diy solar

diy solar

Want To Build Small Inexpensive System

MichaelK said:
An important point to remember in your power audit is that the inverter itself is a load, that needs to be included in the calculations. Inverter draws power just being turned on. How much depends on the brand/model. A general rule of thumb is that background idle is related to the quality of design, and the inverter size. Bigger inverters consume more power. Poorly designed inverters of a certain size consume more power then quality inverters of the same size. Most inverters publish their background idles. If they don't, that's a good reason to avoid it.

To help this thread along, I'll mention my own consumption numbers. In the winter, on days when I'm not there but the frig is on 24/7, I consume as little as 1.5kWh. In summer, when more cooling is required that's 2.5kWh. For you, to keep the frig running, some lights on, and a bit of TV, let's say you need 3.0kWh, or 3000Wh of electricity.

In Kentucky, I'd guestimate you get maybe 3sunhours in winter and maybe 5-6 sunhours in summer. Let's say your power goes off in the winter. If you need 3000Wh per day, and you get 3.0sh per day, then you need 3000Wh/3.0sh = 1000W of panels. You are better off at 24V for this much power. Charging at 25V minimum, you will max out at 40A, so a less expensive controller like an Epever Tracer 4210 will work for you. You can get 60-cell residential panels dirt-cheap. Wire four 250W panels 2S2P, and that 4210 controller will work just fine.

You could wire your existing batteries in series right now for 24V, but only 100Ah at 24V is still rather light. You might want to add a second parallel string of batteries in the near future as finances allow. If the batteries are not yet used, and they can be returned, it might be a better choice to upgrade to four 6V golf-cart batteries, such as Trojan T-105s. That would give you 250Ah of power at 24V, and a better size for 1000W of panels.
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Can you provide ball park cost for your suggestion? this will help OP to understand cost wise.
 
I think I'll let the idea of running the refrigerator go for now because what I already have seems like a mismatch for doing that. I'll just be running some lights, my wife's CPAP and sometimes a radio or tv.

Would the Epever Tracer 4210 that MichaelK mentioned be a good match for 325 to 400 watts of panels and a 700 watt inverter? I was also looking at a Rich Solar 40A charge controller.


 
HOU_Castle said:
Can you provide ball park cost for your suggestion? this will help OP to understand cost wise.
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Panel prices vary by region. I'm in a abundent sunlight area, which means panels are dirt-cheap here. I like 60-cell 250W residential panels, and over the last year or so I've bought them for 52$ each, 62$ each, 68$ each, and my last purchase just two months ago of 40$ each. I have seen prices as high as 80$, which I passed on. If you assume the buyer is in an area where the prices are more like 80$ instead of 40$ that means 1000W will run ~320$. That Epever 4210 is ~125$ on ebay right now, and Trojan T-105s ~150$ each. Four for a 24V system would be 600$. A quality 24V inverter I'd consider is Samlex's PST2000. That's running ~620$.
 
MichaelK said:
Panel prices vary by region. I'm in a abundent sunlight area, which means panels are dirt-cheap here. I like 60-cell 250W residential panels, and over the last year or so I've bought them for 52$ each, 62$ each, 68$ each, and my last purchase just two months ago of 40$ each. I have seen prices as high as 80$, which I passed on. If you assume the buyer is in an area where the prices are more like 80$ instead of 40$ that means 1000W will run ~320$. That Epever 4210 is ~125$ on ebay right now, and Trojan T-105s ~150$ each. Four for a 24V system would be 600$. A quality 24V inverter I'd consider is Samlex's PST2000. That's running ~620$.
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Plus: 24V batteries, cables/wires both (from panels to MPPT and from batteries to inverter), fuses, tools, etc.
 
I'm trying to learn but my mind doesn't absorb things like it did 50 years ago when I was in school.

I have a question, are rated load current and rated discharge current the same thing? Both chargers have 40A charge current but one has a rated load current of 20A and the other has a rated discharge current of 40A.

Tracer AN Series (10~40A) MPPT Charge Controller

EPEVER Tracer-AN adopts MPPT(Maximum Power Point Tracking)technology. This mppt solar charge controller capacity range from 10A to 40A.
www.epever.com www.epever.com
 
Some charge controllers have load output terminals on them, just for convienence. They are usually low amperage rated, and it's best to just ignore them completely. Wire ALL your loads so they come off the battery. Either DC loads, or your inverter.

There are really only three values to think about, the optimal and maximal amperage rating of your battery, and the maximal amperage rating of your controller. Traditional lead-acid likes charging best at ~ 1/8th of C, though some AGMs like charging at as much as 1/5th of C. The maximal discharge rate of your particular battery is likely to be the same as the maximal charging rate, but check with your battery manufacturer first. That's just a rough guideline.

