Why is mppt better than pwm?
- Thread starter Bossrox
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A 300W panel will have a Voc close to 40V so two in series is more like 80V.
I measured it with my meter and it read 40 volts from 2 panels in series
timselectric
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Are you sure that they are in series, and not parallel?
What is the VOC of each panel?
Maximum power (Pmax): 300W
Output tolerance: ±3%
Maximum system voltage: 700V DC
Open circuit voltage (Voc): 19.2V
Short circuit current (Isc): 3.43A
Maximum power supply voltage (Vmp): 18V
Maximum supply current (Imp): 3.12A
Battery efficiency: 19.5%
Working temperature (NOCT): 45±2℃
Temperature range: -40℃～+80℃
Output tolerance: ±3%
Maximum system voltage: 700V DC
Open circuit voltage (Voc): 19.2V
Short circuit current (Isc): 3.43A
Maximum power supply voltage (Vmp): 18V
Maximum supply current (Imp): 3.12A
Battery efficiency: 19.5%
Working temperature (NOCT): 45±2℃
Temperature range: -40℃～+80℃
timselectric
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You are correct.
Two panels in series, would be just under 40v.
That charger should be fine with it.
Two panels in series, would be just under 40v.
That charger should be fine with it.
timselectric
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Something is definitely off.
Where did you get these panels?
You should check the isc.
Where did you get these panels?
You should check the isc.
Crappy chinese panels
timselectric
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DerpsyDoodler
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Also, if you're using pwm, you're wasting potential power by connecting in series. Assuming you're charging a 12V battery bank, put them in parallel. If you're charging a 24V bank, I guess you have no choice based on those specs. Try to consult the forum here before making purchases in the future. We'll help optimize the money you spend.
Thanks for that offer I really appreciate it
SanTan Solar T Series 250W Snail Trails
Due to constantly changing stock, these panels may come with silver frames or black frames.These panels are $64 each, your thoughts?
Features:
- 60 cell, polycrystalline
- Weather resistant. Certified for salt mist and ammonia resistance
- Anti-Reflection surface treatment
Specifications:
- Rated Power: 250W
- Open circuit voltage (VOC): 37.6 V
- Max power voltage (VMP): 30.3 V
- Short circuit current (ISC): 8.85 A
- Max power current: 8.27 A
- Power Tolerance 0/+3%
- Maximum system voltage: 600V (UL)
- Fuse Rating: 15 A
- IP65 Junction Box w/MC4 Compatible Connectors
- Frame: Anodized aluminum alloy
- Weight: 41 lbs.
- Dimensions: 64.95 × 39.05 × 1.37 inches (1650 × 992 × 35mm)
timselectric
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I currently have 22 of these panels, on my roof.
They are producing very well.
turbineinfo
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Just Wondering, when you switched from pwm to mppt I’m assuming that you keep your panels wired in parallel….you current mppt pv panel configuration is not in series…right?
turbineinfo
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I understand that if you want to use LifePo4 batteries, a mppt controller is highly recommended. From what i have read, the pulse charge algorithm of a pwm controller is hard on lithium
PWM and MPPT are actually two different things, but marketing confuses the consumer and can lead to urban myths. Warning - long, but perhaps entertaining!
A mythical story might help explain:
You are stranded on an island with a nominal 12v panel that actually puts out 20v unregulated. You have a nominal 12v battery that is rated with a CV charge of no greater than 14.4v.
Long ago, the controller broke. All you have left is an on/off toggle switch as your only means to prevent overcharge.
Early years of use: You wire it up, and sitting at the toggle switch, you watch your voltmeter on the battery terminals rise to 14.4v. You open the switch. You let the battery "settle" back to say 13.2v and then close the switch again. Watching for 14.4v, you open the switch and repeat this process. As the battery charges, the time interval between you opening and closing the switch gets longer and longer. Unfortunately, this results in a battery that is not fully charged before the sun sets.
This is also known as "hysteresis" charging.
In a desire to be more efficient, you come across a Morningstar pwm controller document in a cave. AHA! You read that the pwm frequency is 38 khz. That simply means that instead of doing an inefficient hysteresis, you just need to flip the switch on and off 38.8 thousand times a second with your hands.
