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electrical:12v:eternal_absorption [2020/07/08 12:08] frater_secessus [insufficient Absorption] |
electrical:12v:eternal_absorption [2021/05/05 11:00] frater_secessus [workarounds] |
Note: this is for deep cycle lead chemistries only.! Lithium chemistries should not be held at full voltage. | Note: this is for deep cycle lead chemistries only! Lithium batteries should not be held at full voltage. |
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| [[lifestyle:words_of_wisdom|Words of wisdom]]: |
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| > "As long as... you cycle the battery daily, you could set float voltage to [Vabs] too without worry. Only when you stop cycling the battery do you need to return float voltage to more regular 13.2v levels." -- sternwake((http://www.cheaprvliving.com/forums/showthread.php?tid=20022&pid=229883#pid229883)) |
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====== dealing with insufficient Absorption ====== | ====== dealing with insufficient Absorption ====== |
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In off-grid solar charging scenarios batteries are most often damaged by [[electrical:batterycide|chronic undercharging]]. Specifically, not holding the [[electrical:solar:charge_controller_setpoints|manufacturer's recomended Absorption voltage]] (Vabs), and not holding that voltage long enough((duration)) for acceptance to drop to endAmps. | In off-grid solar charging scenarios batteries are most often damaged by [[electrical:batterycide|chronic undercharging]]. Specifically, not holding the [[electrical:solar:charge_controller_setpoints|manufacturer's recommended Absorption voltage]] (Vabs), and not holding that voltage long enough((duration)) for acceptance to drop to endAmps. |
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Causes of insufficient Absorption: | Causes of insufficient Absorption: |
* solar conditions - not enough good sun long enough to finish Absorption | * solar conditions - not enough good sun long enough to finish Absorption |
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===== set Vfloat to Vabs ===== | ===== workarounds ===== |
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| While you may not be able to increase the //actual// duration,((as when the controller setpoint is maxxed out)) you can achieve a similar effect with one or more of these techniques: |
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| * if duration setpoint is maxxed then **set Vfloat == Vabs**. Absorption duration will effectively be "until the sun goes down". |
| * **charge at a lower current** (charging minimum). While [[opinion:frater_secessus:charging_faster|overall charging will take about the same amount of time]], Bulk's share of that time will increase and [[electrical:12v:charging#absorption|Absorption will take somewhat less time]]. |
| * **Absorb at a higher((but still manufacturer-sanctioned)) voltage** (Vabs), this will decrease Absorption duration. Keep a close watch on water levels for flooded batts, and also mind the max allowable voltage for AGM/Gel. |
| * **Float at a higher((but still manufacturer-sanctioned)) voltage** (Vfloat). |
| * [[electrical:12v:alt_and_solar|supplement]] solar charging with another charging source during Bulk, allowing more time for solar to finish absorption. |
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| Some controllers/chargers have a "restart Absorption" option allows one to override Float and get more time at Vabs. Best use of this feature would be to look at the controller display a few minutes before the Absorption timer is due to expire. If acceptance is good let it go. If acceptance is too high give the bank another round of Absorption. |
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The Eternal Absorption approach completely forgoes Float stage, forcing the controller to stay in Absorption by setting Vfloat to Vabs. This addresses the controller issues above. | If those approaches are insufficient, //Eternal Absorption// approach completely forgoes Float stage, forcing the controller to stay in Absorption by **setting Vfloat to Vabs**. This addresses the controller issues above. It will not address the insolation problem on a given day, but extended Absorption will help reduce damage from previous days of poor harvest. |
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===== gotchas ===== | ===== gotchas ===== |
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* increased Vabs duration will require more frequent watering, due to increased outgassing | * increased Vabs duration may require more frequent watering, due to increased outgassing.((but see [[http://bdp.mousetrap.net/index.php/2020/09/18/watered-batteries-after-three-weeks-of-eternal-absorption/|this blog post]] which suggests no dramatic increase)) |
| * calcium-enhanced batteries (typically starter batteries and some hybrid "marine" batteries) can be damaged((positive grid corrosion)) by long periods of excess voltage. The question is which is worse for them: chronic undercharging or grid corrosion from higher voltage. Pick your poison. |
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