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Started by zoneblue, October 28, 2013, 04:39:57 PM
Quote from: boB on October 29, 2013, 01:49:26 AMIn theory, it should be fairly simple to calculate SOC. You have to know the actual amp-hour capacity of the batteries, the amp-hour efficiency (around 95%) and when it is fully charged. It ~should~ be fully charged when it goes to Float. It's never that simple though, is it ? This is where constant calibration is needed at transition toFloat using the normal timing or End Amps means... At least every few charge cycles.
QuoteThe best reference is probably the Trimetric. There is some recent talk/research about usingKalman filtering for battery SOC estimation.
QuoteGetting within a few percent of real SOC is probably pretty good I would think.But testing of the actual amp-hour capacity will have to be done at least once to get an idea ofwhat the batteries are actually good for. Also, this should be done once every so often becauseof aging. Then, the efficiency might also be found at those measurement times and the meterupdated accordingly.
QuoteAll this sounds like too much fun, doesn't it ?boB
Quote from: zoneblue on October 30, 2013, 04:57:58 PMI dont know if you know Northguy from NAWs forum, i asked how he does it, here:http://www.wind-sun.com/ForumVB/showthread.php?21012-Battery-manager-and-generator-start/page4His theory is that Ah in/Ah out is 100% efficient, with the primary exception of absorb stage hydrolysis (self discharge being the other factor). He also debates the topic at some length here:http://www.wind-sun.com/ForumVB/showthread.php?20759-Internal-battery-function-%28from-another-thread%29Frankly im still having a hard time understanding it, but the basic idea to not to try to compute SOC rather just the negative Ah from a known charged state. Seems to be a very good starting place. Its how to account for the bubbling stage that i need to go back and reread NG's post.
Quote from: boB on October 31, 2013, 02:27:26 AMAnd you can measure battery capacity. You do have to get thebattery to almost 0% by measuring its resting voltage. Deep cycle batteries aremade to be discharged all the way but you don't get nearly as many cyclesso you don't want to measure capacity very often because of that.
QuoteIf you do not know battery capacity, then you can only know when it isat 100% SOC, but not percentage of its actual capacity below that 100%You might get lucky though and the batteries might actually have a similarcapacity to what their rating is ?
QuoteThe Trimetric has pretty much been the standard in the industry and itstarts out at 94% A-Hr efficiency by default. I wonder why ?Ralph at Bogart (Trimetric) and others have been making SOC meterssuccessfully for many many years now and I believe they have beenthrough this all quite a bit.
Quote from: zoneblue on October 31, 2013, 08:01:55 PMBecause of their low self discharge, they don't really need float at all.
Quote from: zoneblue on October 31, 2013, 08:01:55 PMHence the well known adage that absorb is less efficient than early bulk, and why some people try to keep their cycles in the 50-80% SOC range (with periodic absorbs).
QuoteBTW mtdoc have you seen this, about floating agms:www.intechopen.com/download/pdf/9712They make a case that AGMs are usually floated at too high a voltage. Because of their low self discharge, they dont really need float at all.