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electrical:solar:shallow_cycling [2018/06/16 17:51]
frater_secessus [shallow-cycling]
electrical:solar:shallow_cycling [2020/07/08 12:51] (current)
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 ====
  
-  - 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. ​
  
 === Low Voltage Reconnect (LVR) setpoint === === Low Voltage Reconnect (LVR) setpoint ===
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 > "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.
 +
 +
 +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/​))
 +
 +===== sample build =====
 +
 +Total cost, ~$140.
 +
 +
 +  * 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 
 +
 +
 +===== charging voltages and starter batteries =====
 +
 +
 +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.  ​
 +
 +Problem: ​ calcium-enhanced grids are more susceptible to "​positive grid corrosion"​ from sustained higher voltages.  ​
 +
 +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. ​
 +
 +==== staged charging ====
 +
 +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))
 +
 +  * 14.4v Absorption
 +  * 13.6v Float 
 +
 +So a charge controller with that configuration should be gentle enough on the battery.
 +
 +
 +==== single voltage charging ====
 +
 +This is the tricky part.  Shunts (or controllers set with [[electrical:​12v:​eternal_absorption|Vabs == Vfloat]]) have one charging voltage. ​ What should we use?
 +
 +  * 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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electrical/solar/shallow_cycling.1529196674.txt.gz · Last modified: 2018/06/16 17:51 by frater_secessus