Tesla Chargers from Energetic Forum

[liber63]

Hi Aaron,

I ‘ve seen you mention above that you use 100w panels that have Voc 26-27 Volts and Vmp 18-21, right?
I have found amorphous panels with Imp: 4,09 / Vmp: 17,6 V / Voc: 24,2 V. I know Vmp is not the best, but that’s all I can find these days. If you have any suggestions, you are welcome.
I understand that these 72 Watt panels have the right specifications to put 4 of them with the S20A12 solar tracker I want to buy. I only doubt about Voc being 24,2 Volts is too high, as I remember Peter mentions that in a video. But seeing that you use 26-27 Voc, I guess I should not worry, right?

[Aaron]

vmp a bit low

Hi Aaron,

I ‘ve seen you mention above that you use 100w panels that have Voc 26-27 Volts and Vmp 18-21, right?
I have found amorphous panels with Imp: 4,09 / Vmp: 17,6 V / Voc: 24,2 V. I know Vmp is not the best, but that’s all I can find these days. If you have any suggestions, you are welcome.
I understand that these 72 Watt panels have the right specifications to put 4 of them with the S20A12 solar tracker I want to buy. I only doubt about Voc being 24,2 Volts is too high, as I remember Peter mentions that in a video. But seeing that you use 26-27 Voc, I guess I should not worry, right?

I got lucky with the 100w amorphous panels I got with vmp around 18.5. Then the company went bankrupt.

17.6 will work but just won't push the battery as good. The VOC should be fine - is the vmp you want at least around 18.5 (optimally).

[liber63]

Hi! Aaron,

yeah i understand inefficient Vmp. The whole point with tesla solar tracker and amorphous is pushing the battery enough. I've read the pdf! I searched again today and found a 100w panel with Vmp20 and Voc27, similar to yours. Do you think it would be ok with Voc27? I can pm you more info. So what's it with Voc? How can you handle the number 27, is it in the range of S20A12?

[Aaron]

high vmp

Hi! Aaron,

yeah i understand inefficient Vmp. The whole point with tesla solar tracker and amorphous is pushing the battery enough. I've read the pdf! I searched again today and found a 100w panel with Vmp20 and Voc27, similar to yours. Do you think it would be ok with Voc27? I can pm you more info. So what's it with Voc? How can you handle the number 27, is it in the range of S20A12?

In addition to pushing the battery enough, it is an extremely efficient circuit with less losses that other other charge controllers. That way, you get more electricity from the panel to the battery as well as pushing it high enough.

The S20A12 is 20 amps so x about 15 volts = 300 watts worth of panels.

The vmp of 20 is a bit high. The circuit would have to dissipate about 20 amps * 1.5 volts (over 18.5 ideal vmp) = 30 watts of excess heat. That S20A12 does have a fan it it so might be ok. I'd have to check.

Please email us at Tesla Chargers and copy and paste these posts and we'll let you know if that will work.

[liber63]

Very good, Aaron! I will contact you. Thanks!

[jajamezsz]

Hi I am thinking a setup with the S40A12...here are some of my thoughts:

4x100Ah deep-cycle flooded lead-acid batteries
600W of Amorphous Thin-Film Silicon Panels

I basically just used the math from previous posts

The numbers match up nicely with 12V and 15V, giving C20 rate: 20h*20A*12V=4800Wh, panels: 4800Wh/10h(1/.8)=600W in the W.C.S., and 40A*15V=600W max power for the S40A12

Now just to find those panels! Seems impossible...

[jajamezsz]

Just bought the S40A12 second-hand...
Wondering if I were to run 19.2Vmp, 26.4Voc with 9 of these panels in parallel if it would get hot...37A*(0.7Volts-above-ideal)=26W excess heat, but running at 37A rather than the full 40A...?
These panels are next to impossible to find...I am almost ready to settle for 37A and a slightly higher than ideal Vmp, but will keep looking. I've heard of Xunlight, Stion, and Uni-solar so far, so I am not quite done searching altogether. It would be nice to get closer to 40A and 18.5Vmp.
("Flexopower": https://www.ebay.com/itm/Flexopower-...26d3df6be1b8fd)

[jajamezsz]

A good night of sleep always boosts my math ability, or brain in general. Maybe it was the reasoning sector telling me to double check the datasheets!

The max power input is on the chart at teslachargers.com -> 18.5Vmp*40A = 740Wmp
9 Flexopower 79W A-Si-Th-Fi's yield a max input power of 711Wmp = 19.2Vmp*37A
looking at this from a non-discrete perspective (instead of 9panels@79Watts; Xpanels@YWatts, where X and Y can be decimal values) also clears something up:
740W = 19.2V*38.5A, so it becomes apparent that 19.2Vmp is not ideal because the current never reaches 40A without exceeding the max power input according to the chart (740W)

Another look at the 19.2Vmp setup reveals that it's really not too far off:
It's safely under the max power limit at 711Wmp, and approaches the value of 740W to a 3.2% error factor, not bad!

