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electrical:solar:charge_controller [2019/07/21 12:23]
frater_secessus [PWM] heat is not dissipated. Switching causes it |
electrical:solar:charge_controller [2020/01/07 23:02]
frater_secessus [how to choose] |
| [[lifestyle:words_of_wisdom|Words of wisdom]]: //"Any Solar is better than no solar, but having too much solar is difficult. The best solar systems are those which can keep the batteries the happiest. Happy batteries are those which are recharged quickly after depletion."//((http://www.cheaprvliving.com/forums/Thread-Should-I?pid=88971#pid88971)) - SternWake | [[lifestyle:words_of_wisdom|Words of wisdom]]: //"Any Solar is better than no solar, but having too much solar is difficult. The best solar systems are those which can keep the batteries the happiest. Happy batteries are those which are recharged quickly after depletion."//((http://www.cheaprvliving.com/forums/Thread-Should-I?pid=88971#pid88971)) - SternWake |
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| ====== Solar charge controllers ====== | ====== Solar charge controllers ====== |
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| A solar charge controller (CC) regulates the [[electrical:12v:charging|charging]] of a [[electrical:12v:deep cycle battery|battery bank]] from the [[electrical:solar:panels|solar panels]]. | A solar charge controller (CC) regulates the [[electrical:12v:charging|charging]] of a [[electrical:12v:deep cycle battery|battery bank]] from the [[electrical:solar:panels|solar panels]]. |
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| Counterintuitively, the primary job of the charge controller (CC) is to keep the batteries from being //over//charged. Solar panels run at higher voltages than batteries, often at voltages high enough to damage the batteries. The CC provides the correct amount of power the battery needs at the correct time; this is called [[electrical:12v:charging|smart or three stage charging]]. | Counterintuitively, the primary job of the charge controller (CC) is to keep the batteries from being //over//charged. Solar panels run at higher voltages than batteries, often at voltages high enough to damage the batteries. The CC provides the correct amount of power the battery needs at the correct time; this is called [[electrical:12v:charging|smart or three stage charging]]. |
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| Charge controllers are generally **rated by the amount of output they can provide**. This output is shared by charging circuits and [[#using_load_output|LOAD circuits]]. For example, a 20A controller might be using 18A for charging and have 2A available for LOAD. | Charge controllers are generally **rated by the amount of output they can provide**. This output is shared by charging circuits and [[#using_load_output|LOAD circuits]]. For example, a 20A controller might be using 18A for charging and have 2A available for LOAD. |
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| Controllers operate based on [[electrical:solar:charge_controller_setpoints|factory- or user-defined setpoints]] (values) stored internally. | Controllers operate based on [[electrical:solar:charge_controller_setpoints|factory- or user-defined setpoints]] (values) stored internally. |
| ===== types of charge controllers ===== | ===== types of charge controllers ===== |
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| [note from frater secessus: PWM vs. MPPT debates can get overheated in forums and comments. It's your money and your build so do it the way that meets your needs.] | [note from frater secessus: PWM vs. MPPT debates can get overheated in forums and comments. It's your money and your build so do it the way that meets your needs.] |
| ==== PWM ==== | ==== PWM ==== |
| [[http://amzn.to/2hcZaj2|{{ https://images-na.ssl-images-amazon.com/images/I/41pwJOriZHL._AC_US160_.jpg}}]]**PWM** (pulse width modulation) controllers charge by connecting panels to battery until a given voltage setpoint is reached. When the desired setpoint is reached the controller switches current on/off to the battery in very fast cycles and in such a duration needed to keep voltage from rising. This time slicing power delivery is called is pulse width modulation, or PWM. Some heat will be generated by the switching. Counterintuitively, the PWM may be cooler the touch when it is running full open because there is no switching going on to limit voltage. | [[http://amzn.to/2hcZaj2|{{ https://images-na.ssl-images-amazon.com/images/I/41pwJOriZHL._AC_US160_.jpg}}]]**PWM** (pulse width modulation) controllers charge by connecting panels to battery until a given voltage setpoint is reached. When the desired setpoint is reached the controller switches current on/off to the battery in very fast cycles and in such a duration needed to keep voltage from rising. This time slicing power delivery is called is pulse width modulation, or PWM. Some heat will be generated by the switching. Counterintuitively, the PWM may be cooler the touch when it is running full open because there is no switching going on to limit voltage. |
