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--- electrical:12v:drop-in_lifepo4 [2022/06/05 13:38]
frater_secessus [myth: you must use DC-DC for alternator charging Li]
+++ electrical:12v:drop-in_lifepo4 [2022/06/16 23:16]
frater_secessus [cell balancing]
@@ Line 162: / Line 162: @@
 Lead batteries require fully charging to 100% state of charge (SoC) but lithium batteries do not.  Charging them fully at higher voltages can cause cells to become further out of balance.  //Leaving// them at 100% SoC can cause degradation.((lithium metal "plating"))
-[[https://www.mdpi.com/2076-3417/8/10/1825|This paper]] found that charging only 50% SoC resulted in extension of
+[[https://www.mdpi.com/2076-3417/8/10/1825|This paper]] found that charging to only 50% SoC resulted in extension of
 >   lifetime expectancy of the vehicle battery by 44–130%. When accounting for the calendar ageing as well, this proved to be a large part of the total ageing.
@@ Line 386: / Line 386: @@
     * cell 2 = 3.400v
     * cell 3 = 3.400v
-    * cell 4 = 3.**500v** <-- balancer will try to slow this one down
+    * cell 4 = 3.**500v** <-- a "passive" balancer will try to slow this one down((an "active" balancer would steal from the rich (#4) and give to the poor (#1))
 In both cases the overall battery voltage is 13.6v, but in the unbalanced battery cell #1 is lagging (reducing capacity) and cell #4 is too high.  The balancer will attempt to rein in #4 but the effect is tiny.  Using a typical balancing current of 50mA, if you are charging at 20A that means the cells are receiving 5A except cell #4 which gets only 4.95A, about a 1% difference.  Tiny balancing currents and the propensity of cells to race away explains why balancing is so gradual.

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