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electrical:solar:status [2019/07/13 20:44]
frater_secessus [afternoon]
electrical:solar:status [2024/01/14 15:32] (current)
frater_secessus [setups with no float]
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 > "Watching how many amps a charging battery is accepting at absorption voltage, is very indicative of state of charge, the less the amps the more charged." -- sternwake((https://vandwellerforum.com/showthread.php?tid=673&pid=11316#pid11316)) > "Watching how many amps a charging battery is accepting at absorption voltage, is very indicative of state of charge, the less the amps the more charged." -- sternwake((https://vandwellerforum.com/showthread.php?tid=673&pid=11316#pid11316))
  
->If you want to see lots more amps coming out of the [charge controller], put on a 5-10A load and drop the battery to 50% depleted in the middle of a sunny day. -- John61CT((http://www.cheaprvliving.com/forums/Thread-Troubleshooting-solar-issues?pid=343191#pid343191))+>If you want to see lots more amps coming out of the [charge controller], put on a [significant] load... in the middle of a sunny day. -- John61CT((http://www.cheaprvliving.com/forums/Thread-Troubleshooting-solar-issues?pid=343191#pid343191))
  
 ====== Is my solar working? ====== ====== Is my solar working? ======
 +
 +Note:  for simplicity's sake this article assumes [[electrical:nominal|nominal]] 12v [[electrical:solar:panels|panels]] and 12v [[electrical:12v:intro|house power]].
 +
  
 It is common for those with new solar configurations to worry about whether or not they are working.  The worry is understandable because:   It is common for those with new solar configurations to worry about whether or not they are working.  The worry is understandable because:  
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 A **poorly running system** is observed to deliver very little power because it isn't set up right (or is shaded, etc) and can't do any better.  Battery voltage is too low((<12.1v)) and doesn't meet needs. A **poorly running system** is observed to deliver very little power because it isn't set up right (or is shaded, etc) and can't do any better.  Battery voltage is too low((<12.1v)) and doesn't meet needs.
  
-Also counterintuitively, systems with lots of panel start generating usable power so early after sunrise that they can finish bulk charging well before solar noon.  This means the user would not see the system at full power during normal circumstances.  This effect is particularly strong when the system is [[electrical:solar:overpaneling#vs_battery_bank|overpaneled]].+Also counterintuitively, **systems with lots of panel** start generating usable power so early after sunrise that they can finish bulk charging well before solar noon.  This means the user might never see the system at full(([[electrical:solar:output|derated]])) power during normal circumstances.((assuming no loads))  This effect is particularly strong when the system is [[electrical:solar:overpaneling#vs_battery_bank|overpaneled]].
  
  
-This page is to help solar beginners tell what their system is doing without special equipment.  +This page is to help solar beginners tell what their system is doing without special equipment.  A [[electrical:12v:battery_monitor|battery monitor]] can be extremely useful but we can tell a great deal without it.  The info here is oriented to typical 12v systems with lead-acid battery banks.  Folks running other battery chemistries or nominal voltages are assumed to already know what they're doing.  :-)
  
 ===== numbers rather than icons or lights ===== ===== numbers rather than icons or lights =====
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 To tell at a glance what your system is doing you need to find a couple pieces of info about your system.  You will only have to look them up once;  it might be worthwhile to write them down on a sticky note near your solar gear. To tell at a glance what your system is doing you need to find a couple pieces of info about your system.  You will only have to look them up once;  it might be worthwhile to write them down on a sticky note near your solar gear.
  
-  * **Vabs** - the charge controller's Absorption [[electrical:solar:charge_controller_setpoints|setpoint]], hopefully tweaked to your battery manufacturer's recommendation+ 
 +{{ https://www.researchgate.net/profile/Kanaga-Gnana/publication/237049790/figure/fig3/AS:299465748566018@1448409606696/Characteristic-Curve-of-The-Solar-Panel.png?125}} 
 + 
 +==== panel specs ==== 
 + 
 +The [[electrical:solar:panels#specifications|specs]] we are interested in are: 
 + 
 +  * **Vmp**, the voltage at which the panel makes max power under laboratory conditions((likely lower in reality)) 
 +  * **Voc**, the highest voltage the panel will put out under normal cirumstances.  At Voc the panel produces no current and therefore no power (Voc x 0A = 0W) 
 +  * when in use, **Vpanel** is the panel voltage reported by the controller.  PWM controllers might not report this value.     
 + 
 +On the curve pictured at the right Vmp is at the peak of the red voltage line, and Voc is on the far right where output crashes to 0W.   
 + 
 + 
 +==== controller ==== 
 +  
 + 
 +  * **Vabs** - the charge controller's Absorption [[electrical:solar:charge_controller_setpoints|setpoint]], hopefully tweaked to your battery manufacturer'[[electrical:12v:charging|charging]] recommendation.  Note:  EpEver and Renogy controllers often refer to Absorption as //Boost//.
   * **Vfloat** the charge controller's Float setpoint   * **Vfloat** the charge controller's Float setpoint
 +  * **Veq** the charge controller's Equalization setpoint, if any
  
