There goes battery charger number 3!

[stranded]

Update - and another question.

Just before I had to leave the boat I discovered that one of the two solid connecting rods in the ammeter shunt had sheared and was making very little contact, and intermittently, perhaps none. I didn't have time to investigate the setup fully (everything I do involves much googling) but assume it is on the negative side of the service batteries as that seems most common. Anyway, I removed the shunt from the circuit and the problem of the engine starter drawing on the domestic bank seemed to be resolved. I daren't connect my latest charger without disconnecting all loads, which I have done, but at some point I am going to have to bite the bullet and connect it up when fully loaded.

So the question is, from this rubbish description, it it possible that the dodgy shunt could cause three different modern chargers to blow, and if so, how did the multiple alleged protections they supposedly contain not work?

 

[mihtjel]

Going from your descriptions, they DID work: none of them exploded or caught fire!

It might well be that the faults are repairable, for example if it's simply overvoltage protection or an output capacitor that's blown.

 

[Rivers & creeks]

There is also the power of coincidence, a huge and terrifying force that humans always seek to explain away. Or a dead short that you haven't found yet.

 

[stranded]

Going from your descriptions, they DID work: none of them exploded or caught fire!

It might well be that the faults are repairable, for example if it's simply overvoltage protection or an output capacitor that's blown.

Well I suppose that's true - although they all smoked! The Mastervolt Mass Combi is still with Mastervolt being investigated, and the Ctek winging its way back to Sweden, though their technical people thought it was probably terminal. I interpret protection as something which avoids back to manufacturer damage, even if reparable.

 

[curiouskb]

I had a similar problem. Turns out if the boat supply switch is set to generator and the generator is started it initially spikes around 400 volts blowing capacitors in the battery charger. The genny is a Fischer Panda.

Interesting indeed. My boat is only 18 months old with an 9K Onan generator and last week the Mastervolt 60 amp charger just suddenly gave up its ghost. Dealer just replaced it under warranty and could found no problem. Would like to ask : is it necessary always to turn off the battery charger first before starting the generator to avoid the voltage spikes as suggested above? I am on a swing mooring with no shore power. Thanks.

 

[RichardS]

Update - and another question.

Just before I had to leave the boat I discovered that one of the two solid connecting rods in the ammeter shunt had sheared and was making very little contact, and intermittently, perhaps none. I didn't have time to investigate the setup fully (everything I do involves much googling) but assume it is on the negative side of the service batteries as that seems most common. Anyway, I removed the shunt from the circuit and the problem of the engine starter drawing on the domestic bank seemed to be resolved. I daren't connect my latest charger without disconnecting all loads, which I have done, but at some point I am going to have to bite the bullet and connect it up when fully loaded.

So the question is, from this rubbish description, it it possible that the dodgy shunt could cause three different modern chargers to blow, and if so, how did the multiple alleged protections they supposedly contain not work?

I would have thought that a shunt with a dodgy connection would simply have caused the ammeter to read incorrectly, although it has presumably been protected from being burned out by the second shunt.

Richard

 

[boatmike]

I would have thought that a shunt with a dodgy connection would simply have caused the ammeter to read incorrectly, although it has presumably been protected from being burned out by the second shunt.

Richard

If I read the post correctly one of the through current connection bars of the shunt itself had partly broken not the small connections to it that the ammeter is connected to. Am I reading that correctly? This would create a high resistance in the main current line if totally broken but if touching intermittently would at the least cause spikes in the current flow. Not sure if this would cause the battery chargers to blow but may well explain the low voltage to the starter motor if the shunt is connected to a common earth. If (as imho it should be) the shunt is on the service battery ground only this would not be so of course but it could well have contributed to the problem so don't rule it out.

 

[RichardS]

If I read the post correctly one of the through current connection bars of the shunt itself had partly broken not the small connections to it that the ammeter is connected to. Am I reading that correctly? This would create a high resistance in the main current line if totally broken but if touching intermittently would at the least cause spikes in the current flow. Not sure if this would cause the battery chargers to blow but may well explain the low voltage to the starter motor if the shunt is connected to a common earth. If (as imho it should be) the shunt is on the service battery ground only this would not be so of course but it could well have contributed to the problem so don't rule it out.

You could well be right. I'm not clear what the OP is describing but am simply deducing that if an ammeter shunt is disconnected then all the current flows through the ammeter. rather than through the shunt. This might be curtains for the ammeter but the OP appears to have a second shunt.

Richard

 

[stranded]

If I read the post correctly one of the through current connection bars of the shunt itself had partly broken not the small connections to it that the ammeter is connected to. Am I reading that correctly? This would create a high resistance in the main current line if totally broken but if touching intermittently would at the least cause spikes in the current flow. Not sure if this would cause the battery chargers to blow but may well explain the low voltage to the starter motor if the shunt is connected to a common earth. If (as imho it should be) the shunt is on the service battery ground only this would not be so of course but it could well have contributed to the problem so don't rule it out.

