User Tools

Site Tools


electrical:solar:shallow_cycling

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
electrical:solar:shallow_cycling [2018/03/02 09:45]
frater_secessus [how it works]
electrical:solar:shallow_cycling [2023/04/08 13:41] (current)
frater_secessus [shallow-cycling]
Line 1: Line 1:
-Note:  this information should be regarded as experimental.  It is [[https://boondockplan.wordpress.com/tag/shallow-cycling/|being tested]] by secessus.+Note:  this information should be regarded as experimental.  It is [[https://boondockplan.wordpress.com/tag/shallow-cycling/|being tested]] by secessus.  Beginners may want to start with a [[electrical:solar:gentle_intro|gentle intro to solar]].
  
-====== microsolar without deep-cycle batteries ======+[[opinion:frater_secessus:car_micropower|Here]] is a trimmed-down version of this page.
  
-This article describes a small, simple, space-efficient, and inexpensive solar configuration that may be of use to cardwellers or minimalist vandwellers.   
  
-Most of the RV world is familiar with [[electrical:12v:deep_cycle_battery|deep-cycle 12v systems]];  these are intended to store power for use overnight.  If most power is consumed [[electrical:solar:nonessential|in the daytime when the system has excess power]] then deep-cycle batteries may not be required. +====== microsolar without deep-cycle batteries ======
  
-Instead of deep-cyclingthe 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))+This article describes a small, cheapsimple, space-efficient solar configuration that may be of use to car-dwellers or minimalist vandwellers.  
  
 +Benefits:
  
-===== non-cycling =====+  * extremely inexpensive 
 +  * provides 12v power and USB power during daylight 
 +  * could run small [[electrical:inverter|inverter]] loads (<100w?), up to the ability of the panels to deliver.  Note:  inverters impose additional losses (typical 10-20%) which can be significant in microsolar setups.  Running loads from native DC power is usually preferable. 
 +  * will never deplete the starter battery so you get stranded 
 +  * actively maintains the starter battery 
 +  * taking power from the controller uses less power than using the car's ACCessory position, since other car electronics are not being energized. 
  
-//Non-cycling// is the use of solar power only when the battery is fully charged.  +Instead of deep-cycling like someone might in an RV, the idea here is the starter battery can be used but never dragged below 100% state of charge)).  
  
-==== how it works ====+It does require a bit of discipline and forethought to run bigger loads during the daytime when excess power is available. 
  
-  - 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 
-  - 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 
-  - 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 
  
-=== Low Voltage Reconnect (LVR) setpoint === 
  
-The LVR is the point at which the controller turns the LOADs back on.  If **running small loads** (charging phones, LED lights) the setpoint may be set fairly low (like 13.0v).  This will allow loads to be run as soon as possible. 
  
-If **running larger loads** (fans, laptop chargers) the setpoint should be set higher (like 13.5v 14.0v).  This is because the panel will be able to make more power closer to Vmp.  Consider the popular [[http://amzn.to/2you3Kj|Renogy 100w panel]] that puts out about 5.29A.  At the lower LVR the panel((under lab conditions)) will make **68.77W**.  At the higher LVRs the panel will make **71.42-74.06W**+===== non-cycling =====
  
-Note:  running a small MPPT [[electrical:solar:charge_controller|charge controller]] would make this immaterial, as the controller would run the panel at max power (Vmp) at 18.9v.+//Non-cycling// is the use of solar power only when the battery is fully charged The starter battery is even more fully charged than in normal vehicles.
  
 +==== how it works ====
 +
 +  - a simple [[electrical:solar:charge_controller#shunt|shunt charge controller]] holds the starter battery at a medium Float voltage (13.2 - 13.8v, see notes [[electrical:solar:shallow_cycling#charging_voltages_and_starter_batteries|below]]) when charging, this is below the gassing point
 +  - power is taken from [[electrical:solar:charge_controller#using_load_output|the controller's 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. 
 +  - the controller's LOAD output disconnects when battery voltage falls to 100% ((LVD))  - no more power is provided
 +  - the controller's LOAD output //re//connects when charging and battery voltage has risen to >= ~13.0v((LVR)) - power once again flows
 +  
  
