PWM or MPPT controller?

oldtrack123 · Guru

RE: PWM or MPPT controller?

oldtrack123 · Guru

swamp wrote:
Hi
Aussie Paul

If u have a PWM controller and it a suitable size use it .
If u are maxed out on panel real estate , can fit no more go Mppt to get the advantage . Only if u need it !!
Then if u are on a budget or not effects your choice also .

budget EP Solar Tracer series Rather large and require space to mount vertically . Some models are programmable .

Medium Victron most compact

High level /cost Morning star

A lot of Info by Morningstar factory instructional on Utube heap &heaps highly recommend

Interestingly Morningstar does not consider Mppt worth while till around 400--500 watts

Day to day operation Morningstar are quoting 20% boost primarily due to there electronics . Up to 30% boost on a discharged battery
My Tracer produces around 13--15 % boost day to day . Up to 30% boost on a discharged battery

Hi Swamp

Guess how many Watts of Panels most of Terry's set ups have including those off grid ones biggrin

kWs & still using PWMs

mr glassies · Guru

Oldtrack if the rest of the world had done the testing and not read it on a sales brochure like Terry has done maybe they would have the rite answered as well

Dibs

Ps took ya time

oldtrack123 · Guru

mr glassies wrote:
Oldtrack if the rest of the world had done the testing and not read it on a sales brochure like Terry has done maybe they would have the rite answered as well

Dibs

Ps took ya time

Did you read Swamp's Actual results????

True life results & notice how they put out much more when the battery is in a low SOC

.When that extra punch is most needed. smile biggrin

Pretty close to what most makers of good MPPTs claim,

Perhaps you are being mislead ,

I doubt that you understand any of the tech details & explanations posted , explaining how they achieve such results.,

IF you did understand you would see that what applies to LIs with their very small change in voltage over operating range & relatively low impedance, gives a totally different result to use with LEAD ACID batteries.!!!

That voltage characteristic of LIs even allows Terry to use lower voltage panels & with those panels, A MPPT would be useless for LAs & would not gain much even with LIs as there is little excess voltage available

All Of which I have tried to explain many many times

,Panels that would barely work with LA batteries, but to understand why also requires some electrical knowledge, or I should say,of basic electrical principles!!

Summed up

Terry ,by experimenting ,has found the best combinations of panels & regulators for efficient LI 12V battery charging

.I Actually admire him for what he has achieved,for that very specific purpose.

I DO understand why it works so well with LI 12V battery set ups

I see no advantage in using MPPT regs with LI & the panels I believe Terry uses.

But to say MPPTS cannot perform as specified [as current boosters ]with suitable panels & LA battery is completely wrong

Yet ,that is the line being pushed, MMPT are no good ,cannot perform as claimed ,PWMS are the only way.

My Electrical Knowledge[including theory biggrin ] allows me to do that &to try to explain why it works well with those specific batteries.

& to further try to explain why the same does not apply to 12V LAs. & /or higher voltage panels

On another thread, sometime ago, Terry was explaining the need for big cables all the way from the panels, I suggest he found out that his system could not tolerate much cable voltage drop before all charging ceased

Again, can be explained & easily understood ,WHY ,with basic theory & the optimal size easily worked out.

That may also have been a factor in his early comparison experiments & testing, how far were the regulator from the panels???

dorian · Guru

oldtrack123 wrote:

A PWM is basically a voltage sensitive relay

Depending on type , it simply:
A/ connects or disconnects the panels from the battery ',"ON" or " OFF"
B/ it may also shunt the panel output current from pos to neg[earth] instead of just open circuiting the panel output
They are always all or nothing
They pull the panel voltage down to the battery voltage but as the panel generate current is constant,does not increase much even under short circuit conditions, the charge current is simply the panel's available output, never higher!!
The good ones have additional features

dorian · Guru

Here is a PWM design:

http://sandysplash.blogspot.com.au/2013/07/pwm-solar-charge-controller-circuit.html
https://2.bp.blogspot.com/-e98al5NcpJw/UdkCIJj088I/AAAAAAAAACU/5KljhvTF68E/s640/Capture1.PNG

It uses a buck topology, so it is not really an all-or-nothing design. AISI, the circuit could be significantly improved by adding a capacitor across the panel. This would enable the panel to store otherwise wasted energy while the "CHG MOSFET" is switched off. The panel current would then be relatively smooth rather than pulsed.

