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Post by JohnV on Jan 11, 2021 19:15:28 GMT
You seem to believe that sophistication of systems is the safest system however my experience is that the simplest solutions are the safest. They might not be as efficient but there is a hell of a lot less components to go wrong. With any fully automatic system people come to depend on it totally and the day it doesn't, means disaster because there is no awareness.
With a semi automatic system with audible alarms you are aware of the state of things. and you keep an eye on it, which is after all what you have to do with every system on a boat
As regards my system not having a top end disconnect, I don't see how you think there is a need ...... My solar panels charge my Li's through a totally programmable MPPT controller with a custom profile to only charge my batteries to 90% maximum and then drop to float. The maximum voltage is controlled by this .... why should I add another layer of complexity to do the same thing. Yes there is the possibility of something going wrong just as there is with your disconnect system
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Post by JohnV on Jan 11, 2021 19:20:18 GMT
Well chaps, I hope we can return to our normal civilised tone of discussion. I would hate to see any ill feeling arise between you guys from a difference in technical viewpoints. You should have read some of the historic rows on Lead acid battery charging system and the Peukert effect on CWDF in the years gone by when it was a vibrant forum with the Gibbo .... now they were spectacular
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Post by Telemachus on Jan 11, 2021 19:39:17 GMT
You seem to believe that sophistication of systems is the safest system however my experience is that the simplest solutions are the safest. They might not be as efficient but there is a hell of a lot less components to go wrong. With any fully automatic system people come to depend on it totally and the day it doesn't, means disaster because there is no awareness.
With a semi automatic system with audible alarms you are aware of the state of things. and you keep an eye on it, which is after all what you have to do with every system on a boat
As regards my system not having a top end disconnect, I don't see how you think there is a need ...... My solar panels charge my Li's through a totally programmable MPPT controller with a custom profile to only charge my batteries to 90% maximum and then drop to float. The maximum voltage is controlled by this .... why should I add another layer of complexity to do the same thing. Yes there is the possibility of something going wrong just as there is with your disconnect system
Obvously the reliability of any safety system, especially one that is rarely put into use, has to be considered. I have a lifetime not just as a helicopter pilot but also working on various aviation safety related projects. I don't know if you have ever heard of Eric "Winkle" Brown? (look him up if not) but I have downstairs on a mantlepiece, a national award for my contribution to helicopter safety presented personally by him (and yes, he is tiny).
The point being that I have some idea about concepts of safety, system design and human factors. It is therefore obvious to me, but it seems not obvious to you, that whilst it is true that a second level protection system can go wrong, that is not a reason to not have it. Since that is your best shot on the matter, to be honest I can't be bothered to argue with you any more. Arguing with stupid people is quite tiring and frustrating. So feel free to come in with the last word.
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Post by Telemachus on Jan 11, 2021 19:43:07 GMT
Well chaps, I hope we can return to our normal civilised tone of discussion. I would hate to see any ill feeling arise between you guys from a difference in technical viewpoints. For my part, I can say that I have been very grateful to hear all of the different approaches that have been described- both the simple and the complex. I've ended up elements from both approaches, to be honest. John's £40 Durite split charge relay for example will be my low voltage disconnect, and I've had a few suggestions from Nick that are simple enough for me to want to employ. I like the idea of an accurate battery monitor showing % SoC for example, so that my future boat guests will have something simple to read, and there will less risk of them damaging my batteries. If I'd been sharper John I would've also picked up on your suggestion of using a big resistor to limit the current to the lithiums, as a cheap option to try out before I spent £270 on a B2B. Many pages ago I did suggest, twice I think, that you simply have a relatively long and relatively thin bit of cable between the alternator and the batteries, which would act as a slight resistance and thus reduce the maximum current, but I guess you missed it. But anyway, the advantage of the B2B over that approach is that it can drop to a float voltage and thus not hold the batteries at the limiting voltage for the remaining hours of cruising on a long cruising day.
Dont worry about me and John, he has always been a grumpy old git and that is why he was banned from CWDF. He is so naughty, but we are used to him.
