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HiFi buzz when running off inverter - any electrical whizzes on here?


Woodfern

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Hi all, new and very confused boater here

 

Set up my hifi on my new (to me) boat and instantly noticed, before it was even turned on, that there was a high pitched buzzing sound which seems to come from the internal PSU

 

The buzz comes through the speakers when the volume is turned up, whether or not any input is plugged in. It gets quieter if I touch the back of the amp enclosure but does not go away completely.

 

I thought it could be a faulty amp, but have noticed that other items (Laptop charger, games console) also produce a similar buzz when connected to the inverter whether or not powered on. The inverter is old, possibly as old as the boat (2001) and think it's modified sine wave rather than pure. Could this be the source of my issues?

 

Just to add to the fun: When a record player is connected and grounded to the amp case, the buzz is much louder than the other inputs (which I understand). However, if you bring your finger closer to the tone arm, the buzzing gets louder like some sort of bizarre static theramin. If you then touch the tone arm, it usually drops down to the level of the other inputs. This part has me most stumped of all but may be a query for the A/V fora rather than here!

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10 minutes ago, Chewbacka said:

If it is a modified sine wave it will have a lot of noise that could be picked up by the amp.  The other problems sound like a bad Earth.  Is your inverter neutral Earth bonded, and is the inverter Earth connected to the boat hull?  

 

It is the inverter - I just tried it with the engine running and there is no buzz. Would that problem be solved/greatly reduced by replacing with pure sine wave?

 

I have no idea how the inverter is earthed I'm afraid, and the boat doesn't have a wiring diagram! How could I check this?

 

With the engine running, there is no buzz at all from any input including the record player, except if you touch the tone arm and then there is...

12 minutes ago, Tony Brooks said:

Any chance it's NOT a pure sine wave inverter?

Yes, I think it's modified. It's a Trace Engineering DR series V 3.2 - seems to be a 1998 design.  Manual shows a modified sine wave

Edited by Woodfern
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2 minutes ago, Woodfern said:

 

It is the inverter - I just tried it with the engine running and there is no buzz. Would that problem be solved/greatly reduced by replacing with pure sine wave?

 

I have no idea how the inverter is earthed I'm afraid, and the boat doesn't have a wiring diagram! How could I check this?

 

With the engine running, there is no buzz at all from any input including the record player, except if you touch the tone arm and then there is...

Yes, I think it's modified

 

1. Some power supplies converting 12V to a higher voltage, like a car computer supply,  do buzz when working with low battery voltage. That suggest that you may do well to measure the battery voltage and check the cable size to any 12V outlets.

 

2. MSW inverters tend to produce a load of harmonic frequencies superimpose on the supply. These can make equipment buzz, so changing to a PSW may well solve the problem but there is still the question of earth loops etc.

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1 minute ago, Tony Brooks said:

 

1. Some power supplies converting 12V to a higher voltage, like a car computer supply,  do buzz when working with low battery voltage. That suggest that you may do well to measure the battery voltage and check the cable size to any 12V outlets.

 

2. MSW inverters tend to produce a load of harmonic frequencies superimpose on the supply. These can make equipment buzz, so changing to a PSW may well solve the problem but there is still the question of earth loops etc.

Thanks Tony.

 

The boat's set up is a bit unusual - it all runs off 24v and so has no 12v circuit or outlets. The lighting and the pumps etc. are 24v, and all domestic sockets are run off the inverter. Are you saying that where the batteries are discharged this could cause the inverter to buzz?

 

Also, If there is an earth loop causing or adding to the buzz, how come this goes away when the 230v circuit is being powered off the alternator?

 

Thanks and sorry if these are stupid questions. I really know nothing about this as you can tell

 

 

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1 minute ago, Woodfern said:

Thanks Tony.

 

The boat's set up is a bit unusual - it all runs off 24v and so has no 12v circuit or outlets. The lighting and the pumps etc. are 24v, and all domestic sockets are run off the inverter. Are you saying that where the batteries are discharged this could cause the inverter to buzz?