BTW, I don't understand why there is a "blocking diode" across the fuse.

Jaahn · Guru

Hi Dorian smile

"In fact I expect that many PWM controllers are really buck regulators or buck-boost types with an inductor and a flywheel diode, plus a capacitor at the panel input."

I do not understand why you would think this when the normal suppliers do not claim it ???? The fact you found some on the web means just that. In fact I would suggest they are most likely provide the basis of the cheap fake MPPT regs that are found on ebay. They do not incorporate the actual function the name describes and the boost design is poor efficiency and the stand by current is high. So losses may exceed the gains as has been claimed by some. furious

Batteries do not mind the on off switching. Indeed the car alternator does just that for output control.

Jaahn

dorian · Guru

Jaahn wrote:
Hi Dorian
"In fact I expect that many PWM controllers are really buck regulators or buck-boost types with an inductor and a flywheel diode, plus a capacitor at the panel input."
I do not understand why you would think this when the normal suppliers do not claim it ????
Batteries do not mind the on off switching. Indeed the car alternator does just that for output control.
Jaahn

When I think of PWM regulators, I assume that they all use inductors. To me it's a given -- it doesn't need spelling out. I would very much like to see a real world example to the contrary. It's like buying a car -- I expect that it would have 4 wheels and a motor.

The car alternator's output is relatively smooth. The old mechanical PWM regulators pulsed the field current, but I would think that modern regulators have relatively linear outputs.

BTW, intelligent AC powered battery chargers would all incorporate PWM regulators with inductors, etc.

dorian · Guru

T1 Terry wrote ...

"a PWM controller simply passes the solar from input to output until the target voltage is reached."

Cupie wrote ...

"If any one wants a spare PWM controller, I have one for free that came with my Panel. I have a MPPT controller built in to my Thunder DC to DC Charger."

Would either (preferably both) of you show us photos of the insides of your PWM controllers?

dorian · Guru

I stand corrected. It seems that the solar industry treats the term, "PWM", very differently than the general electronics world.

For example, the CMTP02 PWM controller in the following teardowns has no magnetics. It seems that oldtrack123's description is spot on for this case.

http://diyprojects.eu/cmtp02-disassembling-solar-charge-controller/
http://diyprojects.eu/cmtp02-5a-solar-controller-photos/

This "MPPT" controller appears to be a fake:

http://vandogtraveller.com/wiring-solar-panels-van-mppt30/
http://vandogtraveller.com/wp-content/uploads/2015/01/inside-mppt30-solar-charger-controller.jpg

Here is a genuine MPPT controller:

http://solarpowerphilippines.weebly.com/mppt-charge-controller.html

IMHO, "PWM" controllers which don't employ inductors are conceptually ugly. I can't see a legitimate reason why properly designed PWM controllers should cost significantly more. In fact, the difference in parts between properly designed PWM and MPPT controllers shouldn't be very great at all. The major difference should be in the firmware.

Jaahn · Guru

Hi Dorian smile

Assumptions are a problem ! Google can be too ! PWM solar regs/controllers are just simple switching devices with (hopefully) a variable set point that might have a simple microprocessor to control that setpoint, the user settings and readout functions. As Terry says they are reliable and simple. Even the cheap ones can be reliable but may have just one fixed setpoint(even when they claim otherwise). hmm

" The car alternator's output is relatively smooth. The old mechanical PWM regulators pulsed the field current, but I would think that modern regulators have relatively linear outputs."

