Custom 6x20 watts solar setup with MPPT

Whenarewethere · Guru

Custom 6x20 watts solar setup with MPPT

Jaahn · Guru

Hi smile

Thanks for the look at your ingenious solar setup. You have done well and designed a very workable rig for your compact camping. Good for you. Looks good too ! biggrin

The outputs are useful to look at. You do get the full output from your panels with the MPPT reg. It shows the theory is correct also. It takes the higher voltage and converts that to extra current with minimal losses even at 8 watts. Screenshot 3 shows how the lower battery voltage enables the MPPT to deliver maximum amps and thus power.

It is a lesson for people who say I do not have anywhere to put panels. aww Bravo !!

Jaahn

-- Edited by Jaahn on Tuesday 15th of January 2019 09:34:50 PM

Whenarewethere · Guru

A few more screenshots. I think it is a bit like good wine that has been cellared properly. Battery & controller together in the right location or at least the best one can do trying to keep compromises to a minimum. Calculate proper size wire for total run there & back + & -. Quality solar panels avoid using builtin controllers which are in the wrong location. A good controller adjusts for battery temperature so it needs to be in the same environment as the battery. Build the best you can do, most things are easy even if you need to make a few changes & you will be able to squeeze a bit more power out here & there.

Screenshot 1: I had drained the battery a bit, 10 amps input.
Screenshot 2: Dropped to 65 watts due to cloud.
Screenshot 3: Dropped to 68 watts due to cloud.
Screenshot 4: 37 watts late in the day & slight soft shadowing.
Screenshot 5: 15 watts late in the day & slight soft shadowing.

Jaahn · Guru

Hi smile

Thanks for some more instructive screen shots. WOW even a couple of extra watts there, when the battery voltage is down low. wink

Just for peoples general information, having portable panels mounted in a ~vertical manner like that enables them to face the sun at 90deg so output is best, but it also keeps the panels much cooler with the hot air rising off the panels and taking away heat. aww Win win !

Jaahn

-- Edited by Jaahn on Wednesday 16th of January 2019 10:49:02 PM

T1 Terry · Guru

Ummm...... they look like quite large area panels for 20w, can you tell us the dimensions of each panel? I see in the 3rd photo in the opening post there is a clamp meter showing 7.9 amps, is that from all the panels together in parallel or a single panel or what????

T1 Terry

Whenarewethere · Guru

The Kyoritsu 2046R cat IV class clamp meter photo was shot when the panels were connected all in parallel & when the panels were a bit below 120 watts, & with 10 metres of extension cables including a 2 metre 12AWG cable which was never intended to be used in this location which was mostly for a Noctua fan in the car while sleeping. If the sun is too far away any cable is better than shadow!

The Projecta solar panels overall size are 638 x 278mm, overall foot print of actual cells is 582 x 237mm, so 78% of the panel area, not brilliant. The solar cells could be stacked tighter & the frame could be reduced in size. But nevertheless when these panels are stacked behind the second spare wheel no bugs hit the forward facing panel. These panels are only 25 mm thick instead of the typical 35mm & don't twist. So total thickness of the 6 panels is only 150mm instead of 210mm, 15.3kgs including added legs & wiring. The 6 panel volume not including handle & hinges is 26.6 litres. Can't complain about that!

I am completely out of room on the roof front to back, including room for sand flag & opening of full tank holders (same space), over by about 32mm, cross bar clamps are not totally clamped on the extruded rails.

I did have a roof platform (still got it) but they are in general poorly designed & simply dead weight. I replaced the platform with a second set of cross bars & reduced weight by 16.4kg. Currently if I have everything on the roof including roof rack rails, cross bars, brackets & 50 litres of fuel & tanks, wheel (not the tyre I normally have, all I could get in Halls Creek), sand tracks, awning..... 142kg! but I can reduce this considerably for off road. Even the bracket for the second spare wheel I have machined out of 5083 alloy to reduce as much weight as possible.