 ==== components ==== ==== components ====
  
-  * vehicle with starter battery+Once you have the car, the rest of the parts will be about $100 if you watch sales.  
 + 
 +  * vehicle with starter battery (you already have this!)
   * simple [[http://amzn.to/2z8Sd8Y|10A controller **with configurable setpoints**]].  The controller should be mounted in a location easy for easy access if the built-in USB ports are going to be used.   * simple [[http://amzn.to/2z8Sd8Y|10A controller **with configurable setpoints**]].  The controller should be mounted in a location easy for easy access if the built-in USB ports are going to be used.
-  * small solar panel; 25w-100W would be fine.  +  * small solar panel; 100W polycrystalline [[https://amzn.to/2Vi37Xhlike this one]] would work well.  Home Depot and others have sales on 100w panels for as low as $73. If you are using a PWM controller a low Vmp spec is preferable.  With MPPT a higher Vmp is preferable.  
-  * connector of some kind if panel is mounted off-vehicle+  * connector of some kind if panel is mounted off-vehicle;  cable gland if the panels are mounted on the vehicle and the wire is passed through the 
   * wiring from panel to controller and from controller to starter battery   * wiring from panel to controller and from controller to starter battery
-  * [[http://amzn.to/2xHjBi7|usb/12v power outlet]].  An outlet with USB ports in it would allow the controller itself to be mounted discreetly and closer to the battery.  +  * [[http://amzn.to/2xHjBi7|usb/12v power outlet]] wired to the LOAD output of the controller, if desired.  An outlet with USB ports in it would allow the controller itself to be mounted discreetly and closer to the battery.
  
 +==== a word about battery voltage and solar power ====
 +
 +Simple solar charge controllers like these make different amounts of power depending [[electrical:solar:output|on a bunch of factors]].  One of them you can control is battery voltage. This is the max output of the 100w HQST at various battery voltages:
 +
 +
 +  * 12.7v (full but resting) == 69.85w
 +  * 13.2v (mild Float charging) == 72.6w
 +  * 13.8v (high Float charging) == 75.9w
 +  * 14.2v (shallow cycle charging) == 78.1v
 +
 +The trick here is to keep battery voltage high enough to allow for good solar harvest while not hurting the battery. 
 + 
 +
 +
 +=== Low Voltage Reconnect (LVR) setpoint ===
 +
 +The LVR is the point at which the controller turns the LOADs back on.  If **running small loads** (charging phones, LED lights) the setpoint may be set fairly low (like 13.0v).  This will allow loads to be run as soon as possible.
 +
 +If **running larger loads** (fans, laptop chargers) the setpoint should be set higher (like 13.5v - 14.0v).  This is because the panel will be able to make more power the higher the battery voltage.
 +
 +Note:  running a small [[electrical:solar:charge_controller#mppt|MPPT]] [[electrical:solar:charge_controller|charge controller]] would be much more $$$ ($40 instead of $10) but solar harvest would no longer be hampered by battery voltage. 
  
  
Line 44: Line 73:
 ===== shallow-cycling ===== ===== shallow-cycling =====
  
-//Shallow-cycling// is a more aggressive approach, allowing for a bit of power after sundown.  It is most **suitable for starter batteries with removable cell caps**.+//Shallow-cycling// is a more aggressive approach, allowing for more power in the daytime and some power for use after sundown.  It may also allow the use of inverter loads that have startup surges.  This approach is most **suitable for starter batteries with removable cell caps** so you can add distilled water;  they will outgas a bit under heavy use.
  
-The charging setpoint is set somewhat higher, ~14.4v.  This will result in minor outgassing and a bit more power (**76.18W** using the panel data above).  [[electrical:12v:charging#watering_batteries|Battery watering]] is mandatory.+The charging setpoint is set somewhat higher, ~14.2v.  This will result in minor outgassing and a bit more power (**76.18W** using the panel data above).  [[electrical:12v:charging#watering_batteries|Battery watering]] is mandatory.
  
 Starter batteries are designed for about 15% depth of discharge((http://forum.solar-electric.com/discussion/comment/60412#Comment_60412)).  We can set the Low Voltage Disconnect (//Vlvd//) to 12.5-12.6v as a floor.  In a typical starter battery this could be 5Ah of power usable at night, enough to run an LED light for hours as well as run a small fan all night.  All device charging should happen in daylight when power is relatively plentiful.   Starter batteries are designed for about 15% depth of discharge((http://forum.solar-electric.com/discussion/comment/60412#Comment_60412)).  We can set the Low Voltage Disconnect (//Vlvd//) to 12.5-12.6v as a floor.  In a typical starter battery this could be 5Ah of power usable at night, enough to run an LED light for hours as well as run a small fan all night.  All device charging should happen in daylight when power is relatively plentiful.  
  
-If the starter battery (when it eventually dies a natural death) were replaced with [[electrical:12v:deep_cycle_battery#chain_store_batteries|12v wally world marine battery]] one might be able to cycle to 25% DoD.  This would mean an Vlvd of ~12.4v and 8-9Ah of power at night.+If the starter battery (when it eventually dies a natural death) were replaced with [[electrical:12v:deep_cycle_battery#chain_store_batteries|the heaviest 12v wally world marine battery]] that would fit one might be able to cycle to 25% DoD.  This would mean an Vlvd of ~12.4v and 8-9Ah of power at night.
 ===== effect on starter battery ===== ===== effect on starter battery =====
  
Line 70: Line 99:
  
  
 +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.
 +
 +
 +===== getting more power into the cabin =====
  
  
 +see [[electrical:12v:alternator#isolator_without_a_house_battery|this article]]
electrical/solar/shallow_cycling.1520001903.txt.gz · Last modified: 2020/10/11 19:48 (external edit)