I believe you will be disappointed, again, on this point. The electronic regs just duplicated the mechanical style of control. Over time they acquired extra auxiliary functions to enhance the reliability and accuracy of the output under all conditions but retained the same style of control. Now an input from the ECU is included too which may vary the setpoint but the style of switching on and off the excitation for control has not changed. furious

Jaahn

-- Edited by Jaahn on Tuesday 5th of December 2017 01:09:49 PM

T1 Terry · Guru

There appears to be some mis-understanding regarding RV MPPT controllers, they can not boost voltage, only reduce it, so a panel voltage to battery voltage mis match is essential for the operation of an RV type MPPT controller.

If Peter wants to maintain his stand on MPPT controllers being superior for lead acid battery charging then we do need some truth in the formula used for the theoretical gains.
Genuine Vmp of the solar output at the actual operating temp the panels see laid flat on the RV roof. It doesn't take much brain power to understand the panel will not remain at 25*C mounted flat on the roof while the RV is stationary, even if there is a 30mm or 50mm gap under it. Heat rises and there is a 30mm to 50mm collar all around the underside of the panel so the heat will not flow out and away from the rear of the panel to any great degree because the hot air is trapped in that area under the panel.

Next is genuine efficiency of the controller. Up to 90% doesn't mean it can converter up to 90% of the advertised solar capacity into something that will charge the battery, it means at best it will only waste 10% of the watts coming in to power itself ..... the more work it has to do the greater that inefficiency becomes, so 10% inefficient is the very best it can do, not a flat line of 10%.

Next is the real battery voltage range people will be expecting their batteries to function in, 12v to 14.8v as the extremes, I'm guessing most will say these are a bit extreme for their set up, more like 12.4v to 14.4v and a float of 13.8v by around lunch time or 2pm at the worst.
This means theoretical gains for a battery at 10.8v is completely irrelevant, so show the gains that can be achieved for the battery voltage range just about all readers here actually use.

Now, how about to size of the solar array, surely this is relevant, a 10% gain on a 200w 12v nominal solar system would be???? If we believe the tales of PWM being restricted to 70% efficiency including the controller losses, then 200 x 70% = 140w. Divide that by 12v and the expected charge current would be around 11.6 amps.
Now Peter, give the readers the theoretical charging rate an MPPT controller could achieve using real Vmp voltages the same panel array would produce in full sun and factor in the losses for the MPPT controller doing the job it is being asked to do, you can do both parallel and series connection if you want, but the inefficiencies must be included ..... we all know nothing is 100% efficient so there is no point in ignoring the losses.

T1 Terry

DeBe · Guru

This is the circuits of 2 PWM solar regulators I built as kits from Oatley electronics back in the 90s. They are still working & doing the job after all this time. I don't think Oatley Electronics are in business any more. SOLAR.4.jpg SOLAR-2.3.jpg

Bagmaker · Senior Member

there is no width modification???

edit - hung around too long with question, please ignore

nothing to see here folks, move alonn

-- Edited by Bagmaker on Tuesday 5th of December 2017 02:51:41 PM

dorian · Guru

Thanks to all for your corrections. It appears that I'm wrong again. The following URLs suggest that the alternator field current is now controlled via PWM.

http://www.microcharge.de/downloads/Understanding_Generator_Ripple_Waveforms.pdf
https://www.nxp.com/docs/en/data-sheet/MC33092A.pdf

Decades ago I built the following circuit:

http://www.epanorama.net/sff/Automotive/circuits/other/Auto_Voltage_Regulator.pdf

Its author claims that it is a switchmode design, but to me it appears linear. Am I having another brain fart?

T1 Terry said ...

"There appears to be some mis-understanding regarding RV MPPT controllers, they can not boost voltage, only reduce it..."

Here's one that can:

https://genasun.com/all-products/solar-charge-controllers/for-lithium/gvb-8a-li-lithium-solar-boost-controller/

"Want to see a 27V grid-tie panel charge a 48V battery pack? ... These controllers boost lower-voltage solar panels up to charge higher voltage lithium batteries up to 48V nominal."

