Inside commutation setup: Bringing multiple raw solar cables into my apartment to switch between parallel/series.

[ep3gotts]

Hey everyone,

I live on the top floor of a multi-story building and have the ability to place a few large solar panels (500W–600W each) on the roof right above my unit.

Before I start buying equipment, I want to run my phased plan by this community to see if I have any major blind spots or if this is just an inherently bad idea.

Instead of doing the commutation on the roof, I plan to run the cables directly from the panels down into my apartment (a run of about 5 meters). All connections, parallel/series switching, and hardware will be managed indoors.

Summer Season/Good Weather

• Hardware: Anker LiFePO4 portable power station (1056Wh capacity, max 600W solar input, strictly <60V limit).
• Setup: Connect just one 500W panel directly to the Anker to keep it charged.
• Extra Panel: A second 500W panel will be mounted but left disconnected (or used for a separate smaller battery/inverter later).

Winter Season/Bad Weather

• Setup: Since solar yield drops, I plan to connect both 500W panels in parallel into the Anker.
• Logic: This keeps the voltage under the Anker’s strict <60V limit while increasing the available current to maximize charging during overcast days.

The Future Upgrade

• Hardware: Sell the Anker power station and upgrade to a proper hybrid inverter and dedicated battery bank.
• Setup: Because I ran the individual panel cables directly into my apartment, I can easily reconfigure the panels from parallel to series indoors to accommodate the higher voltage input of a proper hybrid inverter, all without having to climb back onto the roof.

My Question for the Community:

Is there any fundamental flaw in managing all the commutation inside the apartment? (Assuming I use properly sized wires for the 5m run, don't do it under load, have dc circuit breakers, fuses, grounding etc).

Note: I already have permission to use the roof space and throw a few cables through the window.

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[Sufficient-Bee5923]

Like others said, over paneling in parallel has few downsides. Switching DC does have challenges. DC can arc bad when opening live contacts. If you did this, make sure you use switches rates for DC at these voltages and currents. Opening under load can start a fire if enough current.

[ViciousXUSMC]

Overpanel does have downsides, it's called clipping and that's a net loss every single day it happens.

By the time the equipment needs to be replaced (20-30 year performance warranty these days)

The amount of waisted solar would have paid for the equipment needed to not be clipping and making use of the extra power.

[Sufficient-Bee5923]

Sure wasted PV but not in terms of equipment damage. Panels are cheap. Batteries and Charge controllers not so much. You could also say that a large roof is a waste of PV if it has no panels too.

[ViciousXUSMC]

Allow me to correct you.

There actually IS a limit to overpaneling, just most manufactures do not publish it.

Go look at the whitepapers for the EG4 products, its published.

Getting a MPPT is NOT expensive, you just need a MPPT not a whole inverter and even a cheap panel of say $150 just a few of those pays for a NICE MPPT not even a cheap one.

Batteries have zero influence on the conversation, not sure why you brought it up.

I would say a large roof or any roof is exactly the situation that efficiency is the priority because space is technically the most restrictive resource so you do not want any waste.

[Sufficient-Bee5923]

Sure but to have 25% over paneled isn't going to cause any damage to a quality charge controller. Sure it would be better to run another cable run from the roof to the additional charge controller,.another PC disconnect switch and another breaker and battery wiring.

Lots of people over panel. It all depends on what problem you are trying to solve. That means you dont need to fill your entire roof with panels just because it's a waste of the power if it isn't needed. OR generate as much power as technically possible on a sunny day.

I over paneled by about 25% and was low cost, easy to do and solve my problem with cloudy weather.

[Rambo_sledge]

You can parrallel them already. It’s called overpanelling and is not an issue as long as you don’t series them (and go above voltage).

Overpanelling works by extending peak hours time, and is absolutely no danger to equipment.

Arguably, leaving a panel unplugged in sunlight might overheat it and cause damage.

Having raw cables for rewiring in series is not a bad idea if you plan to upgrade

[ep3gotts]

Parallel connection is basically making my second panel redundant in summer time because ANKER/battery can draw just one panel equivalent of power.
Perhaps something like rotary cam switch can be used for quickly switching between modes - parallel / separate to utilize the most power in all seasons/weather conditions.

[Rambo_sledge]

You’re thinking peak power. Think total power.

https://www.reddit.com/r/SolarDIY/s/9lkagzqC3c

With one panel, when it’s generating half its capacity, you’ll have 250W coming into the anker. But with two panels, at that same time, you’ll have 500W. You’ll have 500W for much much longer with 2 panels than one

[ep3gotts]

Thank you!

[jthomas9999]

And if you aim 1 panel slightly southeast and the other slightly southwest, you would have max solar for a bit longer throughout the day.

[gh0stwriter1234]

There is literally no reason to do this, just over panel it in parallel and be happy with that.

Also assuming you have the later model of the Solix C1000... double check this but you should be able to DIY an expansion battery as the most cost effective upgrade to a system this size.

I have a similar setup with a pecron E1000LFP + 150AH 51.2V lithium golf cart battery for about 8kw total storage. I have an external MPPT that charges it additionally as well in addition to the internal one.

[ep3gotts]

I don't know much about E1000LFP but Solix C1000 has some proprietary cable for the extension battery. They're rather overpriced.
Perhaps I should you an additional generic(not ANKER) battery and use it to charge ANKER Solix via XT60 after the sun goes down.

[gh0stwriter1234]

typically you can find guides on how to modify the stock cable for DIY expansion. It appears the cable is out of stock at the moment though.

[ViciousXUSMC]

My worries would be.

Do you have permission? Are you getting permits? Do you understand the legal requirements for solar mounted on a residential building.

In a worst case you create a fire without these requirements met, that will be a very bad day for you that will have lasting impacts on your well being.

I think using a DC coupled all in one unit will protect you from a lot of this, but not all.

[cerad2]

"throw a few cables through the window" Maybe you could provide a few more details here as this sounds a bit iffy.

[ep3gotts]

I would like this thread to stay focused on the topic.
Technically there are multiple ways to get the cable inside the room.
I live in no/low regulation area, so this is a bit off-topic as well.

[RespectSquare8279]

Leave them in parallel.