Curious about voltages

I am wondering if the panel voltages are supposed to match the system one is building. Currently i am attempting to get an idea of what panels i am aiming for and how many, then i am looking at charge controllers. I am aiming at a 3000 w 24 v system, i have the inverter and one 100 amp server rack battery currently, but i lack the understanding to figure out the panel situation as of yet. Looking at the panels in the company referred to on this website/forum is showing voltages not in line with the 12,24,48 scheme so i am wondering if the panel voltages are not as a big of a concern in that regard.

Yeah, panel voltages are not matched to batteries like "24v panels" anymore, except for certain kinds of simple PWM or uncontrolled systems. For nomads in Mongolia, they do still just buy a "12v panel" and hook that up to their car battery.

For your purposes, you want to identify a charge controller first, and then it will have an MPPT operating range, and max voltage rating, and your panel array can be designed to fit well within that.

There has been a step change from an era of MPPT solar, where they used 150v controllers with paralleling panels, 2s2p, 3s4p etc., nowadays most people move to 500v and 600v controllers, with much longer strings, 8s1p, 8s2p, etc.

hwy17 said:

Yeah, panel voltages are not matched to batteries like "24v panels" anymore, except for certain kinds of simple PWM or uncontrolled systems. For nomads in Mongolia, they do still just buy a "12v panel" and hook that up to their car battery.

For your purposes, you want to identify a charge controller first, and then it will have an MPPT operating range, and max voltage rating, and your panel array can be designed to fit well within that.

There has been a step change from an era of MPPT solar, where they used 150v controllers with paralleling panels, 2s2p, 3s4p etc., nowadays most people move to 500v and 600v controllers, with much longer strings, 8s1p, 8s2p, etc.

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I called a solar distributor company about that and i was told by the sales representative that deoended on the panels. Any decent way to gauge the controller i would need?

andrew hite said:

I called a solar distributor company about that and i was told by the sales representative that deoended on the panels. Any decent way to gauge the controller i would need?

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Yeah it is kind of complicated because it is all interdependent so each part depends on the rest.

A good place to start would be to decide how many kwh of load you are trying to serve per day.

On this forum, go to "resources", then find "planning and sizing tools." There's great information there. Sunshine_Eggo has a spreadseet which you should look at. The time will be well spent.
This is the spreadsheet

3000 w is what i am initially aiming for, kind of doing that now with a generator and would like to transition to something quieter and with a bit more longevity.

I do plan to expand from there and switch my batteries to a vanadium flow setup, just need to figure out the cell stack arrangement and if i can lay my hands on enough sulphric acid to load it up.

24V/3000W will provide 120VAC/25A.
24V @ 250A Draw from battery bank can support up to 6000W (pushing it)
1x 24V/100AH Battery (if using standard LFP) can discharge up to 100A for 1 Hour and take up to 50A for 2 hours to charge from 0% SOC.

Choosing a Solar Charge Controller that can charge your current & future battery packs is what really counts here.
For example a 2000W Array using "24V" panels can produce 200VDC @ 2000W and with the right SCC can charge your batteries between 80-95A without issues.

Example Case: Component System (NOT AIO).
I am 24V, have 2 arrays.
Array 1 = 2080W configured as 4 panels in Series, X 2 Parallel (4s2p) connected to a Midnite Classic 200 providing 80A charge.
Array 2 = 2370W configured as 2 panels in series, X 3 Parallel (2s3p) connected to a Midnite Classic 150 providing 94A charge.
#1 uses Canadian Solar 260P (Poly) monofacial panels.
#2 uses Q-Cell 395W HJIT Panels which work super well in shade, shadow & low sun (also monofacial)

If using an AIO (All-In-One) there are advantages but also many trade-offs. If going "Component" based with separate SCC's Inverter/Charger etc you get a lot more flexibility & option but it is more complex and a lot more BOS (Balance of system) bits to take into account.

Good Quality Solar Controllers (Victron, Midnite etc) can use smaller solar arrays and output considerably more charging amps than combined units and are far more efficient. Some will argue that - facts are well known so no point. Also the good controllers can be setup in parallel and work together for optimal performance & management.

You CAN Add more LFP Battery Packs in Parallel over time, there is no problem with adding packs, 6 months, 1 year or even 3 years later. Lead Acid Battery rules DO NOT APPLY !

WARNING - HEADS UP !!!
Pending on WHERE you are and what Rules/Regs etc apply directly TO YOU in your location, various shutdown and safety requirements can come into play. Things can get wonky once you cross certain voltages.

Interesting so the amperage going into the battery does not seem to matter outside the material limits, always thought the entire circuit needed to be one thing everywhere.

Any recommedations on a place to get panels from? As in a place where i do not need to get a quote? Or have minimum quanties on orders?

andrew hite said:

Any recommedations on a place to get panels from? As in a place where i do not need to get a quote? Or have minimum quanties on orders?

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try facebook marketplace or craigslist.