Here's another one:

http://www.roadtechmarine.com.au/in-vehicle-dc-dc-boost-charger-with-mppt-solar-controller-30a/p/TES444

"The DC-DC charger is a full buck-boost type DC to DC charger, which boosts or reduces the incoming DC voltage to produce the FULL output voltage required to properly charge your deep cycle battery to a full 100% with true 4-stage charging. ... When you are camping, the MPPT solar controller takes care of charging, providing up to 95% efficiency. The wide input voltage allows you to have either a 12V or 24V solar array to charge your deep cycle (12V or 24V) ..."

Here is one IC that seems to do it all:

LT8490, High Voltage, High Current Buck-Boost Battery Charge Controller with Maximum Power Point Tracking (MPPT):
http://www.farnell.com/datasheets/2005283.pdf
http://www.farnell.com/datasheets/1970697.pdf
http://www.linear.com/solutions/5096 (LT8490 demo board schematic, design files, manual)

"The LT8490 is a buck-boost switching regulator battery charger that implements a constant-current constant-voltage (CCCV) charging profile used for most battery types, including sealed lead-acid (SLA), flooded, gel and lithium-ion. The device operates from input voltages above, below or equal to the output voltage and can be powered by a solar panel or a DC power supply. On-chip logic provides automatic maximum power point tracking (MPPT) for solar powered applications. The LT8490 can perform automatic temperature compensation by sensing an external thermistor thermally coupled to the battery. STATUS and FAULT pins containing charger information can be used to drive LED indicator lamps."

Here is a kit based on the above IC:
https://www.mictronics.de/projects/lt8490-mppt-solar-charger/

dorian · Guru

Here is a PCB based around the LT8490 chip (USD$75):
https://es.aliexpress.com/item/400W-MPPT-solar-controller-LT8490-single-chip-intelligent-control-Battery-charging-Lite-Edition/32799908234.html

https://ae01.alicdn.com/kf/HTB1MQpdRpXXXXcAXVXXq6xXFXXXK/400-W-MPPT-regulador-solar-Lite-Edition-LT8490-solo-chip-de-control-inteligente-de-carga-de.jpg_640x640.jpg

Here is an LT8490 based controller in a box with a fan (USD$84):
https://es.aliexpress.com/item/500W-MPPT-solar-controller-LT8490-single-chip-intelligent-control-battery-pack-charge/32817217235.html

https://ae01.alicdn.com/kf/HTB18X_ORVXXXXbWXXXXq6xXFXXXZ/500W-MPPT-solar-controller-LT8490-single-chip-intelligent-control-battery-pack-charge.jpg_640x640.jpg

https://ae01.alicdn.com/kf/HTB1e5u_RVXXXXa7aXXXq6xXFXXXk/500W-MPPT-solar-controller-LT8490-single-chip-intelligent-control-battery-pack-charge.jpg_640x640.jpg

https://ae01.alicdn.com/kf/HTB1vDS2RVXXXXaHapXXq6xXFXXXe/500W-MPPT-solar-controller-LT8490-single-chip-intelligent-control-battery-pack-charge.jpg_640x640.jpg

https://ae01.alicdn.com/kf/HTB1BvvQRVXXXXbcXXXXq6xXFXXXE/500W-MPPT-solar-controller-LT8490-single-chip-intelligent-control-battery-pack-charge.jpg_640x640.jpg

Lots of Google hits:
http://www.google.com.au/search?q="LT8490"+mppt+solar+site:aliexpress.com

T1 Terry · Guru

I stand corrected Dorian, it appears there are a few controllers out there that do have the capacity to boost solar voltage, their efficiency while doing this would be interesting to see, I know the DC to DC chargers with this capability are woefully inefficient with more than a 30% loss between input and output watts from some brands/models, makes them a rather expensive solar controller as far as the number of panels required to get the same battery charging ability.

T1 Terry

dorian · Guru

My previous post was withheld by the spam filter.

