Series/parallel panel combo to take full advantage of 150V/15A/1600W MPPT

[MacGyver0013]

Looking to install 8x 200w RichSolar (RS-M200) panels with 20.4Vmp and 9.8Imp (1600 watts total). The MPPT solar charge controller is 150V/15A/1600W. All panels in series gets you 163V @ 9.8A and panels in parallel gets you 20.4v @ 78A. How would you configure this group of panels to be under 150V and 15A?

Or maybe...of all the amazing electronic contraptions out there, is there a device that I can install between the solar panels and MPPT SCC that would cap the voltage @ 150V in the rare cases it did go over? I like the idea of pushing closer to the limit and taking away the extra 10% of the time rather than under sizing 90% of the time for the rare 10% chance the temps and sun are perfect to produce over 150V.

This MPPT SCC is built into the upcoming EcoFlo Delta Pro: https://ecoflow-delta-pro-the-portable.kckb.st/fa1aa9a6

 

[DThames]

If you have not purchased the panels, you would do better to get higher voltage panels, like a 60 cell, made for a 24v system. Those would be lower amps. If you are stuck with the 12v (20Voc) you can connect 4 in series, times two in parallel. Your max amps output would be your 9.8x2 about 20amps. The charger should limit itself to 15a....should. If you don't like that solution you could just run 7 in series.

 

[MacGyver0013]

I have not made any purchases yet so I have the option of 24v panels! And looking up the Rich Solar RS-M200D, they are the same size as the 12v version. These will be installed on an RV roof with low profile unistrut.

For my own understanding on the limits of an MPPT: the MPPT on the EcoFlow Delta Pro (or any MPPT for that matter) doesn't care if the individual panels are 12v or 24v right? The MPPT just needs max voltage from the entire solar array getting tossed at it to be within (under) its max voltage rating? Did I incorrectly assume that if the batteries were in 12V, then the MPPT would be in 12V and hence the panels would be 12V?

So if I instead go with the RS-M200D 24v panels, I think I would need to still go with 2 parallel sets of 4 in series giving me 150.4V and 10.64A. No wasted voltage or amperage. Am I on the right track?

 

[DThames]

With a PWM controller a 12v battery needs a 12v panel. With MPPT, (think about it your willing to put almost 150v in) the charger will do a DC to DC conversion and charge the battery with the best power to match what the panels can output under current light conditions. So 2, 12v in series is really about the same as a 24v. The slight difference in this case is the 12v has a Voc of 20.4v (you said) and the M200D has a Voc of 37.6v. 4 times 37.6v is better than 8 times 20.4v in regards to staying under the 150v max input. Considering the charger is built inside the battery/inverter unit, I would not suggest you get close to the 150v limit unless you know there is safety factor above that. Also, some of those limits are derated to lower voltages if it is hot operating conditions.....and the Voc on the panel is at a given temperature as well, with it going higher when it is cold.

You think if "wasted power" when in fact it is rare that conditions allow a panel to make rated output. It is a common practice to "over panel" so a charger that might charge with 1500w could be connected to 2000w of panels and maybe get something close to 1500w more of the time. My original statement about 4 in series (about 80v) with 20amps max would be safer on the charger than pushing it right to 150v on the input.

Not sure about your space but 5 of the 12v in series would be just over 100v times 2 (in parallel) would give you more power available with less than ideal light conditions. One thing many people don't understand about MPPT chargers is that they act as a variable load on the panels. They try to load the panels in such a way that they pull the power that they can deliver to the battery (also depends on what the battery charge state is). 2000w of max solar power doesn't force 2000w of power through the charger. It makes 2000w available if the charger can consume that much. A normal MPPT charger will current limit itself at some preset value or will be throttle base on heating or maybe both. Amps make heat. Amps times volts makes watts.

Are those charger specifications published? I didn't see them (quick look at the product offering).

 

[DThames]

Comment....I am in the process of building (for my adult son) a portable battery/inverter/charging power station after he started looking at a "solar generator" type device. If a person learns enough to put together off the shelf components, then they should also be able to replace those components, 1. if they fail
2. if needs or desires change

If you have your own system and you want to add more charging power, you can replace the charger. If you want more battery (longer run time) you can beef up your battery bank. These systems that are packaged all together, I wonder how many of them will be junked out because of something internally that fails when otherwise it would be just swapping out a component. I know my opinion is very much slanted based on confidence from experience and it is hard for me to see things from a place of less experience. But if a person enjoys learning and enjoys the power that knowledge gives, DIY.

