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electrical:12v:drop-in_lifepo4

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electrical:12v:drop-in_lifepo4 [2022/06/16 23:08]
frater_secessus [myth: you have to charge Li to 100%] 		electrical:12v:drop-in_lifepo4 [2022/07/04 13:17]
frater_secessus [myth: you must use DC-DC for alternator charging Li]
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 === testing your isolator with Li === === testing your isolator with Li ===
  
-Here an order of operations one might use to assess whether or not isolator charging will work in a given install:+Here an order of operations one might use to assess whether or not isolator charging will work in a given install:((discontinue at once if you observe unacceptable results, and consider DC-DC or increasing solar)):
  
-  - Read and understand your Li battery manufacturer's charging specs+  - Read and understand your Li battery manufacturer's charging specs - undercharging is fine((assuming one stays above 20% State of Charge)); overcharging is less so but is relatively rare in an isolator context.
   - Read and understand your alternator's specs   - Read and understand your alternator's specs
   - 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.
-  - If that works test it with longer drives and/or with the Li at lower states of charge.  Bring a passenger to observe battery monitor if needed. +  - test it with a drive. 
 +  - repeat the last two steps with the Li bank at lower and lower states of charge, down to the lowest expected state of charge you expect to recharge from alternator. 
  
 **Caveats**:   **Caveats**:  
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   * Only alternator charge while driving ([[rv:idling|no idling]] except for brief preliminary test).     * Only alternator charge while driving ([[rv:idling|no idling]] except for brief preliminary test).  
   * Pay attention while charging from alternator to keep from overcharging the Li or holding for long periods at high [[electrical:depth_of_discharge|states of charge]].   * Pay attention while charging from alternator to keep from overcharging the Li or holding for long periods at high [[electrical:depth_of_discharge|states of charge]].
-  * You may want a manual disconnect or [[electrical:12v:alternator_charging_hvd|HVD]] to shut off alternator charging.  These can be added on the D+ wire (ignition triggered) or electronics ground wire (VSR, solenoid, or voltage-triggered DC-DC)+  * You may want a manual disconnect or [[electrical:12v:alternator_charging_hvd|HVD]] to shut off alternator charging due to excess voltage or if the bank is already charged.  These can be added on the D+ wire (ignition triggered) or electronics ground wire (VSR, solenoid, or voltage-triggered DC-DC)
  
 === but that Victron video! === === but that Victron video! ===
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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: 2024/05/21 22:08 by frater_secessus

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