God said go to the boat!

[Asureyez]

God must have been speaking to me directly this past Tuesday Morning.

I was at my desk at 9:00 and had been working for an hour to more, and I began to get the idea I needed to go to the boat. I did have a lot to do there, but I'd planned to go later in the day once the sun was below 3:00PM. it is just too hot in the ER when the sun is high.

I couldn't shrug off the idea and so I went ... got there about 10 and climbed into the ER to plan my work, i was still in street clothes. As I thought through my tasks I smelled something and my mind was trying to place the odor when I saw a flash out of the corner of my eye, deep in the back of the ER and as i turned my head it flashed again and I linked the ID of the odor to buring wire. I ducked and went aft to see the battery charger for the BOW thruster sparking chunks into the ER and smoke beginning to billow. I thought OH Sh*t! And crawled out of the ER to the cabin and killed the AC to the charger and raced back to the ER with a 8 LB. fire extinguisher in hand. Killing the power stopped what turned out to be a total burn out of the 24V battery charger to the bow thruster bank.

I waited with FE in hand and watched as things cooled down.

I rapidly pulled the beast off the bulkhead wall and got it off the boat ... Which casused me to find out just how small I can make my 300LB frame.

PICs follow.

WHY did this happen? It seems that where SR installs these units, behind the overboard thru hulls for the common grey water discharge, bilge pumps and main engine exhaust by pass, there is just going to be some small amount of salt moisture being blown by the clamps. Over the years corrosion set in and increased the DC side resistance on the DC charger lugs until they simply burnt out. With the DC side resistance being so high the charger worked harder and harder to send current. The AC side burnt out its connectors ... total global meltdown!

The DC lugs were covered by an end cap and that end was shoved back as far in to the aft port corner of the ER as possible, well behind these through hulls. You can look for ever and not see trouble brewing.

Needless to say had I been a few minutes later ... Asureyez could easily caught fire and burnt to the waterline at the dock. I was there just in time to prevent disaster ... call it coincidence, providence or a call from God ... I picked up the call!

The ProTech/Pro Mariner charger folks were fantastic. They found me a stocking dealer in town, and I was able to get a $900 charger for 360 bucks. The factory offered me a 50% credit (unit was 5 years old) to a new one from them direct (which was more than I paid at the local distributor) But they were very helpful and the CS dept is super on helping with install and other issues on settings. A Big Thumbs up to Pro Marinier Chargers.

 

[Dave S]

It does make you wonder why you felt the need to go to the boat doesn't it? Glad you spotted the problem and got it taken care of. Those terminals look real nasty.

Dave

 

[Sorrento 25]

Wow! Pick up a can of CorrosionX or something similar for the new one.

 

[penbroke]

WOW! That's scary. Glad you were there to catch it.


Frank
Fire-Bad.

 

[Morpheus]

And just before your big trip with everyone to the Bahamas that could of ended bady, I'm glad god got ahold of ya before real damange could of occured.

 

[wkearney99]

Yikes, glad to hear you caught it in time! I'd also double-check why your fuses and/or breakers didn't blow. And consider ADDING an in-line fuse to prevent it from ever happening again!

But this highlights an annual maintenance issue some folks forget to check. It's a good idea to go around the engine compartment and make sure various hose clamps are tight and electrical terminals are clean and not showing signs of corrosion.

It helps to have a nut-driver handy for the clamps. Using a regular screw driver is just a recipe for busted knuckles and a stripped head on the clamp's bolt. That and keep a supply of the common clamp sizes on board. When the clamp screw threads into the band there's a chance the small grooves will get bent. This is usually the result of the bolt having been over-tightened. Best to use a straight nut-driver not a socket wrench to avoid applying too much torque.

 

[osd9]

Very good catch Chad....I'd like to stay and chat, but I think I just heard a voice telling me to go out and buy a Lottery Ticket..($375M)....I sure do hope the voice is coming from the same source as yours.... :grin:

 

[ImpulseIII]

Dominic, just remember who your new best friend is..... :thumbsup:

 

[elreyos]

With that much current draw why didn't the breaker on the main panel open?

AHMEN!

Andre'

 

[Dave M.]

Chad, I don't buy your explanation for how this happened. It has been bugging me since you posted this whether I should say so or not. But, I did not see the pictures until this evening. Now I know.

First off, my objection to your theory is that the charger really does not work much harder to overcome the terminal connection resistance. I think that is a red herring. I do agree that you can have corrosion caused resistance, and I have calculated that about 0.1 to 0.25 ohms on the DC side are probably the worst. They are also low enough to be hard to check. You could get 100 watts of heating at a bad connection. But when I saw the photos, I realized the work I had done calculation connection resistance and trying to write about that was for naught.

You are looking at a problem here that, as you say, could easily have burned your boat to the waterline. It's my opinion that when you have electrical equipment burns like this, you have a lot more than connection problems. This smells to me of high current flow, the type you would get when you make a serious electrical error, or have a large fault.

It appears to me that the real problem occurred at the output terminals for the battery. The negative (ground) post is burned clear off. Probably whatever caused that also set the circuit board on fire. Then that caused problems with the AC input side that you were able to stop. But by then, the damage had been done except for setting your boat on fire.

Next question I then had was, how can you get enough current to flow into and through the circuit board to cause this sort of damage. We may be talking hundreds of amps here. Why did the battery fuse not blow? So I downloaded a copy of the boat manual to take a look. You will find the schematic for the bow thruster on page 12.39. Here is a selected portion of it. I have colored the wire from the battery to the charger in red. And guess what? It does not go through the fuse, it is directly connected. So, if the schematic is correct, you have a circuit board directly connected to a battery that has enough power to vaporize parts of it, with no protection. :smt018

You need to know if your boat is really wired like this or not. I would hope not, but your photos suggest to me that it is. If it is, then you have the same disaster waiting to happen again, maybe some night when you are sleeping on the boat. All it would take is for some part in the output circuit to short between +12 and ground, and you have a direct short across the battery. The battery will burn it open.

In my opinion, you have some investigating to do.

PS edit:
This is from a manual for one that looks like yours. Note the wording in bold, which is theirs, not mine.

 

[Asureyez]

Fuses

Perhaps you'r eonto something. But there are several fuses mounted on the bulkheads. I'll take photos and trace some wires thru the circuits.

I can tell you that the 12V lead from the converter goes to a rather long and sizable fuse and is so labled. The negative cable I'll have to trace to the Batt terminal. The harnesses back there are quite difficult to access and unsheath, but you're right on this number ... if the boat is built as shown ... there is a real potential problem.

Thanks for the persistance.

 

[Dave M.]

Chad, if the wiring diagram is correct, then there is no fuse or breaker you can open that will disconnect the battery from the charger. So if you removed AC power from the charger, and monitored the DC output terminals, you would be unable to open any fuse or breaker and remove the DC being applied there by the battery.

If you did that test, and found a fuse that did remove the battery supplied 12 V measured at the charger output, you would at least prove the diagram wrong. And then hopefully you could also see the amp rating of the fuse or breaker that does that job.

 

[Asureyez]

Not forgotten

I returned from Freeport to be welcomed by a blown AC untit at the house and I've been jumping between boat for sell and house for repairs. The YC wireless is also down and I'm beginning to mold!

Damn its hot.

I'll get this stuff up soon. Thanks to all