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Author Topic:   Battery Connections
jimh posted 10-09-2005 11:27 AM ET (US)   Profile for jimh   Send Email to jimh  
Here are two very simple suggestions which cost just pennies to implement, yet both of them can save you hundreds of dollars in future repairs:

Mark your battery terminals with tape to clearly indicate polarity. Use RED tape for the positive (+) terminal and YELLOW tape for the negative (-) terminal. Also mark all cables that attach to these terminals with the same color coding.

Color-coding the connections will help to prevent connection of the battery with reversed polarity. If you ever connect the battery with reversed polarity you are almost guaranteed to destroy the diodes in your engine's battery charging circuit. A repair of the diodes will cost hundreds of dollars.

Remove the wing nuts on the battery terminals and replace them with proper hardware consisting of star-washers, flat washers, lock-washers, and hex-nuts. Tighten the connections with a wrench--but be careful not to short the terminals with the wrench!

The stacking order on the battery terminal post should be:

--lugs (engine first, then other accessories)

Use a copper star-washer if you can find one. Use stainless steel hardware for the remaining fasteners.

Wing-nut connections can easily become loose. A loose battery connection has the potential to cause damage. Loose connections tend to cause sparking. Interruption of a circuit with inductive loads (like electric motors) can cause very high voltage transients to be developed. These high-voltage transients can damage any electrical device connected, including the engine itself or electronic accessories.

If the negative connection to the engine becomes loose, there may be other paths to the negative battery terminal through wiring harnesses or accessory wiring which will suddenly try to supply the current. If a heavy current draw is required, such as operating a trim/tilt motor, the current may destroy the wiring. Replacement of melted engine wiring harnesses can be very expensive.

Many OEM manuals explicitly state that installations with wing-nut battery connections will not be covered by warranty. From the Bombardier BOAT RIGGING instructions:

"IMPORTANT: Do not use wing nuts to fasten ANY battery cables. Wing nuts can loosen and cause electrical damage not covered under warranty."

Chuck Tribolet posted 10-09-2005 08:11 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
I just put a crescent wrench on the wing nuts and give them
a gentle twist.


bobeson posted 10-09-2005 10:46 PM ET (US)     Profile for bobeson  Send Email to bobeson     

Do wing nuts loosen more easily than an equivalently tightened hex nut? I'd think not, but I don't know. I can see how people would tend to not tighten wing nuts as much as hex nuts in general.
swist posted 10-10-2005 07:13 AM ET (US)     Profile for swist  Send Email to swist     
I do agree battery terminals should not come with wing nuts, but there is no difference between a wing nut and a regular nut if tightened to the same torque. Problem is that people finger-tighten them.

Also I question your stacking order - a star washer will only conduct at those points that dig into the adjacent metal - for a high-current connection like this you want the main starting cable contacting the battery terminal over as much surface area as possible. I would not use the star washer.

Jim, EE

Robob2003 posted 10-10-2005 10:14 AM ET (US)     Profile for Robob2003  Send Email to Robob2003     
Chuck Tribolet,

Good idea about the crescent wrench.

Since I always have one in the boat I just use a pair of long nosed fishing pliers padded with a towel so as not to mar the nut.

Bob on Tampa Bay

davej14 posted 10-10-2005 01:43 PM ET (US)     Profile for davej14  Send Email to davej14     
I made a slotted piece oak that I use to hand tighten the wing nuts. First I drilled a hole to accomodate the battery bolt, then made a few cross cuts with a table saw. No more concern with shorting the terminals when tightening or loosening the wing nuts. I haven't had any problems with them, but I think I will add a lock washer to the top of the stack as insurance.
jimh posted 10-10-2005 11:43 PM ET (US)     Profile for jimh  Send Email to jimh     
If you are going to the trouble of using a tool to tighten the fastener on the battery terminal, why not use the most common arrangement of fastener and tool--the hex nut and appropriate wrench.

The goal is to get a secure, tight connection--not to see how many oddities can be used to tighten a fastener designed so as not to fit any tools except your fingers.

jimh posted 10-10-2005 11:44 PM ET (US)     Profile for jimh  Send Email to jimh     
I guess what I should have advised was this:

By all means, keep the wing nuts. Get a pair of pliers and a rag to tighten them, or make your own tooling from wood. But never, never, replace these fasteners with a hex nut.

davej14 posted 10-10-2005 11:56 PM ET (US)     Profile for davej14  Send Email to davej14     

The reason I like my "odd" approach is that I have shorted battery terminals with a socket wrench before. It is quite impressive and the auto response tends to test the integrity of your console opening with the back of your head.

Dick posted 10-11-2005 11:24 AM ET (US)     Profile for Dick  Send Email to Dick     
I think the suggestion by jimh of a star washer or lock washer on TOP of the lugs is a good idea.

