Off-grid solar charge controllers

[russ]

This thread should have been deleted 2-1/2 years ago when it was posted, or moved to the Fiction sub-forum. How it ever became to be a STICKY is beyond me, and does not look good on a Solar Forum by endorsing Voo-Doo as fact.

If I had been the Moderator or Admin it would have been Nuked within minutes.

Dereck - Control the blather

[FloridaSun]

This thread should have been deleted 2-1/2 years ago when it was posted, or moved to the Fiction sub-forum. How it ever became to be a STICKY is beyond me, and does not look good on a Solar Forum by endorsing Voo-Doo as fact.

If I had been the Moderator or Admin it would have been Nuked within minutes.

I agree but it would be nice to have a sticky in 'off grid systems' concerning charge controllers. I nominate YOU to write it as you have the experience and ability to write in an understandable fashion.

[Sunking]

This thread should have been deleted 2-1/2 years ago when it was posted, or moved to the Fiction sub-forum. How it ever became to be a STICKY is beyond me, and does not look good on a Solar Forum by endorsing Voo-Doo as fact.

If I had been the Moderator or Admin it would have been Nuked within minutes.

[Beanyboy57]

Cool ! Except that the voltage is meaningless.

Of course that is meaningless hahahaha...

I have 5 120w panels which provide power for the lighting, occasional stereo, power tools and a small fridge in my shed (theoretically could produce 600watts) but are producing 504watts at peak performance.

90v x 5.6 amps = 504 watts

The panels are rated at 7amps. Is 5.6amps reasonable or too low?

[Mike90250]

...... I am still surprised at how much voltage those panels produce however, even when the sun is not at the optimal angle. ......

Panels produce their voltage, when they get lit from almost any amount of light. As the intensity of the light increases, the AMPS they produce, begins to increase.
For generating power, you need both amps and volts. This is why properly sizing the panels is so important, if under sized, they won't be able to recharge the batteries, if oversized, you have wasted $

[FloridaSun]

Cool ! Except that the voltage is meaningless.

Exactly...
wow, I'm getting 17.5 volts off one 145W panel right now
and a whopping 1 amp

[russ]

Since I wired my PV array in series (5 x 12v panels) I have noticed that it seems to be much more efficient at 90v as opposed to the 30v series parallel system I had previously. I am still surprised at how much voltage those panels produce however, even when the sun is not at the optimal angle. I was expecting an absolute max of (5 x 17v) 85v as the panels do not face North as they should, they face North west. When they were in a parallel setup they were just not that efficient at recharging the batteries. It seems that a series connection with higher voltage is more efficient that lower voltage and greater amperage for batteries and for PV arrays. Am I correct in making this assumption just based on my own experience?

Cool ! Except that the voltage is meaningless.

[Beanyboy57]

That is the same reasoning for most Industrial complexes. Distributing the power around a large plant is better if the voltage is higher than the usage voltage. Most of the plants I have worked in used 4160volt distribution systems and then transformed the power down to 480 volts for motors and 208/120 for offices. The wires size at 4160 volt was roughly 1/10 the size and cost compared to wires needed to distribute 480 volts over long distances.

As the experts like Sunking and Vern Faulkeron on this sight have suggested, the same principle works with solar panels. Connect the panels to obtain a higher output voltage which will allow you to reduce the wire size due to the lower current or amps being run through the cables.

Since I wired my PV array in series (5 x 12v panels) I have noticed that it seems to be much more efficient at 90v as opposed to the 30v series parallel system I had previously. I am still surprised at how much voltage those panels produce however, even when the sun is not at the optimal angle. I was expecting an absolute max of (5 x 17v) 85v as the panels do not face North as they should, they face North west. When they were in a parallel setup they were just not that efficient at recharging the batteries. It seems that a series connection with higher voltage is more efficient that lower voltage and greater amperage for batteries and for PV arrays. Am I correct in making this assumption just based on my own experience?

[russ]

Jonathan Cole, MBA
Author & Solar Energy Consultant
**********************

Hey Bubba - We got rid of your blather a couple of years back - all BS & smoke mixed with no knowledge.

No need for a rerun.

[Vern Faulkner]

Rather than ask the question, maybe you should search first. Your question has already been answered multiple times.

