best low light performance

For me it's only about total amp hour haul per day. Any solar I get will reflect that. Even if I full-timed off-grid, I'd only be interested in total amp hours.

bdosborn, I have a MH and don't have enough roof space to put anything but the most watts I can fit. I really don't get the purpose of the Unisolars despite the explanations, charts and graphs. Of course, it could just be over my head. I won't rule that out.

HiTech wrote:

Actually look at that spread all along the bottom. Those are days or portions of days that hardly get over 200 even mid day. They might matter a lot to some people.

The data is for a year: The spread across the bottom is winter, the data at the top is summer. We don't camp much in winter so we don't need panels optimized for that. So yeah, if you full time in your trailer, low light levels might be important. Me, I'll just tilt my panels or buy more. Like I said, I just don't have the roof area.

HiTech wrote:

And that narrow high density portion for a few hours after sunrise and before sunset? That is a *lot* of hours. That's why it is so dark.

It's not a lot of hours compared to the whole day. Like I said, it doesn't make sense where we live (sunny Colorado) to optimize our system for the shoulder or low light conditions. Not when the low light panels are more expensive and take up so much space. Of course YMMV.

Bruce

Hi,

Misleading information, panels intended for charging a 12 volt battery are never 12 volts. Very optimistic numbers. Even worse if pwm is used. MPPT has conversion losses of between 2 and 4%, and losses increase as input voltage rises.

harold1946 wrote:
Watts = amps x volts. cant have one without the other.
a 12 volt, 256 watt panel is capable of producing 21.3333 amps maximum.
12 volt, 460 watts will produce 38.3333 amps maximum.

harold1946 wrote:
Watts = amps x volts. cant have one without the other.
a 12 volt, 256 watt panel is capable of producing 21.3333 amps maximum.
12 volt, 460 watts will produce 38.3333 amps maximum.

So then what's your explanation as to how Tuna can get more amps in the shade and rain than I can with near close to 200 watts more in my panels combined?

bdosborn wrote:
Here's something else to ponder, take a look at the irradiance levels throughout the day. The 200W/m2 or less area under the curve is a pretty small fraction of the overall day. For where I live, it makes much more sense to pick a solar panel that is optimized for the irradiance levels during most of the day, rather than the shoulder hours at dawn and dusk.



Bruce

Actually look at that spread all along the bottom. Those are days or portions of days that hardly get over 200 even mid day. They might matter a lot to some people.

And tht narrow high density portion for a few hours after sunrise nd before sunset? That is a *lot* of hours. That's why it is so dark.

Jim

Watts = amps x volts. cant have one without the other.
a 12 volt, 256 watt panel is capable of producing 21.3333 amps maximum.
12 volt, 460 watts will produce 38.3333 amps maximum.

Harold

It has nothing to do with watts, foot print, charts, graphs or reviews. It has to do with amps and being able to meet our basic needs in all light which I can't do with the Scott poly or Canadian solar mono.

2x230 watts = 460 watts, which would give 195 watts more than 256.
2x 128 watts = 256 watts.
A 256 watt panel produces 256 watts at its peak output, no more.

If you know you are going to be in low light situations, it's best to prepare for them, don't ya think.

To me unisolar panels are not what's available in bright light but what you can get when the others get either too little to help or nothing at all.

You want to talk footprint. It would take four of my Schott poly 230w panels to get what Tuna gets in the shade with 256w. That's 920 watts and the controller to handle them in bright light at up to 15a each would be way too expensive not to mention I don't have the roof space.

I still may sell off my two panels and buy a pair of 128w or 144w Uni solar strips. They will provide for the 30-40 ah we use daily in shade or bright light and that means the Champ stays quiet.

Here's something else to ponder, take a look at the irradiance levels throughout the day. The 200W/m2 or less area under the curve is a pretty small fraction of the overall day. For where I live, it makes much more sense to pick a solar panel that is optimized for the irradiance levels during most of the day, rather than the shoulder hours at dawn and dusk.



Bruce