 

Also, If there is an earth loop causing or adding to the buzz, how come this goes away when the 230v circuit is being powered off the alternator?

 

Thanks and sorry if these are stupid questions. I really know nothing about this as you can tell

 

 

 

Yes, an inverter may buzz at low voltage, in fact they may buzz at any voltage. The fact it stops buzzing when the batteries are on charge and therefore at up to about 28.8 volts suggests yours does buzz at lower voltages.

 

Earth loops relate to audio equipment, not inverters (I think). Not my specialist area, but some on here who are.

 

How are you monitoring the battery state of charge?

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3 minutes ago, TheBiscuits said:

 

Have you got a TravelPower as well as an inverter?

 

Yes, I do. As I understand it, the battery charger/inverter bypasses itself when the TravelPower is on and the batteries are charging, and connects the TravelPower (or shore mains) directly to the 230v circuit

 

1 minute ago, Tony Brooks said:

 

Yes, an inverter may buzz at low voltage, in fact they may buzz at any voltage. The fact it stops buzzing when the batteries are on charge and therefore at up to about 28.8 volts suggests yours does buzz at lower voltages.

 

Earth loops relate to audio equipment, not inverters (I think). Not my specialist area, but some on here who are.

 

How are you monitoring the battery state of charge?

 

does the fact that it's a TravelPower and the inverter is bypassed make a difference to this Tony?

 

I put a shunt in to monitor the battery state of charge. Right now having just turned the engine off it's showing 94% charge and 25.9V under a 50W load. I understand this may be a bit high since it's just come off charge, but it should still be pretty full and the buzz is the same as usual

 

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1 minute ago, Woodfern said:

 

Yes, I do. As I understand it, the battery charger/inverter bypasses itself when the TravelPower is on and the batteries are charging, and connects the TravelPower (or shore mains) directly to the 230v circuit

 

 

does the fact that it's a TravelPower and the inverter is bypassed make a difference to this Tony?

 

I put a shunt in to monitor the battery state of charge. Right now having just turned the engine off it's showing 94% charge and 25.9V under a 50W load. I understand this may be a bit high since it's just come off charge, but it should still be pretty full and the buzz is the same as usual

 

 

No idea, but the Travelpower is more likely to produce a PSW than an old or cheap inverter.

 

Shunt, Monitor, what is the monitor, do you understand how to use and look after it? It may be telling lies on certain scales. A fully charged 24 volt battery bank will read around 26.4 volts when fully charged, rested, and just off charge would read rather higher than that. Any voltage measured under a load is not a reliable indicator of battery state of charge. You need the rested voltage off load for that.

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2 minutes ago, Tony Brooks said:

 

No idea, but the Travelpower is more likely to produce a PSW than an old or cheap inverter.

 

Shunt, Monitor, what is the monitor, do you understand how to use and look after it? It may be telling lies on certain scales. A fully charged 24 volt battery bank will read around 26.4 volts when fully charged, rested, and just off charge would read rather higher than that. Any voltage measured under a load is not a reliable indicator of battery state of charge. You need the rested voltage off load for that.

 

I think I do yes - the shunt measures the current going in and out, against a 'fully charged' reference point that it locates when the charger goes into float? I know it's not reliable if it hasn't got up to float in a while. The solar sometimes tricks it into thinking it's full when it's not, by happening to produce the float voltage and a low current

 

I'll try fully charging and then see if that makes a difference to the buzz

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15 minutes ago, Woodfern said:

Yes, I do. As I understand it, the battery charger/inverter bypasses itself when the TravelPower is on and the batteries are charging, and connects the TravelPower (or shore mains) directly to the 230v circuit

 

That's why you lose the buzz when the engine is running, so I suspect the buzz is entirely down to your inverter.

 

Switch off the TravelPower and try again with the engine running and I predict you'll still get the buzz when the 230v is coming from your inverter.  Tony's not wrong about some kit doing it more at lower battery voltages, but I reckon you have a noisy inverter.

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So make and model of this monitor?