 

[MacGyver0013]

In regards to your DIY comment, I total agree. I enjoy having my home automation components, networking devices, etc. built from separate, reliable and understood components for reasons such as troubleshooting, replacement and upgrading.

I have most of the knowledge to build a custom solar/inverter system for my camper but there are a couple of reasons I am wanting to go down the road of this all in one. When all was said and done, I was looking at a system with half the battery power (200 or 300ah SoK batteries) for about $9K after panels, inverters, Honda backup generator, smaller components and accessories. It would have been enough to run 1 AC unit for a small handful of hours and maybe a bit more with solar. And I would have wanted a more expensive 240v inverter for my 50 amp input.

I got in with one of the early bird specials on kick starter. My package has about 600ah of lithium (main unit plus 1x expansion) plus a smart generator for $5K, add about $2K for panels and Unistrut and I am around 7K. It has just about everything I was looking for like a remote panel and app/phone control. Plus, the space the units takes up is less which allows me to install them towards the back of my trailer in a storage area to distribute trailer weight better (most components would have been installed near the tongue otherwise and I am already close to my tongue weight). Also, during winter storage (or any long term storage for that matter), I can have them in the home so I have backup power when needed. It has a 30A RV receptacle on it which most other lithium packs did not which saves me needing to worry about more adapters to plug it into the camper. They added a 5 year warranty (and currently close to a 10 year with stretch goals) so I'm not too worried about a unit crapping out, especially if they are not going to be used full time I will have periods to deal with warranty claims if needed.

Admittedly, it was almost a wash which direction I went and if I wasn't getting almost half off MSRP of what these will sell for after the kick starter it would have been a no brainer to go with piece meal components instead.

As far as the specs of the MPPT, multiple folks have asked ok KS but they have not released any manufacture specific specs on the MPPT device, just 150v/15a/1600w (which was 150v/12a/1200w just a couple of weeks ago, apparently they found a way to upgrade the MPPT portion ahead of their initial release).

I was looking at 8 panels only because the roof space I had would fit them evenly and look more consistent up there and that would meet the 1600w max of the MPPT. I was going to install the Unistrut to hold 8 either way.


Reading your statement about getting closer to 20A rather than 150v is understood. A lower voltage to the MPPT while raising the amps (especially when I had about 5 amps left to begin with) makes sense to me. I already have a run of DC 10AWG wire from the roof with MC4 connectors pre-installed.

So my main take away here is (and with this particular unknown MPPT in mind), an MPPT is designed to limit the amps (in my case 15a) from the panels but not usually voltage. And getting closer to an MPPTs max voltage will put more wear and tear on it as apposed to getting closer to its max amps. So I should stick with 12v panels in 4S2P for ~80v/20a rather than 24v panels in 4S2P for ~150v/10a. Is this an accurate take away?

You stated that the higher amps makes the heat so I would assume that a higher voltage and lower amps would make less heat on an MPPT, no?

 

[DThames]

So I should stick with 12v panels in 4S2P for ~80v/20a rather than 24v panels in 4S2P for ~150v/10a.

You stated that the higher amps makes the heat so I would assume that a higher voltage and lower amps would make less heat on an MPPT, no?

Yes, on 12v 4S2P or 24v 2S4P would be about the same, if for some other reason 24v panels look better. Large residential panels (60 cell) made for 24v have Voc of 35v-30v range. Likely too wide to use on your trailer setup.

On the electronics heating, the heat comes from what is commonly known as (I^2)*R heating...say, "I squared R heating. It is the current that causes the heat in the resistance of the circuit. You will see chargers say things like 500 watts at 12v and 1000v at 24v for max power (image below). If you do the math you can see they both have the same current (I). NOTE that it is most common that the current rating of the charger is its output current, not its input current. That is why I asked to see the specs on the charger. We were (previous posts) talking about the PV current, which really only applies to the wire going to the charger from the panels......unless the 150v/15a/1600w's 15 amps has a meaning that is not the output max current. Note in the image below, the 10Amp unit. I took one of these and put 2, 295w 60cell panels on it for a 24v battery. That is way more PV than the numbers but because of its internal current limiting, no problem. It would max out at 10 amps going into the battery. 260v/24v = 10.8 amps. Also 260v/10a =26v, which is about the output needed to charge a 24v battery. Hope that helps.

 

[MacGyver0013]

Looking more at size/weight specs of RichSolar's panels, they are all the same size and weight (12v 160w, 170w, 200w and 24v 200w). They don't start getting lighter and smaller until 150w.

Anyhow, not too sure what direction to go yet (12v 200w or 24v 200w). I think I'm going to play it safe and wait for more reviews to surface of the Delta Pro and maybe someone will perform an in depth MPPT test that will provide additional data in helping make a more informed decision.