Whenarewethere · Guru

Today I tried 3 panels in series in 2 sets. Due to the haze humidity in the air & around 4 pm I could only get up to 116 watts. The problem with this setup is if you get a small shadow on one series set, half your harvesting is gone!

Screenshot 1: 11 watts.
Screenshot 2: 12 watts.
Screenshot 3: 13 watts.
Screenshot 4: 115 watts.
Screenshot 5: 116 watts.

Back to 2 panels in series in 3 sets. Could not get more than 110 watts due to haze humidity & a bit later in the day. 110 watts & than shadow over each series set, & you still get 2/3 of the power.

Screenshot 1: 110 watts no shadow.
Screenshot 2: shadow over first set.
Screenshot 3: shadow over second set.
Screenshot 4: shadow over third set.
Screenshot 5: 110 watts no shadow.

I have no diodes in any of the setups. To double check for any issues I have alternately plugged each series set in, or 2 sets in & 1 set out. So doesn't seem to be any issues.

3 panels in series x 2 sets.gif

Whenarewethere · Guru

The fridge I have replaced the fan with a more efficient one, shortened the power lead & inside replaced 55 cm (110 cm +& of very thin 16AWG 12 volt lead to the circuit board with 12AWG as part of making the fridge more efficient (extra insulation in another thread)

T1 Terry · Guru

As a suggestion, try connecting 2 x 3 panels in parallel and then these 2 groups in series. The aim is to minimise shade effect, any one of the 3 panels in group one can provide one half of series circuit to any panel in group 2. Also, even if 2 panels out of the 3 panels in series suffer some shade, by grouping them together you get a total of the output of those 3 panels and that can often be enough when added with the output from the other 3 panels to drive the MPPT controller at a lower Vmp but still enough to get more output than either 2 sets in parallel of 3 panels in series or 3 sets in parallel of 2 panels in series. The less work the MPPT controller has to do in regards to changing the input voltage and current to the required output voltage and current, the more efficient the MPPT controller operates. As long as the input voltage is 5v or more than the output voltage, the MPPT controller will turn on.

T1 Terry

T1 Terry · Guru

Whenarewethere wrote:

The Projecta solar panels overall size are 638 x 278mm, overall foot print of actual cells is 582 x 237mm, so 78% of the panel area, not brilliant.

The reason I asked about the clamp meter reading was that it didn't add up, nor do the panel sizes.

I have a number of Chinese Sista 60w 540mm x 630mm outside frame dimensions, the Projecta 20w solar panels overall size are 638 x 278mm, the Sista 60w panel actual solar module dimensions are 505mm x 570mm, the Projecta 20w panel actual solar module dimensions are 582 x 237mm. Clearly the panel may be labelled as 20w but the actual area compared to the 60w Chinese panel is a lot more than 1/3rd the sq area.
The other issue is the output, a cheapie 8 yr old ebay 120w panel optimistically claims the Imp is 6.57amps, yet the parallel string of panels rated at 120w shows 7.5 amps in less than optimal conditions. The 60w Sista panels have an optimistic Vmp of 3.43 amps, so 2 panel in parallel would make a 120w and 2 x 3.43 = 6.86 amps, not 7.5 amps. the Chinese panels are renowned to be a tad optimistic when it comes the stuff they write on their labels so the 6.57 amps from technology 8 yrs ago and the 6.86 amps from more recent technology should be read as the maximum with the sun and planets all correctly aligned, not what one would normally see from them even if aligned optimally angled to the sun and connected to a battery. If you get more than 5 amps consider it a bonus.

So, what is the true capacity of these panels rather than the information printed on the label? Anyone have a lightbox to flash test these panels as per STC standards?

T1 Terry

Whenarewethere · Guru

I haven't tried 3 in parallel as 2 sets as I am not using diodes. The 120 watts is simply one large mass of 36, 72 or 108 cells.

