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?