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electrical:12v:lvd [2018/06/23 16:50] frater_secessus [challenges] |
electrical:12v:lvd [2020/11/20 11:13] frater_secessus [Low Voltage Disconnect (LVD)] |
A low voltage disconnect is used to stop loads from dragging a battery bank below a given voltage (Vlvd). | A low voltage disconnect is used to stop loads from dragging a battery bank below a given voltage (Vlvd). |
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The simplest way to implement an LVD is to wire all loads go through the LOAD output of the charge controller, and set the controller's Vlvd. If system load is heavier than the LOAD output can provide, one may use: | The simplest way to implement an LVD is to wire all loads go through the LOAD output of the charge controller, and set the controller's Vlvd. If the controller has no LVD or if the load is heavier than the LOAD output can provide, one may: |
* a stand-alone LVD with higher current rating (more expensive) | |
| * use a [[https://amzn.to/3m2OTp3|stand-alone LVD]] |
* or run loads off a [[electrical:12v:relay|relay]] triggered by the LVD (less expensive) | * or run loads off a [[electrical:12v:relay|relay]] triggered by the LVD (less expensive) |
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except the [[electrical:inverter|inverter]], due to the heavy current draw. The inverter will have its own internal LVD. | except the [[electrical:inverter|inverter]], due to the heavy current draw. The inverter will have its own internal LVD. |
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===== common LVD setpoints ===== | ===== common LVD setpoints ===== |
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Lead-acid deep cycle batteries last the longest with best capacity if they are never cycled more than 50% [[electrical:depth_of_discharge|Depth of Discharge]]((and fully charged afterwards)). That point is somewhere around 12.20v when rested or very lightly loaded. | Lead-acid deep cycle batteries are typically discharged 50% [[electrical:depth_of_discharge|Depth of Discharge]] or less ((and fully charged afterwards)). That point is somewhere around 12.20v when rested or very lightly loaded. |
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This following chart((http://www.trojanbattery.com/pdf/GEL_Trojan_ProductLineSheet.pdf)) shows DoD vs expected duty cycles. In an offgrid scenario we will assume the bank is cycled every night. If the bank is drained to the usual 50% DoD the bank((under lab conditions)) is predicted to last 1000 cycles, or about 3 years. If the bank cycle is shallower to 20% DoD the bank is expected to last 2500 cycles, or about 7.5 years. If the bank is deeply cycled to 80% DoD the bank is expected to last 500 cycles, or about 1.5 years. | This following chart((http://www.trojanbattery.com/pdf/GEL_Trojan_ProductLineSheet.pdf)) shows DoD vs expected duty cycles. In an offgrid scenario we will assume the bank is cycled every night. If the bank is drained to the usual 50% DoD the bank((under lab conditions)) is predicted to last 1000 cycles, or about 3 years. If the bank cycle is shallower to 20% DoD the bank is expected to last 2500 cycles, or about 7.5 years. If the bank is deeply cycled to 80% DoD the bank is expected to last 500 cycles, or about 1.5 years. |
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[[electrical:12v:lifepo4_batteries_thread|LiFePO4]] nominal 12v banks can be safely drained to 80-90% Depth of Discharge. That point is something like 12.0v.((http://rvwiki.mousetrap.net/doku.php?id=electrical:12v:lifepo4_batteries_thread#notable_voltage_reference_points)) | [electrical:12v:deep_cycle_battery#lithium_chemistries[electrical:12v:lifepo4_batteries_thread|LiFePO4]] nominal 12v banks can be safely drained to 80-90% Depth of Discharge. That point is something like 12.0v.((http://rvwiki.mousetrap.net/doku.php?id=electrical:12v:lifepo4_batteries_thread#notable_voltage_reference_points)) |
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===== challenges ===== | ===== challenges ===== |