Today I was getting about 123 to 124 watts with minimum light cloud (see photo) & up to 126 watts with a clear sky (still a bit of haze with the humidity). So I can't complain about the panel output, probably better than the "no name" panels. The panels were fairly hot, as I do not have a suitable thermometer, so by the technical process of touch probably somewhere about 50C.

I thought I would apply some seriously high technology to the panels to reduce their temperature, reducing the panels temperature to roughly 35C to the touch. I sprayed water on the panels at roughly 4 litres per hour with a hand pressure pump. So if one has access to water it might be worth setting up a sprinkler system to push a 120 watt system to 135-136 watts, even briefly reaching 137 watts.

The photo of the back of the panels is a bit of a mess due to the various temporary rewiring.

Screenshot 1: 123 watts typical.
Screenshot 2: 126 watts maximum about 30% of the time.
Screenshot 3: 135 watts water cooled.
Screenshot 4: 136 watts water cooled 8.7 + 0.8(mobile charging) total 9.5 amps.
Screenshot 5: 136 watts water cooled 6.2 + 3.4(fridge starting up) total 9.6 amps.

Jaahn · Guru

T1 Terry wrote:
The reason I asked about the clamp meter reading was that it didn't add up, nor do the panel sizes.
I have a number of Chinese Sista 60w 540mm x 630mm outside frame dimensions, the Projecta 20w solar panels overall size are 638 x 278mm, the Sista 60w panel actual solar module dimensions are 505mm x 570mm, the Projecta 20w panel actual solar module dimensions are 582 x 237mm. Clearly the panel may be labelled as 20w but the actual area compared to the 60w Chinese panel is a lot more than 1/3rd the sq area.
The other issue is the output, a cheapie 8 yr old ebay 120w panel optimistically claims the Imp is 6.57amps, yet the parallel string of panels rated at 120w shows 7.5 amps in less than optimal conditions. The 60w Sista panels have an optimistic Vmp of 3.43 amps, so 2 panel in parallel would make a 120w and 2 x 3.43 = 6.86 amps, not 7.5 amps. the Chinese panels are renowned to be a tad optimistic when it comes the stuff they write on their labels so the 6.57 amps from technology 8 yrs ago and the 6.86 amps from more recent technology should be read as the maximum with the sun and planets all correctly aligned, not what one would normally see from them even if aligned optimally angled to the sun and connected to a battery. If you get more than 5 amps consider it a bonus.
So, what is the true capacity of these panels rather than the information printed on the label? Anyone have a lightbox to flash test these panels as per STC standards?
T1 Terry

Hi Terry smile

I do not want to start anything here but you are the living end Terry. Just because the post has some discussion about the performance of MPPT you choose to cast aspersions on the panels and insult the poster. You infer they are more than that said by the poster. No wonder you have been banned from other forums. You have no idea of reasonable discussion. Every discussion is slanted to your biased point of view.

Indeed what does it matter. He has designed a very neat system that suits his use well. It performs as it should and he does actually give reading for different circumstances. His only crime is they do not support your bias against MPPT.

Jaahn

Whenarewethere · Guru

I have had zero experience at best in solar when I set this up early in 2018. I really only wanted to build the system once! I have better things to do than keep rebuilding things because they don't work the first time whether it is electrical or a fuel tank holder!

As I mentioned above, the solar panels have to go on the roof. Not be covered in bugs. Access for everything else on the roof.

The Projecta 20 watt panel was the only one with the right proportions, 25 mm thickness being a critical issue, that would fit the available space.

I bought the MPPT controller as I had no idea which would be best, but from a layman perspective it seemed to offer bit more flexibility in electrical options.

Maybe I'm wrong, but in principle I am only running a 28 litre fridge, and for 3 months in NT & WA the system has performed faultlessly. Actually better than l allowed for. I have also rebuilt the fridge so it is more efficient.

I am also using 3 x 26 AH gel batteries as that is all I can fit in the car. The driver's side has 2 compressors. There is no room in the engine bay for an auxiliary battery & I don't want the battery in the rear footwell as that is where 60 litres of water sits.

