How much power will a 50w 12v panel actually produce over the course of a summer day?

[SPL Tech]

I was thinking of getting the below listed 50w monocrystalline panel for use with my GoalZero Yeti 400. I was going to mount the panel on the top of my car to charge the Yeti 400 when my car is parked in a parking lot and I am away. Anyway, what I want to know is how many w/hr I can actually expect out of the panel over the course of a day. I know they only produce 50W at optimal sun angles, and most of the day does not represent an optimal sun angle.

http://www.ebay.com/itm/50W-Mono-Semi-flexible-Bendable-Efficiency-Lightweight-Solar-Panel-/271552580174?pt=LH_DefaultDomain_0&hash=item3f39cb8a4e

Does anyone have a link to a YouTube video or website showing real-world testing of monocrystalline panels and a corresponding graph so I can see how they perform over the course of the day?

[Sunking]

Depends on location, tilt angle, controller type (MPPT or PWM) and shade issues. The math is simple and You Tube is not going to help you. Assuming 0 degree tilt angle, PWM controller, Kansas City in July, and no shade issues can generate up to 6.6 Sun Hours x 50 watts x .5 efficiency for PWM = 165 watt hours. Same panel in December is 1.9 Sun Hours x 50 watts x .5 efficiency for PWM = 47.5 watt hours.

In practice for a parked car none of that matters because the battery only self discharges a few watt hour per day, and the panel will only replace whatever is self discharged at night like 3 to 5 watt hours. So a 50 watt panel for this is way overkill. All you need is a flexible 5 wat panel, a diode and plug into your cigarette lighter.

Any car with a good battery can sit a month without needing a trickle charger.

[SPL Tech]

The panel is not maintaining the battery, it's charging it. I have a 12v freezer connected to it which draws about 35 watts on and off depending on the temp. The panel is replacing the lost energy, and whatever it cant replace I will replace by chagrining it with the car at the end of the day.

And the math is far more complicated than you are making it out to be. The panel is not just on or off, it's in between with infinitely variable changes. As the light changes, the output changes. In December the sun might only be at an optimal angle for 1.9 hours, but there is still enough light to generate output for at least 8 hours. That is why I was asking for a test of someone testing a panel in their back yard or something. A flat roof on a car is not much unlike placing a panel flat on the grass in your back yard, and I have seen a few videos like that around, just not one testing a monocry panel.

Also, 50% efficiency for the voltage controller is awfully low. Even the cheapest eBay controllers are better than that.

[sensij]

I was thinking of getting the below listed 50w monocrystalline panel for use with my GoalZero Yeti 400. I was going to mount the panel on the top of my car to charge the Yeti 400 when my car is parked in a parking lot and I am away. Anyway, what I want to know is how many w/hr I can actually expect out of the panel over the course of a day. I know they only produce 50W at optimal sun angles, and most of the day does not represent an optimal sun angle.

http://www.ebay.com/itm/50W-Mono-Semi-flexible-Bendable-Efficiency-Lightweight-Solar-Panel-/271552580174?pt=LH_DefaultDomain_0&hash=item3f39cb8a4e

Does anyone have a link to a YouTube video or website showing real-world testing of monocrystalline panels and a corresponding graph so I can see how they perform over the course of the day?

It may not produce even 50 W at the optimum sun angle. 50 W is under test conditions that might never be experienced in the real world. Give PVWatts a shot... enter your location and the angle you want to put it at, and it will give you some idea of how much energy you would get out in a typical grid-tied system throughout the year. Using a PWM charge controller will kill the efficiency, but at least it represents an upper bound.

[Sunking]

The panel is not maintaining the battery, it's charging it. I have a 12v freezer connected to it which draws about 35 watts on and off depending on the temp. The panel is replacing the lost energy, and whatever it cant replace I will replace by chagrining it with the car at the end of the day.

And the math is far more complicated than you are making it out to be. The panel is not just on or off, it's in between with infinitely variable changes. As the light changes, the output changes. In December the sun might only be at an optimal angle for 1.9 hours, but there is still enough light to generate output for at least 8 hours. That is why I was asking for a test of someone testing a panel in their back yard or something. A flat roof on a car is not much unlike placing a panel flat on the grass in your back yard, and I have seen a few videos like that around, just not one testing a monocry panel.