[Naptown]

Hi I'm thinking of buying an mppt controller I have narrowed it down to outback 60 amp controler and the Stand Alone which is an asian brand 60 amp do I spend $800 on outback or just over $300 for[asian brand.would like some feedback thanx.; QUOTE=Jonathan Cole;14127]Here is a bit more in depth info on charge controllers.


There are several approaches to charge control. These are Pulse Width Modulation (PWM), Maximum Power Point Tracking (MPPT), and in some cases power diversion when the batteries are full. See the descriptive technical articles in the Appendix.

You can simply connect the PV panels directly to the battery or inverter. The older charge controllers, simply turned the panels on or off according to the battery voltage and capacity. This is not advisable, however, due to over-voltage conditions, over-heating, shortened battery life and decreased battery capacity. The investment in a charge controller is well worth the savings in battery life and capacity.

As a result of the deficiencies of these older on-off devices, a class of charge controllers using Pulse Width Modulation (PWM) were developed that give an optimal charging regime for the deep cycle batteries used in solar applications. Highly efficient and very low cost per watt of controlled power, these have become very sophisticated and usually include volt, amp, and accumulating kwHr metering.

The Maximum Power Point Tracking (MPPT) charge controller differs in that it calculates the voltage at which the module is able to produce maximum power. The MPPT system then operates the PV modules to extract the full wattage, regardless of present battery voltage. A high efficiency DC-to-DC power converter converts the module voltage at the controller input to the appropriate battery voltage at the output.

With MPPT, if the whole system—wiring and all—was 100% efficient, a charge current increase of 42% would be achieved by harvesting module power that would have been left behind by a conventional controller. But nothing is 100% efficient and actual charge current increase will be somewhat lower as some power is lost in wiring, fuses, circuit breakers, and in the charge controller itself.

Actual charge current increases from MPPT controllers vary with operating conditions. The greater the difference between the PV module maximum power voltage and the battery voltage, the greater the charge current increase from an MPPT controller will be.

Cooler PV module cell temperatures tend to produce greater charge current increase. A highly discharged battery will also increase charge current since battery voltage is lower, and output to the battery during MPPT could be thought of as being “constant power.”

What can be expected of MPPT controllers in cool temperatures with typical battery conditions is a charge current increase of between 10–25%. Cooler temperatures and highly discharged batteries can produce increases in excess of 30%.

Customers in cold climates have reported charge current increases in excess of 40%. What this means is that in colder climates, current increase tends to be greatest when it is needed most; in cooler conditions when days are short, the sun is low on the horizon and batteries may be more highly discharged. In conditions where extra power is not available (highly charged battery and hot PV modules) a MPPT charge controller will perform as a conventional PWM type controller.

However, an important caveat is that MPPT charge controllers tend to be a lot more expensive than PWM controllers. For example, an Outback 60 amp MPPT charge controller with a 2 year warranty costs around $490.00 plus shipping. A Morningstar 60 amp PWM charge controller with a 5 year warranty costs $200 plus shipping.

So, the advantage of MPPT controllers in warmer climates may not be worth the extra cost. If you have a 1200 watt system on a fixed tilt, it will put out around 60 amps peak output at 12 volts. The MPPT may give you less than a 10% gain or less than 120 watts advantage and only part of the time. The $300 extra that you pay for the MPPT controller could purchase you an additional 70 watts of PV panels which have a 25 year warranty. The MPPT controller only has a 2 year warranty (5 year extended warrant costs extra). I would go for the extra generating capacity and use the lower cost charge controller.


_____________________________
Jonathan Cole, MBA
Author & Solar Energy Consultant

[/QUOTE]

Prepare to be flamed

[wedgehead]

decision between 2 types of mppt controller

Hi I'm thinking of buying an mppt controller I have narrowed it down to outback 60 amp controler and the Stand Alone which is an asian brand 60 amp do I spend $800 on outback or just over $300 for[asian brand.would like some feedback thanx.; QUOTE=Jonathan Cole;14127]Here is a bit more in depth info on charge controllers.


There are several approaches to charge control. These are Pulse Width Modulation (PWM), Maximum Power Point Tracking (MPPT), and in some cases power diversion when the batteries are full. See the descriptive technical articles in the Appendix.

You can simply connect the PV panels directly to the battery or inverter. The older charge controllers, simply turned the panels on or off according to the battery voltage and capacity. This is not advisable, however, due to over-voltage conditions, over-heating, shortened battery life and decreased battery capacity. The investment in a charge controller is well worth the savings in battery life and capacity.

