How to wire my new batteries?

[Parrot6909]

Hello all:<br /><br />I have read thru post after post in the search and can't seem to find my answer so...here goes...<br /><br />Specifics: 20' Wellcraft V20, 200hp Merc + Fishfinder, VHF and lights. <br /><br />Just purchased this boat about two months ago, batteries were shot. The cables were off of one of the batteries so I am not sure if they were wired in series or parallel. What would be the best setup? I purchased new batteries today (Seavolt from Westmarine) Dual purpose 12v's. Should I hook them up pos to pos and neg to neg for the connections or pos to neg? The other question is when I hook up the motor cables to the battery to I need to put the negative on one battery and the positive on the other? Any help you can provide would be greatly appreciated!

 

[Silvertip]

Re: How to wire my new batteries?

Not enough information!! Do you have a battery switch and are you talking about the engine starting battery and a single accessory/trolling motor battery, or are the two batteries used to power a 24 volt trolling motor and you have a third battery for starting. Series connection provides a 24 volt system that will fry 12V electronics. Parallel connection provides a 12 volt system with double the capacity of a single battery. Series connection is used only for 24 volt trolling motors (or 36 volts with three batteries for a 36 volt motor).

 

[Parrot6909]

Re: How to wire my new batteries?

Sorry about that!<br /><br />No battery switch at all. Just a large disaster of wires. I will rewire the boat in the fall but need to get through this season as is...(and if my boat isn't in the water by 5/1 I lose my slip!<br /><br />No trolling motor, just the 200hp Merc and the accessories. Does that help?

 

[Ralph 123]

Re: How to wire my new batteries?

They could have been just wired in parallel or not hooked together at all. One battery could have been acting as the "main" starting battery and the other as some sort of house battery with accessories wired directly too it. Who knows? You should try to contact the person you bought the boat from and find out or find someone who can look at it and help you dope it out by tracing some of the wires.<br /><br />[edit] if you find some short battery cables with lugs on both ends not hooked to anything that will tell you they were likely hooked together.

 

[Parrot6909]

Re: How to wire my new batteries?

I know they were hooked together, the guy had taken the battery out to charge it for a quick test run but didn't remember how they were hooked up either........

 

[Silvertip]

Re: How to wire my new batteries?

Sounds like they were indeed wired in parallel. Locate the two battery cables that go to the engine. The Positive cable usually has a red band or marking on it. If you aren't sure, the positive cable connects to the starter solenoid on the engine. The negative cable is bolted to the engine block. Mark those cables and set aside for now. If the batteries were wired in parallel there should be two large cables, about the same size as the engine battery cables laying loose. If this was a home-brew set-up, both wires may be the same color but if there is a red & black cable, place the red cable between the POS post on both batteries. Place the loose NEG cable between the two negative posts. Add the engine POS cable to the POS terminal on either battery. Connect the NEG battery cable from the engine to the NEG terminal of the same battery the POS cable is attached to. Now connect the positive and negative cables from your accessories to the respective POS and NEG terminals of either battery. Make sure all terminal ends are clean and tight. If using wing nuts, use a pliers to tighten them. Finger tight won't do.

 

[Parrot6909]

Re: How to wire my new batteries?

Thanks for the help! I greatly appreciate it. I was just worried about frying the electronic's if I put them on the wrong way. Everything is marked red and black so I should be good to go! Thanks again!

 

[Silvertip]

Re: How to wire my new batteries?

You might want to install a battery switch. Connecting batteries in parallel can cause a weaker battery to suck the life out of the good one. A battery switch lets you use one battery for starting, the other for accessories, and the switch has a BOTH setting to allow charging both batteries when under way. If the starting battery (#1 for example) should die on you, you simply switch to #2, crank the engine and away you go. Switch to BOTH (or #1) to charge the weak battery. It also has an OFF switch to serve as a total power disconnect. They are relatively inexpensive.

 

[Parrot6909]

Re: How to wire my new batteries?

I'll install one of those in the fall when I rewire! Thanks again!