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| [[http://www.electronics-tutorials.ws/blog/pulse-width-modulation.html|{{ http://www.electronics-tutorials.ws/articles/pwm2.gif }}]] | [[http://www.electronics-tutorials.ws/blog/pulse-width-modulation.html|{{ http://www.electronics-tutorials.ws/articles/pwm2.gif }}]] |
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| This runs the panels at((or very close to)) battery voltage (Vbatt). Vbatt is usually much lower than the panels' Vmp((unless the panels are very hot)) and so PWM generally cannot capture the panels' maximum available power((adjusted for temperature, insolation, etc)) under typical conditions. A side effect of this is the PWM controller will have **highest power output when Vbatt is highest**: Absorption (Vabs) and Float (Vfloat). Setpoints can be tweaked for longer duration Absorption and higher Vfloat to [[electrical:solar:pwm tweaking|maximize power output of a PWM controller]]. | This runs the panels at((or very close to)) battery voltage (Vbatt). Vbatt is usually much lower than the panels' Vmp((unless the panels are very hot)) and so PWM generally cannot capture the panels' maximum available power((adjusted for temperature, insolation, etc)) under typical conditions. A side effect of this is the PWM controller will have **highest power output when Vbatt is highest**: Absorption (Vabs) and Float (Vfloat). Setpoints can be tweaked for longer duration Absorption and higher Vfloat to [[electrical:solar:pwm tweaking|maximize power output of a PWM controller]]. |
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| PWM controllers are **simple, inexpensive, and sufficient** for many uses, particularly if ambient temperatures are fairly high, paneling is ample, and batteries are not [[electrical:depth_of_discharge|deeply cycled]]. | PWM controllers are **simple, inexpensive, and sufficient** for many uses, particularly if ambient temperatures are fairly high, paneling is ample, and batteries are not [[electrical:depth_of_discharge|deeply cycled]]. |
| ==== MPPT ==== | ==== MPPT ==== |
| [[http://amzn.to/2iD3WKf|{{ https://images-na.ssl-images-amazon.com/images/I/51bi9IjcsRL._AC_US160_.jpg}}]] | [[http://amzn.to/2iD3WKf|{{ https://images-na.ssl-images-amazon.com/images/I/51bi9IjcsRL._AC_US160_.jpg}}]] |
| **MPPT** (maximum power point tracking) controllers have two defining abilities: | **MPPT** (maximum power point tracking) controllers have two defining abilities: |
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| - discover (track) and utilize various power points along [[http://samlexsolar.com/learning-center/solar-panels-characteristics.aspx|the panel's power curve]]. Sometimes this is the maximum power point (MPP); often in a 'dweller context the system needs less power and the controller runs the panels at some other power point. It might be more accurate to call them PPT controllers. | - discover (track) and utilize various power points along [[http://samlexsolar.com/learning-center/solar-panels-characteristics.aspx|the panel's power curve]]. Sometimes this is the maximum power point (MPP); often in a 'dweller context the system needs less power and the controller runs the panels at some other power point. It might be more accurate to call them PPT controllers. |
| - DC-DC downconvert excess voltage to amps | - DC-DC downconvert excess voltage to amps |
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| When maximum power is required((in Bulk or at other time when loads + charging >= panel output)) the controller will run the panels at Vmp (the maximum power point). At other times the controller will find a less-than-maximum power point to match panel output to system needs. | When maximum power is required((in Bulk or at other time when loads + charging >= panel output)) the controller will run the panels at Vmp (the maximum power point). At other times the controller will find a less-than-maximum power point to match panel output to system needs. |
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| [[http://amzn.to/2yP01Ob|{{https://images-na.ssl-images-amazon.com/images/I/512x3hbc6jL._AC_US160_.jpg }}]] | [[http://amzn.to/2yP01Ob|{{https://images-na.ssl-images-amazon.com/images/I/512x3hbc6jL._AC_US160_.jpg }}]] |
