Both sides previous revision
Previous revision
Next revision
|
Previous revision
Next revision
Both sides next revision
|
electrical:solar:shallow_cycling [2020/07/08 15:42] frater_secessus [how it works] |
electrical:solar:shallow_cycling [2021/06/06 13:40] frater_secessus [how it works] |
====== microsolar without deep-cycle batteries ====== | ====== microsolar without deep-cycle batteries ====== |
| |
This article describes a small, simple, space-efficient, and inexpensive solar configuration that may be of use to cardwellers or minimalist vandwellers. | This article describes a small, cheap, simple, space-efficient solar configuration that may be of use to car-dwellers 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. | Benefits: |
| |
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)) | |
| |
| * provides 12v power during daylight |
| * will never deplete the starter battery so you get stranded |
| * actively maintains the starter battery |
| * the controller has built-in USB ports |
| |
| 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)). |
| |
| It does require a bit of discipline and forethought to run bigger loads during the daytime when excess power is available. |
| |
| |
==== how it works ==== | ==== how it works ==== |
| |
- 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 | - 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 |
- the controller's LOAD output disconnects (LVD) at 100% SoC (~12.7v) | - 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 //re//connects (LVR) at ~13.0v); see discussion below | - the controller's LOAD output disconnects when battery voltage falls to 100% ((LVD)) - no more power is provided |
- 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]] | - the controller's LOAD output //re//connects when charging and battery voltage has risen to >= ~13.0v((LVR)) - power once again flows |
| |
| |
=== Low Voltage Reconnect (LVR) setpoint === | ==== components ==== |
| |
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. | Once you have the car, the rest of the parts will be about $100 if you watch sales. |
| |
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** | * 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. |
| * 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. |
| * 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 |
| * [[http://amzn.to/2xHjBi7|usb/12v power outlet]] wired to the LOAD output of the controller. An outlet with USB ports in it would allow the controller itself to be mounted discreetly and closer to the battery. |
| |
Note: running a small [[electrical:solar:charge_controller#mppt|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. | ==== 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: |
| |
==== components ==== | |
| |
* vehicle with starter battery | * 12.7v (full but resting) == 69.85w |
* 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. | * 13.2v (mild Float charging) == 72.6w |
* small solar panel; 25w-100W would be fine. | * 13.8v (high Float charging) == 75.9w |
* connector of some kind if panel is mounted off-vehicle | * 14.2v (shallow cycle charging) == 78.1v |
* 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. | |
| |
| 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. |
| |
| |
===== shallow-cycling ===== | ===== shallow-cycling ===== |
| |
//Shallow-cycling// is a more aggressive approach, allowing for more power in the daytime and some power for use 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 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. |
* 13.6v Float | * 13.6v Float |
| |
So a smart charger fitting that profile should be gentle enough on the battery. | So a charge controller with that configuration should be gentle enough on the battery. |
| |
| |
This is the tricky part. Shunts (or controllers set with [[electrical:12v:eternal_absorption|Vabs == Vfloat]]) have one charging voltage. What should we use? | 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 the cycling | * 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. | * 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. |
| |
| |
| |
| |