This means that the actual panel voltage of 20v is applied to the battery in very very short connections, thirty-eight-thousand times per second. But by doing this, the NET EFFECT is that of applying a 14.4v CV when time spent at connection is considered.
Amped on coffee, stashed sports-drink, and the island's own go-go juice, you sit at the table and flick the on-off toggle switch 38000 times a second. Villagers witness a veritable buzz of activity at your table. They can't even see your hand moving!
The villagers are happy since charging the battery in this way is a vast improvement over the early years of hysteresis. Being promoted to village elder, they are expecting even more performance than this! How can this possibly get even better?
Ah, knowing that in the end, all you have to do is prevent the battery from exceeding 14.4v from a *NET OVERALL* high-speed toggle switch, what if we allow that speed to vary and by careful use of your ammeter skills, you manually raise or lower the speed so that you always get the highest current going into the battery as possible?
Like tracking your prey on the island, you adjust your pwm hand-toggling speed according to need and feedback to make it the best possible all the time. Unlike the early method, where given enough go-go juice to toggle that switch exactly at 38000 times a second, AND read a book in the other hand, now you need to concentrate a little more to adjust that speed as conditions change.
The villagers have now promoted you to being the "Maximum Power Point Tracker".
Sorry for the editorial license. The overall point to the story is that MPPT controllers use varying pwm techniques for best benefit. PWM controllers are just using this method of nomenclature to differentiate themselves early on from the older "hysteresis" controllers. MPPT is an *additional* measure added to a controller using PWM.
Ie, your panel is never actually "seeing" the full unregulated voltage from the panel because the full-panel-voltage switching is so fast, that the *net effect* is that of a lower voltage overall.
A mythical story might help explain:
You are stranded on an island with a nominal 12v panel that actually puts out 20v unregulated. You have a nominal 12v battery that is rated with a CV charge of no greater than 14.4v.
Long ago, the controller broke. All you have left is an on/off toggle switch as your only means to prevent overcharge.
Early years of use: You wire it up, and sitting at the toggle switch, you watch your voltmeter on the battery terminals rise to 14.4v. You open the switch. You let the battery "settle" back to say 13.2v and then close the switch again. Watching for 14.4v, you open the switch and repeat this process. As the battery charges, the time interval between you opening and closing the switch gets longer and longer. Unfortunately, this results in a battery that is not fully charged before the sun sets.
This is also known as "hysteresis" charging.
In a desire to be more efficient, you come across a Morningstar pwm controller document in a cave. AHA! You read that the pwm frequency is 38 khz. That simply means that instead of doing an inefficient hysteresis, you just need to flip the switch on and off 38.8 thousand times a second with your hands.
This means that the actual panel voltage of 20v is applied to the battery in very very short connections, thirty-eight-thousand times per second. But by doing this, the NET EFFECT is that of applying a 14.4v CV when time spent at connection is considered.
Amped on coffee, stashed sports-drink, and the island's own go-go juice, you sit at the table and flick the on-off toggle switch 38000 times a second. Villagers witness a veritable buzz of activity at your table. They can't even see your hand moving!
The villagers are happy since charging the battery in this way is a vast improvement over the early years of hysteresis. Being promoted to village elder, they are expecting even more performance than this! How can this possibly get even better?
Ah, knowing that in the end, all you have to do is prevent the battery from exceeding 14.4v from a *NET OVERALL* high-speed toggle switch, what if we allow that speed to vary and by careful use of your ammeter skills, you manually raise or lower the speed so that you always get the highest current going into the battery as possible?
Like tracking your prey on the island, you adjust your pwm hand-toggling speed according to need and feedback to make it the best possible all the time. Unlike the early method, where given enough go-go juice to toggle that switch exactly at 38000 times a second, AND read a book in the other hand, now you need to concentrate a little more to adjust that speed as conditions change.
The villagers have now promoted you to being the "Maximum Power Point Tracker".
Sorry for the editorial license. The overall point to the story is that MPPT controllers use varying pwm techniques for best benefit. PWM controllers are just using this method of nomenclature to differentiate themselves early on from the older "hysteresis" controllers. MPPT is an *additional* measure added to a controller using PWM.
