Dname Posted July 25 Share Posted July 25 (edited) I spoke to my supplier today whilst doing firmware updates across my bank. I've got 3 100AH LifePO4 batts in parallel which have been serving me well. I recently noticed the master/primary batt is dropping lower than the other 2. I didnt see this as normal, hence me being on the line. I was I formed this is normal and no issues found. Apparently the master batt will always take more load than the other 2. Doesn't this defeat the purpose of a bank? Shouldn't all 3 stay equalized on the way down? What's the use hammering 1 battery to supply, and then having 2 of equal rating supplementing? Wouldn't this kill the first battery way ahead of schedule ? Doesn't make sense. Edited July 25 by Dname Spelling Quote Link to comment Share on other sites More sharing options...
zivva Posted July 25 Share Posted July 25 (edited) If you want to reduce deviation between batteries in //, the only way is using bus bars and batteries wires of *** exactly *** the same size and length, terminated with the exactly same lug with the exact same contact area, torqued at the same strength. Otherwise ... Electricity will *** always *** follow the path of least resistance : more energy flowing thru the shorter (then less resistance) cable, or with the less contact area etc ... When I say exactly the same length of cables : millimeters matter Is it worth the effort ? Probably not for "only" 3 batteries ... Edited July 25 by zivva JayMardern 1 Quote Link to comment Share on other sites More sharing options...
JayMardern Posted July 25 Share Posted July 25 6 minutes ago, zivva said: If you want to reduce deviation between batteries in //, the only way is using bus bars and batteries wires of *** exactly *** the same size and length. Otherwise ... Electricity will *** always *** follow the path of least resistance : more energy flowing thru the shorter (then less resistance) cable. When I say exactly the same length of cables : millimeters matter Agreed, Also internal resistance of each battery may differ somewhat (slight manufacturing differences from the factory, as well as differences in cell age/etc) so over the lifespan of a set of batteries, it's going to be difficult to achieve perfect equality between them. My own batteries stay in sync pretty well at the top and bottom of their SoC's but in the middle they drift by up to around 15% (and I'm using a busbar with carefully measured wiring). As long as you're not dealing with massive discrepancies, I wouldn't overthink this one! Quote Link to comment Share on other sites More sharing options...
Dname Posted July 26 Author Share Posted July 26 Thanking you kindly. Quote Link to comment Share on other sites More sharing options...
Beat Posted July 26 Share Posted July 26 (edited) 19 hours ago, zivva said: If you want to reduce deviation between batteries in //, the only way is using bus bars and batteries wires of *** exactly *** the same size and length, terminated with the exactly same lug with the exact same contact area, torqued at the same strength. Otherwise ... Electricity will *** always *** follow the path of least resistance : more energy flowing thru the shorter (then less resistance) cable, or with the less contact area etc ... When I say exactly the same length of cables : millimeters matter Is it worth the effort ? Probably not for "only" 3 batteries ... It is my assessment that packs internal resistance differences are far greater than cable length differences at 25mm² or even 16mm². My newest pack, same type, same manufacturer, is connected last in row, thus has the longest cabling yet it shows the highest charge and discharge currents. I presume it has significantly lower internal resistance than the others probably due to improved manufacturing procedures. A propo equalizing: I observed that Packs do equalize during charging when reaching full charge. This is due to the physics of batteries and Ohms law. Edited July 26 by Beat Quote Link to comment Share on other sites More sharing options...
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