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--- electrical:12v:charging [2019/01/03 16:50]
frater_secessus
+++ electrical:12v:charging [2020/04/27 20:54]
frater_secessus [absorption stage]
@@ Line 10: / Line 10: @@
-In general, manufacturers of lead chemistries specifiy a charging at [[electrical:12v:battery_capacity|C/10]]; this assumes more charging time than solar power allows.((http://www.cheaprvliving.com/forums/showthread.php?tid=23606&pid=288284#pid288284))  Regularly cycled banks may benefit from firmer charging at C/3.  There may not be a practical maximum charging rate for cycled FLA batteries //when charged from solar//.  As Sternwake put it when describing a C/1.5 (!) charging scenario, "solar is not instant max output."((http://www.cheaprvliving.com/forums/showthread.php?tid=23606&pid=288284#pid288284))
+In general, manufacturers of flooded lead chemistries specify charging at [[electrical:12v:battery_capacity|C/10]] to C/5; this assumes more charging time than solar power allows.((http://www.cheaprvliving.com/forums/showthread.php?tid=23606&pid=288284#pid288284))  AGM are typically charged at C/5 to C/3.  There may not be a practical maximum charging rate for cycled FLA batteries //when charged from solar//.  As Sternwake put it when describing a C/1.5 (!) charging scenario, "solar is not instant max output."((http://www.cheaprvliving.com/forums/showthread.php?tid=23606&pid=288284#pid288284))
 ===== three stage charging =====
@@ Line 31: / Line 31: @@
 ==== absorption stage ====
-The absorption stage, sometimes called //acceptance// or //boost//, is a constant voltage stage during which the battery is brought to full charge.  This stage requires a **great deal of time** but decreasing amounts of current.
+The absorption stage, sometimes called //acceptance//((which makes sense)) or //boost//((doesn't make sense!)), is a constant voltage stage during which the battery is brought to full charge.  This stage requires a **great deal of time** but decreasing amounts of current.
+Absorption **begins when the battery reaches the absorption voltage** ([[electrical:12v:electrical notation|Vabs]], 14.8v in our example) and **ends when the battery tapers off current acceptance** to something like [[electrical:12v:battery_capacity|C/100]] ("End Absorb", "endAmps"),  and/or when a period of time has elapsed.
+Example:  if you have a 100Ah battery bank and the manufacturer states that endAmps is C/100, then the battery is fully charged when it is only accepting 1A of current((100Ah/100 = 1A)) **at Vabs**.  An endAmps recommendation of C/200 would be the battery accepting 0.5A of current.((100Ah/200 = 0.5A)) at Vabs.
+In practice absorption takes longer when the battery has been discharged deeply and shorter when it has not.((http://www.cheaprvliving.com/forums/Thread-Can-a-solar-panel-and-charge-controller-over-charge-a-battery?pid=96965#pid96965))
+**Mythbuster:** although it is commonly said that Vabs is attained at ~80% capacity...
+> 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**
+  * 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**
-Absorption **begins when the battery reaches the absorption voltage** ([[electrical:12v:electrical notation|Vabs]], 14.8v in our example) and **ends when the battery tapers off current acceptance** to something like C/100 ("End Absorb", "endAmps"),  and/or when a period of time has elapsed.  In practice absorption takes longer when the battery has been discharged deeply and shorter when it has not.((http://www.cheaprvliving.com/forums/Thread-Can-a-solar-panel-and-charge-controller-over-charge-a-battery?pid=96965#pid96965))
 Some controllers will allow the user to configure the time or ratio of capacity/current (C///n//).  Sternwake says:
-> If your charge controller only holds [absorption] voltage for an hour or two, that is likely not enough time. As long as [there is a load] and you cycle the battery daily, you could set float voltage to 14.8v [to match absorption] without worry. Only when you stop cycling the battery do you need to return float voltage to more regular 13.2v levels. Premature application of float voltage by automatic charging sources is a battery killer.((http://www.cheaprvliving.com/forums/Thread-Solar-or-Battery-Problem?pid=229883#pid229883))
+> If your charge controller only holds [absorption] voltage for an hour or two, that is likely not enough time. As long as [there is a load] and you cycle the battery daily, you could set float voltage to 14.8v((for example - secessus)) [to match absorption] without worry. Only when you stop cycling the battery do you need to return float voltage to more regular 13.2v((for example - secessus)) levels. Premature application of float voltage by automatic charging sources is a battery killer.((http://www.cheaprvliving.com/forums/Thread-Solar-or-Battery-Problem?pid=229883#pid229883))
 ==== float stage ====
@@ Line 46: / Line 64: @@
-=== charge-and-hold ===
+===== charge-and-hold =====
 Charging can be achieved with a simpler methods like charge-and-hold where the charger has a single setpoint which it holds;  current will drop as the battery accepts less.
