system check,

[Burning2nd]

So, a renogy 2x100watt panel set with the renogy rover 20amp Mppt charger,

4xtrojen T125 6 VOLT's *wired series, parrelle

2000 watt PI20000X inverter



my 2 pannels are currently wired serires... So 24v input
and the controller is set to flooded bank, and is charging 12

Ive got 2 more of the same panels coming and the 4to1 parallel connectors coming

do i wire the 4 panels parallel?
or do i wire them series parallel?

the 4 panels cant be wired series because what would be 48v

my math tells me 4x parallel will give me about 90 volt

thats also what renogy says


advice please

[Burning2nd]

Well worked good... got it all done,

Thanks for the help!

[sdold]

I’m not sure why I didn’t see this thread, I look pretty carefully for new messages a couple of times a day, and since no one else responded I’m wondering if it was some sort of forum glitch. Do you still need help?

Edit: I'll give it a shot. I see a couple of problems:

1. You didn't say the panel model so I looked at a one Renogy panel that had 24.3V open circuit voltage. Two in series would be 48.6V, still well under the 100V that the Renogy Li 20A Rover can handle (100V). That 200W into the MPPT controller would give around 16A current to the battery in ideal conditions. The controller is spec. 20A so that's a good match, but a little small for the battery you have.

2. If you use four panels in series you'd be close to the 100V max input voltage, and maybe over that in cold weather, so I wouldn't do series unless you limit it to three panels. With four panels I would do series-parallel (two of what you have now, in parallel).

3. But I don't think adding two panels would give you much because the controller is limited to 20A. In ideal sun four panels could get you 32A with a larger controller.

4. It's typical to see 80% of the panel wattage available instead of 100% so in real world conditions you probably wouldn't lose as much as above, but what I would do is go with 4 panels, series-parallel, and upgrade the controller to maybe a 30A unit. That's still less than the 45 or so that would be better for that size battery, but it's better than 20A. A good rule of thumb charge rate is 1/10 of the battery's AH rating, you're under 1/20 with 200W of panels.

You could also add a single panel for three in series, well under the controller's max voltage limit and enough to max out its 20A capability.

Another option (check with Renogy) is to add two additional panels on a second 20A controller and connect to the same battery. Two charge controllers feeding the same battery isn't normally a problem. That would give you the ability to add a third panel to each string someday if you decide 400W isn't enough.

The inverter is pretty big for that battery which has two negatives: 1) it's probably capable of pulling way more than the batteries were designed for (over 160A), so it would need pretty large cables, and 2) it's likely to use a lot more standby power than a smaller inverter more appropriately-sized for the battery, Some could argue that you could fuse protect the battery at some lower value to address the first issue, I'll leave that to others to debate.

Hope that helps and maybe others will chime in.

[Burning2nd]

im sorry i didn't really explain clearly, written english is not my thing, Im a industrial mechanic

So, since i wrote this, i already had a over current warning, I now have 2 sets of 2 wired series, and then parallel (*with the y connector)

(*im actually over spec for the 20 amp rover charger controller)


since the 4 panels are series parallel, im well under the voltage, and pretty close to the amp

If my math is correct, its 18.6x2= 37.2 volts (*at 100%) *which correct me if im wrong, we dont really ever achieve?

(*ive learned a lot in the last two weeks, ive been on the roof reconfigure'n in blistering sun over and over and over)

total voltage out put would be 37.2vDc
current, is 5.38A+5.38A= 10.76 (*this is where im in trouble)
total ampage is 10.76A

power = 37.2v x10.76a =400.272watt
10.76amp
37.2volt

(*that is what ONE PV set should do) and then parallel that

brings the amps over 20

(*but i only get about 4 hours of direct sun)

Im already at the limitation of my controller... and used battery's from work is not the best idea to start with..

I do plan on stepping up to a larger controller, and better NEW battery's, in the future.. but for right now, i have enough power to run something big if i had to for a little.. OR always have a few outlets for emergency situation.. (*on top of all the other redundancy's ive installed)

actually last night i discovered my inverter is way way way to big...

realistically, i just wanted to provided for ever power to a small fridge, so in a dooms day event, we would still have a small fridge to keep meat good longer
but it came to my attention, that even with the inverted not on.. not doing anything.. im pulling way to much power,

its stand by power is killing me


So I took the 300watt one i had in the bmw and wired that in,

i was wondering about another controller, i dont know if i want to pull cable and do that all again, I think id wait a few years, get battery's and a new controller

again, thanks for the help, at least i got someone to talk to with about this..

you guys know way more about this, and how its done and what works and what does.. I just work in 480v cabinets, If you ever want pictures let me know ill show you guys some amazing stuff.... battery room with 300 36v d series flooded 2057lb battery's

at the end of the day.. Im just going to drive home from with two battery's on a pallet and a fork lift lol When it goes down

[sdold]

The charge controllers are usually spec'd for the output to the battery, not the solar panel input, so the 20A limit is likely the most the controller will put out to the battery even if you have enough solar for more than that. On a good day (cold, full sun) you might achieve close to the panels' rated output. Normally you'll probably see 80% or so of that, just based on my and others experience.

An MPPT controller allows the panel to operate at its Vmp (max power voltage) and Imp (max power current). I'm going to use 18.5V and 5.5 Amps below since I don't know exactly what they are for your panels. The actual numbers are probably close. Also the following is what would happen in ideal conditions where you are getting rated "nameplate" power from the panels).

Your math might be off a little because when you put two panels in series, the current does not go up, only the voltage. If you have two panels in series into an MPPT controller in good sun with a discharged battery, you'll probably have about 37V at 5.5A out of the panels. If you put two of those strings in parallel, you'll double the current, so with 4 panels together in series/parallel, you'll have about 37V at 11A. That's about 400W.

With a larger controller (say, a 40A controller) your input to the controller would be 37V x 11V = 400W, and the output of the controller to the battery would be 12V x 33A = 400W. The power is the same, but since the voltage wend down to 12V, the current went up to 33A. That's the cool thing about MPPT controllers, the output current can be much more than the input.

Except that your charge controller will limit that output current to 20A, so you're not getting the full power from the panels. Some options are to change charge controllers to something like a 30 or 40A (I'd do 40 so you could add panels later if you want), add another charge controller like you mentioned, or aim one string east and the other one west to get more time of solar-collection instead of more power for a shorter time.

Again I hope others chime in because I'm no expert. But I see potential to really improve what you have.

Edit: I would like to see some pics of those batteries and that installation. What kind of facilities? Ours are state telecommunications (radio) sites, The biggest one we have is 48V at 13K Ah with 600A charging, most are around 500AH or so.