9 times out of 10 we sleep in the car as we couldn't be bothered putting up the tent, so everything has to go in the front & solar panels on the roof.

I have bought quality solar products that fit many parameters which I will not have to rebuild, priceless!

The compressor photo is 2 of 3 compessors with added external & internal heatsinks which make a huge difference in pre-cooling the air to reduce moisture together with air tank & moisture trap, also fan cooled. Very handy for blasting dust from the car!

Whenarewethere · Guru

Clamp meter, Victron MPPT & voltage & amp meters all give readings within more than reasonable tolerances of each other.

A bucket of water over the solar panels provides far more improvement than fiddling around with electrics!

T1 Terry · Guru

Jaahn wrote:
T1 Terry wrote:
The reason I asked about the clamp meter reading was that it didn't add up, nor do the panel sizes.
I have a number of Chinese Sista 60w 540mm x 630mm outside frame dimensions, the Projecta 20w solar panels overall size are 638 x 278mm, the Sista 60w panel actual solar module dimensions are 505mm x 570mm, the Projecta 20w panel actual solar module dimensions are 582 x 237mm. Clearly the panel may be labelled as 20w but the actual area compared to the 60w Chinese panel is a lot more than 1/3rd the sq area.
The other issue is the output, a cheapie 8 yr old ebay 120w panel optimistically claims the Imp is 6.57amps, yet the parallel string of panels rated at 120w shows 7.5 amps in less than optimal conditions. The 60w Sista panels have an optimistic Vmp of 3.43 amps, so 2 panel in parallel would make a 120w and 2 x 3.43 = 6.86 amps, not 7.5 amps. the Chinese panels are renowned to be a tad optimistic when it comes the stuff they write on their labels so the 6.57 amps from technology 8 yrs ago and the 6.86 amps from more recent technology should be read as the maximum with the sun and planets all correctly aligned, not what one would normally see from them even if aligned optimally angled to the sun and connected to a battery. If you get more than 5 amps consider it a bonus.
So, what is the true capacity of these panels rather than the information printed on the label? Anyone have a lightbox to flash test these panels as per STC standards?
T1 Terry
Hi Terry
I do not want to start anything here but you are the living end Terry. Just because the post has some discussion about the performance of MPPT you choose to cast aspersions on the panels and insult the poster. You infer they are more than that said by the poster. No wonder you have been banned from other forums. You have no idea of reasonable discussion. Every discussion is slanted to your biased point of view.
Indeed what does it matter. He has designed a very neat system that suits his use well. It performs as it should and he does actually give reading for different circumstances. His only crime is they do not support your bias against MPPT.
Jaahn

My apologies to Whenarewethere if it appeared I was having a go at you, that was not my intent at all. What I was pointing out was that the panels may be labelled as 20w but the figures indicate they actually produce more than 20w. The physical size of the panels are larger than a 20w panel would normally be so there is every likelihood the total array is actually greater than 120w. My guess is they are actually 30w or maybe even 40w panels and wrongly labelled, you have been very lucky to pick them up.

I doubt anyone here would claim an MPPT controller can extract more out of a solar array that it can actually produce at 25*C on a light box using the STC testing method, yet the results clearly show even hot panels are producing more than the advertised output and further proof is the increase in output when the panels were cooled using a water spray.

I'm not sure if the water spray was on the front or the back of the panels, it would be interesting to see if there were different results between using the two different cooling methods.

As for your attack Jaahn, get off your high horse and look at the figures with both your eyes open and your logic circuit switched on and you will see exactly what I mean.

