Ultrasonic antifouling

[jtwebb]

The instructions say it uses 3W or less. This is 0.25A at 12V. This is 6Ah per day, to be supplied by a solar cell if on a mooring. Worst case daylight 9 hours? 50% of that reasonable light, 4.5 hrs? Hence one needs to get 6Ah in 4.5 hours which even at low northern latitudes efficiences should be possible from a 50W cell supplying say 1.5A peak during the day and less for most of it? If the boat is not on a swinging mooring might be able to angle the solar cell to improve efficiency.

 

[davidej]

Well it averaged out at 0.6666666666666 reoccurring according to my excel spreadsheet

So 16Ah per day

Now lets be seriously pedantic :

the word is 'recurring'

-just having fun

 

[Champagne Murphy]

As I shall shortly have a Jaycar store just around the corner I was thinking of giving it a try. What are the latest experiences on effectiveness and current drain?

New store in Cornwall? Any others in the UK? Or is the order still coming direct from Australia?

 

[snowleopard]

New store in Cornwall? Any others in the UK? Or is the order still coming direct from Australia?

No, The store in question is in Melbourne. Looking forward to summer starting in a couple of weeks

 

[nigelmercier]

The instructions say it uses 3W or less. This is 0.25A at 12V. This is 6Ah per day...

May I make a suggestion: that the term Ah be added to the list of swear words that this forum blocks; it causes no end of confusion

It is much easier to simply state the current that a device draws, such as 0.25A above. Even using watts is fraught with danger.

If you think I'm crazy, answer me this: how many Ah does a 120W solar panel give in a day?

 

[elton]

May I make a suggestion: that the term Ah be added to the list of swear words that this forum blocks; it causes no end of confusion

It is much easier to simply state the current that a device draws, such as 0.25A above. Even using watts is fraught with danger.

If you think I'm crazy, answer me this: how many Ah does a 120W solar panel give in a day?

Is it fixed on top of a geostationary satellite, directly facing the sun? Or a boat in Hartlepool in November, behind the flats?

 

[mjcoon]

May I make a suggestion: that the term Ah be added to the list of swear words that this forum blocks; it causes no end of confusion

It is much easier to simply state the current that a device draws, such as 0.25A above. Even using watts is fraught with danger.

If you think I'm crazy, answer me this: how many Ah does a 120W solar panel give in a day?

Of course you may make the suggestion. That doesn't mean it is sensible, though!

The problem for any intermittent device such as a fridge is that both the normal current is significant because the cabling must be adequate, and so is the average current (which for a fridge, or a solar panel, will depend on non-electrical features).

I don't know of any meter that can measure an average current, but maybe there are that will measure Ah or energy (if voltage is sensed as well as current). But surely anyone who is going to discuss electrical matters will/should understand basic ohm's law and the definitions of ampere-hours, watts and so forth? (Adding coulombs to that list might be going too far!)

Mike.

 

[Sybarite]

Back to the original point, so far so good. Launched in Marmaris in the spring, and no barnacles except one on the rudder when I left the boat (still in the water) on 18th October. I did get some fouling at the waterline forward of the mast and mainly to starboard. I then found that the forward transducer, which is to port of centre, was slightly unscrewed, so probably only partly effective. The real test will be the condition of the hull at haul out next October.

I often think that barnacles attached to the propellor must get really dizzy.

 

[nigelmercier]

But surely anyone who is going to discuss electrical matters will/should understand basic ohm's law and the definitions of ampere-hours, watts and so forth? ...

Sadly, this is not the case; even in magazine articles. I'm not knocking those who don't understand, just that a lot of nonsense gets spouted as advice.

 

[mjcoon]

fine except ohms law doesn't work on inductive loads - like a fridge, so we are left with comlpexity

While there are other sorts of fridge (why did I mention that side-issue?) the usual sort I see on yachts has a DC motor drving a pump and thus a constant load. I don't think that the inductive nature of the windings need concern us in this context! There may even be interference-suppression capacitors...

Mike.

 

[DaveS]

While there are other sorts of fridge (why did I mention that side-issue?) the usual sort I see on yachts has a DC motor drving a pump and thus a constant load. I don't think that the inductive nature of the windings need concern us in this context! There may even be interference-suppression capacitors...

Mike.

Are you sure about this? My understanding is that a hermetically sealed compressor contains an AC motor, i.e. it is a standard mains voltage off the shelf product, and that the black box with the wiring terminals contains an inverter.

 

[mjcoon]

Are you sure about this? My understanding is that a hermetically sealed compressor contains an AC motor, i.e. it is a standard mains voltage off the shelf product, and that the black box with the wiring terminals contains an inverter.

You could well be right; I shall ask next time we have to have a fridge looked at during a fortnight's charter (it's happened!).

None of that has any relevance to the drain as seen in the DC circuit. Presumably the inverter is itself switched-mode and not very sinusoidal...

Mike.

 

[DaveS]

Presumably the inverter is itself switched-mode and not very sinusoidal...

Mike.

Don't know, and as the 230V wiring is not readily accessible it isn't possible to easily investigate. I would have thought, however, that a close approximation to a sine wave would be beneficial to minimise heating of the motor winding. It can certainly be done: I've put a scope on the output of my Kipor inverter generator and, while not a perfect sine, it's pretty close. A huge improvement over the "double square wave" produced by the wee El Cheapo inverter I keep on board.

 

[Champagne Murphy]

No, The store in question is in Melbourne. Looking forward to summer starting in a couple of weeks

Jammy Snow leoparD!

 

[jtwebb]

I fail to see where the confusion comes from. The use of standard units should not be a problem. Confusing simple concepts with questions about how much power does one get from a solar cell is pointless.

 

[xxyyzz]

I fail to see where the confusion comes from. The use of standard units should not be a problem. Confusing simple concepts with questions about how much power does one get from a solar cell is pointless.

Yes, why not a watt?

 

[Monique]

My GF always asks why i laugh when reading you lot..

We suffered a dread thrift here

My electronic bug repulsor is now going to Coppercoat just like Snooks

thanks Ewan!