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electrical:solar:shallow_cycling [2018/06/16 20:51]
frater_secessus [shallow-cycling] |
electrical:solar:shallow_cycling [2020/07/08 15:51]
frater_secessus [how it works] |
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| Instead of deep-cycling, the starter battery is //non-cycled//((never discharged below 100% state of charge)) as described below. It can also be [[electrical:solar:shallow_cycling#shallow-cycling|shallow-cycled]].((discharged to 90% state of charge)) | Instead of deep-cycling, the starter battery is //non-cycled//((never discharged below 100% state of charge)) as described below. It can also be [[electrical:solar:shallow_cycling#shallow-cycling|shallow-cycled]].((discharged to 90% state of charge)) |
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| ==== how it works ==== | ==== how it works ==== |
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| - a simple [[electrical:solar:charge_controller#shunt_controller|shunt charge controller]] holds the battery at a mild Absorption voltage (14.0, - 14.2v) when charging, just below the significant gassing point | - a simple [[electrical:solar:charge_controller#shunt|shunt charge controller]] holds the battery at a mild Absorption voltage (14.0, - 14.2v, see notes [[electrical:solar:shallow_cycling#charging_voltages_and_starter_batteries|below]]) when charging, just below the significant gassing point |
| - the controller's LOAD output disconnects (LVD) at 100% SoC (~12.7v) | - the controller's LOAD output disconnects (LVD) at 100% SoC (~12.7v) |
| - the controller's LOAD output //re//connects (LVR) at ~13.0v); see discussion below | - the controller's LOAD output //re//connects (LVR) at ~13.0v) |
| - power is //only// taken from the controller's LOAD output;((or from a circuit control by a relay on the LOAD output)) this ensures the starter battery is never discharged below the intended setpoint | - power is //only// taken from the controller's LOAD output;((or from a circuit control by a relay on the LOAD output)) this ensures the starter battery is never discharged below [[electrical:12v:lvd|the intended setpoint]]. Since the load is disconnected below 12.7v the battery cannot be run down by loads. |
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| === Low Voltage Reconnect (LVR) setpoint === | === Low Voltage Reconnect (LVR) setpoint === |
| > "most of the "defective" batteries returned to manufacturers during free replacement warranty periods are good"((https://www.batterystuff.com/kb/articles/battery-articles/how-do-batteries-die.html)) | > "most of the "defective" batteries returned to manufacturers during free replacement warranty periods are good"((https://www.batterystuff.com/kb/articles/battery-articles/how-do-batteries-die.html)) |
| ... A charging regime might even extend the perceived longevity of the starter battery. | ... A charging regime might even extend the perceived longevity of the starter battery. |
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| | Anecdote: TreborEnglish runs his 75A flooded 12v wally world deep cycle to 87% SoC regularly and it has lasted 3 years as of this writing. He reports it requires 20-30ml of water/month.((https://www.reddit.com/r/vandwellers/comments/enwq70/best_car_battery_for_van_life/fe670is/)) |
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| | ===== sample build ===== |
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| | Total cost, ~$140. |
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| | * 100w poly((for least expensive and best performance with [[electrical:solar:shunt_tweaking|shunt]]/[[electrical:solar:pwm_tweaking|pwm [[electrical:solar:charge_controller|controllers]]]])) panel on the roof, either a [[https://amzn.to/2snWQOL|rack-mounted framed panel]] that fits rack dimensions or a [[https://amzn.to/30rmAGD|flex panel]] adhered to the surface. |
| | * [[https://amzn.to/2ToGWyX|cable gland]] for getting wires through roof |
| | * panel wires runs down the vehicle A-pillar inside the passenger area((can be on driver or passenger side depending on where starter battery is located)) and into the PANEL terminals of a [[electrical:solar:shunt_tweaking|$10 shunt]] solar [[electrical:solar:charge_controller|charge controller]] mounted in the footwell or elsewhere |
| | * [[https://amzn.to/2RhbHmD|wire]] run from controller's BATTERY terminals to the starter battery. |
| | * wire run from controller's LOAD terminals to [[https://amzn.to/3adk9vJ|12v/usb outlet]], power bus, etc |
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| | ===== charging voltages and starter batteries ===== |
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| | The chemistry of starter and "hybrid" ("marine") batteries is somewhat different than deep cycle batteries. Speciically, starter batteries typically have calcium added to the positive grid to minimize self-discharge and outgassing. |
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| | Problem: calcium-enhanced grids are more susceptible to "positive grid corrosion" from sustained higher voltages. |
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| | The question is this: **what voltage can starter batteries be held at without damage**? One answer might be be "alternator voltage" since that's already happening when we drive vehicles, and they are not damaged by long journeys. |
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| | ==== staged charging ==== |
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| | CTEK's starter battery charger designed to be left on charges thusly:((https://www.ctek.com/storage/9E4D59B2526B4C3C54C61873C881CAACFC4C93F306DE1C8A2788E26EA6E506DA/f9b26d5eaeeb4787a51e5fc933ae1eae/pdf/media/687dd00827b44e44afee8695c5d0efab/MXS_3.8-manual-low-UK-EN.pdf)) |
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| | * 14.4v Absorption |
| | * 13.6v Float |
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| | So a charge controller with that configuration should be gentle enough on the battery. |
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| | ==== single voltage charging ==== |
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| | This is the tricky part. Shunts (or controllers set with [[electrical:12v:eternal_absorption|Vabs == Vfloat]]) have one charging voltage. What should we use? |
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| | * folks who shallow cycle might charge to 14.4v to help counteract sulfation from overnight cycling. |
| | * folks who non-cycle might charge to 13.6v as if the battery is simply being maintained. This leaves some power on the table (~8.5%) for non-MPPT controllers but may be easier on the battery. |
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