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Post by Clinton Cool on Aug 23, 2020 9:11:19 GMT
And just to pick up on earlier points, there is an effect called “surface charge” that temporarily raises the battery voltage during and shortly after charging. So whilst 12.7-12.8 does represent a fully charged battery, this only applies some time after charging is stopped (several hours, or after some moderate discharge). It doesn’t apply during charging so if during charging you see 12.8v and then stop charging, you batteries will be way less than fully charged. You need to charge at at least 14.4v until the charge current drops to around 1 or 2% of capacity. When you stop charging the voltage will rapidly fall to 13.5 or so, and then over a few hours or a few Ah, down to the 12.7 which represents a fully charged battery. After that the voltage will fall much more slowly towards the 12.2v (no-load voltage) which represents 50% charge. So in summary the amount of charge taken out of a just-fully-charged battery to get from 14.4v to 12.7v is minimal. Once the battery gets to 12.7v the voltage will decay much more slowly. Yes. Hopefully Tony can meet a member with a meter that read DC amps. He can then understand when his batteries are fully charged/ approaching being fully charged. From this and reading volts taking into account any loads he should then have a fair idea of the state of charge at all times, and know when he should next run his engine/ genny, and for how long. Hopefully he can then avoid the years of misunderstanding (and wrecked batteries) that I, and the vast majority of those who live aboard have suffered. By the way Nick re. the 1-2% of battery capacity you quote as being a 'fully charged' tail current. While this might be true for practical purposes, it's wasteful to run hours on end to put tiny amounts of energy into batteries, my solar system suggests different. Single 105AH Trojan, the current settles around 0.5A after an hour or so on float voltage. So perhaps 0.5% or thereabouts, is the true figure?
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Post by Telemachus on Aug 23, 2020 9:25:03 GMT
And just to pick up on earlier points, there is an effect called “surface charge” that temporarily raises the battery voltage during and shortly after charging. So whilst 12.7-12.8 does represent a fully charged battery, this only applies some time after charging is stopped (several hours, or after some moderate discharge). It doesn’t apply during charging so if during charging you see 12.8v and then stop charging, you batteries will be way less than fully charged. You need to charge at at least 14.4v until the charge current drops to around 1 or 2% of capacity. When you stop charging the voltage will rapidly fall to 13.5 or so, and then over a few hours or a few Ah, down to the 12.7 which represents a fully charged battery. After that the voltage will fall much more slowly towards the 12.2v (no-load voltage) which represents 50% charge. So in summary the amount of charge taken out of a just-fully-charged battery to get from 14.4v to 12.7v is minimal. Once the battery gets to 12.7v the voltage will decay much more slowly. Yes. Hopefully Tony can meet a member with a meter that read DC amps. He can then understand when his batteries are fully charged/ approaching being fully charged. From this and reading volts taking into account any loads he should then have a fair idea of the state of charge at all times, and know when he should next run his engine/ genny, and for how long. Hopefully he can then avoid the years of misunderstanding (and wrecked batteries) that I, and the vast majority of those who live aboard have suffered. By the way Nick re. the 1-2% of battery capacity you quote as being a 'fully charged' tail current. While this might be true for practical purposes, it's wasteful to run hours on end to put tiny amounts of energy into batteries, my solar system suggests different. Single 105AH Trojan, the current settles around 0.5A after an hour or so on float voltage. So perhaps 0.5% or thereabouts, is the true figure? Yes 1-2% is definitely a compromise figure. The problem is that there is no real definition of “fully charged” - it is a gradual process whereby the charge current asymptotically approaches its minimum value (which depends on charging voltage, battery condition and temperature) over many hours. But as you suggest, it is not practical to run an engine or genny for hours on end just putting in a few amps. Of course this is where solar is great for ensuring as close to “fully charged” as matters ... - in summer of course!
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Post by Deleted on Aug 23, 2020 10:05:49 GMT
Once again thanks a lot for the info folks, much appreciated. A quick apology, the volt reading I was looking at last night was the solar charger panel, not the main panel.
I've got a couple of pics of both panels, taken a few mins ago, as I think that will explain the setup far better than I could.
Not enough signal to upload pics at the mo, but I'll try later
I think things are running fine in general, but I'd still be interested in any thoughts about the characteristics or features you can discern from the pics of solar and batteries etc (when I get the pics up)
Cheers guys
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