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electrical:depth_of_discharge [2020/05/13 11:26] frater_secessus [Depth of discharge / State of Charge] |
electrical:depth_of_discharge [2020/06/23 10:55] frater_secessus |
====== Depth of discharge / State of Charge ====== | ===== Depth of discharge / State of Charge ===== |
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{{ 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 between [[electrical:12v:charging|full charges]]. 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 between [[electrical:12v:charging|full charges]]. DoD is the inverse of //State of Charge (SoC)//. Example: a battery at 30% DoD is at 70% SoC. |
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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]]. |
| ===== effect of SoC on battery life ===== |
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| How deeply one regularly discharges lead-chemistry batteries will have a **direct effect on how long the battery bank will last**.((Banks are typically replaced when they have lost 20% of their capacity)) |
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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.)) |
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===== SoC by amps ===== | ===== estimatating SoC ===== |
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| ==== SoC by specific gravity ==== |
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| > "The truest measure of a [lead chemistry] battery's state of charge is the specific gravity of the battery acid." -- Rolls battery.((http://support.rollsbattery.com/support/solutions/articles/428-state-of-charge-charging-flooded-lead-acid-batteries)) |
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| Only flooded-type batteries are practical for SoC assessment by SG of the electrolyte. Needed for this operation: |
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| * temperature of the battery |
| * SG chart from the battery manufacuturer |
| * [[https://amzn.to/3dOHGEU|battery SG tester (hydrometer)]] |
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| ==== SoC by amps ==== |
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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). | 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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| Note that deep cycle battery [[electrical:12v:battery_capacity|capacities]] are given at the "20 hour rate", roughly depleting the battery over the course of a day/night cycle. Heavier loads will cause apparent capacity to decrease. Lithium is much less susceptible and tends to deliver more predictable capacity. |
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===== SoC by voltage ===== | |
| ==== SoC by voltage ==== |
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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]]. |
* 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 |
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===== partial state of charge ===== | ===== partial state of charge ===== |
This section [[electrical:12v:psoc|has moved]]. | This section [[electrical:12v:psoc|has moved]]. |
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