12v or 24v

[Rednecktek]

then it became an obsession.

I only have 3 solar systems... OK 4... I can quit any time I want! :D

Anyways, planning oversize if you can will reduce the wear and tear on components as well. I'm rolling a 24v system at my camp when I get home, should have enough overhead left to run a mini-split in the future too.

 

[KellyDood]

"1. We admitted we were powerless over solar — that our systems had become unmanageable...." https://www.aa.org/the-twelve-steps

 

[JWLV]

Solar is like tattoos. You say to yourself just one or two because all your friends have it. Then a few months later, you say just one more and that's it. And a year later, you'll want 6 more. And in 3 years time, you'll have 20 panels running 6000 watts and a face full of tattoos.

 

[joeExotic]

I started with a single 100 w panel and now I'm running a 600 w array with 12 v system. Thanks to the great folks and their knowledge on this forum. So yeah go BIG because you'll want more and you'll have plenty of things to charge. Now I want more power and want to convert to 24 v with the 40a CC that I have. I'm guessing I'll need more panels and something to convert 24v to 12v? Not sure. But yeah go BIG

 

[Scph9002]

i would say you only need to up the system voltage if your charge/discharge is a lot above 100 amp. Mostly for convenience but also cost and safety. You need quite thick and short cables and if any connection is not proper it will melt.. literally

1500 watt is about max i would go for a 12v system.

If you are planning on upgrading later on I would use a 48v system from start. 48 volt inverters and 48v ssc is not rare

 

[Scph9002]

I started with a single 100 w panel and now I'm running a 600 w array with 12 v system. Thanks to the great folks and their knowledge on this forum. So yeah go BIG because you'll want more and you'll have plenty of things to charge. Now I want more power and want to convert to 24 v with the 40a CC that I have. I'm guessing I'll need more panels and something to convert 24v to 12v? Not sure. But yeah go BIG

i started with 1 x 110 wattpanel and pwm 10 amp 12v ssc a random led acid car battery and 150watt inverter.

I now have 20x 335 watt panels and 100amp 48v mppt ssc. 30 kwh lifepo4 battery for 48v system and 2000watt inverter in house and 7kwh battery for 12v system and 1500watt inverter in a caravan. Mars to oktober im offgrid

My electric company dont like me going offgrid, they threathend with basically fines if i go offgrid.
Ironically they cant just shut up about green and fossile free energy. Its all greed. They would use human babies as fuel if it would be profitable and if they would get away with it. fuck them

I just "moved" and they cant fine me. I intend to "move" back in winter

 

[joeExotic]

Dang that's a lot of $$$. 30 kwh LFP batteries gotta be at least 8k. I don't know if I'll ever be able to do that but a guy can dream. Good stuff

 

[chrisski]

Dang that's a lot of $$$. 30 kwh LFP batteries gotta be at least 8k. I don't know if I'll ever be able to do that but a guy can dream. Good stuff

$8k is about three and a half years of Arizona electric bill especially cause Air COnditioning.

 

[joeExotic]

I've been to Arizona. Much hotter than Vegas. I had to walk around with a cup of ice in my hands.

 

[NwCali]

I'd only start with 12V if you have a reason to go to 12v myself. My barn has a 12v battery for the genset...but even then I went to 24v and then using a 24 to 12volt battery maintainer to keep the 12v genset battery good.

 

[quadna71]

I think it have a little better grasp now. When I first starting researching panels and the differences between 12v and 24v, I thought for a 12v system you’d use 12v panels and for a 24v system you‘d use 24v panels. Not sure why it didn’t dawn on me to just split the wiring to both parallel and series so that you are upping the voltage and not needing excessive wiring. Duh. Still not going huge on the wattage since I’m physically limited to the one side of my shed. Repositioning it isn’t feasible and I don’t want to have anything that is over the edge. I do get the reasoning behind everyone recommending to go big (or at least bigger) from the start and there is good value in that. But it’s just not in the cards for this go around. I’m trying to design the layout in such a way that I can upgrade down the road. Such as positioning the panels higher on the roof to allow for maybe another row below them some day. Thank you everyone that chimed in - your patience and tips are much appreciated.

 

[pollenface]

Not sure why it didn’t dawn on me to just split the wiring to both parallel and series so that you are upping the voltage and not needing excessive wiring.

I'd need a picture you understand what you mean.

If you are wanting to use 12 & 24v simultaneously from a 24v battery bank I think you will need to charge each 12v side of the battery separately or use some pretty heavy duty blocking diodes.

Personally I have a 12v 120ah battery sitting next to my 24v bank with it's own charge/load circuits for all 12v requirements.