I will report back if I obtain more technical data about the MPPT of the Delta Pro. 5 days left of KS.

 

[Bud Martin]

I have not made any purchases yet so I have the option of 24v panels! And looking up the Rich Solar RS-M200D, they are the same size as the 12v version. These will be installed on an RV roof with low profile unistrut.

For my own understanding on the limits of an MPPT: the MPPT on the EcoFlow Delta Pro (or any MPPT for that matter) doesn't care if the individual panels are 12v or 24v right? The MPPT just needs max voltage from the entire solar array getting tossed at it to be within (under) its max voltage rating? Did I incorrectly assume that if the batteries were in 12V, then the MPPT would be in 12V and hence the panels would be 12V?

So if I instead go with the RS-M200D 24v panels, I think I would need to still go with 2 parallel sets of 4 in series giving me 150.4V and 10.64A. No wasted voltage or amperage. Am I on the right track?

One thing in mind is not to never exceed the PV input max Voltage, and you should add 15 ~20% to the Voc in colde weather, so I suggest to make Voc to the PV input to be well below 150V.
The MPPT is basically a smart Buck converter, it will PULL the power from the panels as needed up to the maximum the battery charger limit, it is not wasting power if you overpanel the system, it will just limit to what it needs from the panels..

 

[MacGyver0013]

So would your recommendation be the 12v 200w panels in 4S2P for ~80v/20a? Or perhaps another high quality panel with different specs that could be recommended? Maybe something like a 28 Vmp panel with about 7.14 Imp would give about 112v/14.3a in 4S2P for 1600w. Do these panel specs even exist?

12v 200w

24v 200w

 

[Bud Martin]

The total Voc is the one you have to keep at below 150V, not Vmp.
I do not have recommendation for panels since I only buy used SunPower residential panels for my system.
Did they ever publish the final full details spec of Delta Pro?
You should find out what the MPPT Voltage range is, it is not the same as the max Voc input, the range is for the MPPT to operate to get the maximum power.
For example on the unit such as MPP Solar PIP-1012LV-MS has max Voc input of 102VDC, MPPT Voltage range of 15 ~ 80VDC.

https://my.sma-service.com/s/article/What-is-meant-by-the-MPP-voltage-range-1523526037054?language=en_US

How To Easily Read a Solar Inverter Datasheet (Solar Power Inverter Specifications) Part 1: Input Data - Power From Sunlight

This article explains easily how to read the relevant terms in a solar power inverter datasheet (solar inverter specifications) and how valuable this information is in order to choose the best one.

www.powerfromsunlight.com

 

[DThames]

Another thing to consider....some might think, using 20Voc panels, 6S1P or using 40v Voc 3S2P (same watts) are effectively the same. That is true in full sun. But minor shading on a 6S1P array can have a larger negative impact than the same shading on a 3S2P array, when that shading is limited to one panel. It doesn't take much shading on any series string to take the entire string down to near zero output. So two strings are better than one if you can manage to keep one of the strings in full sun.

On total Voc, my personal feeling is about 130v would be my max for a 150v max Voc input charger. I have 3, 60 cell panels in series on one array and they hit about 125Voc some of the time. So 6 "12v" panels in series would put you in the 120v range, as would 3 "24v" panels in series.

 

[MacGyver0013]

Is Voc also about the highest voltage these particular panels would go during the coldest of temps or can they go even higher?

 

[Bud Martin]

It will go higher than what is shown on the stIcker which is shown at 25C.

Adjusting Solar Panel Voc for temperature

When designing you solar panel system, it is important to adjust you solar panel Voc for temperature in order to ensure you do not over-voltage the PV inputs of your solar charge controller. This paper shows how to calculate the Temperature...

diysolarforum.com

Care to Check My Reasoning and Math before I blow Everything up?

But you can program it to draw from batts then go to grid. Is this wrong? This is exactly what I said in my previous post. They can do this as well.

diysolarforum.com

 

[MacGyver0013]

Got it. Meanwhile, the MPPT solar max questions are starting to pile up at the KS page for the EF Delta Pro with about 3 days left, including wanting more info about their new rooftop solar integration news.

 

[Jillest]

Got it. Meanwhile, the MPPT solar max questions are starting to pile up at the KS page for the EF Delta Pro with about 3 days left, including wanting more info about their new rooftop solar integration news.

Hi MacGyver0013, I am new to solar and just purchased the EF Delta Pro (1600w input) and I am reading all this here to find out what size solar array to connect to it.
What did you end up purchasing and how did you connect them? Thanks~~