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--- electrical:solar:charge_controller [2024/04/16 20:28]
frater_secessus [specs]
+++ electrical:solar:charge_controller [2024/06/01 21:57]
frater_secessus [specs]
@@ Line 25: / Line 25: @@
 Cautionary example:  [[https://www.youtube.com/watch?v=z5RtZe9AW2E|12W Unregulated Panel vs. 220Ah AGM Bank]]
+==== sensors ====
+To charge correctly the controller needs to know the precise voltage and temperature of the battery bank.
+In the best case scenario these measurements are done with an external **temp sensor** and **voltage sense**((not a typo, it's called voltage sense)) that plug into the controller or talk to the controller via bluetooth.
+In the absence of external sensors the controller tries to use any internal sensors it might have.  The values will be inaccurate:
+  * battery voltage will read [[electrical:12v:voltage_sag|falsely high during charging]], and
+  * temperature will read high because of the controller's own heat from electronics
+With lead-chemistry batteries both conditions cause [[electrical:12v:psoc|chronic undercharging]], a key cause of [[electrical:batterycide|premature battery failure]].  Many LiFePO4 batteries have [[opinion:frater_secessus:agm2lifepo4#wait_lfp_can_be_damaged_by_charging_in_cold_weather|low temperature charging cutoff]] if the charger cannot disconnect when battery temps are ~freezing.
 ===== specs =====

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