| Since panel voltage at a given power point is usually too high for system needs((particularly with higher than nominal 12v panels )) the controller performs a DC-DC conversion to bring the voltage down to a directly usable level. Because **current through a conductor is directly proportional to voltage**((https://en.wikipedia.org/wiki/Ohm%27s_law)) this downconversion effectively turns excess voltage into increased amps.(minus conversion losses). | Since panel voltage at a given power point is usually too high for system needs((particularly with higher than nominal 12v panels )) the controller performs a DC-DC conversion to bring the voltage down to a directly usable level. Because **current through a conductor is directly proportional to voltage**((https://en.wikipedia.org/wiki/Ohm%27s_law)) this downconversion effectively turns excess voltage into increased amps.(minus conversion losses). |
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| This ability to decouple panel and bank voltage can result in 10%-30% more power harvested from 12v nominal panels than with a PWM controller. Marketers like to call this "boost" or "gains" but it really just full capture of whatever power the panel[s] can provide under given conditions. | This ability to decouple panel and bank voltage can result in 10%-30% more power harvested from 12v nominal panels than with a PWM controller. Marketers like to call this "boost" or "gains" but it really just full capture of whatever power the panel[s] can provide under given conditions. |
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| === "boost" effect === | === "boost" effect === |
| {{ https://media.licdn.com/mpr/mpr/AAEAAQAAAAAAAAwtAAAAJGJhNjE1OGY3LTM3OWQtNGQ2Mi05NWEwLTI2Mzc3MGY3MDk3MA.png?150}}When compared apples-to-apples on identical systems with //only the controller being different//, the "boost" effect is most pronounced: | {{ https://media.licdn.com/mpr/mpr/AAEAAQAAAAAAAAwtAAAAJGJhNjE1OGY3LTM3OWQtNGQ2Mi05NWEwLTI2Mzc3MGY3MDk3MA.png?150}}When compared apples-to-apples on identical systems with //only the controller being different//, the "boost" effect is most pronounced: |
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| * during bulk stage and the early part of absorption stage when the battery can take in the most power | * during bulk stage and the early part of absorption stage when the battery can take in the most power |
| | * anytime the system is fully loaded down (charging and/or loads) |
| * when the battery is most depleted (ie lowest resting voltage). This is the result of a cascade of factors: | * when the battery is most depleted (ie lowest resting voltage). This is the result of a cascade of factors: |
| * When a battery is deeply discharged it will go into Bulk charging mode until it reaches the Absorption voltage (Vabs). For the purpose of illustration we will assume the bank is depleted to 12.2v (~50% [[electrical:depth_of_discharge|state of charge]]), a commonly recommended lower limit for deep cycle batteries. | * When a battery is deeply discharged it will go into Bulk charging mode until it reaches the Absorption voltage (Vabs). For the purpose of illustration we will assume the bank is depleted to 12.2v (~50% [[electrical:depth_of_discharge|state of charge]]), a commonly recommended lower limit for deep cycle batteries. |
| * PWM controllers can only run the panel at whatever voltage they are charging at right now. In our example that is 12.2v. | * PWM controllers can only run the panel at whatever voltage they are charging at right now. In our example that is 12.2v. |
| * Nominal 12v panels usually have max power output (Vmp) around 17v.((https://www.altestore.com/howto/solar-panels-pv-and-voltages-a98/)) | * Nominal 12v panels usually have max power output (Vmp) around 17v.((https://www.altestore.com/howto/solar-panels-pv-and-voltages-a98/)) |
| * when a typical 100w panel((Iop = 5.6A)) is run at 12.2v in lab conditions it puts out **~68.32W**. The same panel run at Vmp (~17v) would put out **100W**. **MPPT is capturing more power than the PWM when the battery needs it most**.((there are minor inefficiencies not considered here)) | * when a typical 100w panel((Iop = 5.6A)) is run at 12.2v in lab conditions it puts out **~68.32W**. The same panel run at Vmp (~17v) would put out **100W**. **MPPT is capturing more power than the PWM when the battery needs it most**.((there are minor inefficiencies not considered here)) |
| * during times of greatest PV efficiency((i.e. highest voltage)) (clear, cold weather) | * during times of greatest PV efficiency((i.e. highest voltage)) (clear, cold weather) |
| * during times of low irradience (low light levels due to low angle or overcast conditions)((this is a function of higher input voltages))((https://www.victronenergy.com/upload/documents/White-paper-Which-solar-charge-controller-PWM-or-MPPT.pdf Section 7.3)) | * during times of low irradience (low light levels due to low angle or overcast conditions)((this is a function of higher input voltages))((https://www.victronenergy.com/upload/documents/White-paper-Which-solar-charge-controller-PWM-or-MPPT.pdf Section 7.3)) |
