Battery problem? Maybe?

[richardh10]

With nothing better to do, I thought I’d check the battery compartment today. Rather surprised to find the outer cover on the positive cables had discoloured


I am at present in a marina, with shore power attached, and prior to that I had motored for a couple of days and nights without any problem. Prior to that when I had checked, everything was as it should be. I’m aware that the battery compartment isn’t as well ventilated as it maybe should be, but would that be enough to cause that discolouration? If not, what could it be?

Thanks

 

[matthewriches]

I don't get a very clear picture on my phone. What colour were the cables? Can't quite make out if they've got hot and gone a funny colour or whether it is soot or something. Common on a few fishing boats that we see occasionally that the whole engine room gets covered in black soot from dry exhausts not being sealed properly. Although more likely I guess for you to have a wet exhaust.

From the pic that looks like 50mm csa cable so would take quite a bit of current to turn them off colour! Are you able to see if the cables are running warm? Happen you are local then I have a thermal imaging camera you could borrow.

All connections tight? Battery voltages reading ok? Starter working ok? Acceptable charge from the alternator(s)?

 

[richardh10]

Hi Matt

Definitely not soot, looks like they’ve got hot and gone a funny colour. Everything else seems to be alright, and where they go back into the (well ventilated) engine room, they go back to normal colour. Maybe I just need to get more ventilation to the batteries.
Not local I’m afraid. Canaries!

 

[macd]

would that be enough to cause that discolouration? If not, what could it be?

Your photo shows no evidence of discolouration to me...or, I suspect, to anyone else not familiar with your battery box.

 

[matthewriches]

What was the the "normal colour"?

 

[Richard10002]

Looks like they may have turned brown from black?

 

[matthewriches]

That was my thought, with the red heatshrink denoting positive connections?

Cable must have got pretty warm! Although PVC insulation tends to blister fairly early on and is quite noticeable from the smell.

Looks like they may have turned brown from black?

 

[macd]

Looks like they may have turned brown from black?

Quite possibly. But even the most skilled diagnosis based on a guess is still a guess.

 

[richardh10]

The red cable was originally the same colour as the shrink wrap. I should obviously have pointed that out. I have now placed a piece of the original cable over the top of the discoloured cable, so that the difference is more obvious. I’m not worried about the black cable. That’s fine.

 

[Keith-i]

Whilst I've never experienced this kind of phenomena, I would have thought the adhesive lined heatshrink would have deformed somewhat if the cables had got so hot as to discolour the pvc sheath. Perhaps you ought to run the charger for a little bit then check to see what's getting hot, if anything. If it was the cables overheating it must have been quite a current flowing to heat up 50mm csa, either that or the batteries themselves have expelled a lot of heat or some form of gas.

 

[matthewriches]

Blimey! I’d be getting the multimeter out to have a look ASAP or someone competent to have a quick look over it all.

Any funny smells? Any fuses inline that have reacted? Batteries making a wheezing sound?

The weird thing is that you say it is contained within the battery box. So could be a potential chemical reaction. My science is somewhat limited on materials but PVC (if that’s what the cable insulation is) is fairly resistant to hydrogen sulfide but not sure regards other gasses that could be present.

 

[richardh10]

Yes, but even though it’s contained within the battery box, the cable from the windlass is unaffected, and is the normal red colour. This is connected to the house batteries, but the cables which join all the house batteries are affected.

 

[Momac]

Take the batteries out and test them individually. This may also allow better inspection of the cables and the batteries.
Overheating battery may distort battery case.

 

[Kukri]

This is just a fool rushing in where angels fear to tread, but could something have happened to one of the batteries that might have drawn a very heavy current for a moment? The “something “ being a short perhaps caused by something landing across two terminals and melting before the wire did?

 

[Richard10002]

Quite possibly. But even the most skilled diagnosis based on a guess is still a guess.

Not quite sure what you mean?

I was obviously wrong, as we now know that they have turned a kind of brown colour from their original red.

The question now is, Why?

 

[Billjratt]

I don't believe it's a heat/high current situation. There would be 'melt' evidence somewhere I'm sure.
I think it's chemical. Red pigments suffer more readily than others under some circumstances and we have a situation where there is only a problem in a confined space - the battery box. Check the electrolyte levels in all the battery cells and have a sniff (literally) around the area for sourness (or burning if I'm wrong). Also, if it is a fizzing-off situation, you need to check other bits in the box for acid damage. Best of luck.

 

[VicS]

I don't believe it's a heat/high current situation. There would be 'melt' evidence somewhere I'm sure.
I think it's chemical. Red pigments suffer more readily than others under some circumstances and we have a situation where there is only a problem in a confined space - the battery box. Check the electrolyte levels in all the battery cells and have a sniff (literally) around the area for sourness (or burning if I'm wrong). Also, if it is a fizzing-off situation, you need to check other bits in the box for acid damage. Best of luck.

I am inclined to think the opposite based on the fact that the windlass cable is unaffected.

I would follow the affected cables way from the batteries to see how far the effect extends and in particular inspect any lighter cables connected directly to the main ones as they could be more seriously damaged. Following the affected cable should led to the source of the trouble if it is a high current one.

If the effect is confined to the battery box then more probably a the result of gassing/ acid fumes from overcharging.

 

[Porthandbuoy]

Does the colour change where the cables exit the battery box? If it does then it’s more likely to be chemical attack.

Is there anything in physical contact with the discoloured cables that is also affected? Eg. A sticky-backed label or painted surface. If ‘yes’ then it’s more likely to be overheating.

Does the discolouration gradually revert to normal the further away you get from the battery post? If ‘yes’ there’s a high resistance connection generating heat which is conducted a short distance up the cable.

Are the crimped ends secure? As above, if not there may be a high resistance connection.

You’ve connected the cables to the small stud on the battery terminal. Is that connection, usually for ancillary devices, rated for the use you’re putting it to?

Finally. You don’t when the cables were fitted. Could you, or whoever made off the ends, have left the heat gun on the cable ends too long?

 

[PaulRainbow]

You’ve connected the cables to the small stud on the battery terminal. Is that connection, usually for ancillary devices, rated for the use you’re putting it to?

Those studs are not for ancillary devices, they are for connecting the battery cables to.

 

[Porthandbuoy]

Those studs are not for ancillary devices, they are for connecting the battery cables to.

Then what are the larger diameter battery posts for? Ornament?
High current, eg. starter motor and windlass, battery posts. Low current, eg. VHF, echo sounder, plotter, etc. stud.