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Robin2

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Posts posted by Robin2

  1. Do they really?

     

    Oh, and here was silly me thinking they used energy to overcome hysteresis losses and eddy current losses in the core. Both of which I thought should be equally balanced with the resistive losses in a correctly designed motor. I also thought there were hysteresis and eddy current losses in the surrounding metalwork.

     

    But what do I know? Thank you for educating me.

     

     

     

    Again, really?

     

    Silly old me thought you could only build a lossless superconducting electromagnet with DC.

     

    I'm learning so much from you tonight.

     

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

  2. What part of that don't you want to happen?

     

    The Solar has raised the charge on the batteries so that the alternator has to work less hard to finish off the charging.

     

    Why is that a bad thing?

     

    Tony

     

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

  3. Jeez...

     

    A motor needs magnets to operate. The electromagnet then has something push against. That's how motors work.

     

    In most small DC motors, those magnets are permanent magnets. In terms of energy they are free, they don't use any energy.

     

    Sounds like it would be a good idea to replace the coils on the armature with permanent magnets also !

     

    In AC motors they are electromagnets. In terms of energy they are not free, they use energy.

     

    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.

  4. and you got replies by people with these boats who told you what their use was but you choose to dismiss them as unconvincing suggestions.

     

    As it happens who cares what they were originally used for. On the SH boats they are purely decorative along with the stick on rivet heads and it seems the builder cant even decide which way he likes them fitted for best decorative effect.

     

    Maybe Alan Fincher could look at his copy of the Bargee again coz I seem to have a dim memory of them being tied upto the wharf using the ring while loading or unloading "barrels, lemon peel"

     

    but then it would be pointless posting yet another picture of it because it still wont convince you. apparantly

     

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

  5. You have taken account that the panels during the day have input amp hours so maybe the batts are better than they were before solar with loads masking the true voltage at engine start up? :cheers:

     

    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,

  6. I don't believe you.

     

    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

  7. Re-read what I wrote.

     

    This is the root of your confusion. If you put a high voltage on a battery, the battery will dictate a high current. If you have somehow got a low current going into a battery then either you have a low voltage or the battery is fully charged.

     

     

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

  8. You're not making much progress here are you!

     

    Most low to medium power DC motors have permanent magnets. Most AC motors have electromagnets. So before you even do anything flash like making the rotor spin round, the AC motor instantly has an efficiency disadvantage because it has to use power to make some magnets.

     

    I hope you are not suggesting that magnets supply energy !

  9. This is the root of your confusion. If you put a high voltage on a battery, the battery will dictate a high current. If you have somehow got a low current going into a battery then either you have a low voltage or the battery is fully charged.

     

    You can control the voltage across the battery or you can control the current through the battery. You cannot control both. You control one, the battery dictates the other.

     

    Therefore a high voltage, low current charge simply isn't possible unless the batteries are full anyway.

     

    Ah ... but a solar panel is bit like a constant current source ...

     

    OK, this is what happens on my boat. Let's say that in the morning my batteries might be reading over 13 V because the solar panel is charging them. They are still far from fully charged. I start the engine and it starts charging at a current I would expect from the state of charge - say 50+ amps.

     

    Mine doesn't seem to be behaving like that.

  10. How do you know it's upside down if you don't believe what people tell you they are for?

     

    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?

  11. Pick a number, let's have 65...

     

    Start at 65% SOC at 5 O'clock in the morning. Sun rises, solar panels start to put a little bit of power into the batteries. Battery voltage rises slightly. 9 O'clock comes, batteries have increased to 68% SOC. You start your engine and the alternator kicks in putting in as much as either it can produce or as much as the batteries will accept (it doesn't matter which).

     

    Now do the same thing, but switch the solar panels off so they do nothing. Start the engine at 9 O'clock and the charge rate will probably be a tiny bit higher, simply because the batteries are starting from 65% instead of 68%. When you get to 68% stop the engine.

     

    Now restart the engine. Is this starting point of 68% somehow different from the starting point of 68% in the first example? If it is then you can expect a different charge rate from the engine. But how can it be different?

     

    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 Steca charger stops putting anything in from the panels when an alternative charging method comes into play, engine or mains charger. I just leave it all to get on with it now and just keep an eye on the Smartgauge for battery state.

     

    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.

  12. OK...

     

    What do DC motors have that AC motors don't?

    What does this do?

    How is this provided in AC motors?

    What does providing the same in AC motors entail?

     

    cheers,

    Pete.

     

    You are not being very helpful!

     

    Are you auditioning for the job of quizzmaster?

  13. No. No one will notice it. Anyone who does notice it, is imagining things.

     

     

    I would very much appreciate it if you would explain where my understanding is faulty.

     

    Not being technical I'm not sure how much this would affect the charging. However if you're using solar and getting some charge at 9am and it's a nice day, then why run your engine unless you have to cruise or you're short of power.

     

    My panels are meeting my demand during the day time but they are not producing enough extra to cover the night time electricity use.

  14. 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?

  15. As you discount every response you don't like, why not write/e-mail Hudson and ask him. None of us will convince you.

     

    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 ..."

  16. Please can someone check my calculations and reasoning?

     

    I have a 0-100A moving-coil ammeter measuring the output from my alternator via a shunt. The shunt was supplied as matching the meter.

     

    I want to use this meter to measure the output from my newly-installed solar panel when the engine isn't running. Clearly, 100A FSD is a bit OTT for a panel, so the plan is to use a suitable shunt to scale it to 0-10A.

     

    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.

  17. Hi all. Planning on going up the Wigan flight in Sept. Had a look on Google Earth. It looks GREAT!!!

     

    What's the best way of setting locks above the flight so you can leave one lock and move straight into the next lock.

     

    In my first year of boating this seemed to be a matter for concern and planning.

     

    Now I just deal with locks when I get to them - I may be slower but what does that matter.

     

    Going up the Bosley locks recently several other boats were very helpful but the result was I went up too quickly and didn't get a chance to look around.

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