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| There are some considerations when [[electrical:solar:mppt design|designing a system around an MPPT controller]]. | There are some considerations when [[electrical:solar:mppt design|designing a system around an MPPT controller]]. |
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| ==== shunt ==== | ==== shunt ==== |
| [[http://amzn.to/2yQppTX|{{ https://images-na.ssl-images-amazon.com/images/I/41Gwyw0BT5L._AC_US160_.jpg}}]] | [[http://amzn.to/2yQppTX|{{ https://images-na.ssl-images-amazon.com/images/I/41Gwyw0BT5L._AC_US160_.jpg}}]] |
| Shunt controllers are very simple devices that charge to a given voltage [[electrical:solar:charge_controller_setpoints|setpoint]] (Vdisconnect) then stop charging. If/when voltage falls to some lower voltage (Vreconnect) charging begins again. This is sometimes called [[electrical:12v:charging#charge-and-stop|charge and stop charging]] or on/off charging. | Shunt controllers are very simple devices that charge to a given voltage [[electrical:solar:charge_controller_setpoints|setpoint]] (Vdisconnect) then stop charging. If/when voltage falls to some lower voltage (Vreconnect) charging begins again. This is sometimes called [[electrical:12v:charging#charge-and-stop|charge and stop charging]] or on/off charging. |
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| > ...PWM [and] shunt controllers apply full panel voltage, or something close to it, across the battery terminals, at a duty cycle (fast for PWM, slow for shunt) that keeps the battery happy, and the controller monitors the battery voltage and then adjusts the PWM duty cycle accordingly, or in the case of a shunt, it clamps the panel output. -- Tx2Sturgis((http://www.cheaprvliving.com/forums/showthread.php?tid=29896&pid=373640#pid373640)) | > ...PWM [and] shunt controllers apply full panel voltage, or something close to it, across the battery terminals, at a duty cycle (fast for PWM, slow for shunt) that keeps the battery happy, and the controller monitors the battery voltage and then adjusts the PWM duty cycle accordingly, or in the case of a shunt, it clamps the panel output. -- Tx2Sturgis((http://www.cheaprvliving.com/forums/showthread.php?tid=29896&pid=373640#pid373640)) |
| | They may be hardcoded with setpoints or allow user configuration. If configurable, you can get better results by [[electrical:solar:shunt tweaking|choosing setpoints to fit your situation]]. Usually on cheap shunts there is one setpoint, which we can think of as the absorption voltage (Vabs). Holding Vabs as long as the sun shines might seem weird but to quote Sternwake again: |
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| | > If your charge controller only holds [absorption] voltage for an hour or two, that is likely not enough time. As long as [there is a load] and you cycle the battery daily, you could set float voltage to 14.8v [to match absorption] without worry. Only when you stop cycling the battery do you need to return float voltage to more regular 13.2v levels. Premature application of float voltage by automatic charging sources is a battery killer.((http://www.cheaprvliving.com/forums/Thread-Solar-or-Battery-Problem?pid=229883#pid229883)) |
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| They may be hardcoded with setpoints or allow user configuration. If configurable, you can get better results by [[electrical:solar:shunt tweaking|choosing setpoints to fit your situation]]. | |
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| ==== DDCCC ==== | ==== DDCCC ==== |
| [note: this is a placeholder for a possible new entry.] | [note: this is a placeholder for a possible new entry.] |
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| There are //DC-DC converting charge controllers// (DDCCC) appearing on the market that claim to be MPPT but do not actually track power points (maximum or otherwise). They do downconvert some excess voltage into amperage. See [[https://boondockplan.wordpress.com/2017/12/15/backchannel-dc-dc-converting-charge-controllers/|this blog post]]. | There are //DC-DC converting charge controllers// (DDCCC) appearing on the market that claim to be MPPT but do not actually track power points (maximum or otherwise). They do downconvert some excess voltage into amperage. See [[https://boondockplan.wordpress.com/2017/12/15/backchannel-dc-dc-converting-charge-controllers/|this blog post]]. |
| ==== how to choose ==== | ==== how to choose ==== |
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| **PWM is the default choice** in most situations because they get the job done in most scenarios and are inexpensive. PWM controllers can cost half or a third of their MPPT workmates for any given rated output.((10A, 20A, 40A, etc)) | **PWM is the default choice** in most situations because they get the job done in most scenarios and are inexpensive. PWM controllers can cost half or a third of their MPPT workmates for any given rated output.((10A, 20A, 40A, etc)) |