T1 Terry

oldtrack123 · Guru

Jaahn wrote:
Hi
[a] Thanks for some more instructive screen shots. WOW even a couple of extra watts there, when the battery voltage is down low.
Just for peoples general information, having portable panels mounted in a ~vertical manner like that enables them to face the sun at 90deg so output is best, but it also keeps the panels much cooler with the hot air rising off the panels and taking away heat. Win win !
Jaahn

-- Edited by Jaahn on Wednesday 16th of January 2019 10:49:02 PM

[a]Yes ,that is when the max input is obtained with a Mppt ..Something that some do not seem to understand. Especially those who have batteries that operate around 14V

yes , I found it well worthwhile to mount my panels on a tilt & swivel arrangement on the roof of the Lawson motor home .Three positioning gave me max available output from sunrise to sunset .The 4 vents on the roof limited the area where I could fit panels

T1 Terry · Guru

Hmmm...... so you have found a way around the temperature coefficient that plagued Kyocera and every other solar panel manufacturer, that dreaded 0.46% per degree Celsius above 25*C . Even the system owner reported that cooling the cells increased the output to 136w and without cooling 123w and all through your much loved MPPT type controller.

Kyocera 140w panel.jpg

Did you mention something about things some people didn't understand Peter?

T1 Terry

oldtrack123 · Guru

just a simple answer ,with no white herrings thrown in
We ALL know that the panels derate with heat, so you do not need to continually repeat that !
What most of us accept is that the bigger the difference between the battery voltage & the panel output voltage the more useful a MPPT will be .
AS I pointed out to you a loooong time ago ,you have tailored your set up to suit LI batteries [after a lot of experimenting you have come up with a set up that is very suitable for Lis with their near constant voltage & & the panels you use [which will also derate with heat]output voltage leaves nothing to convert .

That is not the same as with the many ,many users of LA batteries whose SOC voltage varies widely [<2V in normal operation ]& panels with a higher output voltage ,[even though they will derate with heat ]The derating rate will be the same in both cases!!!
Don't you /or can't you understand THAT!!!!!
Even a 1volt difference is significant when charging
Your graphs /specs are irrelevant since they apply in all cases!!

I might just go back, Find & repost that loooong post that I posted some time ago which could help others understand the above differences in greater detail.
Why cannot you just accept that you have ,with a lot of experimenting, tailored a system that is imminently suitable for use with LI batteries,but would not perform anywhere near the same with LAs?

"there are none so blind ,as those who do not want to see"

Jaahn · Guru

Terry and Peter, Have you no self control ! This thread was bubbling along until you Terry came on and just had to push your own barrow, then Peter starts up too and wants to bring up some old fight from the past.
Butt out and let those who would like to see some real interesting discussion, not the same out claptrap that has shut down other threads. PLEASE.

Maybe the panels are a bigger output than he paid for ?? And all six too! Just lucky I say and everyone should queue up for those panels. Terry says so. It does not matter as you can clearly see the MPPT action in the figures on the readouts. If you were using a PWM regulator you would only get the panel amps to the battery. I can see that with my one eye.
Jaahn

-- Edited by Jaahn on Saturday 19th of January 2019 09:02:39 PM

-- Edited by Jaahn on Saturday 19th of January 2019 09:07:30 PM

Whenarewethere · Guru

At the end of the day if we cannot sleep in our car solar is irrelevant then I will go back to my previous custom built esky where ice would last a week & stayed cool for 10 days!

The thread I started is about a custom built solar setup that would not take over the car. I simply bought the MPPT controller as it seemed to have more options in reducing wire resistance. A bit like my 300 amp continuous welding cable jumper leads with 2mm solid copper clamps, even 2 sets end to end (12 metres +&- ) have never failed to start a car!

I simply don't have room for panels to take over the car & no off the shelf folding kit I found by the date I needed it would do the job. In the forth photo under the Victron controller there is a fridge custom mounting bracket which might be more interesting reducing the height of the Waeco bracket to 6mm rather than a few watts here or there on a particular solar setup!

I am simply showing you my custom build to squash X parts into Y space. If you want a parts list of the legs I have added to the solar panels I can post that. I have bought anodised aluminiun & nylon hinges with stainless pins. All screws & bolts & Nyloc nuts are stainless 304 or 316. Anderson plugs are original & soldered everything & heatshrinked.