 If you have an MPPT controller also look up these pieces of info: If you have an MPPT controller also look up these pieces of info:
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 ===== then observe the controller ===== ===== then observe the controller =====
  
-These checks are admittedly crude but will help see if your system is getting it done.  No [[electrical:12v:battery_monitor|expensive or specialized equipment]] is required.((but use them if you have them!)) MPPT controllers in particular will reveal a great deal of information by how they interact with the panels. +These checks are admittedly crude but will help see if your system is getting it done.  No [[electrical:12v:battery_monitor|expensive or specialized equipment]] is required.((but use them if you have them!)) MPPT controllers in particular will reveal a great deal of information by how they interact with the panels. For the purposes of this article, consider [[electrical:solar:shunt_tweaking|single-stage/shunt controllers]] to work the same way as PWM except they only have one voltage setpoint.((Absorption OR Float))
  
 For the examples below we will assume the system is set up this way: For the examples below we will assume the system is set up this way:
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 **During bulk charging with MPPT** **During bulk charging with MPPT**
-  * Vpanel == Vmp+  * Vpanel == Vmp((although [[electrical:solar:output|temperature derating]] will cause Vmp to drop))
   * Vbatt climbing toward Vabs   * Vbatt climbing toward Vabs
-  * Current delivered to battery holds steady +  * charge delivered to battery holds steady((assuming sunlight holds steady))  Note:  in a lab environment with DC power supplies the current (measured in Amps) could stay steady as the battery approaches Vabs.((the charger would get more and more wattage from the wall socket))  When charging off-grid we are typically limited by charging wattage, say 300w from the alternator or panels.  At 12.1v you would see ~25A charging (300w/12.v = 24.79A) but at 14v you'd only see ~21.5A (300w/14v = 21.43A) 
-  * **Example:**  Panel voltage at Vmp == 17v, battery voltage 12.9v and rising, controller output steady at 4A.+  * **Example:**  Panel voltage at Vmp == 17v, battery voltage 12.9v and rising, controller output steady-ish at 4A.
  
 **During bulk charging with PWM** **During bulk charging with PWM**
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-**During Absorption charging with MPPT** the battery will need less and less current.+**During [[electrical:12v:charging#absorption#absorption_stage|Absorption]] charging** batteries will need less and less current. 
 + 
 +**with MPPT controllers** 
   * Vpanel starts to creep up from Vmp toward Voc   * Vpanel starts to creep up from Vmp toward Voc
   * Vbatt == Vabs until the controller's criteria for ending absorption is met   * Vbatt == Vabs until the controller's criteria for ending absorption is met
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   * **Example:**  Panel voltage 17v and rising, battery voltage held at Vabs == 14.6v, controller output amps 2A and dropping   * **Example:**  Panel voltage 17v and rising, battery voltage held at Vabs == 14.6v, controller output amps 2A and dropping
  