Yes, it's one of two solid heavy duty connecting rods that has sheared. Not sure on the common ground point, but now I have removed the shunt ammeter now reads the maximum on the gauge - i.e not zero, as this numpty would have expected. Not sure whether this is in any way relevant, but It has never measured amps in, only amps out. Also, if relevant, the voltmeter was showing flaky values which were unstable and fifty percent of the time wildly wrong (under-reading) for both the engine and service batteries. That seems to have corrected itself now.

 

[RichardS]

Yes, it's one of two solid heavy duty connecting rods that has sheared. Not sure on the common ground point, but now I have removed the shunt ammeter now reads the maximum on the gauge - i.e not zero, as this numpty would have expected. Not sure whether this is in any way relevant, but It has never measured amps in, only amps out. Also, if relevant, the voltmeter was showing flaky values which were unstable and fifty percent of the time wildly wrong (under-reading) for both the engine and service batteries. That seems to have corrected itself now.

As mentioned in post #28, you will probably burn out the ammeter if the shunt is left disconnected. Even if it doesn't burn out, it will never read the correct value.

Richard

 

[stranded]

As mentioned in post #28, you will probably burn out the ammeter if the shunt is left disconnected. Even if it doesn't burn out, it will never read the correct value.

Richard

Even though I have disconnected the little wires that run from the shunt to the ammeter? I had just assumed that the way it worked (it is a swinging needle type) must mean that when it is not connected it rests at maximum rather than zero - you think it is because it is actually measuring a huge current by some other means?

 

[RichardS]

Even though I have disconnected the little wires that run from the shunt to the ammeter? I had just assumed that the way it worked (it is a swinging needle type) must mean that when it is not connected it rests at maximum rather than zero - you think it is because it is actually measuring a huge current by some other means?

Now that is curious! If you have also disconnected the one of the 2 small cables that run to the back of the ammeter then the ammeter should read zero. I have never heard of an analogue ammeter which will read maximum deflection/current when it is disconnected. Even a zero-centre ammeter returns to the zero resting position when disconnected. Something is not right.

I should add that it is not necessarily reading a huge current ..... it could be a small current as without the shunt the scale on the ammeter is meaningless.

Richard

 

[stranded]

Now that is curious! If you have also disconnected the one of the 2 small cables that run to the back of the ammeter then the ammeter should read zero. I have never heard of an analogue ammeter which will read maximum deflection/current when it is disconnected. Even a zero-centre ammeter returns to the zero resting position when disconnected. Something is not right.

I should add that it is not necessarily reading a huge current ..... it could be a small current as without the shunt the scale on the ammeter is meaningless.

Richard

Thanks Richard - think I had better get back down to Nooka and investigate further - I thought I had left her safe!

 

[RichardS]

Thanks Richard - think I had better get back down to Nooka and investigate further - I thought I had left her safe!

Just to be sure, I assume that normally when you leave the boat with all the battery switches "off" the ammeter needle falls over to the left and reads zero?

If you've now left the boat, and presumably turned off the same switches, but the ammeter needle is over to the right and reading 10 amps or whatever (although it's not actually 10 amps because of the disconnected shunt), then a current is possibly still flowing.

An alternative explanation is that you have, unfortunately, overloaded the ammeter by disconnecting the shunt and it has burned out with the needle jammed on full deflection. You might be able to give it a tap and see if it flicks back. However, even it it does, it will not be useable again. The acid test is if you remove one of the connections directly from the back of the meter itself so there is no possibility of a stray current. If it still show max deflection then it has burned out I'm afraid.

Having said all that, the dodgy shunt could well be part of your overall problem so the ammeter might have sacrificed itself for the greater good. (trying to look on the bright side here, as I think that is the more likely explanation)

Richard

 

[stranded]

Just to be sure, I assume that normally when you leave the boat with all the battery switches "off" the ammeter needle falls over to the left and reads zero?

If you've now left the boat, and presumably turned off the same switches, but the ammeter needle is over to the right and reading 10 amps or whatever (although it's not actually 10 amps because of the disconnected shunt), then a current is possibly still flowing.

An alternative explanation is that you have, unfortunately, overloaded the ammeter by disconnecting the shunt and it has burned out with the needle jammed on full deflection. You might be able to give it a tap and see if it flicks back. However, even it it does, it will not be useable again. The acid test is if you remove one of the connections directly from the back of the meter itself so there is no possibility of a stray current. If it still show max deflection then it has burned out I'm afraid.

Having said all that, the dodgy shunt could well be part of your overall problem so the ammeter might have sacrificed itself for the greater good. (trying to look on the bright side here, as I think that is the more likely explanation)

Richard

Yes, its 0 when the batteries are off - I should have thought of that shouldn't I. But I will happily sacrifice the ammeter if it helps me resolve the underlying problem - I'll try to get a replacement but in any case the 'EasyView' attached to the Mastervolt Bus shows all the info I need when it is working so the ammeter is just for a quick check if needed (and I like analogue devices - want to get an old hi-fi amplifier with those swingy needle things!). Thanks very much for your advice.

