multi volt panels ?

Supervstech said:

Many microgrid inverters use overpaneling to achieve overall constant charging.
They often deal with strings of inverters.
With a single panel, the goal is to get as much wattage into the battery as possible, and undersizing a controller won’t do that. It will limit peak charging. And have zero impact vs a 10A controller on morning/evening sun angle, or shading…

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Thank you, you may be very much on spot on that info.
If I may just ask one question and then I will let this lie.
In your opinion, do solar panels produce advertised stated wattage in the real world? I am not saying could they but do they? I am not asking if it happens once with all the planets lined up perfectly in row in perfect conditions because that rarely ever happens. On an average do they produce what they are rated for in a general statement

GLC said:

Thank you, you may be very much on spot on that info.
If I may just ask one question and then I will let this lie.
In your opinion, do solar panels produce advertised stated wattage in the real world? I am not saying could they but do they? I am not asking if it happens once with all the planets lined up perfectly in row in perfect conditions because that rarely ever happens. On an average do they produce what they are rated for in a general statement

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Not even close most of the day, unless on sun trackers. It depends on how the panel angle is optimized in most cases, and the temp in the area. On hot summer days, the heat limits wattage by around 25% in early or late sun angles, wattage can be limited by 90%

Supervstech said:

Not even close most of the day, unless on sun trackers. It depends on how the panel angle is optimized in most cases, and the temp in the area. On hot summer days, the heat limits wattage by around 25% in early or late sun angles, wattage can be limited by 90%

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Thank you. I was just wondering how far my setups were out of wack. I am running 2 setups, 4 panels each rated at 305 watts each with a 40 amp controllers. At best case scenario at the best time of the year and at a specific time of day, I have only documented a 905 watt collection. That is an efficiency of only 74 %. I think from what I remember, best collection days were 4.3 kilowatts each side.

sunshine_eggo said:

This is a split cell panel. It's basically two 60 cell panels in parallel, thus the 120 cell count. The upper half is one panel and the bottom half is a second panel. These are more tolerant of partial shading.

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If you engineer your shade wisely.

Each PV array series/parallel configuration has various power/voltage curves, and some will trap a not-very-clever MPPT controller at a "peak" that isn't the highest available. The "half cell" panels which are effectively two parallel panels in one frame may be particularly good at that.

If you know where shade is coming from, how it will fall on panels, you may be able to select panels, orient them, and configure array for better results.

PV panels are normally labeled with "STC" wattage, standard test conditions of flash with 1 full sun and measure output while panel is still at 25 degrees C, hasn't heated up. They will produce that power under those conditions initially, and will degrade over time (exposure).

They may also quote a "PTC" rating, which is about what you will get under nominal field conditions.
On an occasional cold day they can meet or exceed STC output.

74% is a bit low. PTC and an efficient SCC or inverter ought to deliver between 80% and 90%.
Some panels have a lower PTC than others.
Most likely, you haven't had 1 full standard sun. Atmosphere containing things that obscure light. Sun's angle due to season passing through longer path of atmosphere.

Okay. You can stop fighting. I understand no panel gives the rated output. The panel will be on a van. I will only have room for one panel. So I'm looking for the highest watts I can get on a 12 volt system.
Using a charge controller to lower the voltage seems like there should be a loss to me. But I guess not. Thanks for the help.

Tired Old Man said:

Okay. You can stop fighting. I understand no panel gives the rated output. The panel will be on a van. I will only have room for one panel. So I'm looking for the highest watts I can get on a 12 volt system.
Using a charge controller to lower the voltage seems like there should be a loss to me. But I guess not. Thanks for the help.

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I apologize sir

In that case you care about what X-Y dimensions are available, and look for a panel that fills it (or two small panels if that fits better.)

Also, some panels are more "efficient", meaning deliver more watts per square meter. The highest of typical silicon construction will give 200 to 220 W/m^2. Early crystalline panels about 130 W/m^2. Some thin film about 60 W/m^2

An MPPT charge controller is best over a wide range of conditions (hot, cold, high or low voltage from panel), but it does have some efficiency loss when lowering voltage a great deal, like from 220V at panel to 12V at battery. For home use with long wires between PV array and MPPT we would say efficiency loss from MPPT is made up for by reduced IR drop in wire, but van is small so that doesn't count for you. Also, low voltage from panel like 16V from a "12V" panel on a hot day may not be sufficient to charge a 12V battery to 14V or 15V.

A PWM charge controller only delivers as many amps as the PV panel produces (unlike MPPT, it doesn't increase current when reducing voltage). So a "12V" panel that delivers 15 Vmp to 18 Vmp should be used for a 12V battery. There are some conditions where a PWM charge controller will deliver a bit more than an MPPT.

Panel flat on roof is good when sun is overhead, but if you need power in winter, you will get much more if panel can tilt toward the sun (on clear day). On heavily overcast day, panel facing straight up is probably as good or better.

