Gibbo

I think that's probably not a bad idea. If it was thought out properly (i.e. with input from lots of industry insiders, qualified engineers, the BMEA, BMIF, ABYC etc etc etc) and I mean properly, not like the half baked ideas that came as a result of the RCD and CE then it could well work. Gibbo I think if it was done properly, and your installation is as good as your posts seem to indicate it is, then you have nothing to fear. It would probably fall perfectly within one of the "categories" of different installations. Gibbo

Indeed. It can get confusing. For everyone. On the one hand there is the natural logic saying "we want the GI to conduct at the lowest voltage possible without causing galvanic corrosion". Hence *most* GI's start to conduct at 1.2 volts. But why? What is the *real* reason behind this? Is it just how they evolved? A lot of later ones are not starting to conduct until (as you state) 2.4 volts. It certainly makes monitoring a lot easier. What is wrong with a GI that conducts at say 10 volts? or even 20 volts? Perhaps even higher? Like almost everything to do with electrickery, what starts out out as a really simply problem to be cracked ends up incredibly compicated when *everything* is taken into consideration. It's a minefield. Gibbo

I'd be interested to see it. Just out of curiosity. And of course I can let you know whether what they say is correct (which I can only assume it is in these days of litigation for everything). But I doubt they'll give it to you! Thing is, unless the monitoring circuit has an external power supply, it's actually far from a trivial task to light an led from 0.8 volts. It can be done, obviously, but it's nowhere near as simple as it at first appears. Gibbo

PS. I'd like to make it quite clear that I do not sell galvanic isolators. I do not sell isolation transformers. I do not make either. I do not install either. I am in no way connected with either equipment or their distributors, agents, dealers etc etc etc. I have nothing to gain by whichever method is best. This whole subject first came to light to me because my company was contracted by a.n.other to carry out a totally independant study of GIs with regard to modern switchmode power supplies. The results surprised me to say the least. So much so that I now wouldn't touch one with a barge pole. Gibbo

You're halfway to answering your own question. In fact I think you actually know the answer Assume the galvanic cell made by your hull and the quayside produces 0.3 volts. With no AC messing up the GI this will register on the GI meter as 0.3 volts. The GI meter shows the voltage across the GI. It does *not* show the current. But the diodes in the GI will not be conducting so no current flows, therefore no galvanic erosion. With a direct connection (i.e. no GI) this will produce a current that depends upon the resistance of the complete circuit, i.e. from hull through earth bond, back the neutral/earth bond (possibly at substation), back through the ground to the quayside. It is the current that produces the erosion. So with a GI there would be no erosion, as there is no current flow, as the galvanic cell made by the hull, quayside and water doesn't produce enough voltage to "breakdown" the GI. The meter reads the nett DC voltage of 0.3 volts. Now if there is sufficient AC voltage (be it 50Hz or RFI or whatever) so that the GI is forced into almost permanent conduction, the nett DC voltage across the GI remains at 0.3 volts. But as you quite rightly state this is now superimposed on the AC signal. And as the GI is now conducting (due to the AC), the superimposed DC voltage causes a current to flow, which is the galvanic corrosion current. The meter continues to show 0.3 volts which is correct. But there is now a current flowing at DC. So, although you didn't actually say it in your post, yes, you are correct Gibbo That's perfectly feasable and possible. If it does indeed do so then you can rely on them with confidence. But I seriously would have my doubts without making tests and measurements or seeing the schematic. Gibbo

No they don't. They indicate the voltage across the GI. Ok Let's split the GIs into two types. There are those that use an analogue meter with something like "safe" and "Not safe" written on them. These measure the DC voltage across the isolator. You could pass 20 amps of AC through one of these things (which of course would be clipped at the clamping voltage of the GI) and the meter would show exactly zero because the DC voltage of an AC signal is the average, which is zero. But the GI would still be permanently conducting (well 99% or so of the time depending on the AC waveshape an frequency etc). The other types use LEDs. These can be made in various different ways. Some of them would show AC conduction of the GI. Others would not. Without seeing the circuit for the indicator (or actually trying the experiment) it would not be possible to know. Gibbo If you want an idea of how quickly your GI will be rendered useless simply disconnect the earth lead from a class I type apparatus and measure the voltage between neutral and the now disconnected earth on the equipment. You will almost certainly find the earth at around half mains potential. i.e. around 115 volts. That will *certainly* switch on a GI! I don't recommend anyone does this unless they have the knowledge and experience to avoid killing themselves. You're absolutely right, if you have any doubt, use an isolation transformer. Gibbo Me. And I think I have answered it. Gibbo

Well at last I am able to post again. A quick word of warning. The RFI (radio frequency interference) that can cause GIs to conduct thus rendering them useless is, of course, AC. It wouldn't be RFI if it wasn't AC. The meters fitted to GIs to supposedly show when they are doing their job will not register this. They will show an average of the RFI which is, of course, zero. So your GI could be hard into conduction due to RFI and the meter will show precislely nothing giving the impression that all is fine. Gibbo

Ok. As requested I'm here :-) What specific questions do people have? I'd like to make a few statements firstly though. Obviously I'm not about to disclose how SmartGauge works. Anyone who asks me to is being rather unreasonable. 3 years research and a huge amount of money went into the design. I'm not about to give that away. To state that 2 wires can only measure voltage is completely incorrect. To the layman voltage possibly is the only measurment that can be made. To an engineer there are a whole host of other measurements to be got down 2 wires. SmartGauge does not measure battery current. Whilst battery current (in and out) can be an extremely useful piece of information it does not show the state of charge of the batteries. Attempts to calculate the state of charge of the batteries by integrating battery current over time have been made. This is what amp hours counters do. For most people amp hours counters do not work. This isn't speculation. It is a fact. Some people can use amp hours counters very successfully. SmartGauge isn't aimed at those people. It is aimed at people who either cannot use one or cannot be bothered using one. The fact is that amp hours counters can and do run out of synchronisation with the batteries. Once this has happened, they are effectively useless. SmartGauge *does* utilise Peukert's Law. It is a rather large part of the algorithm. But it calculates the required parameters itself. This allows the figures to be automatically adjusted as the batteries age. This does not happen with amp hours counters. SmartGauge incorporates a voltmeter. But it is not *just* a voltmeter. It is far more. I will be more than happy to answer any questions. Except "how does it work" ! Gibbo PS Just to be pedantic...... In actual fact *most* electrical gauges actually measure current! PPS The name is Gibson :-)

I bet it's just the mod to fit the optional external controller. I believe this mod is now standard on Beta engines. Gibbo

I wouldn't trust the part numbers on Iskra alternators. I've seen identical units with different numbers on them. Most of the Beta engines I've seen with Iskras all used the standard AAK series though I have seen some with the AAK compact alternators on them. These may been aftermarket mods. I'm not sure. When I've ordered these alternators I've simply said "AAK series 65 amp" or whatever. Their website has pictures and ratings. http://www.iskra-ae.com/eng/alternators.php Can't be of any further help I'm afraid. Gibbo

I just joined this group sepcifically to reply to this post and some of the responses in this thread. None of the replies are what I would consider to be wrong. But it is quite an involved subject. All the answers the various points raised in this thread are freely availabe here..... Are alternator controllers required? http://www.smartgauge.co.uk/technical1.html#controllers How big should a charger be? http://www.smartgauge.co.uk/technical1.html#charger Increasing alternator voltage http://www.smartgauge.co.uk/tricks1.html#alt_mod This isn't a plug for a company. It just seems easier to paste the links rather than type all the information in again! Gibbo