As a result of the deficiencies of these older on-off devices, a class of charge controllers using Pulse Width Modulation (PWM) were developed that give an optimal charging regime for the deep cycle batteries used in solar applications. Highly efficient and very low cost per watt of controlled power, these have become very sophisticated and usually include volt, amp, and accumulating kwHr metering.

The Maximum Power Point Tracking (MPPT) charge controller differs in that it calculates the voltage at which the module is able to produce maximum power. The MPPT system then operates the PV modules to extract the full wattage, regardless of present battery voltage. A high efficiency DC-to-DC power converter converts the module voltage at the controller input to the appropriate battery voltage at the output.

With MPPT, if the whole system—wiring and all—was 100% efficient, a charge current increase of 42% would be achieved by harvesting module power that would have been left behind by a conventional controller. But nothing is 100% efficient and actual charge current increase will be somewhat lower as some power is lost in wiring, fuses, circuit breakers, and in the charge controller itself.

Actual charge current increases from MPPT controllers vary with operating conditions. The greater the difference between the PV module maximum power voltage and the battery voltage, the greater the charge current increase from an MPPT controller will be.

Cooler PV module cell temperatures tend to produce greater charge current increase. A highly discharged battery will also increase charge current since battery voltage is lower, and output to the battery during MPPT could be thought of as being “constant power.”

What can be expected of MPPT controllers in cool temperatures with typical battery conditions is a charge current increase of between 10–25%. Cooler temperatures and highly discharged batteries can produce increases in excess of 30%.

Customers in cold climates have reported charge current increases in excess of 40%. What this means is that in colder climates, current increase tends to be greatest when it is needed most; in cooler conditions when days are short, the sun is low on the horizon and batteries may be more highly discharged. In conditions where extra power is not available (highly charged battery and hot PV modules) a MPPT charge controller will perform as a conventional PWM type controller.

However, an important caveat is that MPPT charge controllers tend to be a lot more expensive than PWM controllers. For example, an Outback 60 amp MPPT charge controller with a 2 year warranty costs around $490.00 plus shipping. A Morningstar 60 amp PWM charge controller with a 5 year warranty costs $200 plus shipping.

So, the advantage of MPPT controllers in warmer climates may not be worth the extra cost. If you have a 1200 watt system on a fixed tilt, it will put out around 60 amps peak output at 12 volts. The MPPT may give you less than a 10% gain or less than 120 watts advantage and only part of the time. The $300 extra that you pay for the MPPT controller could purchase you an additional 70 watts of PV panels which have a 25 year warranty. The MPPT controller only has a 2 year warranty (5 year extended warrant costs extra). I would go for the extra generating capacity and use the lower cost charge controller.


_____________________________
Jonathan Cole, MBA
Author & Solar Energy Consultant
[/QUOTE]

[SunEagle]

Not just industrial complexes. It is for the whole elctrical industry. That is why POCO transport at up to 1 million volts.

Good point. Utilities require much higher voltages to run their lines over many miles. The last place I worked was fed by Utility power lines at 138kv which is relatively low voltage as compared to the longer and larger power runs.

[Sunking]

That is the same reasoning for most Industrial complexes.

Not just industrial complexes. It is for the whole elctrical industry. That is why POCO transport at up to 1 million volts.

[SunEagle]

Chiming in here on an old thread.... in doing some back-perusing, for my own knowlege, I've noticed a number of folks struggle with the idea of higher voltage leading to lower losses.

It seems to me that somewhere, a basic primer on the good ol' I^2R factor is needed: that is, energy loss over wires is a function of current and resistance ... that raising the voltage (putting panels in series, rather than parrallel, for example) decreases current, and thus the loss due to the internal resistance of ye olde wire.

That is the same reasoning for most Industrial complexes. Distributing the power around a large plant is better if the voltage is higher than the usage voltage. Most of the plants I have worked in used 4160volt distribution systems and then transformed the power down to 480 volts for motors and 208/120 for offices. The wires size at 4160 volt was roughly 1/10 the size and cost compared to wires needed to distribute 480 volts over long distances.

As the experts like Sunking and Vern Faulkeron on this sight have suggested, the same principle works with solar panels. Connect the panels to obtain a higher output voltage which will allow you to reduce the wire size due to the lower current or amps being run through the cables.