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electrical:solar:nonessential [2020/07/08 11:26]
frater_secessus [LVD + timer]
electrical:solar:nonessential [2023/10/18 19:08] (current)
frater_secessus [when to run opportunity loads]
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 ===== when to run opportunity loads ===== ===== when to run opportunity loads =====
  
-**The best time to run non-essential loads is when there is surplus current** over what battery charging needs.  This means **during Float, or after current has started dropping off in Absorption**.  For [[electrical:12v:deep_cycle_battery#lithium_chemistries|LiFePO4]] there is excess power any time after the bank has reached the intended charge state. +The optimal time to run loads is when there is **power available in excess of battery charging requirements**.  When done at the right time, the loads are effectively run [[electrical:solar:offthepanel|off the panels]] rather than off the battery bank.  This results in the bank having a higher state of charge both at sundown and morning 
  
-Opportunity loads should not be applied during [[electrical:12v:charging|Bulk stage]] since Bulk, by definition, means the battery is taking all the available current.((assuming no charging limit has been configured in the [[electrical:solar:charge_controller|charge controller]]))+With **lead** this means **during Float**, or **in late Absorption** when charge current acceptance has fallen enough that the system can run the loads //and still maintain the Absorption voltage setpoint//  
 + 
 +There is a little more wiggle room with [[electrical:12v:deep_cycle_battery#lithium_chemistries|LiFePO4]];  the loads can be run with no net negative effect on a Lithium system when 
 + 
 +  * the bank has reached the intended charge state; or 
 +  * any time the bank can be //projected// to reach the intended charge state by sundown while carrying the extra loads. In effect, lithium allows you to "borrow" against future charging without penalty..   Exception:  Lithium setups with PWM [[electrical:solar:charge_controller|solar charge controllers]] will make [[electrical:solar:pwm_tweaking|most power]] when bank voltage is highest.  So waiting for Float or Absorption to run opportunity loads will mean the solar can make more Wh per day.
  
  
  
 ===== timing opportunity loads ===== ===== timing opportunity loads =====
 +
 +The trickiest part of running opportunity loads is running them at the right time so battery charging is not affected.
 +
 +
 +==== manual model ====
 +
 +
 You can start the loads **manually** (ie, start using the power when you have extra).  This is error-prone but is free and requires no equipment (except your own memory). You can start the loads **manually** (ie, start using the power when you have extra).  This is error-prone but is free and requires no equipment (except your own memory).
  
-The most precise way to do it **automatically** is to use a charge controller which turns on the LOAD output only when the batteries are in Float stage.  Charge controllers with this feature tend to be expensive.+==== charge controller ==== 
 + 
 + 
 +The most precise way to do it **automatically** is to use a charge controller that can act as a diversion controller.  Charge controllers with this feature tend to be expensive, and tend to run in either solar **or** dump load mode.  This may be preferable with lithium or other chemistries that do not require multistage charging. 
 + 
 +Read the documentation and ask their techs questions before taking this $$$ approach.   
 + 
 +Related:   
 + 
 +  * you can also build a Pi or similar that talks to the controller over its communication port/protocol and checks when the controller is in Float, and then triggers the diversion. 
 +  * [[https://www.youtube.com/results?search_query=AC7391|some hobbyists are using AC7391 controllers]] to directly run dump loads w/out battery charging. Not necessarily a solution for vandwellers but may help our thinking.    
 + 
 + 
 +==== diversion controller ==== 
 + 
 +The [[https://amzn.to/3f6Aogh|Victron BMV-700 battery monitor]] can act as a programmable relay controller((https://www.victronenergy.com/upload/documents/Manual-BMV-700-700H-702-712-EN-NL-FR-DE-ES-SE.pdf)), turning loads off/on at a given state of charge. 
 + 
  
-You can also build a Pi or similar that talks to the controller over its communication port/protocol and checks when the controller is in Float. 
 ==== LVD only ==== ==== LVD only ====
  
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 In this approach the LVD is set just below Vfloat as above, but activation of the loads is delayed by some amount of time.  Observation of the system during charging will suggest how long it normally takes takes charging amperage to drop off (ie, when the system has surplus current). In this approach the LVD is set just below Vfloat as above, but activation of the loads is delayed by some amount of time.  Observation of the system during charging will suggest how long it normally takes takes charging amperage to drop off (ie, when the system has surplus current).
  
-Suggested delay for conservative opportunity loading == the time from [passing Vlvr setpoint during Bulk] to [completed charging].((settling to Float)).  This delay might be 2-3hours.+Suggested delay for conservative opportunity loading == the time from [passing Vlvr setpoint during Bulk] to [completed charging].((settling to Float)).  This delay might be 2-5hours.
  
  
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 ==== LVD + timer - eternal Absorption ==== ==== LVD + timer - eternal Absorption ====
  
-This setup avoids timer juggling/estimation and does not affect Absorption charging.+This setup avoids timer juggling/estimation and does not affect Absorption charging.The downside is the opportunity circuit engages much later
  
-  - set Vfloat to Vabs +  - [[electrical:12v:eternal_absorption|set Vfloat to Vabs]] 
-  - observe measure how long Absorption actually takes to drop to [[electrical:solar:charge_controller_setpoints|endAmps]] on your system+  - observe how long Absorption actually takes to drop to [[electrical:solar:charge_controller_setpoints|endAmps]] on your system
   - set the LVD to just under Vabs, set the timer to the Absorption duration   - set the LVD to just under Vabs, set the timer to the Absorption duration
  
 +Similar to the above, this setup looks like: [LVD or controller LOAD output] –> timer –> relay –> load
  
 ===== uses for opportunity loads ===== ===== uses for opportunity loads =====
 +
 +For best results the opportunity load should be sized to the excess power.  Otherwise the system could go into dump/recharge cycling.
 +
 +
 +
   * heating water   * heating water
   * [[hvac:dehumidifier|dehumidification]]   * [[hvac:dehumidifier|dehumidification]]
   * [[electrical:12v:laptop|laptop]] and phone charging   * [[electrical:12v:laptop|laptop]] and phone charging
-  * rice cooker((http://www.cheaprvliving.com/forums/Thread-How-much-solar-do-I-need?pid=141508#pid141508))+  * [[food:cooking:excess_power|cooking with small appliances]]
  
electrical/solar/nonessential.1594221997.txt.gz · Last modified: 2020/10/11 19:48 (external edit)