Maybe I am getting up to 126 watts without water on a not perfect day because I have not skimped on wiring, it is pretty much all 6AWG on a tiny setup!

The Projecta panels come with a 20 page instruction manual covering mounting, mounting hole spacings, charging, connecting multiple panels in series, parallel & series & parallel for people like me, with diodes & cable size for various distances, but I am well on top of that particular issue!

Projecta SPP20 specs:
Polycrystalline
Rated power 20 watts
Open circuit 21 volts
Short circuit 1.25 amps
Peak power 17.5 volts
Peak power current 1.14 amps
Test conditions 1000W/m2 25C
Tempered low iron glass

Panels were $42 each in 2018, the cheapest part of this whole project so to speak!

I did spray water on the rear as well as an after thought, maybe it was keeping the panels well into the upper end of 136 watts & brief moments into 137 watt territory & this was not even a stunningly clear Sydney day. But water on the front reached 136 watts without problems.

On a hot sunny day I will put blocks on the bottom edge to lift the entire panel off the ground for increasing free air flow. If I can design some folding legs I might give that a go.

A few more screenshot figures. The battery current & load current you will need to add together for total current. Some battery figure are negative as the load was higher.

The highest wattage to date without water cooling is 126 to very occasionally into 127 watts & this was not with a perfect Sydney sky.

The other half of this entire project, almost entirely for the fridge, is reducing electricity consumption in the first place! It's about my fridge (another little project is in the wings in this department!). Reducing consumption from 0.0140 kWh to 0.0116 kWh under a 35C ambient temperature over a 3 day test (I did get it down to 0.0082 kWh but an extra 60mm of XPS insulation on the fridge was a bit thick) has more benefits than fiddling at the other end. It's easier to save than earn!

Photos:
Screenshots: No water.
Screenshots: Water cooling.
Screenshots: 1 to 22 watts (today was a miserable day & really no break in the cloud but nevertheless the panels hit 122 watts briefly)
Screenshots: 24 to 122 watts.
Fridge (Waeco replacement) 6mm high mounting bracket so we can sleep in the car & not feel it.
Stainless front guide for fridge.
Stainless rear guide for fridge.

Whenarewethere · Guru

As I said it is about the fridge so here are a few more photos. The first photo shows the first Noctua fan (hanging) I put in the fridge, now replaced with another Noctua fan. I blew out the Outback dust from the fridge with my car's compressors. Frightening how quickly dust builds up inside the fridges compressor & makes the fridge work harder. While at it I replaced 55cm (110 cm +&- ) of under sized 12volt cable to the fridge's circuit board with 12AWG cable & installed a circuit breaker.

T1 Terry · Guru

Thankyou for posting the specs on the panel label, it does answer the question. The peak power current of 1.14 amps x 6 panels = 6.84 amps and not the 7.5 amps shown on the multimeter clamped around the cable at the solar panel output, not the MPPT controller output. This clearly shows the panel output is significantly more than the labelled specs so the output from the MPPT controller will/should be greater than 120w and all your screen shots show that.
I agree with your logic for choosing an MPPT controller to minimise the cable size required when using portable panels. I have said in the past that this was a good idea if that was going to be the only charger/controller working on the battery because the long cable runs required posed a serious voltage drop unless quite heavy cable was used.

I've said my bit, you have verified what I was saying, so no need for me to post any further on your thread. I wonder if all those claiming just how much better the MPPT controller made the "120w" of solar perform will now admit they didn't bother to actually look at the over all picture but rather run with the end numbers .......

T1 Terry

Jaahn · Guru

Hi smile

I do not wish to argue with anyone. I accept the panels are putting out a good wattage. All i wist to show, using the figures given here the difference gained by the MPPT reg. The figures are just calculated by my calculator from the actual figures shown and from the adjusted current for the second one. No discussion entered into except if there is a mistake.