 

Going into float means nothing in respect of battery monitoring or state of charge. It should be monitoring the tail current and re-setting itself when that has dropped to a certain value. Unfortunately, many are factory set to 4% or 6% of battery capacity that you need to tell it, but that is far from fully charged.0.5% to 1% is a better value.

 

Too many chargers, alternator controllers and solar chargers do what is known as adaptive charging and drop into float too early.

2 minutes ago, TheBiscuits said:

 

That's why you lose the buzz when the engine is running, so I suspect the buzz is entirely down to your inverter.

 

Switch off the TravelPower and try again with the engine running and I predict you'll still get the buzz when the 230v is coming from your inverter.  Tony's not wrong about some kit doing it more at lower battery voltages, but I reckon you have a noisy inverter.

 

So do I, and at present  suspect undercharged batteries as well.

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5 minutes ago, Tony Brooks said:

So make and model of this monitor?

 

Going into float means nothing in respect of battery monitoring or state of charge. It should be monitoring the tail current and re-setting itself when that has dropped to a certain value. Unfortunately, many are factory set to 4% or 6% of battery capacity that you need to tell it, but that is far from fully charged.0.5% to 1% is a better value.

 

Too many chargers, alternator controllers and solar chargers do what is known as adaptive charging and drop into float too early.

 

So do I, and at present  suspect undercharged batteries as well.

 

It's a Victron 'SmartShunt'. The tail current is set to 4% as default as you suspected. I will adjust this as you suggest and do a full charge, then try again

 

17 minutes ago, TheBiscuits said:

 

That's why you lose the buzz when the engine is running, so I suspect the buzz is entirely down to your inverter.

 

Switch off the TravelPower and try again with the engine running and I predict you'll still get the buzz when the 230v is coming from your inverter.  Tony's not wrong about some kit doing it more at lower battery voltages, but I reckon you have a noisy inverter.

 

Just tried this and you're exactly right.

 

So it's a new inverter then. Nice and cheap fix... would it be possible to have a separate, small PSW inverter just for the hifi to save money? The old MSW one works fine for everything else and I'm loathe to mess around with something that works given my general ineptitude!

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1 minute ago, Woodfern said:

So it's a new inverter then. Nice and cheap fix... would it be possible to have a separate, small PSW inverter just for the hifi to save money? The old MSW one works fine for everything else and I'm loathe to mess around with something that works given my general ineptitude!

 

It is possible, but reasonably priced PSW inverters are available ...

 

I recommend these ones quite often, good value for money from a real business rather than cheap kit from an unknown seller online.

 

https://www.sunshinesolar.co.uk/Category/PureSineWave24V

 

For others reading, they do 12v kit as well but the OP needs a 24v one.

 

 

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1 minute ago, TheBiscuits said:

 

It is possible, but reasonably priced PSW inverters are available ...

 

I recommend these ones quite often, good value for money from a real business rather than cheap kit from an unknown seller online.

 

https://www.sunshinesolar.co.uk/Category/PureSineWave24V

 

For others reading, they do 12v kit as well but the OP needs a 24v one.

 

 

 

Thanks - these are cheaper than I expected.

 

I would probably need an inverter/charger in one though as that's what I currently have, unless it's easy to rewire to have separate inverter and charger

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2 minutes ago, Woodfern said:

 

Thanks - these are cheaper than I expected.

 

I would probably need an inverter/charger in one though as that's what I currently have, unless it's easy to rewire to have separate inverter and charger

 

It has more redundancy if you buy separates. If one fails, you still have the other working. How easy it is depends upon your understanding or mains wiring, but it is likely to require a new cable run from distribution box to the charger.

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Just now, Woodfern said:

 

Thanks - these are cheaper than I expected.

 

I would probably need an inverter/charger in one though as that's what I currently have, unless it's easy to rewire to have separate inverter and charger

 

If your combi has an off switch for the inverter part then you should be able to keep it as a charger and only have one inverter wired into the cabling.  Check the manual first, but I'd strongly  recommend physically disconnecting the mains output wiring from it if adding a separate inverter - you really must not have two inverters wired on the same circuit*.

