diy solar

diy solar

Cabin in Big 5 country South Africa

Bushkey

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Joined
Oct 3, 2022
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Good day. My setups for my camps cabins as follow.

Victron 100/30 MPPT, 1X JASolar 265W 30.92Vmp pv connected to 4x Narada 12NDT200 batteries for a total of 800Ah. This setup powers 13x 12volt lights and a small pressure pump.

Victron 75/15 MPPT, 1x ACDC 180W 26.5Vmp PV conected to 3x Narada 12NDT200 batteries for a total of 600Ah. This setup powers 4x 12 volt lights, a small pressure pump and a energiser for my electric fence. Everything is 12 volt.

The cabins is within a private nature reserve that borders the Kruger National park. We typically do not stay longer than two nights, so the PV's has more than enough time to replenish the batteries. I know I am under panelled and could benefit from more PV. I am just unsure how much would be enough within the constraints of the MPPT chargers. I would ideally like to connect an inverter to make use of 220volt vans. That would put me firstly in a position to stay longer and secondly make it possible for me to go there outside of winter. It gets unbearable hot.

Cooking happens mostly outside on open fire. Water gets heated by gas geyser. Drinks and meat we keep cold with ice and a gas freezer. Water is provided from a borehole connected to a generator. We do not watch TV as we enjoy the outside and night sounds. I basically need lights, fans and electric fence. I know I can have a more efficient setup with the right panels. I hope to charge quicker basically.
 
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The spec sheet for the PV conected to the 100/30. If my calc are correct I can safely connect three in paralel for a total max amp output of 28A in perfect conditions. Should I go 4 as one hardly get 100% perfect conditions?
 

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Same reasoning applies to my 75/15. It seems 2 PV's for 13.58A would be perfect in ideal conditions but a third because one never see 100% ideal conditions.
 

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And then my other question, the one nagging me the most. Do I go PV in paralel for same voltage but higher amp or do I go PV in series for higher volts vs lower amp. What would be the advantage and disadvantage of both setups in a 12volt systems except for wiring?
 
You have a basic misunderstanding here. The amperage limits of your controllers are the amperages OUT, not amperages in. So, assuming your battery bank will charge at ~12.5V at maximal amperage, you'd expect to be able to wire together 12.5V X 30A = 375W of panels. But, panels are almost never putting out their rated output, so I normally include a 85% fudgefactor to compensate. So, that works out to be 375W/85% = 441W of panels.

So, two of those panels, facing due North would be too much for the controller. Maybe the controller will just clip off the extra amperage at noon, or maybe it will suffer some damage. I can't tell you what will happen with a lower end controller.

Here is one option for you that will work. Get a second 265W panel, wired in parallel to the first one, but face them in two different directions. One for example facing Northeast, and the other Northwest. That will tend to dampen the noon peak, but spread out charging over a longer period of the day.

With three panels, maybe one facing East, one North, and one West. Three of those panels all facing in the same direction will put out just too many amps for that low-capacity controller.

The other option is to just spend the money on a higher capacity controller.
 
You have a basic misunderstanding here. The amperage limits of your controllers are the amperages OUT, not amperages in. So, assuming your battery bank will charge at ~12.5V at maximal amperage, you'd expect to be able to wire together 12.5V X 30A = 375W of panels. But, panels are almost never putting out their rated output, so I normally include a 85% fudgefactor to compensate. So, that works out to be 375W/85% = 441W of panels.

So, two of those panels, facing due North would be too much for the controller. Maybe the controller will just clip off the extra amperage at noon, or maybe it will suffer some damage. I can't tell you what will happen with a lower end controller.

Here is one option for you that will work. Get a second 265W panel, wired in parallel to the first one, but face them in two different directions. One for example facing Northeast, and the other Northwest. That will tend to dampen the noon peak, but spread out charging over a longer period of the day.