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| If more power is needed (and there is physical space) additional PV can be added to match the charging output of an MPPT charger, often at a lower cost. [There are no prizes for fanciest or most expensive charge controller! Do what is best for you -- frater secessus] | If more power is needed (and there is physical space) additional PV can be added to match the charging output of an MPPT charger, often at a lower cost. [There are no prizes for fanciest or most expensive charge controller! Do what is best for you -- frater secessus] |
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| MPPT controllers also tend to consume more power to run themselves than PWM models due to additional processing and electronic components. | MPPT controllers also tend to consume more power to run themselves than PWM models due to additional processing and electronic components. |
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| | There are also edge cases where PWM can make more power than MPPT on poly [[electrical:solar:panels|panels]] during Absorption stage in very hot weather, due to MPPT DC-DC conversion losses and [[electrical:solar:output#panel_temperature|temperature derating]]. |
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| **MPPT may be a better fit** when: | **MPPT may be a better fit** when: |
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| * battery banks are cycled deeply on a regular basis so more time is spent in Bulk | * battery banks are cycled deeply on a regular basis so more time is spent in Bulk |
| * nominal 12v panels have a relatively high Vmp (>=18v) for [[https://www.reddit.com/r/vandwellers/comments/bmlosu/is_vandwelling_a_frugal_lifestyle/emz5lsf/?context=1|reasons discussed here]]. | * nominal 12v panels have a relatively high Vmp (>=18v) for [[https://www.reddit.com/r/vandwellers/comments/bmlosu/is_vandwelling_a_frugal_lifestyle/emz5lsf/?context=1|reasons discussed here]]. |
| * if temperatures are very low (greater harvest) | * if temperatures are very low (greater harvest) |
| * the increase in cost is not an undue burden | * the increase in cost is not an undue burden |
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| **MPPT is effectively required** when: | **MPPT is effectively required** when: |
| * using panels with nominal voltages higher than 12v | * using panels with nominal voltages higher than 12v |
| * [[#overpaneling|overpaneling]] | * [[#overpaneling|overpaneling]] |
| * making [[electrical:converter#diy_converters|DIY converters]] | * making [[electrical:converter#diy_converters|DIY converters]] |
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| We say "effectively required" because one //can// use 24v panels with PWM and 12v banks -- it just doesn't work very well. The 24v panels will be run at 12v voltages, yielding about half the power you would get with MPPT. | We say "effectively required" because one //can// use 24v panels with PWM and 12v banks -- it just doesn't work very well. The 24v panels will be run at 12v voltages, yielding about half the power you would get with MPPT. |
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| **Shunt controllers are useful for [[electrical:solar:shallow_cycling|shallow-cycling configurations]]** or for battery chemistries that are not damaged by [[electrical:depth_of_discharge|partial state of charge (PSoC)]]. Their relative inexpense makes them useful for even very small systems and test configurations. | **Shunt controllers are useful for [[electrical:solar:shallow_cycling|shallow-cycling configurations]]** or for battery chemistries that are not damaged by [[electrical:depth_of_discharge|partial state of charge (PSoC)]]. Their relative inexpense makes them useful for even very small systems and test configurations. |
| | Their simple ON and OFF setpoints may also make them useful for charging [[electrical:12v:deep_cycle_battery#lithium_chemistries|lithium]] chemistries. |
| Their simple ON and OFF setpoints may also make them useful for charging [[electrical:12v:lifepo4_batteries_thread|lithium]] chemistries. | |
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| Further reading: | Further reading: |
| [[https://www.victronenergy.com/upload/documents/White-paper-Which-solar-charge-controller-PWM-or-MPPT.pdf|an excellent and readable whitepaper by Victron]] (PDF). | [[https://www.victronenergy.com/upload/documents/White-paper-Which-solar-charge-controller-PWM-or-MPPT.pdf|an excellent and readable whitepaper by Victron]] (PDF). |
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| ===== multiple charge controllers ===== | ===== multiple charge controllers ===== |
