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Post by Telemachus on Nov 2, 2016 17:42:15 GMT
happy to so I suppose I will have to add the "trouble makers" name to the credits Only if you want to!
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Post by tonyqj on Nov 2, 2016 17:57:15 GMT
happy to so I suppose I will have to add the "trouble makers" name to the credits Only if you want to! Now now, don't sulk, it doesn't become you 😝
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Post by Deleted on Nov 11, 2016 22:34:37 GMT
Tony
Well done, good explaination, any chance of expanding it to explain why a Smart gauge will also lie to you during charging. Whilst the message that amphour meter lie many people still believe their Smart gauges.
Top Cat
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Post by tonyqj on Nov 11, 2016 23:31:39 GMT
Tony Well done, good explaination, any chance of expanding it to explain why a Smart gauge will also lie to you during charging. Whilst the message that amphour meter lie many people still believe their Smart gauges. Top Cat TC, I've already covered the fact that it can be up to 10% out when charging in the more relevant post about charging. thunderboat.boards.net/thread/817/battery-charging-primer
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Post by Deleted on Nov 12, 2016 8:06:54 GMT
Ok thanks Tony, I hadn't yet read your thread when I made that comment, now I have. So feel free to ignore what I said
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Post by Telemachus on Nov 12, 2016 9:53:30 GMT
Tony Well done, good explaination, any chance of expanding it to explain why a Smart gauge will also lie to you during charging. Whilst the message that amphour meter lie many people still believe their Smart gauges. Top Cat I know you have a "downer" on the Smartgauge but I'll humour you anyway since you are new here! the Smartgauge measures voltage. During discharge the voltage is provided by the battery and so what the SG sees is all down to the battery. During charge what the SG sees is the voltage from the charger. Chargers come in different flavours, max currents, voltage profiles etc and so it is an inexact science to try to guess the SoC from the voltage. However in terms of reaching 100% SoC the Smartgauge is pretty good since ultimately batteries tend to take much the same time to reach 100%. I find the SG not that good mid-charge (although of course if charging is stopped, it soon recovers) but by the time 100% is approached it is pretty good, within a few %. Bearing in mind there is no hard and fast definition of 100% - in fact a big variation between say 4% tail current (Victron) and 0.1% tail current (Nick Norman) SG's vagaries at 100% are of minimal consequence. However it is ideal to have an ammeter that allows one to choose the tail current of one's personal preference as the trigger to stop charging.
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Post by Deleted on Nov 12, 2016 10:03:45 GMT
I thought it would be helpful if the limitations of all types of battery instrumentation were aired so that people can decide how to use and interpret their equipment. Too many people blindly follow what their gauge says and kill their batteries.
Top Cat
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Post by Telemachus on Nov 12, 2016 10:22:57 GMT
I thought it would be helpful if the limitations of all types of battery instrumentation were aired so that people can decide how to use and interpret their equipment. Too many people blindly follow what their gauge says and kill their batteries. Top Cat However given that the SG is normally the first port of call for those looking to gain some insight into what their batteries are doing - the previous step being no monitoring at all - they are likely to have a pretty good charging regime if they blindly follow the SG. When it reaches 100%, the tail current will be within the range 4% to 0.1%. I generally find it's around 1.5 to 2%. so blindly following the SG is vastly better than having no monitoring at all, even if it isn't perfect.
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Post by Deleted on Nov 12, 2016 10:29:01 GMT
True, but lets admit the imperfection
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Post by smileypete on Nov 12, 2016 11:39:39 GMT
However given that the SG is normally the first port of call for those looking to gain some insight into what their batteries are doing - the previous step being no monitoring at all - they are likely to have a pretty good charging regime if they blindly follow the SG. When it reaches 100%, the tail current will be within the range 4% to 0.1%. I generally find it's around 1.5 to 2%. so blindly following the SG is vastly better than having no monitoring at all, even if it isn't perfect. Helps if the charge voltage is correct. I guess when charging the SG relies on some sort of timer when it sees a constant charge voltage. But I wonder if this is dependent on that charge voltage or whether it would hit a 100% indication too early with a slightly lower than normal charge voltage. I guess the SG can be a useful interim step to understanding volts/amps, trouble is most users fall under the thrall of the magic percentage reading without understanding its limitations....
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Post by Telemachus on Nov 12, 2016 12:34:20 GMT
True, but lets admit the imperfection I don't think it's ever been denied. The SG manual quotes and accuracy of 10% during charge.
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Post by Telemachus on Nov 12, 2016 12:40:39 GMT
However given that the SG is normally the first port of call for those looking to gain some insight into what their batteries are doing - the previous step being no monitoring at all - they are likely to have a pretty good charging regime if they blindly follow the SG. When it reaches 100%, the tail current will be within the range 4% to 0.1%. I generally find it's around 1.5 to 2%. so blindly following the SG is vastly better than having no monitoring at all, even if it isn't perfect. Helps if the charge voltage is correct. I guess when charging the SG relies on some sort of timer when it sees a constant charge voltage. But I wonder if this is dependent on that charge voltage or whether it would hit a 100% indication too early with a slightly lower than normal charge voltage. I guess the SG can be a useful interim step to understanding volts/amps, trouble is most users fall under the thrall of the magic percentage reading without understanding its limitations.... Yes it definitely takes charging voltage into account in what is otherwise an integration (ie time-counting) function. Although it won't be linear - as we know you don't reduce charging time in proportion to increasing charging voltage. As I've mentioned before we have a large alternator whose output is 39% of battery capacity and that results in the SG lagging behind during charging up to perhaps 90% SoC, but by the time 100% is reached the SG has caught up. It would be interesting to discharge the batteries and then recharge using shore power with the max current turned down to say 25A and see how the SG copes at this other extreme ... it's just a matter of finding the time / opportunity to do it!
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Post by tonyb on Nov 16, 2016 11:52:45 GMT
A sort of update.
By coincidence in the November edition of the mag. I commented on the fact that such meters help boaters destroy batteries and now a reader has asked for my justification. I have just prepared my reply in the form I send to the editor and felt that I could do no better that supply the text of my first post in the thread. I have asked that Thunderboat be acknowledged. To save word numbers I have removed the attributions to Graham, Tonyqj & Telemachus. This is in no way me trying to claim their input. I hope the editor gives the full web address of TB so it is brought to more boaters attention.
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Post by tonyqj on Nov 16, 2016 11:54:22 GMT
Nice one, Tony. Well done sir
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