Question About My Setup

LeoLopez

New Member
Joined
Sep 29, 2021
Messages
22
That's because the 49.86Voc is determined at a controlled temperature of 25C. Voltage goes up when the temperature goes down. What are the winter lows at your location? On paper, those two panels in series would be 99.7V at 25C, but the voltage would go up to 112V on a frosty morning. You need a string calculator to determine it exactly.

It looks like what I wrote above about using 2S2P would be incorrect for your particular panel. Two in series would go over the 100V limit in cold weather. Looks like the only way to wire them would be in parallel, two panels per controller. The Vmp is ~40-41V? That would be ~ 10A + 10A at 40-41V. Once transformed by the MPPT controller, your output for a 24V system would be 810W/25Vcharging = 32.5A. So, one 50A controller could work with two panels, at 24V. If instead you decided to go back to 12V, the numbers would be 810W/13Vcharging = 62A, more than the controller can handle.
Ok thanks! I am definitely going with the 24v then in a parallel connection. This helps a lot!
 

Dzl

Perpetual Newbie & Unofficial Forum Librarian
Staff member
Moderator
Joined
Dec 10, 2019
Messages
4,778
FWIW I agree with Michael, Joey, etc that 3000W @ 12V is pushing it, however I don't agree with the black/whiteness of how its being characterized. There are plenty of highly reputable manufacturers selling 12V inverters in the 2500-3000W range (Victron, Samlex, Outback, Magnum are a few examples). While it is 'unideal' I dont think crazy, in a mobile or marine context.

Also the point about UL listing is overstated and not accurate. While there are many brands that egregiously manipulate/inflate the ratings for their inverters. The 4 brands I mentioned above are all reputable respected brands and all have inverters in the 2400-3000W range that are UL listed.

That said, I think you would be making a strong choice if you go with 24V, adds a bit of complexity, but is a solid choice for a medium sized system in my eyes, and makes a few things a bit cheaper or easier (saves on the solar charge controller, and makes finding a decent circuit breaker easier).
 

smoothJoey

mumble...
Joined
Nov 30, 2019
Messages
9,317
FWIW I agree with Michael, Joey, etc that 3000W @ 12V is pushing it, however I don't agree with the black/whiteness of how its being characterized. There are plenty of highly reputable manufacturers selling 12V inverters in the 2500-3000W range (Victron, Samlex, Outback, Magnum are a few examples). While it is 'unideal' I dont think crazy, in a mobile or marine context.

Also the point about UL listing is overstated and not accurate. While there are many brands that egregiously manipulate/inflate the ratings for their inverters. The 4 brands I mentioned above are all reputable respected brands and all have inverters in the 2400-3000W range that are UL listed.

That said, I think you would be making a strong choice if you go with 24V, adds a bit of complexity, but is a solid choice for a medium sized system in my eyes, and makes a few things a bit cheaper or easier (saves on the solar charge controller, and makes finding a decent circuit breaker easier).
I can't prove it but I suspect that when the lower end of the market started having success flogging 3000 watt inverters, the rest of the market was forced to follow suit.
Losing a sale to a competitor makes them stronger and you weaker.
Allow me to speak in generalizations.
3000 watt 12 volt inverters are the super size option of the inverter market, they look like a good value proposition to first time buyers.
That being said I'm sure there are use cases where a 3000 watt inverter at 12 volts is indicated.

If my memory serves the whole 12 volt 3000 watt inverter gold rush started after I joined this forum.
 
  • Like
Reactions: Dzl

Dzl

Perpetual Newbie & Unofficial Forum Librarian
Staff member
Moderator
Joined
Dec 10, 2019
Messages
4,778
I can't prove it but I suspect that when the lower end of the market started having success flogging 3000 watt inverters, the rest of the market was forced to follow suit.
Losing a sale to a competitor makes them stronger and you weaker.
This could be, I wouldn't be surprised, also with the explosion of 'vanlife' and related trends of people building DIY camper/vans/busses etc, I imagine the 12V market has expanded considerably, and many of these people dont really have much knowledge or awareness of the systems they are designing, which I'm sure leads to more demand for high power at 12V.

But on the other hand, I think Victron has roots in the Marine world going back a good ways, and 12V has been common in that world too.

3000 watt 12 volt inverters are the super size option of the inverter market, they look like a good value proposition to first time buyers.
That being said I'm sure there are use cases where a 3000 watt inverter at 12 volts is indicated.
To me, its the far upper end of realistic @ 12V. Definitely beyond optimal, arguably beyond sensible in most cases, but not yet outside the realm of reason if that is where your priorities lie.

2000W @ 12v seems like a more realistic upper limit. And even then after accounting for inverter inefficiency you are looking at upwards of 200A, so even ~1500W could arguably be considered a reasonable top end for 12V.

But I think its also important to consider that, many people size their inverters to exceed what they expect to actually use, and just want to build in some margin for error, etc. In this context, is where I see a high power 12v inverter being semi-reasonable, if you have other compelling reasons to want to stick to 12V, and maybe only intend to use 2/3 of that max, but would rather oversize than undersize. Of course oversizing carries a cost penalty, beyond just the cost of the inverter.

I think you are right though, the bread and butter of the high power 12v market is new and uninformed buyers, attached to 12v due to familiarity (and often pre-existing 12v components/systems) but wanting unrealistic amounts of power. The good ole' 200W of solar paired with a 5000W 12v inverter builds :D
 
Top