This was the first part of it:

Here is a PCB based around the LT8490 chip (USD75):
https://es.aliexpress.com/item/400W-MPPT-solar-controller-LT8490-single-chip-intelligent-control-Battery-charging-Lite-Edition/32799908234.html

https://ae01.alicdn.com/kf/HTB1MQpdRpXXXXcAXVXXq6xXFXXXK/400-W-MPPT-regulador-solar-Lite-Edition-LT8490-solo-chip-de-control-inteligente-de-carga-de.jpg_640x640.jpg

Here is an LT8490 based controller in a box with a fan (USD84):
https://es.aliexpress.com/item/500W-MPPT-solar-controller-LT8490-single-chip-intelligent-control-battery-pack-charge/32817217235.html

https://ae01.alicdn.com/kf/HTB18X_ORVXXXXbWXXXXq6xXFXXXZ/500W-MPPT-solar-controller-LT8490-single-chip-intelligent-control-battery-pack-charge.jpg_640x640.jpg

dorian · Guru

... and the second part.

https://ae01.alicdn.com/kf/HTB1e5u_RVXXXXa7aXXXq6xXFXXXk/500W-MPPT-solar-controller-LT8490-single-chip-intelligent-control-battery-pack-charge.jpg_640x640.jpg

https://ae01.alicdn.com/kf/HTB1vDS2RVXXXXaHapXXq6xXFXXXe/500W-MPPT-solar-controller-LT8490-single-chip-intelligent-control-battery-pack-charge.jpg_640x640.jpg

https://ae01.alicdn.com/kf/HTB1BvvQRVXXXXbcXXXXq6xXFXXXE/500W-MPPT-solar-controller-LT8490-single-chip-intelligent-control-battery-pack-charge.jpg_640x640.jpg

Lots of Google hits:
http://www.google.com.au/search?q="LT8490"+mppt+solar+site:aliexpress.com

oldtrack123 · Guru

For those ,who are possibly getting confused by the various claims view this;www.youtube.com/watch

IMHO it is a straight forward comparison .

It does not take into account Efficiency but the general claim is 95 to 97 %
You will note the Importance of panel Voltage available to either types
If you are going to use panels whose PPP voltage is only enough to charge the battery, a MPPT will not give any gains ie 30 cell panels Versus 36 cell panels

T1 Terry · Guru

oldtrack123 wrote:
For those ,who are possibly getting confused by the various claims view this;www.youtube.com/watch

IMHO it is a straight forward comparison .

It does not take into account Efficiency but the general claim is 95 to 97 %
You will note the Importance of panel Voltage available to either types
If you are going to use panels whose PPP voltage is only enough to charge the battery, a MPPT will not give any gains ie 30 cell panels Versus 36 cell panels

I hope you saw the last part of my post

Now Peter, give the readers the theoretical charging rate an MPPT controller could achieve using real Vmp voltages the same panel array would produce in full sun and factor in the losses for the MPPT controller doing the job it is being asked to do, you can do both parallel and series connection if you want, but the inefficiencies must be included ..... we all know nothing is 100% efficient so there is no point in ignoring the losses.

Hopefully you will see your way clear to either grace the readers here with a proper answer, or admit you really don't know and you are simply repeating things you have read have accepted their figures as being accurate for a system actually installed on an RV.

T1 Terry

Dickodownunder · Guru

Well lets summarise what I have learned so far.
MPPT in a perfect world will be a better controller than the PWM.
In the real world each system will need to be assessed to justify the extra cost of changing to MPPT.
MPPT seems to be the choice of controller on larger systems and systems without batteries such as a house panel to grid application.
Can anyone add any more info that I may have not considered in my summary?

oldtrack123 · Guru

T1 Terry wrote:
oldtrack123 wrote:
For those ,who are possibly getting confused by the various claims view this;www.youtube.com/watch

IMHO it is a straight forward comparison .

