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electrical:12v:drop-in_lifepo4

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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 [2022/07/04 13:09]
frater_secessus [myth: you must use DC-DC for alternator charging Li]
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 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")) 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. >   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.
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   - Read and understand your isolator's specs and functionality   - Read and understand your isolator's specs and functionality
   - observe your vehicle's chassis voltage during normal operation - note that the voltage //at the battery's location// will likely be lower due to long wiring and also lower when the wiring is carrying a hefty charging current   - observe your vehicle's chassis voltage during normal operation - note that the voltage //at the battery's location// will likely be lower due to long wiring and also lower when the wiring is carrying a hefty charging current
-  - decide whether this will work for your alternator, your isolator, and your Li battery+  - make a first approximation about the ability of alternator, your isolator, and your Li battery to cooperate
   - install [[electrical:12v:battery_monitor|a battery monitor]] so you can observe current and voltage at the battery.  Or use the battery's own BT access.   - install [[electrical:12v:battery_monitor|a battery monitor]] so you can observe current and voltage at the battery.  Or use the battery's own BT access.
   - make the first test run a brief one and with the Li fairly well charged.((higher states of charge will typically lessen current demands to some degree))  Start the engine and see if the charging current and voltage is acceptable.  Turn off the engine.   - make the first test run a brief one and with the Li fairly well charged.((higher states of charge will typically lessen current demands to some degree))  Start the engine and see if the charging current and voltage is acceptable.  Turn off the engine.
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     * cell 2 = 3.400v     * cell 2 = 3.400v
     * cell 3 = 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. 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.
electrical/12v/drop-in_lifepo4.txt · Last modified: 2024/04/12 23:02 by frater_secessus

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