-**During Absorption charging with PWM** +**with PWM controllers** 
-  * Vpanel & Vbattery == Vabs until the controller'criteria for ending absorption is met+  * Vpanel starts to creep up from Vbatt toward Voc (the more OFF((open circuit)) switching the closer to Voc) criteria for ending absorption is met
   * Controller output decreasing as current demand drops.   * Controller output decreasing as current demand drops.
   * the controller may get warmer as current demand drops((percentage of time the PWM circuit is turned OFF increases))   * the controller may get warmer as current demand drops((percentage of time the PWM circuit is turned OFF increases))
   * **Example:**  Panel and battery voltage held at Vabs == 14.6v, controller output 2A and dropping   * **Example:**  Panel and battery voltage held at Vabs == 14.6v, controller output 2A and dropping
 +
 +==== transitioning to float ====
 +
 +When transitioning from Absorption to Float the voltage needs to drop about a volt.  The system will "free-fall" (make little or no power) to allow the voltage to fall.((with MPPT controllers you may see Vpanel go quite close to Voc))   The transition may take seconds or minutes, depending battery chemistry and  how/if the system is loaded.
 +
 +  * Vbatt starts at Vabs
 +  * power harvest is cut off or greatly curtailed (Vpanel spikes toward Voc)
 +  * Vbatt drops to Vfloat 
 +  * when Vbatt reaches Vfloat the system will start making power to hold //that// setpoint.
 +
 +==== setups with no float ====
 +
 +Configurations with no float ("charge and stop", found on some Lithium profiles) will 
 +
 +  - charge to the Absorption ("boost") setpoint((with or without some amount of Absorption duration))
 +  - **stop charging**
 +  - until voltage falls to the rebulk ("reboost", "boost return voltage") setpoint
 +  - repeat
 +
 +The fall to reBulk looks like the transition to Vfloat [[electrical:solar:status#transitioning_to_float|described above]]. In both cases the controller makes no (or practically no) power until the lower setpoint is reached. 
 +
 +A constant cycling 14.4v->13.2v->14.4v might seem extreme but in practice there is little actual cycling occurring.  A fully-charged 4S LFP with no loads will rest somewhere around **13.6v**. So for actual SoC changes we are talking about the difference between 13.6v and 13.2v.  With significant loads applied 13.2v observed could mean SoC as high as 90% and with trivial loads as low as 70%.((with trivial loads there might be only 1 cycle a day since voltage would not fall to reBoost))  In normal use the real cycling might be 100%->85%-100% and the solar is helping carry the loads during charging periods.  
 +
 +
 +=== Renogy confusion ===
 +
 +By default Renogy Li profiles work this way, and cause much concern for Renogy users who have not read their manuals and/or who are not familiar with how solar charge controllers / chargers work. [The required information is present [[https://www.renogy.com/support/downloads|in the manuals]] but Renogy really should spell it out for first-timers. -- secessus]
 +
 +  * **Rover series** - the table on page 37 of [[https://www.renogy.com/content/RNG-CTRL-RVR40/RVR203040-Manual.pdf|the manual]] shows there is no boost duration and no float in the Li profile.  The "boost return voltage" field shows **13.2v**. 
 +  * **DC-DC/MPPT combo charger** - the table on page 2 of [[https://www.renogy.com/content/RBC3050D1S-G1/RBC3050D1S-Manual.pdf|the manual]] shows there is no boost duration and no float in the Li profile.  The "boost return voltage" field shows **13.2v**. 
 +  * **DC-DC charger** (20A/40A/60A) 
 +    * page 18 says "lithium batteries will only have an absorption charge and no float charge"
 +    * there is no setting for Float charge, as shown in the table on page 17 of [[https://www.renogy.com/content/RNG-DCC1212-60-BC/DCC1212-204060-Manual.pdf|the manual]] and it says "for lithium... there will not be a float voltage"
 +    * page 18 says that Float is for lead only
 +    * the manual does not state the 13.2v boost return setpoint [an egregious error - secessus]
 +
 +Users uncomfortable with this behavior can set up the USER profile to meet their needs, including defining [[electrical:12v:drop-in_lifepo4#mythyou_shouldn_t_float_lithium|a quasi-Float setpoint]].((low temp charging cutoff, when available, may only be available in canned Li profiles))
 +
  
 ==== in float ==== ==== in float ====
  
 **During Float with MPPT** **During Float with MPPT**
-  * Vpanel close to Voc+  * Vpanel closer to Voc
   * Vbattery == Vfloat   * Vbattery == Vfloat
   * controller output minimal((assuming no loads))   * controller output minimal((assuming no loads))
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 **During Float with PWM**  **During Float with PWM** 
-  * Vpanel & Vbatt == Vfloat+  * Vpanel closer to Voc (PWM switching panel OFF((open circuit)) most of the time) 
   * controller output minimal((assuming no loads))   * controller output minimal((assuming no loads))
   * **Example:**  Panel and battery voltage holding at Vfloat == 13.8v, controller output < 1A.   * **Example:**  Panel and battery voltage holding at Vfloat == 13.8v, controller output < 1A.
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 When **adding loads to PWM during absorption (or float)** When **adding loads to PWM during absorption (or float)**
   * Vpanel & Vbatt held at Vabs (or Vfloat) if possible((by reducing the OFF timeslices in the PWM circuit, perhaps until the panel and battery are 100% connected at full output))   * Vpanel & Vbatt held at Vabs (or Vfloat) if possible((by reducing the OFF timeslices in the PWM circuit, perhaps until the panel and battery are 100% connected at full output))
-  * If enough power is available no change will be observed but the controller may run cooler+  * If enough power is available no change will be observed but the controller may run cooler((as PWM switching reduces in frequency.))
   * If demand outstrips supply the Vbattery & Vpanel will drop((causing a bit of a "death spiral", as PWM produces less power as panel voltage drops))   * If demand outstrips supply the Vbattery & Vpanel will drop((causing a bit of a "death spiral", as PWM produces less power as panel voltage drops))
-  * **Example**:  Upon adding load, the controller releases power it had been dissipating in the PWM circuit Current output spikes to meet load demand.((this is reflected in either battery charging amps or load amps depending on how the loads are wired))  Output is limited to whatever power the panel puts out at Vabs & Vfloat.((almost certainly less than what the panel could put out at Vmp))+  * **Example**:  Upon adding load, the controller releases power it had been constricting (modulating the pulse width). Current output spikes to meet load demand.((this is reflected in either battery charging amps or load amps depending on how the loads are wired))  Output is limited to whatever power the panel puts out at Vabs & Vfloat.((almost certainly less than what the panel could put out at Vmp))
  
