WotEver Posted January 21, 2017 Report Share Posted January 21, 2017 By measuring the cell voltage. I'm confused. Why didn't the charge source dictate the voltage? You can put circa 2.2V across a cell and that voltage will remain constant while the current slowly falls. Or did the charge source only supply a very low current and wait for the voltage to rise? Link to comment Share on other sites More sharing options...
cuthound Posted January 21, 2017 Report Share Posted January 21, 2017 The charge source supplied up to 66.5 volts to a 50 volt battery. The transistorised shunt measured individual cell voltage and when each cell reached 2.67 volts per would shunt excess current to the next cell. Don't forget that the "apparent cell resistance" increases, to the voltage dropped across a full charged cell is slightly higher than one which is not yet fully charged. Link to comment Share on other sites More sharing options...
WotEver Posted January 21, 2017 Report Share Posted January 21, 2017 It must be my day for being thick 'cos I'm not getting this at all. The charge source is supplying 66.5V to 25 cells in series. If 15 of those cells are bypassed after x hours then that's 66.5V across 10 cells, giving them 6.6V each... Or do the shunts also lower the charger's voltage each time? Sorry, it's simply not computing for me at all. Link to comment Share on other sites More sharing options...
cuthound Posted January 21, 2017 Report Share Posted January 21, 2017 The source rectifier certainly monitored and controlled the shunts as well as the overall charge current. Charging was done automatically. The shunts simply passed more current to the lesser charged cells to allow them to charge quicker. Rather than apply excessive voltages to fewer cells as the battery approached fully charged, the rectifier presumably reduced it's output voltage to suit. Link to comment Share on other sites More sharing options...
WotEver Posted January 21, 2017 Report Share Posted January 21, 2017 I can appreciate the theory but I can't get my head around the implementation. Thanks anyway. Link to comment Share on other sites More sharing options...
cuthound Posted January 21, 2017 Report Share Posted January 21, 2017 I just googled it (shunt based battery charging). There are a couple of pdfs describing it, but they refer to Lion and ni-cad batteries. Principle remains the same though. Link to comment Share on other sites More sharing options...
MtB Posted March 27, 2017 Author Report Share Posted March 27, 2017 Right, dragging the thread back on topic again! I tried equalising my battery bank last week using the equalising function on my Sterling Pro Charge Ultra. I equalised for 3.5 hours at 31.5v. The average SG of six of the cells started at 1.220, and finished at an average of 1.236. The current at start was 8.0A and after 3.5 hours was 3.6A Not much of a change in SG. Is this a typical rate of improvement or does something seem wrong? Link to comment Share on other sites More sharing options...
WotEver Posted March 27, 2017 Report Share Posted March 27, 2017 3 minutes ago, Mike the Boilerman said: Right, dragging the thread back on topic again! I tried equalising my battery bank last week using the equalising function on my Sterling Pro Charge Ultra. I equalised for 3.5 hours at 31.5v. The average SG of six of the cells started at 1.220, and finished at an average of 1.236. The current at start was 8.0A and after 3.5 hours was 3.6A Not much of a change in SG. Is this a typical rate of improvement or does something seem wrong? What's the SG supposed to be for your batts? Link to comment Share on other sites More sharing options...
MtB Posted March 27, 2017 Author Report Share Posted March 27, 2017 So at this rate of improvement I'm gonna need to equalise for about 12 hours I reckon. My thoughts are turning to equalising using the alternator whilst cruising. This seems more sensible than trying to find the time to do it with the genny. I know DMR has a modified Adverc for this purpose, but are there any 24v 'off the shelf' alternator controllers that allow custom configuring of the equalising function available? I'm inclined to think I need to equalise at 32.0v at least. Link to comment Share on other sites More sharing options...
MtB Posted March 27, 2017 Author Report Share Posted March 27, 2017 On 27/03/2017 at 13:41, WotEver said: What's the SG supposed to be for your batts? I don't actually know. I've had individual cells as high as 1.276 in the past so I'd imagine 1.277 is correct, same as Trojans. Link to comment Share on other sites More sharing options...
WotEver Posted March 27, 2017 Report Share Posted March 27, 2017 Just now, Mike the Boilerman said: I don't actually know. I've had individual cells as high as 1.276 in the past so I'd imagine 1.277 is correct, same as Trojans. In that case I think that a higher voltage would be more advantageous than a longer time spent at too low a voltage. Link to comment Share on other sites More sharing options...
smileypete Posted March 27, 2017 Report Share Posted March 27, 2017 (edited) I'd just do a bit every week or two with the solar. Edit: The numbers don't sound too bad at all, 1220 to 1236 is about 20Ah for that size batt (200Ah?), which isn't miles away from what EQ charge was put in. I s'pose it's possible the EQ process stirred up some denser stratifed acid from the bottom of the cells, contributing to the rise in SG. Of course the fully charged cells will be gassing away as they don't need that extra charge. Edited March 27, 2017 by smileypete Link to comment Share on other sites More sharing options...
BEngo Posted March 27, 2017 Report Share Posted March 27, 2017 (edited) 8 hours ago, Mike the Boilerman said: So at this rate of improvement I'm gonna need to equalise for about 12 hours I reckon. My thoughts are turning to equalising using the alternator whilst cruising. This seems more sensible than trying to find the time to do it with the genny. I know DMR has a modified Adverc for this purpose, but are there any 24v 'off the shelf' alternator controllers that allow custom configuring of the equalising function available? I'm inclined to think I need to equalise at 32.0v at least.n Probably one for Snibbs but you could do this if there was a 24 v version of the Tractor regulator for the A127 alternator. The 12 v version is easily adjusted. N Edited March 27, 2017 by BEngo Speelinge Link to comment Share on other sites More sharing options...
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