@@ Line 57: / Line 75: @@
-=== charge-and-stop ===
+===== charge-and-stop =====
-[[electrical:solar:charge_controller#shunt_controllers|Shunt chargers]] have a charge-and-stop approach where they:
+[[electrical:solar:charge_controller#shunt_controllers|Shunt]] (on/off) chargers have a charge-and-stop approach where they:
   - charge to [[electrical:12v:hvd|High Voltage Disconnect]] (Vhvd) and stop
   - fall in voltage to a High Voltage Reconnect (Vhvr)
   - repeat
+**This differs from PWM** because PWM can hold an average voltage by cutting power hundreds or thousands of times a second.  If you make a setpoint for 13.6v it will hold 13.6v as long as sun and [[electrical:12v:loads|loads]] cooperate.  A shunt programmed to charge to disconnect at 13.6v and reconnect at 12.7v will average 13.05v.
 These setpoints may or may not be user-configurable.
 Charge-and-stop may be useful when charging battery chemistries like lithium, or when [[electrical:solar:shallow_cycling|shallow-cycling]].
-=== charging AGM batteries ===
+===== charging AGM batteries =====
 AGM batteries are kept healthy by:
-  - vigorous Bulk charging, sometimes greater than solar-only charging can provide.((http://www.cheaprvliving.com/forums/Thread-anyone-familiar-with-Worker-AGM-batteries?pid=97068#pid97068))  Consider augmenting with alternator or shore power charging.
+  - vigorous Bulk charging((minimum current of [[electrical:12v:battery_capacity|C/5]] up to C/3)) sometimes greater than solar-only charging can provide.((http://www.cheaprvliving.com/forums/Thread-anyone-familiar-with-Worker-AGM-batteries?pid=97068#pid97068))  Consider augmenting with alternator or shore power charging.
   - long Absorption stages
   - but lower Absorption voltage (to prevent outgassing)
@@ Line 79: / Line 100: @@
 Many charge controllers have AGM or GEL modes that handle these setpoints and durations.
-=== charging other chemistries ===
+===== charging other chemistries =====
-See [[electrical:12v:lifepo4_batteries_thread#charging|LiFePO4 (lithium) charging]]
+See [[electrical:12v:lifepo4_batteries_thread#charging|LiFePO4 (lithium) bare cell charging]]
-=== equalization ===
+===== equalization =====
 Sometimes called the fourth stage, "equalizing is an overcharge performed after fully charging deep-cycle flooded/wet batteries. An equalizing charge prevents battery stratification and reduces sulfation which are leading causes of battery failure. Trojan recommends equalizing every 30 days or when batteries have a low specific gravity reading after fully charging... Deep-cycle AGM or gel batteries should NEVER be equalized."((http://www.trojanbattery.com/pdf/TrojanBattery_UsersGuide.pdf))
@@ Line 92: / Line 113: @@
-Water levels should be topped off //after// equalization.((exposed plates should be covered before EQ, though)) Doing so before equalization could result in spillover.
+If water levels are below the plates, add enough water to cover the plates before equalizing.  Then top off //after// equalization.  Topping off before equalization could result in spillover and loss of electrolyte.
-=== temperature compensation ===
+===== temperature compensation =====
 Accurate charging requires the charger know the temperature of the batteries being charged. In hot temps a full charge will require somewhat lower voltage. Cold temps will require higher voltage((https://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/)), enough to trip overvoltage protection in some 12v gear.
@@ Line 108: / Line 129: @@
   - in the absence of actual measurements the charger will likely use the 77F laboratory standard.
-=== watering batteries ====
+This automatic voltage tweaking for temperature may result in your actual battery voltages being observably higher in cold temps and lower in hot temps.
+===== watering batteries ======
 {{ http://www.trojanbattery.com/wp-content/uploads/2013/07/WaterDia_B.jpg?150}}
 Flooded lead-acid batteries outgas during Absorption, causing a slow loss of water.  They outgas intentionally in Equalization.  To counteract this, the 'dweller must remove the caps and inspect the water level.  If low, distilled water is added.
@@ Line 120: / Line 143: @@
-A [[http://amzn.to/2gEtVwL|battery waterer]] can make the job easier, and does not require one to judge water level visually.
+A [[http://amzn.to/2gEtVwL|battery waterer]] can make the job easier, and does not require one to judge water level visually.  The water "bloops" as it fills and stops blooping when the water is at the correct level.
 Batteries that are older, in poorer health, or are charged at higher voltages will be "thirstier".  Check water levels 1x/month until you know how they behave.
-=== charging while using the 12v system ===
+===== charging while using the 12v system =====
 Smart chargers handle charging under load gracefully. As long as there is enough solar power coming in to hold the absorption or float voltage steady those charging stages will not be disturbed. If there is not enough power to hold the prescribed voltage the charger may restart Bulk charging. This behavior may be configurable by the user.

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