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--- opinion:frater_secessus:lifepo4_charging_voltage [2023/06/28 23:32]
frater_secessus [the full process]
+++ opinion:frater_secessus:lifepo4_charging_voltage [2024/02/10 11:33] (current)
frater_secessus [the full process13.6v example
@@ Line 1: / Line 1: @@
 DRAFT
-====== Problems caused by excessive LiFePO4 charging voltage ======
+====== Problems caused by lithium charging profiles ======
+You'd think that a "lithium profile" would be suitable for lithium.  That may or may not be so for your particular use case.  Read on...
+===== excessive charging voltage =====
 [[https://img.mousetrap.net/misc/toohigh.jpg|{{ https://img.mousetrap.net/misc/thumbs/toohigh.jpg}}]]
@@ Line 14: / Line 17: @@
-===== TLDR =====
+==== TLDR ====
-If this is the problem then reducing the charging voltage will cause the symptoms to improve or disappear.
+If excessive charging voltage is the problem then reducing the charging voltage will cause the symptoms to improve or disappear.
 [[opinion:frater_secessus:pareto|about these summaries]]
-===== the full process =====
+==== the full process ====
@@ Line 27: / Line 31: @@
   - if it starts acting up again drop charging voltage back down a notch or two
-==== why lower-voltage charging works ====
+=== why lower-voltage charging works ===
 LiFePO4 will fully charge at voltages as low as the mid-13s,  but it will take more time.  That extra time is called "Absorption duration"(("boost duration in Renogy- and EpEver-speak)).  At the kinds of current levels we usually see in offgrid charging((~0.2C)) the duration looks like this:
-  *  ≥14.0v will charge to 100% SoC with zero minutes of absorption durations: hit the voltage setpoint and //stop//. Cell voltages tend to diverge as charging voltage increases above 14.0v because they are further up the knee (see below)
+  *  ≥14.0v will charge to ~100% SoC with zero minutes of absorption durations: hit the voltage setpoint and //stop//. Cell voltages tend to diverge as charging voltage increases above 14.0v because they are further up the knee (see below)
-  * 13.8v will charge to 100% SoC with a small amount of Absorption (10-30 minutes?) and cells tend to stay in balance.
+  * 13.8v will charge to ~100% SoC with a small amount of Absorption (10-30 minutes?) and cells tend to stay in balance.
-  * 13.6v will charge to 100% SoC with several hours of Absorption  <-- where we are starting
+  * 13.6v will charge to ~100% SoC with several hours of Absorption ([[https://diysolarforum.com/threads/victron-dcdc-12-12-30-charger-no-bluetooth-on-new-install.78373/post-1003471|example]] with data)  <-- where we are starting
-  * 13.4v will //eventually// fully charge the bank but it would take days.  It takes so long we can use 13.4v as a Float voltage.
+==== why the problem occurs ====
-===== why the problem occurs =====
 {{  https://us.v-cdn.net/6024911/uploads/editor/ty/18vvr0fd7cff.jpg?135}}
@@ Line 60: / Line 55: @@
-===== further reading =====
+==== further reading ====
   * [[electrical:12v:drop-in_lifepo4#why_are_manufacturer-recommended_charging_voltages_so_high|an approach to greater LiFePO4 longevity]]
+===== lack of pseudo-float =====
+So your charge controller isn't charging even though battery state of charge is dropping?
+This can be intentional behavior, caused by a Li profile that
+  - charges to a high voltage (see above)
+  - then allows the battery to discharge until it hits the [[electrical:solar:charge_controller_setpoints|Rebulk setpoint]]...
+  - at which point it charges to the high voltage again...
+  - rinse and repeat until the sun goes down
+During the discharge stage the controller will appear to stop working.  In reality it's waiting to hit that rebulk setpoint to start the party again.
+To avoid this problem. configure a "float" voltage of 13.3v-13.4v.  [[electrical:12v:drop-in_lifepo4#mythyou_shouldn_t_float_lithium|This will hold state of charge without overcharging]].

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