Correct charge controller for USED panels

[kbrawlz]

I’m trying not to overthink this, but also not underthink it.

I have some used Trina 250w panels (TSM-250PA05.18). My understanding is that they only put out about 75% of their rated specs.
Vmp: 30.3v
Imp: 8.27a
Voc: 37.6

I want to pick out the correct charge controller or grid tie inverter, but if I account for the diminished output, it falls out of range for the min/max on some most of the units specs.

I plan on using one panel for a 12v system (2 parallel 100ah LiFePo sealed drop-ins). If there is room, I will add a same 2nd panel, but real estate is slim.

I have to imagine that I can just pair it to the specs on the used panel and disregard the lower numbers it puts out, because after all, the panels don’t put out 100% all day and I’d imagine charge controllers still put out some juice even first thing in the morning.

But I’d like someone to give me their input on how serious I should be trying to match the numbers. I obviously don’t want to over voltage/current a unit, but how much can I under power it?

The easy answer is to buy smaller new panels and size it accordingly, but if I’ve learned anything from Will’s videos, you can bend some rules and hodge-podge things together.

I’m out of town very often and once I order something, it’s mine. I don’t get to it in time to send it back if I ordered in error.
So I’m having to make choices without being able to mount and test them on a regular basis.

I’m not necessarily asking for a solution to my problem, just asking what I can get away with in terms of pairing units in the system.

I wanted to either get that EpEver 40a 4215BN that Will recommends OR a Victron 100/30 SmartSolar

I’m trying to pick something that will let me run either 1 or 2 of those Trina panels and the flexibility to go parallel or series to make it work for the controller.

Sorry it’s long-winded. Hope I put in enough details.

 

[Q-Dog]

The Victron only needs 5 volts above battery voltage to start charging. Since you have a 12 volt system, a single panel would be enough to start charging.

You still need to be careful not to overvolt the charger, so use the label VOC. That means the 100/30 could do 2 panels in series.

 

[kbrawlz]

The Victron only needs 5 volts above battery voltage to start charging. Since you have a 12 volt system, a single panel would be enough to start charging.

You still need to be careful not to overvolt the charger, so use the label VOC. That means the 100/30 could do 2 panels in series.

Aww see, now that’s a perfect answer. Thank you. I stared at that victron pdf for a while and I see that in the sub notes now.

Awesome. I appreciate it.

 

[hwy17]

You will probably get nearly full voltage out of them, even used.

 

[Rednecktek]

If you design your system to handle the maximum, it'll always handle the minimum. Not so much the other way around.

If you get an SCC that can take 150v of input that opens up 3s strings to you. Having a 12v system calls for higher amperage rated controllers, and most things 60a and up are easy to find with the 150v input. Rule of thumb with 12v systems is 10a of controller per 100w of panel .

 

[kbrawlz]

Thank you all. Excellent info. I guess what got me down this rabbit hole was the requirements listed on grid-tie inverters.

Most of the requirements are approx: Vmp:26-37v & Voc:34-46v

So if my panel at its best is 190w/Vmp23v/Voc29v

Then, does just mean it would never work with my panels?
And does that mean even people with new panels in that range only get output during peak sun hours when their panels fall into those “parameters”?

Or does it simply mean I would be able to still use it and get output… just not as efficiently and where the equipment likes to be to work?

I’m just trying to wrap my head around the “rules” without buying the equipment and experimenting.

Screenshots for examples of current models and requirements.

 

[Rednecktek]

Grid tie is a LOT of hoops and rules and costs to make happen, are you sure you want to spend $4000 to set up $100 worth of system?