Robin2

I'm delighted. Let me know if I can help some more.

The impression I have is that the increased voltage is just superficial and does not reflect extra amp-hours that have been added.

Sounds like it would be a good idea to replace the coils on the armature with permanent magnets also ! They only consume energy due to heating losses in the coil. If you had superconductors they wouldn't use energy. If we start discussing the practical inefficiencies in different types of motor the list for DC motors will be as long as for any other type.

I thought that people with historic boats cared, but if that's the general feeling I will turn my attention to something else.

That's an interesting thought. A lot more useful than the answers from the resident expert! Part of the problem is that I don't like to get up sufficiently early to measure voltages in the dark. As the seasons march on this will be less of a problem,

Let me try again... Overnight the fridge laptop etc consume 30Ah. Before I got the solar panels the battery voltage at 9am was about 12.2 to 12.3 volts. The charge current from the alternator then started at about 40A and declined from that. Early in the morning the solar panels produce, say, 2A most of which is consumed by the inverter but some goes into the battery - say 0.5A for an hour or so. That seems to be enough to raise the battery voltage to 12.6 / 12.8 volts and the alternator charge current starts at only 15 to 20 amps. I am wondering if anyone else has experienced this, and if not, what might I be doing wrong. An answer that takes more than 4 words would be much appreciated

If they don't supply energy (and they don't) how could magnets improve efficiency?

No. I'm dead serious.

I sort of assumed that people with boats with these bits would already know what they were designed for, or simply say that they don't know. But instead there have been several less than convincing suggestions which I have responded to. What's wrong with that?

So how does the battery make the solar panel produce more than 2 amps even if the solar panel can supply it at 20v?

This arrangement looks more natural - intended for holding something firmly against the cabin wall - but what? Dunno why Tim shouted. I was answering your post

I hope you are not suggesting that magnets supply energy !

Ah ... but a solar panel is bit like a constant current source ... Mine doesn't seem to be behaving like that.

What have magnets got to do with it?

I don't "know". I am just trying to summarize the collective view on this forum based on a picture that somebody posted of an old boat with original fittings that are the opposite way round to the Hudson version. Unless, of course, you think they were a later and incorrect addition to the old boat?

I understand what you have said, but I wonder if it is applicable to the situation where the battery is subjected to a "high" voltage low current charge in the phase that you describe as 65% to 68%. My suspicion is that the solar panels make the battery appear to be as charged as if the engine provided the 65% to 68% charge but they have actually not put anything like as many amp-hours into the battery. My point is not about competition between the two charging sources while the engine is running - rather it is about the effect the solar panels have in the period before you start the engine.

You are not being very helpful! Are you auditioning for the job of quizzmaster?

Its Practical Boat Owner that does the techy stuff - but they don't have a Smartgauge expert

I would very much appreciate it if you would explain where my understanding is faulty. My panels are meeting my demand during the day time but they are not producing enough extra to cover the night time electricity use.

From my limited experience with my solar panels there seems to be one downside that I have not seen mentioned elsewhere. I think it is generally accepted that when a battery is being charged the initial charge settles on the surface of the plates raising the apparent voltage and you have to leave the batteries disconnected for several hours to allow that charge to diffuse into the plates by which time the voltage will have fallen to the "proper" level for that state-of-charge. Without solar panels the batteries get partially depleted over night and when you start the engine to charge them they can take a good current for a reasonable period of time which makes good use of your charging fuel. However when you have solar panels they will have put a little bit of charge into the batteries by 9am and in the course of doing so will have raised the voltage on the battery plates considerably more than tiny improvement in SOC would justify. Then when you run the engine the batteries only accept a much smaller current which significantly increases the fuel cost per amp-hour. Has anyone else noticed this?

You should know by now that they are not going to give in!

I thought it was accepted here that the Hudson version is upside down - which is not much of a recommendation for his advice. I will be convinced when someone comes up with an answer that is supported by historical evidence or by engineering and operational logic. What's the point in being satisfied with answers like "well I use it for ..."

The web page you referred to is about the efficiency of control systems !

What about buying a cheap digital multimeter that can measure 10amps - £6 ? ETA (because I have been thinking of this subject for myself) what you really need with solar panels is an amp-hr counter because the amps can fluctuate so much that instantaneous readings on an ammeter are no more than interesting reassurance.