One thing that bothers me, however, is that the max input power of a standard 40A12V charge controller (recommended by the seller of the panels, the Tracer4210an) came in at 520Wmp...at 40A, that's only 13V!! What in tarnation is going on here??

More investigation and creative number crunching comin atchya!

[jajamezsz]

Whoa, Nelly! A big confus-o-rama!

37A * 15V = 555W, which would be the output power with 9 Flexopower 79W A-Si-Th-Fi panels. This is well below 600W, a whole 7.5%!

What I am seeing is a 3.2% drop in input power yields a 7.5% drop in output power - the higher Vmp of 19.2? With 18.5 at 37A, we get 7.5% error factor (684.5W/740W)- beautiful! My only question now is whether or not the higher voltage will push the 37A out more efficiently or if it will just show up as heat since the conversion is set to operate at the 18.5 to 15V rate. The output seems to be set at 555/600W, or 7.5% less than ideal, which leads me to believe that the operating efficiency is maxed out at a rate proportional to 18.5 to 15V, and any extra voltage would show up as heat, rather than contributing to the conversion and transfer of power.

While there is slack in terms of power from 37 to 40A, it doesn't seem like this can be taken advantage of due to the fixed output of 15V at 37A. It seems like the excess power due the higher voltage of 19.2Vmp on the input side is doomed to show up as heat in the conversion process, of about 26W. Yep, 26W of pure excess heat, even though we're running 3A less than max power. This leads me wonder if the slack in the amps will run the whole thing cooler anyway and make up for the excess heat that seems inevitable due to voltage, again, under the assumption that the output rate is fixed at 15V at 37A, and I'm pretty sure it is. Whew!

I need to go outside now! Maxed out on screen-time, time for the old clipboard to follow me around. Until next time!

[jajamezsz]

OK one more question:

Is the max input power of the S40A12 15 * 40A = 600W or 18.5 * 40A = 740W?

I am wondering now if the panel voltage of 18.5V, or in my case 19.2V is matched with a lower amp value which is then converted within the charge controller? From 600W at 18.5V, that would be around 32A, and at 19.2V it would be more like 31A (the 740W figure came from combining 18.5 with 40A, rather than 32). It would then be converted into 15V and 40A within the charge controller. According to the official chart, the input power is listed at 40A and 18.5V, again giving us 740W, but if we were to assume that this figure should be 600W on both the input and output side of the charge controller that chart should be saying 18.5V and 32.4A on the input side with 15V and 40A on the output side. It really makes me wonder...

Again, the answer is dependent on that first question of 600W input vs 740W input. My brains is splitting over how to quantify the damn input value with regards to Vmp input vs output. At 18.5Vmp, are there only 32.4A flowing through the panels which are then converted to 15V and 40A within the controller, that is, are the input and output values both 600W? Or is the input power really 18.5V * 40A = 740W which is then converted to an output of 15V * 40A = 600W within the controller? Am I blindly missing something about this 140W discrepancy? Seemingly so...

Once again, the panel setup I am looking at to approximate 740W yields 711W with 9 panels of 19.2Vmp and 4.1A each, which gives a total of 37A. The approximation from the other perspective of 600W with these same panels gives 553W with 7 panels, for a total of 28.7A at 19.2Vmp, way under 40A....but nearly so when the same 553W is "converted" to 15V and 37A (that same familiar number!) How the hell did I end up in this rabbit hole? Well, my scratches on the wall will hopefully reveal something or other at some point in time...

This is an important distinction, I think! We'll find out eventually...

[jajamezsz]

The more I stare at the problem, the more convinced I am that I should be working with 19.2Vmp and 28.7A (for 553W) or 31A (for 600W) on the input side, which converts into 15V and 37A for 553W...

**or 553 + 26 (heat due to 0.7Vmp above ideal) = 579W if an earlier quandary regarding the accuracy with regards to the ideal 18.5Vmp value comes true.

>>Fortunately I am also leaning towards the idea that running at 37A instead of the full 40A, or 553W rather than 600W, would allow for the higher Vmp to contribute to the output efficiency rather than show up as "extra heat" as it surely would if we were maxed out at 40A and 600W!

I am starting to feel better about things, but we're not out of the cold yet! Heh, rabbits...always end up chasin em into dark places!

[jajamezsz]

I find it hard to believe that the only option for A-Si-Th-Fi panels currently available near 18.5Vmp are the 79W Flexopower's mentioned above, but it is truly the only option I seem to have at the moment. Just hard to believe there is only one choice! I am about 30 seconds to midnight on buying 7 panels for 553W, but only because I can't seem to be able to get any closer to 18.5Vmp input for 40A output. Still hangin on for that game changing discovery...