 

[*Pedant footnote: unless they are special ones designed and wired for exactly this task - most are not, so don't try this at home ...]

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4 minutes ago, Tony Brooks said:

 

It has more redundancy if you buy separates. If one fails, you still have the other working. How easy it is depends upon your understanding or mains wiring, but it is likely to require a new cable run from distribution box to the charger.

 

That makes sense

 

3 minutes ago, TheBiscuits said:

 

If your combi has an off switch for the inverter part then you should be able to keep it as a charger and only have one inverter wired into the cabling.  Check the manual first, but I'd strongly  recommend physically disconnecting the mains output wiring from it if adding a separate inverter - you really must not have two inverters wired on the same circuit*.

 

[*Pedant footnote: unless they are special ones designed and wired for exactly this task - most are not, so don't try this at home ...]

 

Ok, will have a look to see if this is possible. Can you have 2 separate inverters running off the same source but to different outputs, just not 2 with their outputs to the same circuit?

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1 hour ago, Woodfern said:

 

That makes sense

 

 

Ok, will have a look to see if this is possible. Can you have 2 separate inverters running off the same source but to different outputs, just not 2 with their outputs to the same circuit?

 

It's a bad idea, but technically possible.

 

@cuthound recently told us that it's best to have at least two metres of separation between each circuit so you can't get about 400v shocks.  2m separation is tough to do inside a narrowboat!

 

It's all to do with different phases from the two circuits, and if if you don't understand that concept stick with the "don't try this at home!"

 

 

 

Edited by TheBiscuits
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19 minutes ago, Woodfern said:

 

It's a Victron 'SmartShunt'. The tail current is set to 4% as default as you suspected. I will adjust this as you suggest and do a full charge, then try again

 

 

So it is an amp hour counter and as such the % charged can not be relied upon, but Ah out can be as can volts and amps.

 

There are too many variables for the inbuilt compensation to be correct, so please stop using the % charged read out (read the "Inverter issues" topic). Learn to use tail current at 28.8V  to decide when the batteries are fully charged and rested voltage to assess the state of charge. Once you get the hang of using rested voltage, you can combine the state of charge inferred from that plus the Ah out since fully charged to infer the actual battery capacity that is very unlikely to be what is written on the label. This will help make the % charged a little less inaccurate for a while.

 

 

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5 minutes ago, TheBiscuits said:

 

It's a bad idea, but technically possible.

 

@cuthound recently told us that it's best two have at least two metres of separation between each circuit so you can't get about 400v shocks.  2m separation is tough to do inside a narrowboat!

 

It's all to do with different phases from the two circuits, and if if you don't understand that concept stick with the "don't try this at home!"

 

 

Ha ok - duly noted. I will not be attempting this!

 

4 minutes ago, Tony Brooks said:

 

So it is an amp hour counter and as such the % charged can not be relied upon, but Ah out can be as can volts and amps.

 

There are too many variables for the inbuilt compensation to be correct, so please stop using the % charged read out (read the "Inverter issues" topic). Learn to use tail current at 28.8V  to decide when the batteries are fully charged and rested voltage to assess the state of charge. Once you get the hang of using rested voltage, you can combine the state of charge inferred from that plus the Ah out since fully charged to infer the actual battery capacity that is very unlikely to be what is written on the label. This will help make the % charged a little less inaccurate for a while.

 

 

 

Thanks for the advice Tony, I will start doing as you have advised

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Thanks all for the helpful diagnosis and advice. I think I will probably end up replacing the inverter/charger with separates as the inverter part can't be turned off according to the manual.

 

If I do this, would it still be possible for the inverter to be bypassed when the Travelpower is on?

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13 minutes ago, Woodfern said:

I think I will probably end up replacing the inverter/charger with separates as the inverter part can't be turned off according to the manual.

 

Try the installation manual not the operator manual ...

 

https://www.manualslib.com/manual/1644904/Trace-Engineering-Sw-Series.html?page=30#manual

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