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| [[electrical:12v:multipoint_charging|Multiple controllers (with separate arrays) can be used to charge a common bank]]. The controllers should be configured with similar charging setpoints for the greatest efficiency.((http://www.morningstarcorp.com/parallel-charging-using-multiple-controllers-separate-pv-arrays/)) | [[electrical:12v:multipoint_charging|Multiple controllers (with separate arrays) can be used to charge a common bank]]. The controllers should be configured with similar charging setpoints for the greatest efficiency.((http://www.morningstarcorp.com/parallel-charging-using-multiple-controllers-separate-pv-arrays/)) |
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| ===== sizing your charge controller ===== | ===== sizing your charge controller ===== |
| | As with [[electrical:inverter|inverters]], sizing the controller correctly will help system efficiency and save money. An oversized CC will have unnecessarily high parasitic drains as it powers itself and will cost more. An undersized CC will not be able to put all the rated solar wattage to use and will leave no room for expansion. |
| As with [[electrical:inverter|inverters]], sizing the controller correctly will help system efficiency. An oversized CC will have unnecessarily high parasitic drains as it powers itself. An undersized CC will not be able to put all the rated solar wattage to use and will leave no room for expansion. | |
| For PWM controllers, the formula is something like (panel wattage / 13) * (1.2 oversize for safety) = charge controller amps.((https://www.altestore.com/howto/sizing-pwm-solar-charge-controllers-a91/)) | For PWM controllers, the formula is something like (panel wattage / 13) * (1.2 oversize for safety) = charge controller amps.((https://www.altestore.com/howto/sizing-pwm-solar-charge-controllers-a91/)) |
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| MPPT controllers have more leeway in sizing since they can control the output of the panels independently of battery voltage. | MPPT controllers have more leeway in sizing since they can control the output of the panels independently of battery voltage. |
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| See also [[electrical:solar:sizing|Sizing a Solar Installation]] | See also [[electrical:solar:sizing|Sizing a Solar Installation]] |
| ===== overpaneling ===== | ===== overpaneling ===== |
| this section [[electrical:solar:overpaneling|has been moved]]. | this section [[electrical:solar:overpaneling|has been moved]]. |
| ===== Using LOAD output ===== | ===== Using LOAD output ===== |
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| It is common for charge controllers to have a LOAD output for powering (or switching) loads. One benefit to doing this is you can define a [[electrical:12v:lvd|Low Voltage Disconnect]] (LVD) setpoint and Low Voltage Reconnect to protect the battery from excessive discharge. | It is common for charge controllers to have a LOAD output for powering (or switching) loads. One benefit to doing this is you can define a [[electrical:12v:lvd|Low Voltage Disconnect]] (LVD) setpoint and Low Voltage Reconnect to protect the battery from excessive discharge. |
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| Not all types of loads should be run from these terminals, though. Morningstar says: | Not all types of loads should be run from these terminals, though. Morningstar says: |
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| > Heavily inductive or capacitive loads such as **pumps, motors, compressors, and | > Heavily inductive or capacitive loads such as **pumps, motors, compressors, and |
| inverters** should not be wired to the controller’s Load terminals. In addition, loads exceeding the Load Current Rating of the controller should not be connected to the controller’s Load terminals.((http://support.morningstarcorp.com/wp-content/uploads/2014/07/ALL.DIG_.Load_Control_Using_A_Relay.01.EN_.pdf)) | inverters** should not be wired to the controller’s Load terminals. In addition, loads exceeding the Load Current Rating of the controller should not be connected to the controller’s Load terminals.((http://support.morningstarcorp.com/wp-content/uploads/2014/07/ALL.DIG_.Load_Control_Using_A_Relay.01.EN_.pdf)) |
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| elsewhere they say: | elsewhere they say: |
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| > Inductive loads can generate large voltage spikes that may damage the controller’s lightning protection devices.((http://www.morningstarcorp.com/wp-content/uploads/2014/02/TS.IOM_.Operators_Manual.04.EN_1.pdf)) | > Inductive loads can generate large voltage spikes that may damage the controller’s lightning protection devices.((http://www.morningstarcorp.com/wp-content/uploads/2014/02/TS.IOM_.Operators_Manual.04.EN_1.pdf)) |
