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diy solar

Help on skoolie build

I found a chart, it mentions nominal voltage and explains how to setup your system. My panels don't mention nominal voltage but did have Voc listed. The chart showed a Voc of ~38 is typically listed for nominal at 20V. The article says 20V can charge a 12V system just fine or if using 2 in series with an MPPT a 24V system.
Since it was suggested I use a 2s5p panel setup I was wondering why the suggested 3s2p battery setup instead of 2s3p?
Ok, I understand what you are saying but here is an example of my controller just as an example.
It is a 24 volt/40 amp controller. I have it hooked up to a 24 volt battery config. My controller is "24 volts" but will allow up to 150 volts, 40 amps and 1050 watts of power. It does not matter if the panels are 12, 24, 36 VOC volts etc. My panels are appx 305 watts, 38 volts and 7 amps ea. I have 4 panels wired 2s/2p. This equals 76 volts and 14 amps but appx 1216 watts. Fortunately I can over panel my setup quite a bit without hurting it. So as you see, you could run a lot of 12 volt panels or less 48 volt panels and achieve the same results. Some configs may be more efficient but you could config a wide variety of arrays as long as you stay within your controllers parameters of max volts, amps and watts.

Wait, I just re-read your statement. Are you going to have a 12 volt system or a 24 volt system? You mentioned both.
My controller is a dual 12/24 controller. If I had a 12 volt battery storage config, I would still have limitations of 150 volts, 40 amps but only 540 watts.

Also a 2s5p that you listed above is 24 volts if you are using 10-12 volt batteries. Your 3s2p is 36 volts if using 6- 12 volt batteries?
To keep it at 24 volts it would have to be 2s3p.
 
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Did not see anywhere that charging off a 12v to 12v DC to DC was integrated. Maybe I missed that. Would it really matter to stay with 12 volt if that is not the case? There seem to be plenty of 12v / 24v refrigerators or at least appears a few with a Google search. With larger loads 24v would be a better option with what you are trying to accomplish.

Also if you are concerned about inverter efficiency, stick another panel up there if you can, to offset and run more items off the inverter. Less worries than trying to stick to 12v. If you are boon docking, get a few extra 100watt panels and make some portable panels to layout when you need them. Just throwing out options.
 
Went back and looked at previous posts.

We're going to be leaning pretty heavy on the inverter since my wife ideally wants AC (not likely I know), a fridge and freezer (5 kids), heating, an induction cook top and daily used blender.

Not to push you in a direction but think you are going to be pushing the limits of 12 volt. Just the induction cooktop could hit 1800 watts if you don't purchase the correct one and use a lower setting.
 
I am leaning away from the 12v and instead considering 24v, that's why I was asking about the battery setup going 2s3p instead of the suggested 3s2p. My math was showing 24v and 36v respectively. I was wondering if there was a reason for the 36v recommendation? Perhaps some hidden factor I didn't take into account.
Also how do you determine in line fuse size? My research shows that you can either do an inline fuse (with up to 2 series panels) or a combiner box (recommended 3+ series panels) but still no one says how they figure size. For the most part it looks like total watts/10 (round up) but I don't see anyone actually saying so.
 
I am leaning away from the 12v and instead considering 24v, that's why I was asking about the battery setup going 2s3p instead of the suggested 3s2p. My math was showing 24v and 36v respectively. I was wondering if there was a reason for the 36v recommendation? Perhaps some hidden factor I didn't take into account.
Also how do you determine in line fuse size? My research shows that you can either do an inline fuse (with up to 2 series panels) or a combiner box (recommended 3+ series panels) but still no one says how they figure size. For the most part it looks like total watts/10 (round up) but I don't see anyone actually saying so.
Yes, you should consider 24 volt instead of 12. You will have more room to grow and more power top produce with one system. As far as fuse size, fuses protect the wire so how large of a inverter you going to have? How many watts will you be pulling at one time? That will tell you your fuse size.
 
@Arkangel111 Are you considering a DC to DC converter also? There are 12v to 24v converters so you could go with that also. From your chassis battery 12v to the house battery 24v. Not sure if there are any 48v out there. Never looked.

I say go 24v and don't look back.
 
I am wanting a DC to DC converter. I haven't looked into 24V options though. Also, I originally purchased a 12V pure sine wave inverter but I am returning it since I am going with the 24V system instead, if anyone has some good recommendations I can look into? it looks like the Watts from solar should be 2400 if my math is right so what size fuse 250? that seems like an awful big fuse to me, but maybe I'm wrong.
 
I am wanting a DC to DC converter. I haven't looked into 24V options though. Also, I originally purchased a 12V pure sine wave inverter but I am returning it since I am going with the 24V system instead, if anyone has some good recommendations I can look into? it looks like the Watts from solar should be 2400 if my math is right so what size fuse 250? that seems like an awful big fuse to me, but maybe I'm wrong.
Fuse size between solar panels and controller or between inverter and batteries?
 
Solar and controller. Though I do need to figure out the size between battery and inverter also.
 
The fusing between the solar array and the controller is going to depend on the configuration, ie 2p5s, 3p3s, etc.
 
Solar and controller. Though I do need to figure out the size between battery and inverter also.
Fuses protect wires so the fuse size needs to be sized for the wire. So the first calculation is the wire size.

For the inverter you need inverter watts divided by system voltage divided by 85% inverter efficiency. This gives the max amps that will be pulled from the battery when the inverter is at max power. For example, let's say you have a 3000W inverter on your 24V system. 3000W / 24V / 85% = 150A. I would use 1/0AWG wire for that. The fuse size would be about 125% that max load size. 150A x 125% = 187A. Round that up to a 200A fuse.

For the fuse between the SCC and the battery you need to look at the max charge current of the SCC. Let's say you have a 100A SCC. I would use 2AWG wire for that. The fuse would be 100A x 125% = 125A fuse.

As stated, fusing the solar panel array depends on the panel arrangement and the specs of the panels.

it looks like the Watts from solar should be 2400 if my math is right so what size fuse 250?
How did you come up with 250A fuse?
 
Solar and controller. Though I do need to figure out the size between battery and inverter also.
Figure out what you are going to do now. What controller, how many panels will it accommodate. Battery storage setup. Inverter size. Once you figure those things out , then stop and think, will they all work together? Then come up with your actual list. Then you will be able to figure out wire size and fuse size.
 
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