To upgrade or not upgrade. That is the question.

[MountainmanBill]

I live in a forest. The opening in the canopy only allows for about two hours of direct sunlight on my nine 275-watt panels in the dead of winter. I also had ten 100-watt panels in the system but some very strong winds took down their not-so-strong support I made for them. They didn't produce much power anyway. Six or seven amps at best. I have 8 L16 400 Ah batteries connected for 48 volts. The most power I was able to produce in the dead of winter, on a clear day, was around 5,000 watts (with the 100-watt panels included). With the sun getting higher every day, a few days ago the system produced 8,000-watts that day (without the 100-watt panels in the system). The system was producing 40 amps during peak sunshine. So here's my question, and some thoughts:

Batteries can accept only a certain amount of power to charge safely. The battery label says their maximum charging amps is 70 amps. Is that 70 amps per battery or 70 amps per battery bank?

I was thinking of ditching the 10, 100-watt panels for 9, 300-watt panels. That would give me 9, 275-watt panels and 9, 300-watt panels in the system. And also adding another 8- L16 batteries to the bank for a total of 38,400 watts of storage capacity. I would have a lot more power to charge the batteries, but a lot more batteries to charge. Is it six of one and a half dozen of the other if I upgrade like I mentioned? The battery bank I have now just doesn't have the storage capacity to get much use out of it if I want to keep them above 50% SOC, which I do. I don't even like going that low. An electric heater kills the bank overnight. Doubling the bank's capacity would help a great deal in this regard but do I have enough sunlight to charge them fully during the day with the limited amount of sunlight I have? During the height of summer, I can only get about four hours of direct sunlight on the panels. The rest of the day is only indirect sunlight; filtered through the trees. Maybe 10 amps with the 275-watt panels, on average, for most of the day. I would get 20 amps, wouldn't I?, if I added another 9 panels. Double the amps but also double the batteries to charge. So is it worth it for me to add another nine panels and eight more batteries? Would I even have enough solar energy to recharge that big of a battery bank in a single day?
Thoughts?

 

[MichaelK]

It's 70A per series string. So, charging at 50V while in bulk, that means 70A X 50V X 1.175 fudgefactor = 4112W of panels.

Don't install the new battery bank until after installing the new solar. Chronic undercharging is what kills lead-acid batteries.

How far of a run in feet would it be to reach a clear unshaded area? Perhaps another alternative is identify a really sunny area some distance away, and run a high-voltage string to a high voltage controller. I myself have located a 120VDC array about 130' away from the controller, and I have no measurable voltage drop with standard 10 gauge wire. If you can give us some numbers, we can put something together for you.

Which brand/volt limit charge controller are you using right now?

 

[MountainmanBill]

2- Morningstar 150-volt MPPT Charge Controllers. The panels I have now have an Open Circuit Voltage of 37.6, Pmax of 8.27 amps. Batteries are L16's 400 Ah AGM's.

The panels are wired 3S3P (I think is the correct way of putting it). The array produces right around one hundred volts.

I'm very limited where I can place an array of panels. Anywhere I place them have a limited supply of solar power. Except one place that would destroy my view of the mountains beyond. I could, perhaps, located an array down the slope a ways but that wouldn't yield better results without having a solar tracker of some kind. But the bedrock on that slope is only about a foot below the soil so I would have a hard time anchoring any support for the array. So I'm stuck with what I have. A limited time with full sun.

 

[caki]

As you are asking for ideas, here is an out of box idea for you: solindra solar panels.
Their shape may give you more flexibility where to put the panels and they are also unidirectional what may give you a best harvest. Here a link

With a guy talking about it.

 

[rhino]

I could, perhaps, located an array down the slope a ways but that wouldn't yield better results without having a solar tracker of some kind.

Why would you say you need a tracker? How much total area is available to put panels in that area down the slope?

But the bedrock on that slope is only about a foot below the soil so I would have a hard time anchoring any support for the array.

You could use heavy ballast (even rock) to hold the array down and also adds guy wires to the array fastened directly to the bedrock if needed.

 

[MountainmanBill]

Why would you say you need a tracker? How much total area is available to put panels in that area down the slope?

Because the slope faces east and west. I could get either the morning sun, the noon sun, or the evening sun without a tracker. But the slope is about 150 feet away and wouldn't produce any more power than where I have them now. After thinking about it for a few days I think what I'm going to do is get the other nine panels and set them up close to the cabin. They won't get but a few hours of direct sunlight per day, but it's got to be better than what I have now. With full sun today I managed just over 7,000 watts with the nine panels that I have. I could probably get another three of four thousand watts with another nine panels. It is what it is. Thanks for all the ideas.

 

[Ampster]

I am in a constant state of upgrading. technology is moving very quickly. The challenge is to be near the leading edge and not the bleeding edge.
I would love to live in a forest, but my significant other wants to grow vegetables and is afraid of trees falling down. It took me six months to chop down two maple trees in the front yard that were eventually going to affect my solar production in winter. I did it myself with inexpensive electric chain saws.