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Post by tonyqj on Nov 1, 2016 20:53:22 GMT
But that is the problem, V isn't constant. It varies from perhaps 13v shortly after charge, to <11v under heavy discharge. Anyway the battery is fundamentally (due to the way the chemistry works) a charge store not an energy store. I agree up to a point. (TBH, I think we're only discussing semantics!), but what most people are interested in is how much energy they get out of a battery, and how much they need to put back in. The answer to the second part is always 'more than you expected'.
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Post by Telemachus on Nov 1, 2016 20:56:20 GMT
But that is the problem, V isn't constant. It varies from perhaps 13v shortly after charge, to <11v under heavy discharge. Anyway the battery is fundamentally (due to the way the chemistry works) a charge store not an energy store. I agree up to a point. (TBH, I think we're only discussing semantics!), but what most people are interested in is how much energy they get out of a battery, and how much they need to put back in. Yes it is just semantics and anyway, TBH it doesn't matter what we think since the industry has settled on its own ideas! I'll just mention that if energy was the measure, the efficiency would seem much worse than if we just looked at the charge efficiency.
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Post by Deleted on Nov 1, 2016 21:26:39 GMT
No further capacity to take a charge given current conditions. The actual capacity is dependent on all sorts of stuff. Temperature, electrolyte, age, number of cycles, charging rate.... sorry, in pub with mate so may have to come back to this. Yup. But you can always squeeze just a bit more in if you try for long enough. Nick has the posh word for that: asymptotically. Ha ha...it is knowing the right point to cut the engine because it's no longer efficient to charge anymore. Another 3 litres of diesel to squeeze in another 1% is pointless.
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Post by smileypete on Nov 1, 2016 21:32:55 GMT
What's a full charge? 100% is unobtainable, all one can ever achieve is 'approaching full charge' as stated in the OP. To my mind, a full charge is that which meets the manufacturers requirements and so should give the expected cycle life. NB: 'expected cycle life' doesn't include the outragous marketing claims for some POS leisure batts.
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Post by smileypete on Nov 1, 2016 21:44:18 GMT
Okay, I can't hear anything over the sound of the engine (the first bit I've highlighted) but what does "moderately gassing" mean? I charge my Trojans at 14.8v and the bubbles are a bit like a glass of pop. That is, about once a second, more or less, I see a small bubble come to the surface. The impression I get, when people mention gassing, is one of a saucepan, more or less, bubbling away. The gassing is from free antimony contaminating the electolyte, antimony is used to make the lead plates more robust. So gassing depends on type, age and conditon of the battery, as well as charge voltage. Maintenance free batts use calcium, which greatly reduces gassing though they won't take as much jarring and vibration as an identical batt with antimony alloyed plates.
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Post by tonyqj on Nov 1, 2016 21:52:48 GMT
Yup. But you can always squeeze just a bit more in if you try for long enough. Nick has the posh word for that: asymptotically. Ha ha...it is knowing the right point to cut the engine because it's no longer efficient to charge anymore. Another 3 litres of diesel to squeeze in another 1% is pointless. Absolutely. Hence the 1% (or 2%) tail current monitoring.
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Post by smileypete on Nov 1, 2016 21:55:42 GMT
This is why I dispensed with "leisure batteries" 3 years ago. They're rubbish! Seems to me a lot of problems are down to sealed 'calcium' leisures, which in a canal boat are more likely to suffer excessivly from a problem called stratification (see earlier CWDF links) That said light use seems to help and some brands seem less problematic, but it looks like a case of suck it and see.... One of the side benefits of calciums is they may be less likely to suffer from boiled batts if left unattended on a high power charger with voltage set too high, so more suited to novice owners. Unfortunately these days it's hard to find cheap non sealed leisures, though the price of decent semitraction batts (Trojan etc) has come down a ways.
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Post by smileypete on Nov 1, 2016 21:58:43 GMT
Yup. But you can always squeeze just a bit more in if you try for long enough. Nick has the posh word for that: asymptotically. Ha ha...it is knowing the right point to cut the engine because it's no longer efficient to charge anymore. Another 3 litres of diesel to squeeze in another 1% is pointless. Doesn't matter where it comes from, solar could do that, even on a sunny winters day if a reasonable size setup and the panels are tilted enough. Could even do it from another batt/bank using a DC converter, though that's far too much hassle for most people.
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Post by Telemachus on Nov 1, 2016 22:02:10 GMT
This is why I dispensed with "leisure batteries" 3 years ago. They're rubbish! Seems to me a lot of problems are down to sealed 'calcium' leisures, which in a canal boat are more likely to suffer excessivly from a problem called stratification (see earlier CWDF links) That said light use seems to help and some brands seem less problematic, but it looks like a case of suck it and see.... One of the side benefits of calciums is they may be less likely to suffer from boiled batts if left unattended on a high power charger with voltage set too high, so more suited to novice owners. Unfortunately these days it's hard to find cheap non sealed leisures, though the price of decent semitraction batts (Trojan etc) has come down a ways. Both the sets we had weren't sealed. Although they barely needed topping up once in their lifetimes.