 

[boatmike]

Hang on. You said you had removed the shunt. I assumed you meant that you had disconnected the wires that go to the ammeter that were connected to either side of the shunt and than unbolted the shunt itself and connected the cable direct to the battery. If so it cant read anything as it isn't connected to anything ??????

 

[stranded]

Hang on. You said you had removed the shunt. I assumed you meant that you had disconnected the wires that go to the ammeter that were connected to either side of the shunt and than unbolted the shunt itself and connected the cable direct to the battery. If so it cant read anything as it isn't connected to anything ??????

That is what I have done - at the shunt. But I didn't check the back of the meter to see if there are any other feeds into it. So I assume from Richard's posts that either there is another supply to it, or more likely, that I sent a big current to it in the process of removing and have buggered it as Richard suggests. The service batteries are completely disconnected from everything but the CTEK charger which is plugged directly into the shorepower cable - no connection to the boats circuits, so if there is any continuing current it must presumably come from the engine battery, which remains connected, or maybe the thruster battery forward, although that seems unlikely as it is isolated at the battery.

 

[boatmike]

That is what I have done - at the shunt. But I didn't check the back of the meter to see if there are any other feeds into it. So I assume from Richard's posts that either there is another supply to it, or more likely, that I sent a big current to it in the process of removing and have buggered it as Richard suggests. The service batteries are completely disconnected from everything but the CTEK charger which is plugged directly into the shorepower cable - no connection to the boats circuits, so if there is any continuing current it must presumably come from the engine battery, which remains connected, or maybe the thruster battery forward, although that seems unlikely as it is isolated at the battery.

Frankly I think you are being misled by other posts. If this is a simple analogue ammeter it simply reacts to the current in the sensing wires which are now disconnected. Digital ammeters sometimes need a separate power connection but analogues rarely do. There may be other connections for backlight but that's all. I don't know why it shows maximum amps now and suspect that you may well have shorted it or overloaded it and it's now buggered. It is indeed quite possible you have as you should never connect or disconnect an ammeter on a live circuit. Always isolate the battery first. But as you need a new shunt anyway you can simply buy a new matched gauge and shunt. The point is your other problems may well have been caused by the broken shunt so your mystery may be solved.

 

[stranded]

The point is your other problems may well have been caused by the broken shunt.

Thanks Mike - that was indeed my question - could the broken shunt somehow have caused three chargers to burn out despite all the protections they say they contain, and if so, do you have any idea what the mechanism could be. I don't think there was a short as the broken conducting rod remained in place - the shear was barely visible and I only discovered it when I deflected it with my finger. In which case to my simple mind wouldn't the absence of half of the conducting capacity of the shunt simply have limited the current rather than causing a burn out?

In any case, Berthon are now preparing to do a full test of the 240v side of the system - which they have completely rewired in fitting the new charger inverter. But the third charger, the CTEK, burnt out when connected directly to the shorepower lead, not touching the 240v side on the boat. So unless that was a hell of a coincidence, doesn't that mean that the problem is much more likely to be on the DC side? This is already costing me thousands and I am keen to avoid unnecessary diagnostic work if possible!

 

[boatmike]

Thanks Mike - that was indeed my question - could the broken shunt somehow have caused three chargers to burn out despite all the protections they say they contain, and if so, do you have any idea what the mechanism could be. I don't think there was a short as the broken conducting rod remained in place - the shear was barely visible and I only discovered it when I deflected it with my finger. In which case to my simple mind wouldn't the absence of half of the conducting capacity of the shunt simply have limited the current rather than causing a burn out?

In any case, Berthon are now preparing to do a full test of the 240v side of the system - which they have completely rewired in fitting the new charger inverter. But the third charger, the CTEK, burnt out when connected directly to the shorepower lead, not touching the 240v side on the boat. So unless that was a hell of a coincidence, doesn't that mean that the problem is much more likely to be on the DC side? This is already costing me thousands and I am keen to avoid unnecessary diagnostic work if possible!

There is nothing wrong with your logic and the fact that there was a partial break in the direct line to your battery earth on the DC line would indeed be at least a possible cause of your problems. It would mean that there was a high resistance at the least and it is quite possible that the break would cause an intermittent connection which could have caused the voltage to fluctuate.
Can't say with any authority that this would cause the problems you have had but as the battery chargers sense voltage and adjust the charge rate to suit it would certainly cause them to malfunction I would have thought? Again not an authoritative diagnosis but a viable theory perhaps? Is the shunt located on a common ground for both batteries or just the service batteries? As I said earlier, if it is on a common earth (which it shouldn't be) it could account for restricted volts to your starter motor also. Think of it as a bad or corroded contact and it might be easier to visualise.