This has been fun for me, but I apologize if the last few posts might have thrown you off...as you can see I went through a lot of math that I eventually tossed out, but that is part of the exercise in my opinion, to go ahead and prove something to be negative, such as the impossibility of an extra 140W between input and output...if you think my posts are raw, just imagine my clipboard! Like I said, lots of fun!

[jajamezsz]

Anyone ever sliced A-Si-Th-Fi to get a chunk with lower amp draw? I am thinking about cutting off 1/4 of one these Flexopower 79W's to get ~50W out of it instead of 79W. That way I could max out my system's potential near 40A. I remember reading somewhere that you can puncture them, run over them, and leave them out in snow and hail...oh well, probably wouldn't work...and no budget for such a trial at the moment, anyway!

Well, the panel saga seems to be coming to an end. I am feeling happy with the idea of 553W of panels at 19.2Vmp for 36.7A of juice on the ouput side. This way I am safely under the max output of 600W and 40A, while only slightly pushing the input voltage over the 18.5Vmp ideal. 553W leaves 7.5% of the potential input power still to be desired, but also gives a little safety cushion, since I will be running at a slightly higher input voltage.

Once again, I'm faced with no other choice, save wait like a sitting duck, so I am just going to go for it, same way I did with the S40A12!

Next step: Batteries

[jajamezsz]

They weren't cheap, but I must say, these panels sure are beautiful!

Before I get the batteries I am going to do some research into monitoring and recording 100% of the battery activity.

If I am investing in something that is supposed to keep the batteries alive practically indefinitely, I am going to want to have definitive evidence if for some reason, many years down the line, something goes wrong. For this purpose I plan to employ a heavy duty data logging system which monitors and makes possible to maintain every last detail of this operation. For science!

This has recently become very important to me in considering the battery purchase, since I heard of a case of someone killing their batteries by floating them for too long on a Solar Tracker 5. I plan to have consistent loads attached, such as a refrigerator, with the aim of making good on the promises of the Solar Tracker 5, Solar Secrets, and the other related materials from this group.

This will all eventually power a truck-bed camper in which I intend to temporarily make my abode to save money on some of the exorbitant costs of living on the grid, such as rent and electricity. I am also excited about the prospect of the people and places I'll be able to see without breaking the bank or losing out on days of paid rent. My plans do eventually include settling down off-grid to explore sustainability, engineering, and all which life might have in store for me at that point.

[jajamezsz]

Long time, no see!

Updates:

- Lots of choice when it comes to monitoring battery activity. Currently stalling here, but at least I've browsed a bit. I want something very specific out of this area, meaning whatever might work to give me the robustness of monitoring I desire. Ideally, I would like to record and store data on the entirety of the batteries' activity, from cradle to grave. The CBAIV is a good example of what might accomplish this, but like I said, there are many options and I haven't found an exact match yet for what I'm picturing in my mind.

- There are a lot of battery dealers in my area so I'm narrowing down the selection and preparing myself to eventually start making some phone calls and get the best deal I can. Looking to spend no more than $600 for anywhere between 400 and 800Ah, hoping to settle around 600Ah. I read something on this site about higher capacity taking longer to charge, but giving more longevity to the battery due to the lower impedance (less heat per current value, similar to increasing wire gauge). What keeps me from going straight for 800Ah is that I want to make sure the batteries are fully charged at the end of each day, even in the worst case scenario of 10, 8, or 6 hours of sunlight. There is a balance here between battery capacity and your ability to charge which is challenging to picture in a camper setup due to the myriad of factors such as geographical location and time of year, parking spot, specific loads and discharge patterns, etc, etc, etc. Luckily, the Amorphous panels help directly with this problem by drawing a relatively even charge in a wide range of conditions.

- I don't know if I mentioned this, but I'm dreadfully poor, having recently worked for the State of California for less than minimum wage - so the Trump money is finally getting me in the position to where I can buy a used Dogde Diesel and some old truck camper to rig this all up in (been saving up for this project for at least 5 years, but the cost of living is very high here). Between me and my dad we should be able to modify the roof of the camper to support the necessary real estate for the Amorphous panels, which require a lot more space than the other types. He's a whiz with fiberglass, not to mention other relevant skills and experience. If I could afford kevlar/carbon fiber, I'd go that route for the roof and camper repairs/mods, so we'll see where I'm at financially when I get to that point. Hopefully this will come to pass very soon, as I'm now in a position to go ahead and do it!

- The rest of the hardware, including the Pure-Sinewave Inverter, is rather trivial compared to what I've just listed, so I guess it's all laid out, more or less.

- I aim to keep posting in this thread until it's all rigged up so I can at least leave something behind that is complete and perhaps useful for others.

Hope you're all living strong and prospering out there! These are tough times, but if we stay positive we should become stronger from the challenge. I wish you all the best!

Peace,
James M.