If a hex nut was better I am sure the battery manufacturers would supply them rather than the more expensive wing nuts. Nice thing about a wing nut is that it can be tightened or loosened with many improvised tools, not so with a hex nut.

davej14 I like your idea on the oak block, no sparks.

andygere posted 10-11-2005 12:24 PM ET (US)     Profile for andygere  Send Email to andygere     
There are two reasons most marine batteries come with wing nuts. The first has been mentioned already: A hex nut invites the danger of shorting across the terminals with a metal wrench. The second is that the battery can be permanently damaged if the nut is over tourqued with a wrench. The use of a wing nut tends to limit this. That said, I think hex nuts are a better solution, as long as proper care is taken. Even better is to use the full size tapered posts for your starter cables, and leave the threaded posts for lower draw accessories. The lead posts have a lot of surface area, allowing for a low resistance connection. I used gold-plated Centerpin terminals on my recent rewiring project, and they are an excellent product. They are a bit expensive, but a lot cheaper than being stranded. Since they are gold-plated, they don't easily oxidize, and the o-ring sealed mechanical connection to the cable is well designed and made.

tomroe posted 10-11-2005 03:57 PM ET (US)     Profile for tomroe  Send Email to tomroe     
One could also use a SST nylon or all metal lock nut and eliminate the lock washer.
tomroe posted 10-11-2005 04:08 PM ET (US)     Profile for tomroe  Send Email to tomroe     
Hit the submit button too soon.

I have never had good success with electrical tape for marine applications. The wet/oily atmosphere seems to turn the adhesive to mush. I color code my terminals with either colored heat shrink tubing or colored zip ties.

jimh posted 10-11-2005 06:17 PM ET (US)     Profile for jimh  Send Email to jimh     
For color tape I recommend SCOTCH-35 brand. It is far superior to the stuff you see sold at RADIO SHACK or in discount stores. You can usually get it from an electrical supply house.


jimh posted 10-11-2005 06:19 PM ET (US)     Profile for jimh  Send Email to jimh     
Fixed long URI.
tomroe posted 10-11-2005 09:56 PM ET (US)     Profile for tomroe  Send Email to tomroe     
I agree that Scotch 35 is a superior tape, but it is recommended for "indoor and weather protected outdoor uses".

I think there are other products better suited for a marine environment.

Dick posted 10-12-2005 12:46 PM ET (US)     Profile for Dick  Send Email to Dick     
I don't understand the need for colored tape.
The positive cable is red and is attached to the post marked +, the negative cable is black and attached to the post marked -.
If the battery has the proper posts and the cables the proper lugs you can't screw it up, positive is a 3/8" lug a negative is 5/16".
Liteamorn posted 10-12-2005 02:14 PM ET (US)     Profile for Liteamorn  Send Email to Liteamorn     
I would use hex nuts ONLY if I had a Battery switch (which I do). Wing nuts could make it a lot easier to disconnect the battery if a major short (and ensuing smoke or fire scenario) were to occur.

I never understood not having at least an on/off switch on a boat.

Robob2003 posted 10-12-2005 05:16 PM ET (US)     Profile for Robob2003  Send Email to Robob2003     
I simply steal a little bit of my wife's red fingernail polish and paint the positive battery terminals on my motor and trolling motor batteries.

The same can be done on the cable terminals and it doesn't wear off.

Bob on Tampa Bay

Robob2003 posted 10-12-2005 05:21 PM ET (US)     Profile for Robob2003  Send Email to Robob2003     

If you insist on using a hex nut on a battery terminal you had damned well better install a battery switch (something most of with simple systems don't need) if something starts to spark or smoke.

Why a hex nut? Use a lug connector like an automotive cable and tighten away. Marine batteries are equipped for both kinds of connectors.

Bob on Tampa Bay

jimh posted 10-13-2005 05:03 AM ET (US)     Profile for jimh  Send Email to jimh     
I have never seen any battery cables or any boat wiring in which the positive conductors connecting to the battery were all made with wire that had red insulation. On my boat, and and all that I have seen, the battery primary wiring cables have black insulation. This includes the cables from the motors and all of the other heavy gauge cable installed.

It goes without saying that if all of the cables which connect to the positive terminal of the battery already have red insulation that there is little benefit to be gained by marking them with red tape. However, this situation is rare. The suggestion to mark the cables going to the battery terminals with color coding to identify their polarity is a reasonably good one, in my estimation, and I have no regrets having made that suggestion.

As I mentioned in the initial suggestion, a few pennies spent identifying the cables can avoid a great deal of expense in repairs if they are connected incorrectly.

