Ammeter failed

[roland elsdon]

Can’t work this one out. Boating down barby straight this am one hour out strong smell of burning in engine room.

Could not locate until I noticed the adverc flash a green light.

Looked at ammeter showing 10 amps and red hot. 
In Hillmorton locks unhooked solar turned off batts disconnected wires, and joined by a bolt through the tails insulated and restarted engine. ( classy did whole job whilst boat descending on one paddle)

At the drugby tesco mooring pulled over removed ammeter and replaced with the old one we took off when we upgraded alternator.

 

So why did it melt.

installed in line between alternator and batteries

60 amp with a 75 amp alternator

batteries were at 12.5 when we started

lastly there were no loads on other than fridge and post adverc charge ( 10a shown)

no earth connection on it and mounted on a non conducting (grp) mount.

The face is melted the wires insulation tracked about an inch with the heat.

 

Any ideas.

 

[Tony Brooks]

1. Moving iron type (no shunt). All I can think of is a short to earth on the load side of the alternator but that should have shown far more than 10 amps charge. A short in the alternator could also burn the ammeter but then the ammeter reading should be negative, (discharge) rather than charge,

 

2. Shunted type. Open circuit in the shunt so all current trying to pass through the ammeter. As this type of ammeter is only a millivolt meter I would have expected full scale deflection but no meter damage.

 

I await other relies with great interest

[Tracy D'arth]

Simply a bad internal connection most likely.

[Tony Brooks]

18 minutes ago, Tracy D'arth said:

Simply a bad internal connection most likely.

 

Agreed it is a moving iron one but not a shunted one.

 

@roland elsdon What type of ammeter is it? How thick are the wires running to it?

[roland elsdon]

Moving iron no shunt.

direct in line. Cables described as ‘ more than adequate on survey.

Boat is super low tech never seen more than 40 a on meter as its a lister with 127 lucas, running an adverc bms.

Only two batteries and as I said they were well up when we started.

cannot have been dead short mounted on abs plastic mount . No earthed stuff near it.

On replacing the ammeter with the spare 30-30 one everything normal.

[Tony Brooks]

Then it sounds like Tracy had the answer. A fault in the gauge.

[roland elsdon]

Thanks well check the battery connection  to the ammeter tomorrow before i start up, but the volts seem normal.

[LEO]

Interesting comments, with regards to ammeters, I find the digital ones which plug into Lighter sockets useful, in cars and on the boat, any views on them?.

[Tony Brooks]

3 minutes ago, LEO said:

Interesting comments, with regards to ammeters, I find the digital ones which plug into Lighter sockets useful, in cars and on the boat, any views on them?.

Apart from the fact that they are VOLTMETERS I would not trust their accuracy unless compared with readings from a calibrated multimeter. However, they are, in my view, fine for a quick glance to say get a VERY ROUGH idea about the degree of battery charge, or perhaps faults on the circuit it is connected to.

[LEO]

5 minutes ago, Tony Brooks said:

Apart from the fact that they are VOLTMETERS I would not trust their accuracy unless compared with readings from a calibrated multimeter. However, they are, in my view, fine for a quick glance to say get a VERY ROUGH idea about the degree of battery charge, or perhaps faults on the circuit it is connected to.

 

Agree...thanks.

[roland elsdon]

Well just fired up. After normal warm up i reved her up to kick in the alternator and it wouldnt trigger. It finally came on as the boat hit about 5 mph  on the ansty straight  with ducks being blown out of the canal and surfers enjoying the point break.

The system is  charging fine but i have the faint red light of death on the warning light.

better dig around and fit the spare alternator.

[roland elsdon]

And now thats fixed itself ! Just as the adverc cut in. .

ill pull the adverc connector probably fried spider.

[Jen-in-Wellies]

Would this be consistent with the poor connection in the Ammeter theory? Ammeter has high resistance joint inside, heats up and melts. Happens while alternator is spinning, so an interruption of connection to the battery fries one or more diodes. Boat now needs to have warp drive engaged before the charge light goes dim/out.

[Alan de Enfield]

1 hour ago, Tony Brooks said:

Apart from the fact that they are VOLTMETERS I would not trust their accuracy unless compared with readings from a calibrated multimeter. However, they are, in my view, fine for a quick glance to say get a VERY ROUGH idea about the degree of battery charge, or perhaps faults on the circuit it is connected to.

 

And, I'd add that they are only measuring the voltage at THAT particular socket (not the battery) if it is wired on a long run with thinnish wires it could easily be a volt or two lower than the battery voltage, it depends what else is on the circuit.

[MtB]

1 hour ago, Alan de Enfield said:

 

And, I'd add that they are only measuring the voltage at THAT particular socket (not the battery) if it is wired on a long run with thinnish wires it could easily be a volt or two lower than the battery voltage, it depends what else is on the circuit.

 

 

Or more accurately, it depends on what else is in use at the time on that circuit. 

[ditchcrawler]

On 04/10/2022 at 08:57, Tony Brooks said:

Apart from the fact that they are VOLTMETERS I would not trust their accuracy unless compared with readings from a calibrated multimeter. However, they are, in my view, fine for a quick glance to say get a VERY ROUGH idea about the degree of battery charge, or perhaps faults on the circuit it is connected to.

I have one and its a good indication an LED light is about to fail, the indicated voltage goes all over the place in both directions.