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Everything posted by nicknorman

  1. Although a PLB has to have an “owner”, that can be an organisation not necessarily a specific person. They can be associated with a specific vessel or aircraft. For example at the gliding club, parachutes have a PLB hooked onto them. For club aircraft the PLBs are “owned” by the club but the details of the specific aircraft and its registration are on the registration. Same applies to a vessel if you so choose.
  2. It took them a long time to introduce the CO alarm requirements because protecting a private boat’s occupants is not within the remit of the BSS, it is supposed to be about protecting 3rd parties. They had to think up some weasel words to make it seem as though the new requirement was within their remit, even though it obviously wasn’t. Not that I object to CO alarms of course, we had one for years before they became mandatory. But still, regulatory mission creep is a bad thing.
  3. No but you did say “That is why it is important to buy a UK registered PLB (frequencies are different) as there are often US ones on ebay”. Frequencies are not different.
  4. Yes I suspect so! Just got a new BSS in November (with Li batteries in situ) so at least I will get another 4 years without hassle! I’m not sure what the objection to mixing Li with “older, more conventional batteries” is. It’s not an elegant way of doing it but I don’t think it’s dangerous.
  5. Well I think I can post my letter: The devil in the lithium detail I refer to the latest NABO News item about lithium batteries. Sorry but I think referring to lithium ion batteries generically is a big mistake. Yes the item does hint that there are different lithium chemistries but it’s a bit subtle! The bottom line is that LiFePO4 batteries are as safe as lead acid, or safer. LiFePO4 is extremely difficult to set on fire either by overcharging or by physical damage, and even in that highly unlikely event it can easily be extinguished. It doesn’t explode and spray hot sulphuric acid around unlike lead acid! By comparison lithium cobalt oxide technologies are quite unstable, easily set alight and continue to burn even when under water (it makes its own oxygen for combustion!) So any talk about Li batteries needs to specify the chemistry, otherwise it is a bit like talking about “fossil fuels” without distinguishing between diesel, petrol or LPG. An area of concern is second hand batteries ex electric vehicles. If they are LiFePO4 then fine. If they are some higher energy density technology, then be afraid! The devil is in the detail and awareness perhaps needs to be raised on these differences. Full disclosure: I have 600Ah of LiFePO4 batteries with home grown BMS and alternator controller. The batteries are fantastic! Nick Norman The reply didn’t seem to indicate that he had got my point.
  6. Surely they all operate on 406MHz, only the hex code is used to divert the alert to US, Falmouth etc. It's true that US used to use 121.500MHz a lot for aircraft beacons but that was for detection by other aircraft/vessels, it doesn't reach a satellite. So yes I suppose a very old US one might be on the VHF frequency but a recent or new model from US will be identical to UK - save for the hex code! So I submit that your point is correct but mostly for the wrong reasons!
  7. They were, but when you visited by road it was a pretty grim area with the factories in a sad state of decline.
  8. I didn't know that Port Loop (Urban Splash) had gone bust. But I see you are right. Their website still seems up and running though.
  9. Smethwick regeneration consultation launched https://www.bbc.co.uk/news/uk-england-birmingham-64540622 https://www.sandwell.gov.uk/download/downloads/id/33670/rolfe_street_masterplan_consultation_document.pdf
  10. Yes I had assumed that the batteries would exclusively be charged from solar. But as we know, assumption is the mother of …
  11. Charge efficiency on battery monitors etc is the efficiency in terms of charge (the physical thing with units of coulombs or Ah). Not the same as energy efficiency because of course charge does not have dimensions of energy. Confusion is caused when people refer to charge as the charging process and others to the physical property of coulombic charge.
  12. Obviously the mains kWh is correct. But the solar kWh is complicated! Efficiency of solar power that is used instantaneously by dc appliances, very nearly 100%. But there won’t be much of that. Solar power going directly to power ac appliances - about 85-90% (inverter losses) But then if you bring batteries into it… about 93% charge efficiency. So for every 100Ah you put in, you get back 93Ah. But energy (kWh) is the multiple of charge (Ah) and voltage. When the solar is charging the batteries, the voltage might be up at say 14.4v. When discharging it may be down at 12.4v. And a bigger difference for faster charge and discharge. So the voltage efficiency is roughly 86% for moderate loads. So energy efficiency is around 80%. That would be the figure for dc loads. For ac loads from the battery you need to add in the inverter efficiency so we are looking at around 70% efficiency. Ie 70% of solar input energy goes to operate ac loads when powered later via the battery.
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  18. inverters tend to have very large capacitors across the dc input. So when the load output switches on, there is a very short term but very large current flow as the capacitors charge up. For a spilt second it seems to the MPPT like a short circuit. Electronic switchery (MOSFETS) doesn’t like that. This is one reason. Also I think if you connect an inverter which is capable of drawing more than the rated load output of the MPPT, this would be considered bad practice even if the intention was never to load the inverter beyond the max load output of the MPPT. Intentions are one thing, what happens in reality in a moment’s carelessness or third party action is another thing!
  19. Nothing is safe. For example, beds are highly dangerous since most people die in bed! You have to look at the risk (severity of hazard x probability of it happening) and no point in focussing effort on reducing a very small risk whilst ignoring much greater ones. I suspect many more people die falling off boats than do so from electrocution. We just tend to focus on stuff like electricity because it’s invisible and a bit mysterious and therefore something to be frightened of. it’s not rational.
  20. no I think there are a few incorrect things there. I was not saying you can’t simply bond NE at the inverter - you can provided the mains terminals are floating relative to earth and/or dc negative. My point was simply that it didn’t matter which terminal you bonded, whichever one you bonded would become the N, the other one the L. You say breakers won’t work without an NE bond but let’s be clear, an overload breaker will still work, it is just an RCD that won’t. The other thing to bear in mind is that some devices such as the travelpower and some inverters have a centre tapped earth bond, such that each terminal has 115v on it, they are in antiphase so the total voltage between them is 230. But the centre tapped earth means that an RCD will still trip at its fault current of 30mA or whatever. I can’t see why Renology said what they did, perhaps they are confused! Of course the NE bond has to occur before (inverter side of) the RCD for it to be effective. Or maybe their inverter’s output is somehow tie to earth or dc negative anyway, in which case an RCD will still work. As to equipment which “could potentially kill” you (pun intended, presumably!), lots of things can do this. A kitchen knife, a bicycle, a narrowboat propellor etc etc etc. What one has to look at is the probability of this happening and in the case of a mains supply that is not protected by an effective RCD, I’d say it’s pretty low. I have lived in 4 houses in my life, plus a couple of rentals when I was a student. None had RCDs on the mains rings, and in my present house still doesn’t. Nobody died yet!
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  22. Yes tidal power does affect planets and moons. Which is why the moon's rotational speed is the same as the planet's so that it always presents the same face to the earth. The energy has to come from somewhere and as you say, ultimately it comes from the moon's orbital kinetic energy. Although if it slows down and moves to a lower orbit, setting up habitations on the moon would be easier (closer).
  23. I don’t think you need to worry about fast discharge of Li batteries, well up to 1C anyway. Fast charge might not be great but I don’t think there is a problem with fast discharge.
  24. But so called renewable energy -hydroelectric, solar, wind - does not come from a source that is constantly replenished. It comes fundamentally from the sun, and the sun has a limited life and will run out of fuel in a few (billion) years.
  25. If I understand the question correctly then unusually I have to disagree with Eeyore. If the inverter output is not already tied to earth (ie it’s floating), there is no live or neutral. Whichever is connected to earth becomes the neutral, the other one being the live.
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