I would suggest a "24V" panel which produces about 34 Vmp and an MPPT charge controller.
Or two "12V" panels connected in series. If you have to buy mail order, shipping is much cheaper for smaller panels that don't have to go by truck on a pallet (although $/watt of larger panels is cheaper.)
Check Craigslist and eBay for local sellers who might have what you need.

Tired Old Man said:

Okay. You can stop fighting. I understand no panel gives the rated output. The panel will be on a van. I will only have room for one panel. So I'm looking for the highest watts I can get on a 12 volt system.

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Physical space constraints are your biggest limitation. You might find you can "tetris" several smaller panels on the roof and get more total power. To insure you harvest maximum available power, divide panel power by 14 to determine how many amps the charge controller needs.

Flat panels perform particularly terrible in Winter. It's not uncommon for a flat panel to harvest only 40% in winter when compared to summer performance. You can offset this by designing a mounting system that can tilt, and/or carrying additional small flexible panels that you can quickly deploy - even hanging them on the side of the van can significantly improve harvest.

Lastly, a DC-DC charger is always desirable to insure you always have a means to charge.

Tired Old Man said:

Using a charge controller to lower the voltage seems like there should be a loss to me. But I guess not. Thanks for the help.

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There is, but it's typically very small, 2-3%. MPPT is a sophisticated DC-DC converter that can find the optimum PV voltage and current to deliver maximum power.

The prior "state of the art" in charge controllers was PWM. PWM works by shorting the panel to the battery, so you have to use panels of suitable voltage, typically 17-18V, and their performance is compromised because they're not permitted to operate at their optimal voltage.

MPPT can permit harvest of near 100% of the available power the panel can produce, where PWM permits only about 80% of available panel power.

Speaking of MPPT vs. PWM, there are a number of bogus "MPPT" controllers that are actually PWM. If you find a cheap MPPT, you've probably found a bogus one.

Will lists several reasonably reputable MPPT SCC on his site:

R

sunshine_eggo said:

Speaking of MPPT vs. PWM, there are a number of bogus "MPPT" controllers that are actually PWM. If you find a cheap MPPT, you've probably found a bogus one.

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Rule of thumb: if it has USB ports, it's PWM. I can't say I've ever seen a real MPPT for less than about $80 so that'll be another clue.

Change of plans. Currently looking at Four 100 watt panels. Still keeping it a 12 volt system. Can I spilt the output of the panels ?
Solar panels feeding two terminals (+/-) . Off of the terminals, one lead feeding a older Kodiak power bank. The Kodiak has a built in charge controller. A second lead off of the same terminals feeding a solar charge controller to a LiPo battery.
I see no problem with this. Am I correct this should work ? I would fuse each line at 10 amp.

Tired Old Man said:

Change of plans. Currently looking at Four 100 watt panels. Still keeping it a 12 volt system. Can I spilt the output of the panels ?

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No.

Tired Old Man said:

Solar panels feeding two terminals (+/-) . Off of the terminals, one lead feeding a older Kodiak power bank. The Kodiak has a built in charge controller. A second lead off of the same terminals feeding a solar charge controller to a LiPo battery.
I see no problem with this. Am I correct this should work ?

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No. The two charge controllers would "fight" over the solar panels. You need to have independent arrays attached to separate charge controllers.

If you had a suitably rated switch that swapped the entire array from one charge controller to the other, that would be fine.

New thought. Could I use the "Load" on the solar charge controller to charge the second battery ?

Tired Old Man said:

New thought. Could I use the "Load" on the solar charge controller to charge the second battery ?

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"Load" is the battery. It's essentially like connecting directly to the battery but with a circuit between them to disconnect under certain criteria.

You could use the load port to power a wide input DC-DC converter that outputs 13.8V - a good voltage for trickle charging and floating FLA/AGM/GEL.

sunshine_eggo said:

"Load" is the battery. It's essentially like connecting directly to the battery but with a circuit between them to disconnect under certain criteria.

You could use the load port to power a wide input DC-DC converter that outputs 13.8V - a good voltage for trickle charging and floating FLA/AGM/GEL.

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Why would I need a DC-DC inverter ? The load output would be going to a Kodiak power box. The old model. It has two different inputs for DC charging.

After doing more reading and then testing the "load" from the charge controller sucks. It could not power a 12 volt road pro oven.

Tired Old Man said:

After doing more reading and then testing the "load" from the charge controller sucks. It could not power a 12 volt road pro oven.

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You need to check to see what your load current amperage is on your solar controller. I have a EPever 40 amp solar controller operating in 24 volts but on the load side it is only rated at 20 amps at 24 volts. What is your amperage rating on your load side at "X" volts? Probably not enough to pull an oven depending on how many amps the oven pulls.

Nothing in the paper work says what the load is rated at. But it couldn't handle 144 watts. Mine is a 30 amp controller.