It would take less time and effort to mark one's battery cables with identifying color coded tape than it has to type out this reply or to read this discussion. I think that puts something of an upper bound on how much further debate is necessary.

Dick posted 10-13-2005 07:37 PM ET (US)     Profile for Dick  Send Email to Dick     

From your last post I have to believe that you have never seen any correct battery instalations. I have been in the marine business since 1969 and every boat that was rigged in the shop or that came pre rigged had a red cable for positive and a black for negative. That is why they make the two different colored cables.

Over the years I have been a dealer for Glastron, Bayliner, Boston Whaler, Sea Ray, Carver, Duckworth and a few others. All of them used the Red +/Black- wiring. If I am not wrong that is a BIA requirement.

If you buy a used boat who knows what the previous owner has done.

LHG posted 10-13-2005 08:17 PM ET (US)     Profile for LHG    
If I remember correct, the engine battery cables on all of my Mercs have the black wiring, but the positive lead has a big RED connector, about 3" long, on the end of it where it connects to the battery post. It's impossible to miss this.
Dick posted 10-13-2005 09:55 PM ET (US)     Profile for Dick  Send Email to Dick     

I had forgot that one. A lot of OB electrical harnesses are black all the way down except for a red covering for a few inches at the end. Enough to tell you where it goes though.

jimh posted 10-13-2005 11:21 PM ET (US)     Profile for jimh  Send Email to jimh     
Please accept my apologies for making the fool-hardy recommendations with which I began this discussion. In light of the comments, I wish to amend them as follows;

--Remove any color coding of your battery cables and any color coding of your battery terminals. Just rely on the original manufacturer to have properly coded the cables and terminals in a clear and unambiguous way so you can connect them without any possibility of getting the polarity wrong. Ignore any advice given to clearly color code them no matter what.

--Always use wing nuts to connect cables to the battery terminals and hand tighten them, or keep a rag and use a pair of pliers, or make your own tool from an old piece of wood. Ignore any advice to replace the wing nuts with other fasteners.

These suggestions should be easier for people to accept.

jimh posted 10-13-2005 11:24 PM ET (US)     Profile for jimh  Send Email to jimh     
I don't understand how having a battery switch or not having a battery switch affects the potential to short out the battery terminals when tightening them with either a wrench or a pair of pliers. Care is always necessary when connecting to a battery as there is always the potential for very high current flow if a short occurs between the battery terminals. No switch can lessen that risk.
jimh posted 10-13-2005 11:28 PM ET (US)     Profile for jimh  Send Email to jimh     
The ability to over-tighten the fastener on a battery post exists in any situation where a tool is being used. Heaving on a pair of pliers to tighten a wing nut is probably more of a threat to the threads than tightening with a proper wrench. Also, due to the potential for slipping, using pliers on a wing nut is probably far more likely to result in damage than using a proper wrench on a hex nut.

Because a hex nut is symmetrical and a wing nut is not, a wing nut is far more prone to be loosened by vibration than a hex nut.

Anyone who says otherwise is itchin' for a fight.

kingfish posted 10-14-2005 08:58 AM ET (US)     Profile for kingfish  Send Email to kingfish     
Hah! (You must listen to the same NPR programs I do-)


Robob2003 posted 10-14-2005 10:27 AM ET (US)     Profile for Robob2003  Send Email to Robob2003     
<Please accept my apologies for making the fool-hardy recommendations with which I began this discussion. In light of the comments, I wish to amend them as follows;>

My, my, aren't we testy when others have (different, therefore, obviously inferior) ideas?

I came to learn from ALL posters not just the Omnipotent One.

Bob on Tampa Bay twiddling his wing nuts:-)

jimh posted 10-14-2005 01:27 PM ET (US)     Profile for jimh  Send Email to jimh     
Never met a battery yet with terminals that were color coded. Throw a little dirt and oxidation on the battery and a (-) and (+) can be hard to distinguish, especially when the battery is located under a deck or console and not in good light. But apparently people think it is nuts to put color coding on things. I guess their eyesight is better than mine.

And, yes, if someone presents an alternative suggestion which I don't think is as effective, I do tend to make a comment on it. Apparently this same motivation inspired all the criticism of my initial suggestions!

But, again, feel free to not add color coding and to use wing-nuts on your small boat electrical system. I just don't think it is a good idea and I continue to recommend using color coding and proper fasteners to identify and install wiring.

jimh posted 10-14-2005 01:38 PM ET (US)     Profile for jimh  Send Email to jimh     
Andy--I like those connectors, however at about $20 each they are bit more expensive than the cost of a few cents of tape and hardware in my recommendation. Given the reluctance shown here to invest about a $1.00 into upgrading a battery installation, I will be surprized if people will spend $40 for a pair of those.