 

[Hedges]

Well this is just for the roof of my shed, lights and garage door opener are likely the largest loads it’ll see, and the inverter will only be used occasionally to charge up my 60v lawn equipment batteries. I think I’ll keep it simple and stick with 12v. Man you guys are smarter at this stuff than I’ll ever be!!!

Garage door opener - what is the current rating on the motor?
Multiply that by 5x to get what starting surge is.
Multiply that by 120V to get the VA (like watts) your inverter is going to have to put out (for about a second).

Starting an induction motor ain't easy!

A 2000W inverter can probably run a refrigerator or a small window air conditioner. Maybe not a garage door opener.

 

[quadna71]

I'd need a picture you understand what you mean.

If you are wanting to use 12 & 24v simultaneously from a 24v battery bank I think you will need to charge each 12v side of the battery separately or use some pretty heavy duty blocking diodes.

Personally I have a 12v 120ah battery sitting next to my 24v bank with it's own charge/load circuits for all 12v requirements.

I meant that if I place 4 panels on my roof, then I would have the wiring paired and then combined. If the panels are “12v” panels, then I take the first pair and connect them in series and then I take the second pair and connect them in series. Then each of those pairs can be considered a single ”24v” panel and I can connect them in parallel. Does it not work that way? I see lots of drawings online that are like that.

This is a drawing Rich Solar shows on their website on connecting 4 panels like that.

 

[quadna71]

Garage door opener - what is the current rating on the motor?
Multiply that by 5x to get what starting surge is.
Multiply that by 120V to get the VA (like watts) your inverter is going to have to put out (for about a second).

Starting an induction motor ain't easy!

A 2000W inverter can probably run a refrigerator or a small window air conditioner. Maybe not a garage door opener.

The garage door opener is one that can be operated by a battery backup. It’s a little 7.2ah 12v battery that runs it but I can connect any 12v source to the opener’s 12v input leads and be good to go. I was going to just run it permanently by that method and not even bother with having it operated by the power inverter. I still might run wiring and install panels in various corners of the shed (and the ceiling over the garage door) in case in the future I am able to increase the AC capability, but for now the goal is to run most things by DC.

 

[Scph9002]

Dang that's a lot of $$$. 30 kwh LFP batteries gotta be at least 8k. I don't know if I'll ever be able to do that but a guy can dream. Good stuff

about 100usd/ kwh with shipping. was back in 2020-2021 when the lifepo4 cells where like 80-90 usd per 280-300ah cell excluding shipping.

Before the world vent to shit economically from war and covid

 

[Samsonite801]

One factor to consider about as well, is how many watts of solar you plan to run, and what your charge controller can support at different battery bank voltages.

Let's use Victron charge controllers for this example. If I look at the specs sheet for say, a Victron 150|35 (under 'Nominal PV power'), they show if using a 12v battery bank, the max solar input power it supports is 500w, where with 24v battery bank it supports 1000w, and 48v bank it supports 2000w (and see footnote 1a in bottom of chart)...

So there is another thing to think about when choosing on a battery voltage.




EDIT: Perhaps someone else already discussed this, I just now realized this was Page 2 and didn't read all the posts on Page 1 before making this comment. If so, please disregard...

 

[Rednecktek]

Such as positioning the panels higher on the roof to allow for maybe another row below them some day.

Just to throw the noodle out there, but you did play tetris with the panel layout to see if you could fit things better if you rotated different panels between landscape and portrait positions, right? There's no "Up" in rotation.

As for future upgrade, if you're running an MPPT controller, all you should have to do (assuming your panel voltage is already up there) is reset the SCC to be a 24v bank instead of 12v which can usually be done by unplugging it from the 12v and plugging it into 24v. Some models will have a Factory Reset button to reset the auto-detect, and some are done in settings. It should be in the user manual somewhere so you can figure it out when the time comes.

 

[pollenface]

This is a drawing Rich Solar shows on their website on connecting 4 panels like that.

gotcha, 2s2p

 

[12VoltInstalls]

I’m trying to design the layout in such a way that I can upgrade down the road. Such as positioning the panels higher on the roof to allow for maybe another row below them some day

I have 800W 4S2P and the highest I ever saw was 46A from the 50A charge controller- four panels face SE and SW respectively. 36-40A more common.
So technically a 40A charge controller could work for me. I went to the 50A because the Epever AN40 has max volts of 100 and the AN50 is good for 150VDC.

What I said that for is to show you how 800W works in real life.

I’d use a 12V battery system myself.

Also, compare your inverter and SCC costs to this unit. When I started solar I had a “survive” plan and was uncertain how far I’d be able to take it. Over four years offgrid now has enabled me to save thousands in areas like rent. If I’d envisioned my success at both putting money in the bank and improving my income I’d probably have explored an AIO like that unit. I may upgrade to it anyways.
Check it out. It may not be what you want or decide on but it’s pretty good for a small system imho