It does not take into account Efficiency but the general claim is 95 to 97 %
You will note the Importance of panel Voltage available to either types
If you are going to use panels whose PPP voltage is only enough to charge the battery, a MPPT will not give any gains ie 30 cell panels Versus 36 cell panels
I hope you saw the last part of my post
Now Peter, give the readers the theoretical charging rate an MPPT controller could achieve using real Vmp voltages the same panel array would produce in full sun and factor in the losses for the MPPT controller doing the job it is being asked to do, you can do both parallel and series connection if you want, but the inefficiencies must be included ..... we all know nothing is 100% efficient so there is no point in ignoring the losses.
Hopefully you will see your way clear to either grace the readers here with a proper answer, or admit you really don't know and you are simply repeating things you have read have accepted their figures as being accurate for a system actually installed on an RV.

T1 Terry

I hope you have read ALL the information available ,including my posts ,& see the effect of using panels with just sufficient voltage @ PPP to charge the battery

You should also try to understand WHY,. with such panels & LI Batteries with their near constant SOC voltage & low internal resistance ,are a totally different situation to LAs where in actual use could easily have a SOC Vof 12 < 14V .

That has a significant effect

Even the fact that Lis batteries have low internal resistance & maintain voltage under loads makes the situation better than it would be with LAs, because of near constant matching . [No Surplus power to convert with the panels you use]

I have many times said that your experiments has resulted with a set up that is near ideal for LIs used with lower PPP panels. for one simple reason .

There is very little power being lost in the panels due to THAT CLOSE LOAD MATCHING over the full SOC of LIs[narrow voltage range]

But THAT is not applicable to those still using LA batteries

Now since you do not like or understand the theory side you may have difficulty in working that out

I will repeat AGAIN your experiments have resulted in a panel to battery match that is near perfect. The regulator is little more than a VSR / multi stage switch

BUT it does not apply to LAs ,try connecting a bank of LAs with a full range of SOC to your system & see the results

Many people have to let their LAs drop to !2V due to limited capacity or weather conditions & those are the times they need to utilize every drop of power available

Few have the capacity to only use the top 25%

Yes, I am giving a plug for LIs for those who want plenty of power available or other justifications for the $$$$ , & would say Terry is probably one of the best to go to

Now I have more interesting things to do.

No more time spent on this subject

Jaahn · Guru

Dickodownunder wrote:
Well lets summarise what I have learned so far.
MPPT in a perfect world will be a better controller than the PWM.
In the real world each system will need to be assessed to justify the extra cost of changing to MPPT.
MPPT seems to be the choice of controller on larger systems and systems without batteries such as a house panel to grid application.
Can anyone add any more info that I may have not considered in my summary?

Hi Dicko smile My take on your suggestion for a summary.

MPPT in the real world is an accepted technology that is used on all or certainly most, large solar systems of all types, battery or grid connect.

In the real world the industry has assessed the benefit of MPPT and uses it even in Australia because they think it works

In a small system like an RV the extra cost of a quality MPPT regulator may not recoup as much extra power, as buying an extra panel with the money

AN RV roof with flat mounted panels is a challenging hot environment in our climate and the panels run very hot and the output drops significantly

Cheap MPPT regulators are probably fake and are only PWM or have very poor efficiency and losses. Only buy a known brand

Jaahn

-- Edited by Jaahn on Thursday 7th of December 2017 10:32:05 AM

Dickodownunder · Guru

Thanks Jaahn,

There has been a lot of very technical information revealed in this topic and I have definately learned the basics.
One most important point that has come from this is that a cheap MPPT unit may be no gain at all.
If buying one anyone would really need to to their homework on the brand.

Cheers

rockylizard · Guru

Gday...

and ask a question on the forum.

Cheers - John

T1 Terry · Guru

Jaahn wrote:
Dickodownunder wrote:
Well lets summarise what I have learned so far.
MPPT in a perfect world will be a better controller than the PWM.
In the real world each system will need to be assessed to justify the extra cost of changing to MPPT.
MPPT seems to be the choice of controller on larger systems and systems without batteries such as a house panel to grid application.
Can anyone add any more info that I may have not considered in my summary?
Hi Dicko My take on your suggestion for a summary.

