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electrical:depth_of_discharge [2020/06/23 10:55]
frater_secessus
electrical:depth_of_discharge [2021/02/21 13:33] (current)
frater_secessus [SoC by voltage]
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 | | | | | | | | | | | | | | | | | | | |
 | | | | | | | | | | | | | | | | | | | |
-|  **DoD**|  **State of Charge**|  **power per cycle**|  **Num. of cycles**|  **lifetime power in Kah((Ah * 1000))**|  **levelled cost / Kah**|  **life in years**|  **Sets needed for target Ah**|  **Weight**|+|  **DoD**|  **State of Charge**|  **power per cycle**|  **Num. of cycles**|  **lifetime power in kAh((Ah *  1000))**|  **levelled cost / Kah**|  **life in years**|  **Sets needed for target Ah**|  **Weight**|
 |  10|  90|  22.5| | | | | | | |  10|  90|  22.5| | | | | | |
 |  20|  80|  45|  3000|  135|  $1.93|  8.2|  3.9|  482| |  20|  80|  45|  3000|  135|  $1.93|  8.2|  3.9|  482|
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 ==== SoC by voltage ==== ==== SoC by voltage ====
 +
 +Note: read [[https://marinehowto.com/under-load-battery-voltage-vs-soc/|this article by mainesail]]
  
 100% SoC (~12.7v) is measured [[electrical:12v:charging|after the bank has been fully charged]] and then rested. It is measured "on the way down";  measuring "on the way up" while charging will lead to false confidence and leaving the battery [[electrical:12v:psoc|less than fully charged]]. 100% SoC (~12.7v) is measured [[electrical:12v:charging|after the bank has been fully charged]] and then rested. It is measured "on the way down";  measuring "on the way up" while charging will lead to false confidence and leaving the battery [[electrical:12v:psoc|less than fully charged]].
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   * constant light loads with measured >=12.2v   * constant light loads with measured >=12.2v
   * intermittent heavier loads that leave the system with measured >=12.2v when that load is removed   * intermittent heavier loads that leave the system with measured >=12.2v when that load is removed
 +
 +The more challenging task is judging when to kill the circuit based on voltage **under heavier loads**. Consider this chart:
 +
 +{{ https://i.stack.imgur.com/bm93G.jpg}}
 +
 +For a 200A bank 50% DoD would be 12.1v at rest, ~12.0v at C/10 (20A discharge), ~11.55v at C/5 (40A discharge), and 11.2v at C/3 (~70A discharge). 
 +
 +It may take experimentation with your system to see where the battery voltage rebounds after removing the heavy loads.  An approach might be:
 +
 +  - apply expected load
 +  - run battery down to 11.5v (then 11.25, 11, 10.75, 10.5 etc until battery no longer rebounds to 12.1-12.2v)
 +  - remove load
 +  - observe battery voltage
 +
 +If the battery rebounds to the desired voltage then repeat to deeper discharge.  Stop when the battery no longer can rebound to the setpoint.  The LVD voltage is the lowest voltage the system can  drop to and still rebound to the desired setpoint when the load is removed. 
  
  
electrical/depth_of_discharge.1592924135.txt.gz ยท Last modified: 2020/10/11 19:48 (external edit)