I am still using the factory-installed lug connections on my engine cables, and other owner-installed wiring has lug connectors that are decent. If I were cutting the battery cables from the engine, I would certainly consider a connector like that. As you said, getting stuck is not pleasant, and most boaters are willing to spend a few dollars to prevent that.

andygere posted 10-15-2005 12:00 AM ET (US)     Profile for andygere  Send Email to andygere     
They are expensive, but when I purchased them at my local Boater's World, they came packaged in pairs, one (+) and one (-). The price was around $18 per battery as I recall. The tinned copper Ancor brand lug connectors run $5-6 in the larger wire sizes, not cheap in their own right.

Another nice advantage of the Centerpin post-style connector is a somewhat less crowded wiring job inside the battery box. I was able to make up the cables such that they made gentle bends and weren't stacked up as they were routed out of the battery box. Considering the cost of a new outboard motor is in the $14,000 range, a nice set of cable ends like these should be standard equipment!

andygere posted 10-15-2005 12:03 AM ET (US)     Profile for andygere  Send Email to andygere     
The Ancor lugs cost $5-6 per pair at West Marine. They were a dollar or so less per package at Boater's World, but they didn't have nearly the selection of sizes, and the store wasn't 10 minutes away from my house late on a Sunday afternoon...
jimh posted 10-15-2005 12:13 AM ET (US)     Profile for jimh  Send Email to jimh     
At $18/pair I am getting tempted!
davej14 posted 10-15-2005 08:57 AM ET (US)     Profile for davej14  Send Email to davej14     
The centerpin website sure doesn't have much information on these connectors. It would be nice to have a dimensional datasheet.

Does anyone know if they available in a ring terminal configuration or just the battery post style? In order to connect the battery cable to a battery switch you would still need to have a ring termination.

Liteamorn posted 10-15-2005 01:59 PM ET (US)     Profile for Liteamorn  Send Email to Liteamorn     
I've used differant colored wire ties to color code my wires also.

My comment about a battery switch is not about connecting a battery correctly . I am addressing the short that occurs while at sea aka "do you smell smoke"? It is nice to know you can kill the power with the turn of a switch (or a wing nut if no switch is available)real fast.

Whalerider posted 10-15-2005 08:03 PM ET (US)     Profile for Whalerider  Send Email to Whalerider     

I must have a one of a kind Whaler. All, and I mean ALL, my positive wires are RED and my negative/grounds are BLACK, including the battery cables. I also use AGM batteries come with 1/4 inch stainless machine bolts (the battery post is tapped to accept the bolt) and split style lock washers to attach the various lugs to the battery.

I agree with you though…. keep it all color coded by whatever method works for you.

2005 Nantucket

Whalerider posted 10-15-2005 08:09 PM ET (US)     Profile for Whalerider  Send Email to Whalerider     
p.s. the AGM batteries I use have a 2"x2" neon RED square next to the positive lug and BLACK square of the same size on the negative.
andygere posted 10-19-2005 01:15 AM ET (US)     Profile for andygere  Send Email to andygere     
It's important to note that both the lead posts and the threaded studs on a marine battery are a different size for positive and negative. If the connectors (such as ring terminal lugs) are the correct size for the wire's respective polarity, you get a better connection and it's much harder to complete the circuit with the wrong wires on the wrong terminal of the battery. Sadly, most wiring jobs I have seen use the same size lugs for (+) and (-). I think it's 5/16" for (-) and 3/8" for (+) but that's from memory and I'd have to check to be sure.
CHRISWEIGHT posted 10-28-2005 06:14 PM ET (US)     Profile for CHRISWEIGHT  Send Email to CHRISWEIGHT     
I'm with you, I have never seen a wing nut on any battery installation in the uk and the damage/danger of these "wing nut" installations far outweigh the advantage of being able to remove the connection should a short occur.
Much more likley to Cause a fire than prevent one.

regards chris

jimh posted 11-08-2005 09:38 AM ET (US)     Profile for jimh  Send Email to jimh     
Fans of the wing nut will love this story of how a loose wing nut battery connection required a trip to the boat mechanic for diagnosis and repair.

More testimony to the fabulous advantage of wing nuts. Of course I am being sarcastic. Throw those wings nuts into a bag and mail them to all the guys in this discussion who swear by them. I swear at them--the wing nuts, not the guys.

jimh posted 11-12-2005 09:15 AM ET (US)     Profile for jimh  Send Email to jimh     
Following up on Andy's observation that the size of the threaded stud terminals on marine batteries were different for each polarity, I checked a number of marine batteries for this condition. My observation is that all the batteries I checked had the same size threaded stud connector for both positive and negative.

According to an experienced marine mechanic, it may have been a standard practice at one time to have different size threaded studs for the positive and negative terminals, but this practice is no longer very common.

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