If the reg was PWM and putting in the direct panel current 7.3A into the battery at 13.77V it would be 100.5Watts, as MPPT it was putting in 115.6 W (13.77 x 8.4) EG +15%

If the reg was PWM and putting in the direct panel current 7.3A into the battery at 11.96V it would be 87.3 Watts, as MPPT it was putting in 117.2 W (11.96 x 9.8) EG +34%

Disclaimer: This is for those who may wish to know exactly from real test results what the difference is between the two types. I do not sell either type or any type at all, and I own a couple of both types.

Jaahn

PS Whenarewethere keep posting your good ideas to inspire others.

Whenarewethere · Guru

Last year in the Kimberley region l had not fired up the Victron software to monitor the system as I had my own panel meters (6th photo from top of thread). It was easy to see solar input. There was plenty of sun around as we were trying to keep out of it most of the time, & the amp meter was pretty much topping out at 3.8 amps & a touch into 3.9 amps.

For argument sake let's say that the Projecta panels are performing a bit above specifications of 6.84 amps (6 X 20 watts), this alone shows that it is simply false economy investing in no name Chinese products.

But it still does not account for the additional Victron Voodoo! So getting 3.7 to 3.9 amps series (7.4 to 7.8 amps) converted to 9.2 to 9.6 amps being pumped into the batteries. Even hitting 10 amps, maybe it could be higher but the 75/10 MPPT cuts off at 10 amps.

7.4amps converted to 9.2amps into battery.

7.8amps converted to 9.6amps into battery.

8.0amps converted to 10.0amps into battery.

So an additional 1.8 to 2.0 amps above the panels' output. Or 2.5amps or more above the panels' specifications.

T1 Terry · Guru

Jaahn wrote:
Hi
I do not wish to argue with anyone. I accept the panels are putting out a good wattage. All i wist to show, using the figures given here the difference gained by the MPPT reg. The figures are just calculated by my calculator from the actual figures shown and from the adjusted current for the second one. No discussion entered into except if there is a mistake.
If the reg was PWM and putting in the direct panel current 7.3A into the battery at 13.77V it would be 100.5Watts, as MPPT it was putting in 115.6 W (13.77 x 8.4) EG +15%
If the reg was PWM and putting in the direct panel current 7.3A into the battery at 11.96V it would be 87.3 Watts, as MPPT it was putting in 117.2 W (11.96 x 9.8) EG +34%
Disclaimer: This is for those who may wish to know exactly from real test results what the difference is between the two types. I do not sell either type or any type at all, and I own a couple of both types.
Jaahn
PS Whenarewethere keep posting your good ideas to inspire others.

It appears you are now in conflict with another member of the MPPT choir

Quote:

For the benefit of those with an open mind smile

https://www.morningstarcorp.com/parallel-charging-using-multiple-controllers-separate-pv-arrays/

As a further explanation , a true mppt controller has two entirely separate operations

[a] the MPPT section, which operates independent of battery voltage ,tracking the panels peak power point continuously..It does NOT sample battery voltage when doing that. It simply is not concerned with battery SOC voltage

It then uses a 2nd stage to convert that MPPT DC power into a suitable DC power source for charging the battery [in simple words, that section becomes a PWM DC charger]

That second stage,PWM ,the battery charging stage, is independent of the first stage[MPPT]

But just as with all PWM controllers ,that section may interact with other,s once the battery comes out of bulk charge mode

But beware of cheap so called MPPT controllers ! . A true Mppt is not/ cannot be cheap

That will be my final post on this thread!!

So which one of you actually does know how one of these things works, Peter has often claimed the low battery voltage was what gave the MPPT controller its advantage, but now it appears he has abandoned that theory and moved on to another theory. So who is right?