Also, 50% efficiency for the voltage controller is awfully low. Even the cheapest eBay controllers are better than that.

Sorry but it is that easy. Isolation tables give daily averages from sun up to sun down. Yep it might be shining on your panel for 12 hours in winter, but you only get 1.9 Syn Hours in the day at very best with no shade issues. All Solar calculators and design work on this principle and very accurate. It is the basis of PV Watts and all professionals. You are confusing Sun Hours and daylight hours. At 0 degree tilt Roof on a car) in KCY with no shade you get 6.6 Sun Hours at very best in late June early July. in Winter 1.9 Sun Hours at best in December/January. The math is so simple a 5th grader can design a system.

PWM efficiency at best is 50% and that is over stating it. Any PWM controller turns a 100 watt panel into a 66 watt panel (66% efficiency just a know fact) Once you factor in 80% charge efficiency and wiring loses you are down to 50% at best. 66% with MPPT. Any more is just wishful thinking or lack of knowledge.

If you are driving daily then you have no need for solar what so ever. 15 minutes engine time will do more than a 50 watt panel can do in a week. Just size the battery correctly and let the alternator do the work while you drive. No need to spend money on something iffy and ugly.

[russ]

The panel is not maintaining the battery, it's charging it. I have a 12v freezer connected to it which draws about 35 watts on and off depending on the temp. The panel is replacing the lost energy, and whatever it cant replace I will replace by chagrining it with the car at the end of the day.

And the math is far more complicated than you are making it out to be. The panel is not just on or off, it's in between with infinitely variable changes. As the light changes, the output changes. In December the sun might only be at an optimal angle for 1.9 hours, but there is still enough light to generate output for at least 8 hours. That is why I was asking for a test of someone testing a panel in their back yard or something. A flat roof on a car is not much unlike placing a panel flat on the grass in your back yard, and I have seen a few videos like that around, just not one testing a monocry panel.

Also, 50% efficiency for the voltage controller is awfully low. Even the cheapest eBay controllers are better than that.

It is fun to blow smoke when you haven't the foggiest idea isn't it! Quit the youtube BS - that is a stupid platform where most posts are by clowns acting like they know what they are talking about.

[SunEagle]

I was thinking of getting the below listed 50w monocrystalline panel for use with my GoalZero Yeti 400. I was going to mount the panel on the top of my car to charge the Yeti 400 when my car is parked in a parking lot and I am away. Anyway, what I want to know is how many w/hr I can actually expect out of the panel over the course of a day. I know they only produce 50W at optimal sun angles, and most of the day does not represent an optimal sun angle.

http://www.ebay.com/itm/50W-Mono-Semi-flexible-Bendable-Efficiency-Lightweight-Solar-Panel-/271552580174?pt=LH_DefaultDomain_0&hash=item3f39cb8a4e

Does anyone have a link to a YouTube video or website showing real-world testing of monocrystalline panels and a corresponding graph so I can see how they perform over the course of the day?

If you look at the specs on that Yeti 400 they show a list of solar panels and the amount of time to recharge that 33Ah battery. Even the Boulder 90watt panel lists 9 -18 hours charging time. So that 50 watt panel will literally take "days" of good sunlight and will never put back what you discharge using your 35watt freezer. You might be looking at 200 - 250 watts to maybe do the job.

[Seahawk]

You guys are awesome. I love how the know it all's try and call you out and you put them in their place with your knowledge. Funny how they then disappear.

[SunEagle]

You guys are awesome. I love how the know it all's try and call you out and you put them in their place with your knowledge. Funny how they then disappear.

I don't try to "put people in their place". I like to educate people on what some of the advertised solar hardware really does in performance so others just don't go out and purchase it before doing some research.

I hate to have someone spend their hard earned money on something that does not performed as advertised.

I also hope that those individuals that we "enlighten" stay around more to learn and maybe provide support to others.

[Seahawk]

I probably worded that the wrong way. You can tell by the posts when someone thought their plan was right and found out the idea was right but they were going about it the wrong way. I also hope they will stick around and listen and heed the advice. I'm one of those who bought a cabin with a system that really wasn't setup properly and I've learned a lot from everyone on here. As you said it can save you a lot of money and headaches to be educated before you jump in head first. It's much appreciated the time that some of you spend replying and educating those of us that are still learning.