  
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 ==== morning ==== ==== morning ====
-**Are your batteries showing at least 12.1v (approx. [[electrical:depth_of_discharge|50% state of charge]]in the morning?**  If so, continue to Afternoon.  +**Are your batteries at a reasonable [[electrical:depth_of_discharge|state of charge]] in the morning?**((≥50% or ~12.1v for lead batts, ≥20% for Lithium))  If so, continue to Afternoon.  
  
 If not, address this issue soon because discharging too deeply will [[electrical:batterycide|damage the batteries]].  Consider these changes: If not, address this issue soon because discharging too deeply will [[electrical:batterycide|damage the batteries]].  Consider these changes:
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 ==== afternoon ==== ==== afternoon ====
-**Are your batteries starting Absorption by noon-ish** and completing Absorption by late afternoon? If so, continue to the next step.  +**Are your batteries starting Absorption by noon-ish** and completing Absorption by late afternoon?((depending on charging voltage and current Lithium may require no absorption at all to reach 100% SoC)) If so, continue to the next step.  
  
 Note:  You can tell your batteries are in Absorption because the bank will be at Vabs, the controller's absorption setpoint. Note:  You can tell your batteries are in Absorption because the bank will be at Vabs, the controller's absorption setpoint.
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 ==== evening ==== ==== evening ====
  
-**Are you hitting sundown with //at least// 12.7v in your bank?**  If so, you can relax;  your system is working well enough. +**Are you hitting sundown with //at least// 12.6-12.7v((depending on your particular battery)) in your lead acid bank?**((~13.2v for LiFePO4))  If so, you can relax;  your system is working well enough.  
 + 
 +If not, either we are not harvesting enough power or we are using too much. Stop running heavier loads when the controller can no longer hold Vfloat.  
 + 
 + 
 +===== sudden voltage spikes ===== 
 + 
 +If you are seeing sudden voltage spikes and have lithium batteries, you may be seeing [[opinion:frater_secessus:lifepo4_charging_voltage|the BMS disconnect the charging circuit]].  When this happens the controller suddenly finds itself making too much power (the charging demand suddenly disappeared);  voltage on the rest of the circuit will spike while the controller reacts to the new demand level.  
 + 
 +The fix, described in the link above, is to **charge at a lower voltage** that does not antagonize the cells and trip the BMS
  
  
 +===== MPPT tracking sweeps =====
  
 +{{ https://img.mousetrap.net/2023/Screenshot_20230208-095220.jpg?150}}
 +An **MPPT** controller must sweep the **P**ower **P**oints along the array voltage curve in order to **T**rack the **M**aximum (and non-maxiumum) power points.  Basically the controller is asking "How much power does it make //here// on the curve?  And //here//?  And over //here//?"  It tracks (remembers) these power points and can return to them as needed.  But solar conditions are always changing so the power point data can get stale quickly and the controller has look again from time to time. 
  
 +Depending on the algorithm the sweep may a small one near presentVpanel, it may be a full sweep from 0v-[[electrical:solar:panels#specifications|Voc]], or anything in between.  It may happen often or seldom.  Victron famously makes a sweep every 10 minutes, resulting in visible dips in the app's graphs (see orange line on image at right). 
  
 +The sweep will interfere with power production so the mfg attempts to find a balance between
  
 +  * constant production, and
 +  * learning whether or not one is operating at the optimal power point for present conditions
  
  
electrical/solar/status.1563065053.txt.gz · Last modified: 2020/10/11 19:48 (external edit)