Melting negative terminal??

[bigturk_80]

Any opinions on this? I have a 4.3 mercruiser in my 22' Starcraft, and at the end of last season she melted the negative terminal on my battery. What would cause this? I took the battery in and had it tested, and it tested bad. It was replaced under warranty.

Strange thing is, I had an alternator go bad last season, on that battery. Would a bad alternator fry a battery, which then caused the melted terminal on that battery?

I'm just in the process of re-installing my engine after re-doing my transom, and want to whip this problem now before I get it back in the water.

[bailey]

I would think somewhere you could've had a short, but i have seen terminals melt from bad connection at them ex loose or dirty. Or a combination of all maybe alternator shorted and a loose cable?

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[mrcanam450x]

It sounds like you had a short somewhere in the boat and since you said you're alternator went bad that could have been the short. Or something had reverse polarity. Shorts will always take the easiest path to ground...negative side. And it doesn't take much to melt a terminal

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[bigturk_80]

What are some common causes or areas that may cause shorts? My battery terminal burnt after my alternator was already replaced.

As far as I can see, I only have one ground that runs from the engine to the transom assembly.

[Xxx]

I would check your starter for excessive draw 250 amp or less, what could cause over draw is a bad connection being at the battery or the cable haveing corroision under the black covering or at the engine block itself, which could of wiped out the neg. side of the rectifyer in the alt. If your electrical system is searching for a ground it will take the path of least resistance, which would be a loose connection at the battery, the alt. wouldn't burn off the neg. post because it is grounded twice, if the alt lost it's ground or part of it's ground you would have noticed a voltage drop like 13.5 or 12.8 unlike the norm 14.2 volts. I would check all your grounds,clean them up, do not use a lock washer, just a flat washer and a new nut to make all the connections, a lock washer acts like a spring and with any corroision it will push your connection apart causing a bad connection, if you have any problems contact me as I will help anyone on this site if I can. 25 years self employed as a auto electric rebuilder F&F Starter & alternator . Tight lines to all PAP.

[Knotlost]

Chicken or the Egg, if your sure the alt went first then what Pap said is a start.

Clean the ground and be very fussy, they are more important than thpositiveve. When you loose positive things just stop working, when you loose ground things are more likely to melt and catch fire. You were very close I would guess to having a fire.

It's possibleable that internaly your battery broke apart on the neg causing the damage, imagine hooking a 6 volt batter to a 12 volt system.

Make sure you have fused everything right. On your positive side you should have a fuse between the battery and everyelseg elce. Many times pdon'te dont then if they ever have a problem they get a fire. I do admit though most of the time they burst solenoidsonoids or starters before they get fires but not all the time.

[BullGator]

Itpossibleable tinternalraly your battery broke apart on the neg scausingeing the heimagineagin hooking a 6 volt batter to a 12 volt system.

Yep, that's what I was thinking........

But seriously....you simply had a loose connection to the battery negative. The damage (melting) would have been caused at heavy amp draw, such as starting the engine or using a downrigger.

If your connection was tight, and you had a short elsewhere..........the melting would have occurred at the short location, not the battery terminal. The terminals, when tight, can handle well upwards of 500 amps. There is no other point on the boat that can handle a larger amperage draw than those terminals. When the terminals are tight, they will not arc or melt.

[buckboardjr]

Unlike Homes and Aircraft, boats and autos don't generally protect thier large amp draw wires such as your heavy possitve battery cable to your starter. In homes that would be your 200 amp breaker at the top. Aircraft use monster current limiters because they just can't risk a moster feeder wire to rub to ground and have a major short. With that said you should verify the routing of your positive battery cable from the battery to the starter to ensure it hasn't chaffed to ground and also that it's connections are corrosion free, tight, and clean. Most likely they have not protected the med. lg charge wire coming off your alternator either. You need to verify along it's length as well that it hasn't chaffed or has poor connections. It would take something capable of carrying some serious amps to melt that neg cable and the unprotected pos feeder side has the ability. When batterys are located a far distance from the starter a very safe mod to do is mount a ford solinoid next to the battery and use that to send the heavy current to the starter on a momentary basis during start only. That way you don't have a 2 Ought feeder wire hot all the time. With this mod you also install a current limiter on the charge wire and med feeder wire to your ditribution fuse block. If you don't find anything during this inspection I'd chalk it up against either your old batt shorted or alternator. Hope this makes sence and helps.

[Knotlost]

http://bluesea.com/files/resources/refe ... cerpts.pdf

These standards came out in 2010 and most dont know about them.

[borderline 350]

Dear BT80,

The primary reason for melting a battery ground terminal is caused by very high resistance in the ground cable. If the cable end melts, replace the entire ground cable and be sure that you have clean bright contact bolts & unpainted contact areas. When you get the old cable off, check the resistance value with an Ohm meter. SHOULD BE ZERO OHMS resistance...bend the cable in several places while watching the ohm meter, any fluctuations tell you that the cable needs to be replaced. Check your new cable before you install it and it should be ZERO OHMS resistance. Use #2 marine battery cable for a replacement. I get to see one or more bad ground cables every year on 1990 and earlier boats. Such melting conditions can easily cause a fire or worse! ...Respectfully Submitted....X-Jet Boat Bill

[bigturk_80]

I'll dig at it over the next couple nice weather days. I'll go over my starter wires and grounds with a fine toothed comb and check all my connections. It's didn't melt my negative wire, it melted the connector that clamps to the post.

On another note, my starter looks like it's got a bit of black crusty build up at the one end, like it may have gotten hot at one time. Who knows, this thing did some funky stuff at the end of last year, I'm sure I'll find one or two things that need changing.

I do remember towards the end of the season, if I turned the key sometimes it would just click, and sometimes it would turn over. I just chalked it up to the whole battery issue.

[Xxx]

Like I posted earlyer the corrosion under the black covering will cause resistance, which will cause exsessive amp draw and in result will damage everything that needs 14 volts to operate correctly, a bad ground creates heat, heat is the worst enemy of all electrical conponents, since the man said it wiped his alt. out I would bet that the neg. side of the rectifyer blew a few diodes, which will cause the alt to lose amperage, but maintian the voltage, thus making the alt. work harder(more heat!) then finally start to blow diodes on the pos. rectifyer, resulting in a voltage spike of 16 -18 volts and then regulator failure, even with that high of voltage there will be little amperage, resulting in no damage to the neg post of battery, I would change the cable, new battery clean all the terms, make sure all the grounds are hooked up, I have 3 grounds on my boat one to the bell housing #2 wire 1 to the alt. 10 guage wire 1 goes to the main gang plug, make sure none of those wires have resistance in them, use battery cables with the ends crimped on!! I'll bet problem solved. Tight lines to all PAP