12v or 24v

joeExotic said:

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

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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

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

joeExotic said:

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

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

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

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.

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.

quadna71 said:

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.

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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.

quadna71 said:

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!!!

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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.

pollenface said:

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.

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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.

Hedges said:

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.

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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.

joeExotic said:

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

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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

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...

quadna71 said:

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

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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.

quadna71 said:

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

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gotcha, 2s2p

quadna71 said:

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

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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

Fast forward 9 months and the only progress made is lighting and the battery. I bought 6 sticks (LED lights) that run on 110v and have so far installed two of them over the work bench. For the battery, I picked up an Anker 767 in July and intend to use it as a dual-purpose unit. For day-to-day use it’ll live in the shed and be the power behind that system and connected to panels on the roof. But occasionally it’ll be pulled to bring along on camping trips, beach trips, tailgating, etc. Seemed like the best fiscal decision for me to accomplish multiple uses. Now we can run crock pots while tailgating, the occasional short air conditioning stint in the camper (it has a soft start), and even run the pellet smoker on the beach. It will also negate the need for a solar controller and a power inverter in the shed. I already picked up two 10’ aluminum super struts from a local supplier for the roof as well as some quickbolt mounts for securing it to the roof.

Next is wiring the shed w/outlets and building a shelf for the power bank. The last piece of the puzzle will likely be the panels as well as mounting them up top. Slow going, but as it’s just a space for working on small side projects, I only a little progress at a time.

quadna71 said:

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!!!

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eventually you will want either a fridge for the beer...or a cooler for the wine racks... this takes more power... go with the 24.. charge controllers can handle more, wiring and cables are cheaper for the same size 24 volt system and if you go with a 1st tier MPPT solar charge controller it will handle the larger cheaper panels (60 or 72 cell units) like you can buy for your house. these means you can get used solar panels from any of the many sources and save moeny.

the realized savings between the cheaper wiring requirements, and the cheaper 9house size/style) solar panels will pay for the more expensive MPPT SCC. not to mention if you do decide as i suggested to get a beer fridge or a wine cooler you will have less issues powering them....

While I agree that more power-consuming items might come along, I don’t think they will be anything that is 24/7 consumption like a fridge or cooler. Those items are in the garage and my shed is mainly for storing stuff as well as a workbench for fixing things that break. It’s not even insulated so a heater or air conditioner won’t be happening either.

The portable power bank should replace the SCC as well as the inverter so at this point my only real decision is which panels and the final configuration of them.

I do have a sweet spot of input for the power bank. It can accept solar inputs between 11v and 60v. If between 11v and 32v, it will charge at a 10A rate. If between 32v and 60v it will step up to a 20A rate. Pretty sure I don’t need the faster 20A charge rate but if the higher voltages will make my solar panel choice decision easier then that is the route I will go. But I can’t configure it any way that would allow for greater than 60V at peak output.

I do like the idea of getting used panels for a cost savings. I’ve never looked into getting used residential panels. I guess I thought they might have been much higher voltage than I could use. Time to do a little digging - thanks for the ideas!

quadna71 said:

I do like the idea of getting used panels for a cost savings. I’ve never looked into getting used residential panels. I guess I thought they might have been much higher voltage than I could use. Time to do a little digging - thanks for the ideas!

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if it can do 60 volts then look for panels that put out 48~54 volts, that gives you some head room for when the panels are cold and put out higher voltage. that or do the actual math. all panels are different so you would need to get the specs off of the back of the panel and then do the temp offset calculations.