T1 Terry

-- Edited by oldtrack123 on Sunday 20th of January 2019 06:16:52 PM

T1 Terry · Guru

Whenarewethere wrote:
Last year in the Kimberley region l had not fired up the Victron software to monitor the system as I had my own panel meters (6th photo from top of thread). It was easy to see solar input. There was plenty of sun around as we were trying to keep out of it most of the time, & the amp meter was pretty much topping out at 3.8 amps & a touch into 3.9 amps.
For argument sake let's say that the Projecta panels are performing a bit above specifications of 6.84 amps (6 X 20 watts), this alone shows that it is simply false economy investing in no name Chinese products.
But it still does not account for the additional Victron Voodoo! So getting 3.7 to 3.9 amps series (7.4 to 7.8 amps) converted to 9.2 to 9.6 amps being pumped into the batteries. Even hitting 10 amps, maybe it could be higher but the 75/10 MPPT cuts off at 10 amps.
7.4amps converted to 9.2amps into battery.
7.8amps converted to 9.6amps into battery.
8.0amps converted to 10.0amps into battery.
So an additional 1.8 to 2.0 amps above the panels' output. Or 2.5amps or more above the panels' specifications.

I think you will find you have already answered that earlier. The higher voltage gained by connecting the panels in series reduced the losses through the cable running from the solar array to the controller. A test would be to connect a single panel through the wiring used for all 6 panels direct to the battery and then measure the amps flowing. Multiply that figure by 6 to cover all the panels output with reduced resistance and that would tell you the true array output.

Another way of looking at it, the current at the panels x voltage at the panels gives the watts output, is this more or less than the output from the MPPT controller to the battery?

T1 Terry

Ron-D · Guru

Cant anyone post here Terry without your comments.you have knowledge so do others I personally would like to here something without your rant on the end..

-- Edited by Ron-D on Monday 21st of January 2019 04:13:03 PM

dorian · Guru

T1 Terry wrote:
It appears you are now in conflict with another member of the MPPT choir
Quote:
For the benefit of those with an open mind
https://www.morningstarcorp.com/parallel-charging-using-multiple-controllers-separate-pv-arrays/
As a further explanation , a true mppt controller has two entirely separate operations
[a] the MPPT section, which operates independent of battery voltage ,tracking the panels peak power point continuously..It does NOT sample battery voltage when doing that. It simply is not concerned with battery SOC voltage
It then uses a 2nd stage to convert that MPPT DC power into a suitable DC power source for charging the battery [in simple words, that section becomes a PWM DC charger]
That second stage,PWM ,the battery charging stage, is independent of the first stage[MPPT]

Yes, that puzzles me, too. AFAICT, an MPPT controller does not have separate hardware for MPPT and PWM modes. Instead it uses the same hardware for both modes, but switches to a different routine in the firmware. In MPPT mode the duty cycle regulates the panel's power output, whereas in "PWM mode" the duty cycle regulates the battery voltage.

It's a kit, not a commercial product, but the software is instructive:

http://web.archive.org/web/20140626064134/http://www.timnolan.com/index.php?page=arduino-ppt-solar-charger (project page)

http://web.archive.org/web/20140626064134/http://www.timnolan.com/uploads/Arduino%20Solar/ppt.pde (software)

Whenarewethere · Guru

I have had a temporary piece of aluminium folded over the divide in the fridge to get the butter department cooler when running the fridge as a fridge. I have replaced it with a neater job! Works well, there is some sail cloth repair tape on the back of the aluminium so the evaporator coils don't get damaged. I used a 1.5mm thick baking tray as the aluminium is a bit softer (but not too solf) to bend than 5005 alloy off the shelf sheet. It will put out for cleaning both sides.

If you notice there are 2 thicknesses of 10 foam sleeping mat stuffed down inside the fridge cover for additional insulation, there are 3 on the opening end, the compressor does not need it.

T1 Terry · Guru

Ron-D wrote:
Cant anyone post here Terry without your comments.you have knowledge so do others I personally would like to here something without your rant on the end..

-- Edited by Ron-D on Monday 21st of January 2019 04:13:03 PM

This adds what exactly to the discussion here besides you having a go at me? My point was to show there appeared to be a number of different views on how the MPPT controller worked and questioned just who was correct ...... what advances has your post made in the understanding of a complex topic Ron?

T1 Terry