The maximal amps that a charge controller can handle is the amps going OUT of the controller, into the battery. If your controller is PWM, then the amps going into the controller is what comes out. A more sophisticated MPPT controller transforms HIGHER raw solar voltage down to the voltage the battery wants to charge at, making extra charging amps out of the extra volts. Any extra volts just gets clipped off once the controller reaches it's max amperage. So, it will clip off any extra amps above 40 and just waste them as a bit more heat.
 
Ok, so when you see ratings on SCC's, that's usually listed in either Max Volts / Discharge Amps or just Amps. For example, a Victron 100/40 means you can put a maximum of 100v INTO the controller and get a maximum of 40 amps of DC OUT to the battery.

Other units will just list the amperage rating OUT to the batteries and you have to dig a bit to find the maximum volts input.

Some units have LOAD ports available to run small loads like lights and such. Many PWM controllers will only suppord about 5a or less, some units will support half the unit's amperage, and some will offer up to the rated amperage of the unit.

So as an example, I have a 20a Weize at the camp that can support 20a out of its load ports, and I have another unit rated for 50a that only supports 25a out of the liad ports. It's all a matter of how the manufacturer builds the PCB inside the controller.

They're pretty limited in discharge so it's really only useful for lights or (as I use them) a power source that can be set for a specific low voltage cutoff so you can prevent a device (like my ATV charging) from draining the main battery in long periods of krappy weather.
 
Rednecktek said:
Ok, so when you see ratings on SCC's, that's usually listed in either Max Volts / Discharge Amps or just Amps. For example, a Victron 100/40 means you can put a maximum of 100v INTO the controller and get a maximum of 40 amps of DC OUT to the battery.

Other units will just list the amperage rating OUT to the batteries and you have to dig a bit to find the maximum volts input.

Some units have LOAD ports available to run small loads like lights and such. Many PWM controllers will only suppord about 5a or less, some units will support half the unit's amperage, and some will offer up to the rated amperage of the unit.

So as an example, I have a 20a Weize at the camp that can support 20a out of its load ports, and I have another unit rated for 50a that only supports 25a out of the liad ports. It's all a matter of how the manufacturer builds the PCB inside the controller.

They're pretty limited in discharge so it's really only useful for lights or (as I use them) a power source that can be set for a specific low voltage cutoff so you can prevent a device (like my ATV charging) from draining the main battery in long periods of krappy weather.
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I wonder why they mislead users with falsely advertising their PWM controllers.
 
Rednecktek said:
Much like paying your IRS bill with gift cards.
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okay I gotta share a story along these lines,
I'm in line at a local drug store and the grey haired lady in front of me has a hand-ful of $500 gift cards - she wants to pay and activate the cards.
I know the cleak, he is part owner of the store, "he asks her do you have a reason to buy so many of these cards today"
"Oh yes I have to pay my taxes or I will be going to jail" she says to him.
He has his daughter take her aside and got the ladies' son on the phone to talk to her.
I thought wow, that store owner was hero of the year that day.
{Too bad the bad guy at the other end of this senario will face no consequences at all, and will go trolling for some other unfortunate soul.}
 
Orkeven said:
I wonder why they mislead users with falsely advertising their PWM controllers.
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Because they know you won't do your homework. Because they know you never get past the W/$ evaluation stage. Because they know you are too cheap to buy a quality unit from the company that stands behind their products. And because they know some US law. They have the right to name their company "MPPT Solar" and put that name on the product. Then they put on the product label "Charge Controller", which is perfectly legal, because it is a PWM controller.

Then they put it together next to each other on the outer case, so the uninformed reads "MPPT Solar Charge Controller".

But, as RNT mentions, by the time you find out you've been duped, the money transfer is complete, and it costs more to send it back to China for a refund then you payed for it at the start.
 
MichaelK said:
Because they know you won't do your homework. Because they know you never get past the W/$ evaluation stage. Because they know you are too cheap to buy a quality unit from the company that stands behind their products. And because they know some US law. They have the right to name their company "MPPT Solar" and put that name on the product. Then they put on the product label "Charge Controller", which is perfectly legal, because it is a PWM controller.

Then they put it together next to each other on the outer case, so the uninformed reads "MPPT Solar Charge Controller".

But, as RNT mentions, by the time you find out you've been duped, the money transfer is complete, and it costs more to send it back to China for a refund then you payed for it at the start.
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I was reading up about solar charge controllers and an author basically extolled PWM controllers as being foremost. In Nigeria, many installers (technicians) use the PWM to set up home units for their customers. I've never really attempted to learn much about solar energy systems until recently as I believe I can comfortably set up a minimal unit. Right now, what I have is a power box that came with a solar panel. I do not have access to the contents of the box but I have been able to experience cutting down electricity usage to essentials. So, for me right now, I want to simply set up something bigger that can provide more than what this provides, so I will be able to use those essentials some more, still minimalistic as I live alone.
 
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