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Post by smileypete on Nov 1, 2016 22:15:04 GMT
Seems to me a lot of problems are down to sealed 'calcium' leisures, which in a canal boat are more likely to suffer excessivly from a problem called stratification (see earlier CWDF links) That said light use seems to help and some brands seem less problematic, but it looks like a case of suck it and see.... One of the side benefits of calciums is they may be less likely to suffer from boiled batts if left unattended on a high power charger with voltage set too high, so more suited to novice owners. Unfortunately these days it's hard to find cheap non sealed leisures, though the price of decent semitraction batts (Trojan etc) has come down a ways. Both the sets we had weren't sealed. Although they barely needed topping up once in their lifetimes. Fair enough, probably suffered from stratification. Though a lot of open batts are 'hybrid', with calcium in the negative/positive grids. (can't remember which) Something you may be able to work out, will a batt with weaker than usual acid gas more at the normal charge voltage (and vice versa - stronger acid gas less), and will a bat with stronger acid need a higher charge voltage to fully convert the sulphate back into acid?
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Post by Telemachus on Nov 1, 2016 22:23:22 GMT
Both the sets we had weren't sealed. Although they barely needed topping up once in their lifetimes. Fair enough, probably suffered from stratification. Though a lot of open batts are 'hybrid', with calcium in the negative/positive grids. (can't remember which) Something you may be able to work out, will a batt with weaker than usual acid gas more at the normal charge voltage (and vice versa - stronger acid gas less), and will a bat with stronger acid need a higher charge voltage to fully convert the sulphate back into acid? I don't think stratification was the issue. When the second set got down to 1/2 capacity after only 6 months I removed all the batteries onto the towpath and then gave them a right good tilting, swishing around and shaking (as well as one can shake a 25kg battery!), put them all back again with absolutely zero change! I then put them on an equalise charge for a couple of hours and they were reborn. For a while, then repeat every 3 - 6 months for the next 18 months until they went pretty weird and I got the Trojans. As to the gassing bit - no idea, sorry!
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Post by tonyqj on Nov 1, 2016 22:24:28 GMT
Both the sets we had weren't sealed. Although they barely needed topping up once in their lifetimes. Fair enough, probably suffered from stratification. Though a lot of open batts are 'hybrid', with calcium in the negative/positive grids. (can't remember which) Something you may be able to work out, will a batt with weaker than usual acid gas more at the normal charge voltage (and vice versa - stronger acid gas less), and will a bat with stronger acid need a higher charge voltage to fully convert the sulphate back into acid? Acid is more conductive than water. Therefore as the acid concentration increases with higher SoC so the gassing voltage falls. However a higher voltage is required to remove the stubborn sulphate. Or wasn't that what you were asking?
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Post by smileypete on Nov 1, 2016 22:31:10 GMT
I don't think stratification was the issue. When the second set got down to 1/2 capacity after only 6 months I removed all the batteries onto the towpath and then gave them a right good tilting, swishing around and shaking (as well as one can shake a 25kg battery!), put them all back again with absolutely zero change! I then put them on an equalise charge for a couple of hours and they were reborn. For a while, then repeat every 3 - 6 months for the next 18 months until they went pretty weird and I got the Trojans. Been there, done that. From what I can tell it's not the stratification itself, but that the lower ends of the plates get sulphated due to excessive acid strength. So shaking the batts won't reverse the sulphation, and an EQ charge will mix the acid anyway. But in a car or lumpy water boat where there's constant motion, it should help prevent these problems.
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Post by smileypete on Nov 1, 2016 22:38:04 GMT
Acid is more conductive than water. Therefore as the acid concentration increases with higher SoC so the gassing voltage falls. However a higher voltage is required to remove the stubborn sulphate. Or wasn't that what you were asking? ISTR Gibbo saying it was the other way round. Maybe we can tempt him back, or else find an answer on t'interwebs. Once I had a Varta truck batt which lasted OK 9+ years on one boat with shore power charger 24/7, then new a but identical batt with same charger on a different boat completely died after 5 or 6 years. Only diffence I could see was that the first boat was moored below a weir so got periods of constant movement in the winter.
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Post by Deleted on Nov 1, 2016 22:39:29 GMT
I'm rather hoping Gibbo will return having thought about it. He didn't really put up any substantial counter argument which makes me think he needed to go away and think about it. Gibbo has other demands on his time... You might have missed this, to your question as to where has he been, 'Bloody hell, look what the cat dragged in! Welcome, where have you been? In hospital most of the time to be honest! Well, sometimes the pub.' Edit. Messed up the quotes again but hopefully people will get the gist of my post without me offending anyone.
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