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Post by JohnV on Jan 11, 2021 20:23:06 GMT
I agree of course but it depends on your point of view who is stupid
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Post by JohnV on Jan 11, 2021 20:24:43 GMT
Well chaps, I hope we can return to our normal civilised tone of discussion. I would hate to see any ill feeling arise between you guys from a difference in technical viewpoints. For my part, I can say that I have been very grateful to hear all of the different approaches that have been described- both the simple and the complex. I've ended up elements from both approaches, to be honest. John's £40 Durite split charge relay for example will be my low voltage disconnect, and I've had a few suggestions from Nick that are simple enough for me to want to employ. I like the idea of an accurate battery monitor showing % SoC for example, so that my future boat guests will have something simple to read, and there will less risk of them damaging my batteries. If I'd been sharper John I would've also picked up on your suggestion of using a big resistor to limit the current to the lithiums, as a cheap option to try out before I spent £270 on a B2B. Many pages ago I did suggest, twice I think, that you simply have a relatively long and relatively thin bit of cable between the alternator and the batteries, which would act as a slight resistance and thus reduce the maximum current, but I guess you missed it. But anyway, the advantage of the B2B over that approach is that it can drop to a float voltage and thus not hold the batteries at the limiting voltage for the remaining hours of cruising on a long cruising day.
Dont worry about me and John, he has always been a grumpy old git and that is why he was banned from CWDF. He is so naughty, but we are used to him.
liar
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Post by Deleted on Jan 11, 2021 20:38:54 GMT
So BMS it is then.
Hear me oh faithful! Buy BMS equipped LFP batteries and fee yourselves from the burdens of control system anxiety disorders.
Just do it!
Now where is that container load of Chinese 3rd rate bin grade stuff I ordered?
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Post by JohnV on Jan 11, 2021 20:47:58 GMT
Well chaps, I hope we can return to our normal civilised tone of discussion. I would hate to see any ill feeling arise between you guys from a difference in technical viewpoints. For my part, I can say that I have been very grateful to hear all of the different approaches that have been described- both the simple and the complex. I've ended up elements from both approaches, to be honest. John's £40 Durite split charge relay for example will be my low voltage disconnect, and I've had a few suggestions from Nick that are simple enough for me to want to employ. I like the idea of an accurate battery monitor showing % SoC for example, so that my future boat guests will have something simple to read, and there will less risk of them damaging my batteries. If I'd been sharper John I would've also picked up on your suggestion of using a big resistor to limit the current to the lithiums, as a cheap option to try out before I spent £270 on a B2B. for your application a B2B is a good solution Tony
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Post by brummieboy on Jan 11, 2021 23:42:24 GMT
I've tried to follow this....... For my part, I think I'll stick with LA and rely on my limited solar and single 70 amp alternator. And Tony, there are so many things that can go wrong when you lend your boat to friends or family, that unless I were getting a Monte Carlo penthouse or similar in return, then I'd never entertain the idea. But then, if they had such a pad, they would not even consider my humble craft.
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Post by Telemachus on Jan 17, 2021 17:47:07 GMT
Your views represent a majority of boaters I think. Time and time again on CWDF we had people whose lights had gone out. They had spent £50-100k on a boat, perhaps £500 on batteries less than a year ago, £2500 on a fancy combi inverter not to mention £8000 on an engine with large alternator. And yet it had all gone horribly wrong. Why had it gone horribly wrong? They had no idea. And why did they have no idea? Because electricity is invisible and the only way you can possibly know what is going on is by having adequate monitoring equipment. They didn’t. And yet when we suggested spending less than £200 on adequate monitoring equipment for their £100,000 investment so they could enjoy it without stress, they baulked. You know- as soon as I wrote that post above I started rethinking... Knowing how much electricity you've got left is not just important in terms of losing power during the night, or when you are away for a day or two- all of which are bad enough events in themselves. But even to be able to look after these batteries properly (which is now the main purpose of my life), I need to know what SoC they have, so I can keep them within that 20-80% band for most of the time. I'm moving towards the smart shunt as a compromise, although that said, is there any significant technical difference between the victron and the AiLi units? From what I can gather they both use the same measuring approach (counting up the Ah that pass through), so at the moment it seems build quality is what separates them? Again, I'm trying to imagine I'm recommending what a new lithium user on a budget will definitely need. There is a clear case to know the SoC accurately, I totally agree. My only remaining question is- how much do I really have to spend to get a reliable and accurate unit? Is the AiLi unit a poor choice, or risky in some way, when compared to a victron unit? Anyway, now that nursey has given the grumpy one his medication and he’s gone sleepibyes, I’ve done a bit of research on SoC vs voltage. I took a rested 200Ah battery, added 10% SoC quite slowly at 5A to take it up to 50% SoC, then started logging the voltage and disconnected the charger. You can see the voltage subsides over many hours towards its ultimate rested voltage - after 16 hours it probably hasn’t quite got there. So in terms of trying to identify SoC from voltage, bearing in mind the very flat discharge curve, that 0.08v droop is quite significant. So even with loads turned off (current temporarily zero) you can’t really work out the SoC unless you know the charge/discharge history or leave it at zero current for a day.
