I'm not doing a very good job of describing what my intentions are of my batteries, sorry 'bout that. I have a battery up front that I DO NOT use for a trolling motor, as I don't have an electric trolling motor. I do however, have a 6hp fourstroke kicker, that I plan on using a great deal during the day. My runs to my fishing spots are not a real great distance with the Honda, which does have PTT. I use the front battery on occasion a 12 volt fillet knife and hook up my Sirius radio boombox too. So, it doesn't really doesn't get drained a whole lot during the day fishing. However, my starting battery will run the livewell and all electronics during the day and will be drained because I will use the 6hp 90 percent of the time, with very little runs between spots. I would like to have the option of using the front battery to start my Honda in case I run down my starter. I really don't need to recharge my front battery, as that will last till I can put a charger on it. I just would like it as backup for the Honda, instead of having to pull both batteries and switching them in case of starter failure. Did that make sense. I can visualize the positive side of both batteries going to the switch. The negative to the starter lead to the negative of the starting battery, but what about the battery up front, negative side. That's where I'm stuped. Thanks a great deal for the help. Junky....

[riverrat56]

I think I understand what your getting at, you want to be able to pull power from the front battery to the back, to start the engine, without moveing the batterys, but you don't want to charge them?

One way would be to somehome run cable from the front battery box to the back of the boat, mount some type of box with battery terminals in it, then just hook up your leads from your motor to start the engine.

[Fishing Junky]

 Originally Posted By: riverrat56

I think I understand what your getting at, you want to be able to pull power from the front battery to the back, to start the engine, without moveing the batterys, but you don't want to charge them? Charging isn't necassary, but would be helpfull for those four day trips camping on an island with no power to charge.

One way would be to somehome run cable from the front battery box to the back of the boat, mount some type of box with battery terminals in it, then just hook up your leads from your motor to start the engine.

Good idea, but if I go through that much trouble, might as wire the switch and get a little charging going on. Thanks for the thought. Junky.......

[riverrat56]

Acctually, doing it that way would charge it as well, as long as you left it hooked up when you ran the motor.

I just did this with my trolling motor battery, to get the weight transfered upfront, and my starting battery went dead, I hooked up to my trolling motor battery, via the terminals installed in the back from the front, and started the motor. It's the same process as going from your motor directly to the battery, just adding some more wires, and another termination, but it would still charge the battery.

I don't know a whole lot about marine electrical accessorys, I just make my own stuff most of the time, but I am going to school to be an electrian so I have some knowledge of how the stuff works.

To just flip a switch, you would need to find some type of box that you could hook both batteries up to, that then had another set of terminals that were switched, only letting voltage from one battery to the output terminals. Do they make something like this, and if they do, where can I get one?

[riverrat56]

I went back and read, apparently they do make such a box.

Marine man, by "ground" do you mean negetive? If so, hooking them together from both batteries would essetially create a series circuit with two 12v sources, causing a 24v output. If I'm seeing this switch correctly there is a B1 and B2 input, and a single output? If there is 2 terminals at each input, you would hook up your positive and negetive, (red and black) wires, and the swich would change by contacting both terminals from 1 input at a time, keeping the output voltage at 12v. If only the hots are switched, like a light bulb, I would think this would cause problems with amount of voltages being put in.

I could be way off, I have only been going to school for a year and most of it has been AC circuits, not DC like the battries would be.

[Fishing Junky]

Don't know what I was thinking, but your correct on it charging the battery. A switch would just be more convient, and I'd have to run the wiring anyways. Hopefully I can ger 'er done. Thanks for your help. Junky............

[marine_man]

 Originally Posted By: riverrat56

Marine man, by "ground" do you mean negetive? If so, hooking them together from both batteries would essetially create a series circuit with two 12v sources, causing a 24v output.

Connecting a negative to a negative would not create a series connection - you'd need to connect the negative to a positive.

marine_man

[marine_man]

If you connect the negatives and put the Guest Battery switch in the "Both" location, you effectively have connected your batteries in parallel, hence the reason I think you're going to need to connect the negatives on the batteries.

marine_man

[riverrat56]

Marine man, I asked my teacher this morning and that is exactly what he said, then I thought about it, and ya, I was just thinking way to much into it.

[Fishing Junky]

Thanks for the help guys. Appreciate it. Junky.........