Ie, your panel is never actually "seeing" the full unregulated voltage from the panel because the full-panel-voltage switching is so fast, that the *net effect* is that of a lower voltage overall.
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Historical note:
If we could roll back the clock 20 years, and had this forum been alive, the question would have been "Is PWM better than Hysteresis charging?"
The ongoing concern was to avoid being ripped off by "fake pwm". Some resellers and vendors advertised pwm, but inside was a simple hysteresis charger. Some even exist today like the smaller Coleman 7A little camping types.
The marketing war was on. Those who had spent $$ on their hysteresis-charge systems floated the concept that pwm was "hard on batteries". This is well before LifePo4 days.
And threads quickly derailed with the hysteresis guys floating this concept of damage, and purposely muddying the waters by delving into pulse or burp-charging, and the thread finally ending when it was finally terminated with a "desulfation" slugfest.
Nevertheless, the FUD campaign worked for some, and stuck to hysteresis controllers, tired or confused about what pwm was really about.
In the end today, just simply remember that MPPT is a tracking algorithm that is added to a basic PWM controller for higher efficiency. Marketing doesn't want consumers to know this.
If we could roll back the clock 20 years, and had this forum been alive, the question would have been "Is PWM better than Hysteresis charging?"
The ongoing concern was to avoid being ripped off by "fake pwm". Some resellers and vendors advertised pwm, but inside was a simple hysteresis charger. Some even exist today like the smaller Coleman 7A little camping types.
The marketing war was on. Those who had spent $$ on their hysteresis-charge systems floated the concept that pwm was "hard on batteries". This is well before LifePo4 days.
And threads quickly derailed with the hysteresis guys floating this concept of damage, and purposely muddying the waters by delving into pulse or burp-charging, and the thread finally ending when it was finally terminated with a "desulfation" slugfest.
Nevertheless, the FUD campaign worked for some, and stuck to hysteresis controllers, tired or confused about what pwm was really about.
In the end today, just simply remember that MPPT is a tracking algorithm that is added to a basic PWM controller for higher efficiency. Marketing doesn't want consumers to know this.
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100 Proof
"Please Lord, don't let me do something stupid."
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Except that if that if the "...nominal 12v panel that actually puts out 20v unregulated..." is rated at 10A Imp, you will never get more than that out of it with a PWM controller. With a legit MPPT controller, you have a shot at about 15ish Amps.PWM and MPPT are actually two different things, but marketing confuses the consumer and can lead to urban myths. Warning - long, but perhaps entertaining!
A mythical story might help explain:
You are stranded on an island with a nominal 12v panel that actually puts out 20v unregulated. You have a nominal 12v battery that is rated with a CV charge of no greater than 14.4v.
Long ago, the controller broke. All you have left is an on/off toggle switch as your only means to prevent overcharge.
Early years of use: You wire it up, and sitting at the toggle switch, you watch your voltmeter on the battery terminals rise to 14.4v. You open the switch. You let the battery "settle" back to say 13.2v and then close the switch again. Watching for 14.4v, you open the switch and repeat this process. As the battery charges, the time interval between you opening and closing the switch gets longer and longer. Unfortunately, this results in a battery that is not fully charged before the sun sets.
This is also known as "hysteresis" charging.
In a desire to be more efficient, you come across a Morningstar pwm controller document in a cave. AHA! You read that the pwm frequency is 38 khz. That simply means that instead of doing an inefficient hysteresis, you just need to flip the switch on and off 38.8 thousand times a second with your hands.
This means that the actual panel voltage of 20v is applied to the battery in very very short connections, thirty-eight-thousand times per second. But by doing this, the NET EFFECT is that of applying a 14.4v CV when time spent at connection is considered.
Amped on coffee, stashed sports-drink, and the island's own go-go juice, you sit at the table and flick the on-off toggle switch 38000 times a second. Villagers witness a veritable buzz of activity at your table. They can't even see your hand moving!
The villagers are happy since charging the battery in this way is a vast improvement over the early years of hysteresis. Being promoted to village elder, they are expecting even more performance than this! How can this possibly get even better?
Ah, knowing that in the end, all you have to do is prevent the battery from exceeding 14.4v from a *NET OVERALL* high-speed toggle switch, what if we allow that speed to vary and by careful use of your ammeter skills, you manually raise or lower the speed so that you always get the highest current going into the battery as possible?