With three panels, maybe one facing East, one North, and one West. Three of those panels all facing in the same direction will put out just too many amps for that low-capacity controller.

The other option is to just spend the money on a higher capacity controller.
Thank you. Yes I was thinking of going the Growatt 5000 route, but I need to consider a solution for my home and camper to. It is becoming costly quickly. So I will have to make due with what I have for my camp for now. Your advice is noted and makes sense, thx again.
 
You have a basic misunderstanding here. The amperage limits of your controllers are the amperages OUT, not amperages in. So, assuming your battery bank will charge at ~12.5V at maximal amperage, you'd expect to be able to wire together 12.5V X 30A = 375W of panels. But, panels are almost never putting out their rated output, so I normally include a 85% fudgefactor to compensate. So, that works out to be 375W/85% = 441W of panels.

So, two of those panels, facing due North would be too much for the controller. Maybe the controller will just clip off the extra amperage at noon, or maybe it will suffer some damage. I can't tell you what will happen with a lower end controller.

Here is one option for you that will work. Get a second 265W panel, wired in parallel to the first one, but face them in two different directions. One for example facing Northeast, and the other Northwest. That will tend to dampen the noon peak, but spread out charging over a longer period of the day.

With three panels, maybe one facing East, one North, and one West. Three of those panels all facing in the same direction will put out just too many amps for that low-capacity controller.

The other option is to just spend the money on a higher capacity controller.
As it is, those panels are facing pretty much due North. The one has little shading from a tree but the other one none. On both I can quite easily go one East and one West.
 

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Part of your limitations are because of the lower capacity electronics you have, and part of it is because you are sticking with 12V.

It depends on how much are you willing to invest in this system, and whether or not you can obtain better components. By switching to 24V, and buying a slightly larger controller handling 40A, you could quickly upgrade to a 1000W system. Doing the math with the 265W panels you already have, you could wire 4 of those panels in a 2S2P configuration and get.....

[ (265W X 4 panels)/25V charging] X 85% =36A of charging current at 25V.

This is going to be making you some real power. I'd expect at least 5kWh in December, and maybe at least 2.5kWh in June. So enough power to run a refrigerator in summer, and maybe year-round if it isn't too big. Maybe even more if you went with 2S3P and staggered the arrays facing NE, N and NW.

The serious "whole-home" electronics start at 24V, so you could put together a really spectacular system with some incremental upgrades. The real question is whether or not you can get better electronics at your location, and how safe they'd be when left unattended. There are ways you can continue to use your 12V items after switching to 24V. One option is inexpensive (well here they are) 24V to 12V DC converters.
 
And then my other question, the one nagging me the most. Do I go PV in paralel for same voltage but higher amp or do I go PV in series for higher volts vs lower amp. What would be the advantage and disadvantage of both setups in a 12volt systems except for wiring?
This question is one I also had for a long time and while each user's situation may dictate a more favorable series vs parallel vs hybrid S+P, this is what finally helped me better understand what's going on:

If you connect in series and your battery only needs 12.5 - 14.6V to be charged, the "excess" voltage (say PV voltage is coming in at 40V) is more or less converted into more amps. Not exactly and not with 100% efficiency, but that's the idea. Now with a 12V system and with an open voltage of a typical 100W panel being 20 or so volts, not a big deal. Our 400W system produces between 15.5 and 18V typically. 16v or above is fine, although cutting it a bit close and 15.5v or lower is likely too low for the charge controller to properly charge our batteries, but it's rare and only on cloudy days. If one could only flip a switch to go back and forth between parallel and series! I'm sure that could be wired, but probably at a greater cost than might be worth it and could be another part that could fail.

And of course series has the problem with partial shading of one panel, will affect all panels in that series string. But if you intend to stick with series (you don't expect partial shading ever and/or have a lot of cloudy days that could lower panel voltage), then you could then get away with smaller gauge wire for reduced cost of wiring and easier cable management.
 
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