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--- opinion:frater_secessus:charging_faster [2020/04/18 13:15]
frater_secessus created
+++ opinion:frater_secessus:charging_faster [2020/04/27 21:05]
frater_secessus [lead-acid]
@@ Line 2: / Line 2: @@
+There is a common misperception that charging one's battery banks //faster// is //better// or worth throwing more money at.  Here are some reasons it is not always true:
+===== lead-acid =====
+**Lead batteries** have a **maximum amount of current** they will accept, typically [[electrical:12v:battery_capacity|C/3]] for AGM and C/5 for flooded. So if you have 100Ah of AGM the most it will want to take is something like ~33A.  Once the battery's limit is hit throwing more charging capacity at it can't charge it any faster.((it may help run loads, though))
+** Deep-cycled lead batteries have a lengthy [[electrical:12v:charging|Absorption]] stage** that cannot be sped up. Depending on use, Absorption typically requires several hours.There is a saying that "it takes 9 months to make a baby, but two women cannot make a baby in 4.5 months".  Same with absorption - it takes what it takes and you cannot hurry it in the normal sense.
+However:
+> charge current affects the SOC transition point from bulk to absorption charging - MaineSail((https://marinehowto.com/how-fast-can-an-agm-battery-be-charged/))
+MaineSail found that
+  * charging AGM at C/2.5 (max rate) resulted in the battery being 63.3% "full" at Vabs and being fully charged in **5hrs, 30 minutes** (20min Bulk, 5hr 10mins Absorption)
+  * charging AGM at C/5 (min rate) resulted in the battery being 77.4% "full" at Vabs and being fully charged in **5hrs, 42 minutes** (76min Bulk, 4hr 26mins Absorption)
+Note that the **using 2x the charging current only sped up the whole process by 12 minutes (3.6%)** due to Vabs starting earlier but taking longer. Getting to Vabs faster could be [[electrical:solar:pwm_tweaking|preferable on PWM controllers]].
+===== lithium =====
+**Lithium batteries** can slurp up current wildly, but shouldn't for their own health.  Lithium lasts longest in sub-C use (ie, less than 100A for a 100Ah Li bank).  C/2 (50A) is a more common limit to keep from stressing them. In commercial examples the BMS will limit current to protect the cells.  A small [[electrical:12v:b2b|DC-DC charger]] can help protect bare cells from their own greediness.
@@ Line 13: / Line 37: @@
   * solar charging - sunlight is only available during a short window, as when camped in a forest canopy with a clear overhead view.  Note that [[electrical:solar:output|poor insolation]] calls for [[electrical:solar:rationing#maximizing_solar_harvest|increased harvest]] / [[electrical:solar:overpaneling|overpaneling]], not faster charging necessarily
   * [[electrical:generator|generator]] charging - for efficiency purposes the generator is shut down after Vabs is reached.  Generators run most efficiently when fully loaded.
-  * [[electrical:converter|shore]] charging - you only have a certain amount of time on the extension cord
+  * [[electrical:converter|shore]] charging - if you only have a certain amount of time on the extension cord
-  * [[electrical:12v:alternator|alternator]] charging - you will driving for short periods only
+  * [[electrical:12v:alternator|alternator]] charging - if you will driving for short periods only

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