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electrical:depth_of_discharge [2018/07/27 09:23]
frater_secessus 		electrical:depth_of_discharge [2019/02/07 13:14]
frater_secessus
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 ====== Depth of discharge / State of Charge ====== ====== Depth of discharge / State of Charge ======
-{{ http://popupbackpacker.com/wp-content/uploads/2013/12/State-of-Charge-Chart-Trojan.jpg?200|}}//Depth-of-discharge (DoD or DOD)// refers to how much low a deep cycle battery is taken before recharging.  DoD is the inverse of //State of Charge (SoC)//.  Example:  a battery at 30% DoD is at 70% SoC.+ 
 +{{ http://popupbackpacker.com/wp-content/uploads/2013/12/State-of-Charge-Chart-Trojan.jpg?200|}}//Depth-of-discharge (DoD or DOD)// refers to how low a deep cycle battery is taken before recharging.  DoD is the inverse of //State of Charge (SoC)//.  Example:  a battery at 30% DoD is at 70% SoC. 
 For solar powered systems the greatest DoD (and therefore lowest SoC) will be in early morning just before the panels start creating power again. For solar powered systems the greatest DoD (and therefore lowest SoC) will be in early morning just before the panels start creating power again.
 +
 DoD has a **significant impact on longevity of deep cycle batteries**.  For this reason [[electrical:inverter|Inverters]] and other high-load devices may have a [[electrical:12v:lvd|low voltage cutoff]]. DoD has a **significant impact on longevity of deep cycle batteries**.  For this reason [[electrical:inverter|Inverters]] and other high-load devices may have a [[electrical:12v:lvd|low voltage cutoff]].
 +
 The **most common discharge limit for deep cycle batteries is 50% DoD**.  This gives a good balance between usability and longevity.  The **lowest cost per Ah** occurs around 30% DoD although this requires buying, installing, and moving //dead lead// or unusable battery capacity.((20% DoD is the limit at which manufacturers rate their battery's cycles.))   The **most common discharge limit for deep cycle batteries is 50% DoD**.  This gives a good balance between usability and longevity.  The **lowest cost per Ah** occurs around 30% DoD although this requires buying, installing, and moving //dead lead// or unusable battery capacity.((20% DoD is the limit at which manufacturers rate their battery's cycles.))  
 +
 Based on the following data on the Trojan T-105: Based on the following data on the Trojan T-105:
   * lowest cost per Ah happens at 30% DoD   * lowest cost per Ah happens at 30% DoD
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 |  80|  20|  180|  800|  144|  $1.81|  2.2|  1.0|  121| |  80|  20|  180|  800|  144|  $1.81|  2.2|  1.0|  121|
 One can choose to [[electrical:severe battery use|run the batteries quite hard]] in emergency or temporary conditions with the understanding that it will likely "hurt" the batteries to some degree.  Consistently going past 50% DoD will greatly reduce the battery's usable cycles.  Some studies suggest discharging to 80% yields 1/10th the number of cycles available at 20%.   One can choose to [[electrical:severe battery use|run the batteries quite hard]] in emergency or temporary conditions with the understanding that it will likely "hurt" the batteries to some degree.  Consistently going past 50% DoD will greatly reduce the battery's usable cycles.  Some studies suggest discharging to 80% yields 1/10th the number of cycles available at 20%.  
 +
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 +===== SoC by amps =====
 +
 +A [[electrical:12v:battery_monitor|battery monitor]], usually a amp/coulumb counter with a shunt, will measure the current going to/from the battery.  It will often show real-time current flow and a state of charge percentage.  It may also show voltage (see below).
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 +===== SoC by voltage =====
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 +
 The voltage level associated with 50% DoD is widely discussed.  **12.1v rested** is generally used as 50% State of Charge (SoC).  A more conservative approach uses **12.2vdc rested**. The voltage level associated with 50% DoD is widely discussed.  **12.1v rested** is generally used as 50% State of Charge (SoC).  A more conservative approach uses **12.2vdc rested**.
 Since resting is rare in most practical scenarios stopping at 12.2vdc under light loads would be a practical approach.  DC expert SternWake((http://www.cheaprvliving.com/forums/User-SternWake)) says: Since resting is rare in most practical scenarios stopping at 12.2vdc under light loads would be a practical approach.  DC expert SternWake((http://www.cheaprvliving.com/forums/User-SternWake)) says:
electrical/depth_of_discharge.txt · Last modified: 2023/08/17 21:36 by frater_secessus

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