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| although an exception is made for the SunSaver MPPT which "Handles inductive loads without problems."((http://support.morningstarcorp.com/wp-content/uploads/2014/07/SunSaverMPPT-FeaturesBenefits.pdf)) | although an exception is made for the SunSaver MPPT which "Handles inductive loads without problems."((http://support.morningstarcorp.com/wp-content/uploads/2014/07/SunSaverMPPT-FeaturesBenefits.pdf)) |
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| One can run loads heavier than the controller is rated for (or inductive/capacitive loads) by connecting those load[s] to a relay((http://support.morningstarcorp.com/wp-content/uploads/2014/07/ALL.DIG_.Load_Control_Using_A_Relay.01.EN_.pdf)), which is in turn connected to the LOAD output. This still allows for Low Voltage Disconnect because the CC will turn off power to the LOAD output, which turns off power to the relay, which turns power off to the load. | One can run loads heavier than the controller is rated for (or inductive/capacitive loads) by connecting those load[s] to a relay((http://support.morningstarcorp.com/wp-content/uploads/2014/07/ALL.DIG_.Load_Control_Using_A_Relay.01.EN_.pdf)), which is in turn connected to the LOAD output. This still allows for Low Voltage Disconnect because the CC will turn off power to the LOAD output, which turns off power to the relay, which turns power off to the load. |
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| You may also be able to use the LOAD output to create a [[electrical:solar:nonessential|separate 12v circuit for non-essential ("opportunity") loads]]. | You may also be able to use the LOAD output to create a [[electrical:solar:nonessential|separate 12v circuit for non-essential ("opportunity") loads]]. |
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| Note: in wind and hydro power applications the output can be sequenced so that LOAD is activated only when batteries are fully charged. This is called a "dump load" because those power sources need to be able to "dump" excess current to prevent damage to themselves. Dump loads are not necessary in solar because panels can be open- or short-circuited without damage. | Note: in wind and hydro power applications the output can be sequenced so that LOAD is activated only when batteries are fully charged. This is called a "dump load" because those power sources need to be able to "dump" excess current to prevent damage to themselves. Dump loads are not necessary in solar because panels can be open- or short-circuited without damage. |
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| ===== positive ground controllers ===== | ===== positive ground controllers ===== |
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| Some controllers are labeled or described as "positive ground", often by their competitors. The term is incorrect and misleading: | Some controllers are labeled or described as "positive ground", often by their competitors. The term is incorrect and misleading: |
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| > ... "positive ground" terminology is wrong. There is nothing connecting positive supplies to chassis ground, earth ground, or any other ground. -- Trebor English((PM correspondence with frater secessus)) | > ... "positive ground" terminology is wrong. There is nothing connecting positive supplies to chassis ground, earth ground, or any other ground. -- Trebor English((PM correspondence with frater secessus)) |
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| A more accurate term would be **Low Side Switched Controllers** (//**LSSC**// hereafter). A how and why of low side switching is found [[#low_side_switching|at the end of the article]]. | A more accurate term would be **Low Side Switched Controllers** (//**LSSC**// hereafter). A how and why of low side switching is found [[#low_side_switching|at the end of the article]]. |
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| **These LSSC can be incorporated into your camper's electrical system** as long as: | **These LSSC can be incorporated into your camper's electrical system** as long as: |
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| - anything powered by the LOAD output does not ground the negative wiring to the vehicle.((https://www.altestore.com/store/charge-controllers/solar-charge-controllers/pwm-solar-charge-controllers/positive-ground-pwm-charge-controllers-c1143/)) | - anything powered by the LOAD output does not ground the negative wiring to the vehicle.((https://www.altestore.com/store/charge-controllers/solar-charge-controllers/pwm-solar-charge-controllers/positive-ground-pwm-charge-controllers-c1143/)) |
| - any communications i/o (like ethernet or other jacks) do not connect to devices that are grounded to the vehicle.((http://forum.solar-electric.com/discussion/comment/291317#Comment_291317)) | - any communications i/o (like ethernet or other jacks) do not connect to devices that are grounded to the vehicle.((http://forum.solar-electric.com/discussion/comment/291317#Comment_291317)) |