Like tracking your prey on the island, you adjust your pwm hand-toggling speed according to need and feedback to make it the best possible all the time. Unlike the early method, where given enough go-go juice to toggle that switch exactly at 38000 times a second, AND read a book in the other hand, now you need to concentrate a little more to adjust that speed as conditions change.
The villagers have now promoted you to being the "Maximum Power Point Tracker".
Sorry for the editorial license. The overall point to the story is that MPPT controllers use varying pwm techniques for best benefit. PWM controllers are just using this method of nomenclature to differentiate themselves early on from the older "hysteresis" controllers. MPPT is an *additional* measure added to a controller using PWM.
Ie, your panel is never actually "seeing" the full unregulated voltage from the panel because the full-panel-voltage switching is so fast, that the *net effect* is that of a lower voltage overall.
Think of it this way:
PWM- Amps in = Amps out.
MPPT- Watts in = Watts out.
Minus system losses of course.
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You are absolutely correct. I guess the main point is that by not knowing that MPPT is efficiency tracking algorithm incorporated into a pwm controller, it makes it much easier for sales departments to prey upon a consumer's ignorance, and accept labels, rather than the science as being "better" as to which to purchase.
"Look - there's no need to buy a Victron! We're mppt too! And we're certainly not pwm! "
The smart one knows to ask "Ok, since I know mppt is an algorithm to modify the pwm technique for maximum efficiency - show me YOUR algorithm!" Salesman gulps - because all he knows is labeling, and not the science.
In the past, the same was done to early pwm controllers that didn't incoporate any mppt algorithm
"Look, we put PWM on the case - we're just like Morningstar! And we're certainly not hysteresis!"
But once opened, all we found in the cheezy unit was NOT pwm, but merely a hysteresis circuit which had CV voltages close to each other - like 14.2 lvd, and 14.4 hvd.
The moral is that marketing only wants a consumer to make blind assumptions based upon labels. They *certainly* don't want an educated consumer asking about how good or bad their mppt algorithm is!
The hope is that you will buy based solely on incomplete knowledge based on labels alone (pwm and mppt), and not dig too deep. Heh, show me the algo frightens them off!
As you can imagine, these algorithms are usually proprietary and you won't get too much detail - other than perhaps charts. At the low end of the spectrum, those who say they are using mppt may be using such a poor algorithm that doesn't actually track well at all, leaves you ripped off.
So the devil is in the details. For the shady products, the hope is that you won't go there and just blindly accept that mppt is almost a brand-name in itself.
Ie, real-world issues to look out for. With MPPT, you *do* get what you pay for. As the brain of your system, is it wise not to skimp out.
"Look - there's no need to buy a Victron! We're mppt too! And we're certainly not pwm! "
The smart one knows to ask "Ok, since I know mppt is an algorithm to modify the pwm technique for maximum efficiency - show me YOUR algorithm!" Salesman gulps - because all he knows is labeling, and not the science.
In the past, the same was done to early pwm controllers that didn't incoporate any mppt algorithm
"Look, we put PWM on the case - we're just like Morningstar! And we're certainly not hysteresis!"
But once opened, all we found in the cheezy unit was NOT pwm, but merely a hysteresis circuit which had CV voltages close to each other - like 14.2 lvd, and 14.4 hvd.
The moral is that marketing only wants a consumer to make blind assumptions based upon labels. They *certainly* don't want an educated consumer asking about how good or bad their mppt algorithm is!
The hope is that you will buy based solely on incomplete knowledge based on labels alone (pwm and mppt), and not dig too deep. Heh, show me the algo frightens them off!
As you can imagine, these algorithms are usually proprietary and you won't get too much detail - other than perhaps charts. At the low end of the spectrum, those who say they are using mppt may be using such a poor algorithm that doesn't actually track well at all, leaves you ripped off.
So the devil is in the details. For the shady products, the hope is that you won't go there and just blindly accept that mppt is almost a brand-name in itself.
Ie, real-world issues to look out for. With MPPT, you *do* get what you pay for. As the brain of your system, is it wise not to skimp out.
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