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--- opinion:frater_secessus:lifepo4_charging_voltage [2023/06/28 23:16]
frater_secessus [TLDR]
+++ opinion:frater_secessus:lifepo4_charging_voltage [2023/07/21 23:11]
frater_secessus [Problems caused by excessive LiFePO4 charging voltage]
@@ Line 1: / Line 1: @@
 DRAFT
-====== Problems caused by excessive LiFePO4 charging voltage ======
+====== Problems caused by lithium charging profiles ======
+===== excessive charging voltage =====
 [[https://img.mousetrap.net/misc/toohigh.jpg|{{ https://img.mousetrap.net/misc/thumbs/toohigh.jpg}}]]
@@ Line 11: / Line 14: @@
   * voltages in the system are spiking, perhaps tripping your inverter
-It's fairly common for **excessive charging voltage** to cause these symptoms.  Unfortunately it's //very// common for preconfigured Lithium profiles to charge at voltages high enough to trigger the issue.
+It's fairly common for **excessive charging voltage** to indirectly cause these symptoms.  Unfortunately it's //very// common for preconfigured Lithium profiles to charge at voltages high enough to start the problematic chain of events.
@@ Line 22: / Line 25: @@
-  - reduce charging voltage (aka "absorption voltage", "boost voltage")) to something like 13.6v and float voltage, if used, to something like 13.4v.  You may have to use a USER profile instead of a canned LITHIUM profile.  If you choose to modify the Li profile itself take a pic or notes of the original settings so you know what they were and can return to them later if desired.
+  - reduce charging voltage (aka "absorption voltage", "boost voltage") to something like 13.6v.  Float if used, can be set to something like 13.3v-13.4v.  You may have to use a USER profile instead of a canned LITHIUM profile to make these changes.((note that the LITHIUM profile may have protections that others do not.  Low temp charge disconnect, for example.  Read the docs for your charger.))  If you choose to modify the Li profile itself take a pic or notes of the original settings so you know what they were and can return to them later if desired.((If a configuraable profile is not available the gentlest canned profile is often GEL, which will charge at ~14.2v.  Not great, but better than 14.4v or 14.6v.))
-  - observe for a few days.  Charging will be slower and may not finish by sundown((you may have to define or increase an Absorption/boost duration)), but we are most interested in whether or not the symptoms above clear up.
+  - observe for a few days.  Charging will be slower and may not finish by sundown((you may have to define or increase an Absorption/boost duration)); we want to see if it can keep on charging rather than trigger BMS cutoff.
-  - if they do clear up you can start to raise the charging voltage back up gradually (13.65v, 13.7v, 13.74v, etc) or you can leave it low.  {note from secessus:  there is little benefit to charging LiFePO4 >13.8v.]  Float can remain at 13.4v.
+  - if symptoms do clear up you can start to raise the charging voltage back up gradually (13.65v, 13.7v, 13.75v, etc) or you can leave it low if you are getting enough charge.  {note from secessus:  there is little benefit to charging LiFePO4 >13.8v.]  Float can remain low at 13.3v-13.4v.
   - if it starts acting up again drop charging voltage back down a notch or two
@@ Line 30: / Line 33: @@
-LiFePO4 will fully charge at voltages as low as the mid-13s, but it will take more time at lower voltages;  that 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:
+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 absorption: hit the voltage setpoint and //stop//. Cell voltages tend to diverge as charging voltage increases.
+  *  ≥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 token 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
-  * 13.4v will //eventually// fully charge the bank but it would take days.  Impractical for solar charging since the sun keeps going down...
+  * 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.

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