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Post by JohnV on Jan 17, 2021 18:19:38 GMT
twat
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Post by Telemachus on Jan 17, 2021 19:17:08 GMT
NURSE!
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Post by Deleted on Jan 17, 2021 20:11:20 GMT
Anyway, now that nursey has given the grumpy one his medication and he’s gone sleepibyes, I’ve done a bit of research on SoC vs voltage. I took a rested 200Ah battery, added 10% SoC quite slowly at 5A to take it up to 50% SoC, then started logging the voltage and disconnected the charger. You can see the voltage subsides over many hours towards its ultimate rested voltage - after 16 hours it probably hasn’t quite got there. So in terms of trying to identify SoC from voltage, bearing in mind the very flat discharge curve, that 0.08v droop is quite significant. So even with loads turned off (current temporarily zero) you can’t really work out the SoC unless you know the charge/discharge history or leave it at zero current for a day. It's useful to know how long they take to get down to a 'stable' resting voltage after a charge, but I think in my case they are almost never going to get that length of time to sit without some load being put on them. I would guess that on a non-cruising day (and in winter) the fridge and other things will be left on during the 100-120 minute daily engine run to charge the batteries- and as soon as the engine is turned off, the inverter load from the fridge etc will make itself felt. So this elongated and very gradual decay period wont normally get a chance to happen. There will be a few summer days when I'm away, the solar will pump the batteries up, and there will be almost zero load on them afterwards. But that said, if I'm not there I wont be looking to read the SoC. And if I am there, they will be getting a bit of a hammering, assuming the requisite beer supplies can be procured to provide a thermal challenge for the fridge. If I know that I'm going to be away for a few days in the summer, I'll switch off the fridge and the inverter, and I'll probably disconnect the lithiums to keep them from being kept at a high SoC for several days by the solar charge. In those periods I'll rely on a single lead acid battery (that I'll leave in parallel with them) for the minimal discharging tasks that might be needed when I'm away. So I will need an SOP or checklist of the jobs when I'm leaving the boat for more than 24 hours. Sadly it might now be a few weeks till I get the lithiums properly set up. I've got the BMV700 and the B2B on board, but my electrician is saying that she's no longer allowed to attend a job in this marina unless its an emergency. I have suggested taking the boat to meet her at a nearby bridge so that the job is done on the towpath whilst I am CCing - and is thus fully legal. But she is very busy for the next two weeks. My guess is there is a small chance of her getting a chance to do it on Thurs 28, but most likely it will be the week after that, and maybe 2 weeks after. Given that the original install took 4 weeks to happen, I feel I have to now look at what other options might be available. But marine electricians are ludicrously thin on the ground in these here parts. So there is the option of calling other marine electricians in the area, but I am now starting to give serious thought to the idea of attempting the B2B install myself, if I can get some guidance from the folks on this forum. People like yourself will know instantly which wire should be connected where. What looks like an impenetrable forest of wires to me, will be easily understood by an expert. The earliest opportunity to electrocute myself will come on Thursday and Friday, so if I know you will be around on those days (or others) to look at photos (which hopefully wont include flesh burns), I think I might give it a shot.
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Post by Telemachus on Jan 17, 2021 20:52:33 GMT
Just remember, Red to red Black to black Blown to bits.
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Post by JohnV on Jan 18, 2021 7:48:02 GMT
Just remember, Red to red Black to black Blown Blue to bits.
With your stupid comments you sound just like a spoilt child trying to impress everyone with his knowledge.
You just end up looking like an insecure individual who requires constant approbation
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