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MoominPapa last won the day on January 23 2017

MoominPapa had the most liked content!

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About MoominPapa

  • Birthday 12/11/1964

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  1. I think you're right, and now I consider it, there's a third right at the end of the arm, also into the Mill stream. MP.
  2. There's a long overflow weir into Castle Mill stream just above Isis Lock, and given that there's a fall across the top gate in that picture, there must have been some fall left across the weir. Out of interest, next to the weir is the outfall from a pump which runs periodically to dump the surface water from Jericho into the Mill Stream. I imagine that's working quite hard at the moment. MP.
  3. Navigation authority and engineering maintenance organisation turns into pseudo National Trust and then has problems running navigations. Who'da thunk it? MP.
  4. Difficult for me to estimate, especially as I don't (can't) charge at 150A either. When I was doing initial test with a lab power supply and 3.5Ah cells, it was possible to get even deeply discharged cells over 3.6V with a charge current of 3C, so in theory the whole of the charging cycle could be in CV mode with a large enough charge source. It's certainly true that the tail current is the marker for 100% charge. The voltage part of the test is just there to discriminate against the situation where the current drops because a large load is using most of the alternator output, or the alternator is being turned very slowly by an idling engine, or similar. One thing I've found is that using charge termination to re-sync an Ah counter works much better if the charge termination point is consistent. It doesn't matter too much is there are always 10% if the Lithium ions in the wrong place when you declare charge termination, but if there are sometimes 5% and sometimes 15% then that really degrades the accuracy of ongoing SoC determination. Getting consistent charge termination is made more difficult by varying loads on the system, and changes in alternator regulation with engine speed, for instance. MP.
  5. You will, of course, suitably fuse all this spaghetti close to the battery terminals? I'm finding that my 200mA balance system is keeping the cells automatically balanced without any messing around. If I need to manually balance, I tell the computer to do it. I can only change the balance by 5 Ah per day, but I just tell the computer how much I want, and it does it over the next few days without me having to worry. MP.
  6. To understand this, it's really worth reviewing CC/CV charging. The principle is that the batteries are charged first at constant current (actually, normally, the maximum current avaliable from the alternator). In this mode the current is constant and the voltage increases as the SoC increases. Once the voltage reaches the threshold, the voltage stops increasing: this is not a function of the batteries, but a function of the charger: It reduces current to limit the voltage. In this mode, the current drops as the SoC increases. That's which charge termination is a function of charge current: in CV mode: the voltage gives you no information about SoC. (actually, this is an over-simplification, the voltage must increase a _bit_ during CV charging to provide the information needed to reduce the current.) What you're proposing is essentially to miss out the CV phase: once the system reaches CV state: you declare the charge complete and terminate. So, what is the effect of eliding the CV phase? The answer answer is that it depends on the magnitude of the CC current. If the current is small, then the SoC will be nearly 100% when the CV voltage is reached, and CV phase would be very short anyway, so there is very little difference. If the CC current is large, then the SoC when the CV voltage is reached will be far from 100%, and missing out the CV phase will ignore a large portion of the battery capacity. This is why your oft-repeated statement that 13.8 corresponds with 80% SoC is nonsense. It may be true for your charging system, but it's not universal: it depends on the maximum available charge current. As an observation: in a true CC/CV system, the actual final SoC is relatively weakly related to value of the transistion voltage. It's more strongly related to the cut-off current. The time taken to reach final SoC is somewhat related to the transition voltage: the higher the voltage, the quicker final SoC is reached, especially on high-current systems. MP.
  7. Our Oxford correspondent sends this picture of Isis lock this morning. I wonder if the river is coming over Dukes cut lock and feeding the canal? MP.
  8. Make sure that the price includes strapping hardware and assembling the cells into two blocks of six cells. MP.
  9. Blimey! It'll be in the Snork Maiden's back garden at this rate. MP.
  10. I'm not saying that it's a good idea, I'd certainly never try. I'm just saying that you'll probably meet your doom be swamping, or burning the engine out whilst being blown backwards, or getting washed off the counter, rather than by capsize. MP.
  11. MoominPapa

    Stove fan

    We've bought one. I've always been very sceptical of their efficacy, so wouldn't ever have forked out Ecofan prices. Still not sure it actually does anything, but for £16 it's a nice bit of kinetic sculpture, and it does tell you roughly how hot the top of the stove is. No rattles yet, but it's only been in use a week. MP.
  12. Yebut, lumpy water botes that have big keels also tend to have big mast full of sails trying to push them over. Bigest waves we've encountered were wash in the Pool of London, and whilst I was sometimes worried that one of them was going to join us in the boat, I never worried that we were not going to stay baseplate-horizontal. It was really very stable. MP.
  13. It means that any grease which escapes from the gland makes indelible black stains on anything it touches. Don't ask me how I know this. MP.
  14. My design used MOSFETs, can't remember which offhand The load resistors are 15 ohm, so the shunt current is only around 200mA. I used opto-isolators to drive the MOSFET gates, to make the circuit design easy and avoid level shifters. MP.
  15. What they need is some boats. cars are no good floating. MP.
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