How do you connect 2 batteries?

W

wet spot

Member
I'm switching from manual to electric downriggers so I am planning to go to a 2 battery set up with a switch than can use either battery or both...I've also added electrical output capability to my kicker. I plan to connect the main motor leads to battery A, the kicker leads to battery B, connect the positive posts from A and B to respective terminals on the switch, and interconnect the battery A and B negative(ground) posts together. The VHF radio will run directly from the A battery while all the other electrics ( downriggers, gps/fishfinder, lights etc.) will run from a bus connected to the output terminal on the switch.

Is this the best way to connect? If I have the switch set at "BOTH" and I have both motors running can it damage anything on either motor?...Do I need some kind of electrical protection in this case?
 
what you want is one starting battery and one "house" battery. One is designed for hard cranking and one is designed for running things like lights, downriggers.

You never want to run both batteries at the same time, when you do this you never really get a good charge on both batteries and the strong battery will always be sucked low by the weak battery. So if one battery stops holding a charge it will drain the good one, defeating the purpose of having 2 batteries. its best to run the switch in 1 or 2, not both. Maybe for a long run on the main motor both is ok for a charge.

The only way the 2 batteries should connect is through your switch, never with wires from post to post.
 
Interesting. I have always run my boat with the perko switch on 'both' so the alternator will charge both batteries at the same time. As long as there's an engine running and charging the system, I'm on both. When I'm drifting or docked and using the house battery, I switch to the '2' position, which in my boat is the house battery. When I want to start the engine, I switch to '1' and once the engine is running, back to 'both'. Never had an issue; always had well charged batteries.
 
Look into an automatic charging relay (ACR), Blue Sea makes them, they are under $80 and its a great little unit. When your batteries are charging it will isolate a fully charged battery and continue charging the other batteries in your system. So even with your battery switch in position 1 (or 2) your engine will still charge your the batteries that are not selected by the battery switch.....pretty sure thats how the system operates but I am new to it myself.....
 
Finished Business said:
Look into an automatic charging relay (ACR), Blue Sea makes them, they are under $80 and its a great little unit. When your batteries are charging it will isolate a fully charged battery and continue charging the other batteries in your system. So even with your battery switch in position 1 (or 2) your engine will still charge your the batteries that are not selected by the battery switch.....pretty sure thats how the system operates but I am new to it myself.....
Click to expand...

that sounds like a perfect solution. Running both on a normal setup will and does work BUT one day one of those batteries is going to stop holding a charge and it WILL kill the other one, possibly leaving you stranded.


I should note I'm no electrician, the above advice was overheard while drunk at a strip bar ;)
 
Poppa Swiss:- you're in a strip bar, drunk, and they still can't stop talking about fishing?.......now that's dedication....LOL...
 
I run 2 batteries on switches too but I always only use the "both" option instead of one or the other. One battery is a deep cycle where all the electronics are attached and the other is a cranking battery that the motors are tied into. Seems to work for me and I am running heater fans with the motors off all the time.
 
wet spot said:
I'm switching from manual to electric downriggers so I am planning to go to a 2 battery set up with a switch than can use either battery or both...I've also added electrical output capability to my kicker. I plan to connect the main motor leads to battery A, the kicker leads to battery B, connect the positive posts from A and B to respective terminals on the switch, and interconnect the battery A and B negative(ground) posts together. The VHF radio will run directly from the A battery while all the other electrics ( downriggers, gps/fishfinder, lights etc.) will run from a bus connected to the output terminal on the switch.

Is this the best way to connect? If I have the switch set at "BOTH" and I have both motors running can it damage anything on either motor?...Do I need some kind of electrical protection in this case?
Click to expand...

The positive leads from the main and kicker go to the common terminal on the switch.

The positive lead from bat 1 goes to the #1 terminal on the switch.

The positive lead from bat 2 goes to the #2 terminal on the switch.

The negative terminals of bat 1 and bat 2 should be joined. The only thing wired directly to a battery should be the bilge pump float switch. Everything else comes off the common terminal on the battery switch. Turn the switch to #1 to start the motors, turn to both while cruising, turn to #2 while trolling or anchored. Turn off when you get back to the dock.
 
Here's a link to a set up I installed recently. Batteries are isolated until after the starting battery reaches a certain voltage level and after that point will allow excess current to feed the house battery. Will not allow a connection under a certain voltage level. Good for me as my kicker does not charge. Just turn the switch to ON and don't have to think about it. Better description and specs at the website. Jeff at HC will put together all the little bits and pieces.


http://www.bluesea.com/products/7650
 
Copper Moon said:
Here's a link to a set up I installed recently. Batteries are isolated until after the starting battery reaches a certain voltage level and after that point will allow excess current to feed the house battery. Will not allow a connection under a certain voltage level. Good for me as my kicker does not charge. Just turn the switch to ON and don't have to think about it. Better description and specs at the website. Jeff at HC will put together all the little bits and pieces.


http://www.bluesea.com/products/7650
Click to expand...

Installed the same kit a couple of years ago and haven't looked back since. These kits are very popular.
 
trendsetter said:
The positive leads from the main and kicker go to the common terminal on the switch.

The positive lead from bat 1 goes to the #1 terminal on the switch.

The positive lead from bat 2 goes to the #2 terminal on the switch.

The negative terminals of bat 1 and bat 2 should be joined. The only thing wired directly to a battery should be the bilge pump float switch. Everything else comes off the common terminal on the battery switch. Turn the switch to #1 to start the motors, turn to both while cruising, turn to #2 while trolling or anchored. Turn off when you get back to the dock.
Click to expand...

Absolutely the best break down on the proper use of a conventional two battery system. Thanks Alex.

Surprising to see posts by folks that run on both all the time. They will find themselves in a bind sooner than later. You want a solid topped up battery to crank that main over after fishing. Downriggers will destroy battery life during a fishing session. If they are both brought down there might not be enough for the one to crank your main. Food for thought.
 
With a ACR installed the battery switches are Set with one to each battery. Ie. switch one to battery one, switch two to battery two. Isolates the house and start completely except when a charge is being added, then the ACR will cycle the charge to the lowest voltage battery.
 
pescador said:
Scuplin/FB- with the ACR installed, in what position are you leaving your battery switch?
Click to expand...

With an ACR you leave the battery switch on #1 in most installations. Switching to both overrides the acr and connects your batteries in parallel. (Charges and draws from both at the same time.)
 
i am using two deep cycle batteries on both all the time and get 3-4 years out of them. the big amp starting batteries are needed for starting a 460 cc engine in -40 c in winnipeg not needed for my 225 yammie in our clime. i am not 100% sure if this is the best route to go but reaching down and remembering to switch batteries is a thing of the past. let me know if i am missing something here.
 
Lucky Tiger said:
i am using two deep cycle batteries on both all the time and get 3-4 years out of them. the big amp starting batteries are needed for starting a 460 cc engine in -40 c in winnipeg not needed for my 225 yammie in our clime. i am not 100% sure if this is the best route to go but reaching down and remembering to switch batteries is a thing of the past. let me know if i am missing something here.
Click to expand...

The purpose of two separate batteries is one battery should have only your starter on it and nothing else. And it should be isolated so it can not be discharged by anything other than your starter. Doesnt matter if your other battery is stone dead you can always start your boat
 
pescador said:
Scuplin/FB- with the ACR installed, in what position are you leaving your battery switch?
Click to expand...

I leave mine on the first position all the time. In an emergency I will switch it to two and have a fully charged starter battery every time.

The beauty of this system, or kit, is not having to change your battery switch all the time. It is automatic.
 
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