MPPT in the real world is an accepted technology that is used on all or certainly most, large solar systems of all types, battery or grid connect.
In the real world the industry has assessed the benefit of MPPT and uses it even in Australia because they think it works
In a small system like an RV the extra cost of a quality MPPT regulator may not recoup as much extra power, as buying an extra panel with the money
AN RV roof with flat mounted panels is a challenging hot environment in our climate and the panels run very hot and the output drops significantly
Cheap MPPT regulators are probably fake and are only PWM or have very poor efficiency and losses. Only buy a known brand

Jaahn

-- Edited by Jaahn on Thursday 7th of December 2017 10:32:05 AM

I know this may be a sign the world is coming to an end, but I agree with most of what you have said Jaahn.

Maybe a bit of twist on it just to save the ground opening up and swallowing the world as we know it......

In the real world the industry has assessed the benefit of MPPT and uses it even in Australia because they think it works

My interpretation of why the industry sees MPPT as a benefit is:

1) The sales pitch already in place that says MPPT is superior to PWM so that makes the unit easier to sell

2) Much easier to wire up, simply link panels together in series and join the 2 ends to the MPPT controller, no designing or thought as to parallel cabling capacity/capabilities or the control gear

3) Who would actually realise that this quick and easy approach was less efficient, the sales brochures say they used the best available method.

4) If it stops working it can be blamed immediately on the MPPT controller or a fuse or something similar.

I'm basing this on the direct feed back from the system I just installed in Crystal Brook. They already had 3kW of solar back to grid, a quick comparison of solar harvest between the 5.6kW of solar we installed and the harvest from the 3kW grid feed calculated back to output per kW puts the new system well ahead of the grid feed system.

Next was the fact (calculating back to per 270w panel output) between the MPPT controller that is part of the MPP inverter and the panels controlled by the PWM method using solid state relays and a single Plasmatronics Dingo 20/20 to control them, the PWM panels out performed the series connected MPPT controlled panels over a full days solar harvest.

I've got to say here that the MPPT system was easier to connect and would have been even easier if I hadn't staggered the connections for each of the 3 paralleled groups that were series connected for the run to the MPPT controller. Why didn't I connected all in series? The max open circuit voltage the MPPT controller could handle was 145V even though it could handle an 80amp output. Each panel has an STC open circuit voltage (Voc) of 38.5v so only 3 panels in series could be used as 4 panels both exceeded the open circuit voltage and the maximum operating voltage of the MPPT circuit of 100v Vmp (30.8v STC per panel) and only 9 panels in total to stay under the 80 amps max. output.

As Peter has already said, the panel Vmp is close to the required max battery voltage, even closer when derated for the actual operating temp as the 30.8v drops to a little over 28v in the middle of the day when the panels get the hottest.

T1 Terry

Dickodownunder · Guru

rockylizard wrote:
Gday...
and ask a question on the forum.
Cheers - John

Hi John,

Your above post has followed on after my post and I do not understand what you are meaning.

Please let me know if your post was directed at me and if so mate, what did you mean?

-- Edited by Dickodownunder on Thursday 7th of December 2017 08:02:56 PM

Dickodownunder · Guru

Thank you T1 Terry,

While some of the technical details goes over my head and probably others, you alway provide an understandable and interesting view.

Cheers

rockylizard · Guru

Gday...

Hope ya not getting sensitive hmm smiley faces to make sure it was taken as a 'friendly comment'. hmm

It was meant as a sensible comment ... if in doubt of something, just ask a question on the forum and a wide and varied range of experience and knowledge will be forthcoming.

Guaranteed to ultimately get information that will resolve doubt, provide assistance, point in a direction, provide alternatives etc - a range of inexhaustive knowledge.

cheers - John