| - solar panels are wired directly to the controller and do not use the vehicle as an electrical path((http://www.cheaprvliving.com/forums/showthread.php?tid=24605&pid=302146#pid302146)) | - solar panels are wired directly to the controller and do not use the vehicle as an electrical path((http://www.cheaprvliving.com/forums/showthread.php?tid=24605&pid=302146#pid302146)) |
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| If you are not using the LOAD output, communicating with the controller, or using the vehicle as an electrical path for the solar panels, LSSC (so-called "positive grounding") doesn't matter.((http://www.irv2.com/forums/f56/renolgy-starter-kit-positive-vs-negative-ground-244437.html#post2557817)) | If you are not using the LOAD output, communicating with the controller, or using the vehicle as an electrical path for the solar panels, LSSC (so-called "positive grounding") doesn't matter.((http://www.irv2.com/forums/f56/renolgy-starter-kit-positive-vs-negative-ground-244437.html#post2557817)) |
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| ==== use of LOAD output on an LSSC ==== | ==== use of LOAD output on an LSSC ==== |
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| If some basic steps are not taken the device may not turn off/on as expected. | If some basic steps are not taken the device may not turn off/on as expected. |
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| Here are some appropriate ways to use the LOAD output with LSSC: | Here are some appropriate ways to use the LOAD output with LSSC: |
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| * run all positive and negative wires back to the LOAD output; or | * run all positive and negative wires back to the LOAD output; or |
| * run them through buses that lead back only to the LOAD output; or | * run them through buses that lead back only to the LOAD output; or |
| * put a relay on the LOAD output and run all the loads through that.((http://www.cheaprvliving.com/forums/showthread.php?tid=24605&pid=307516#pid307516)) | * put a relay on the LOAD output and run all the loads through that.((http://www.cheaprvliving.com/forums/showthread.php?tid=24605&pid=307516#pid307516)) |
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| ==== low side switching ==== | ==== low side switching ==== |
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| LSS means //switching// (turning on-off) is done on the negative (or //low//) side rather than on the positive (or //high//) side. Referring to a low side switched PWM controller, Trebor says: | LSS means //switching// (turning on-off) is done on the negative (or //low//) side rather than on the positive (or //high//) side. Referring to a low side switched PWM controller, Trebor says: |
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| > All three plus connections, solar panel, battery, and load, are tied together. Loads are turned on with a switch (transistor) between the load minus terminal and the battery minus terminal. Charging is turned on (bulk) or pulsed with a switch between panel minus terminal and battery minus terminal.((http://www.cheaprvliving.com/forums/showthread.php?tid=24605&pid=307539#pid307539)) | > All three plus connections, solar panel, battery, and load, are tied together. Loads are turned on with a switch (transistor) between the load minus terminal and the battery minus terminal. Charging is turned on (bulk) or pulsed with a switch between panel minus terminal and battery minus terminal.((http://www.cheaprvliving.com/forums/showthread.php?tid=24605&pid=307539#pid307539)) |
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| He goes on to explain why this is the case: | He goes on to explain why this is the case: |
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| > The reason for the low side switching is the intersection between physics and economics. N-channel field effect transistors are faster, better, cheaper than P-channel parts. The designer can A) use good parts in a simple circuit or B) use more expensive not so good parts or C) make a complicated circuit that uses 18 volts to control a 15 volt switch.((http://www.cheaprvliving.com/forums/showthread.php?tid=24605&pid=307539#pid307539)) | > The reason for the low side switching is the intersection between physics and economics. N-channel field effect transistors are faster, better, cheaper than P-channel parts. The designer can A) use good parts in a simple circuit or B) use more expensive not so good parts or C) make a complicated circuit that uses 18 volts to control a 15 volt switch.((http://www.cheaprvliving.com/forums/showthread.php?tid=24605&pid=307539#pid307539)) |
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