Any solar power experts around ?

[eryk2kartman]

Hi All,

Not strickly tree question but related
So i set up my small solar power station, i got kit from amazon - 20W solar power + controller, separately i got 2 7Ah gel batteries that i connected to increase capacity to 14Ah.
All looks good(sort of) controller shows 12.4V etc
so i hooked up some small 12v fans in the greenhouse for a test. panel is in sunny spot, fans are running full power.
The battery eventually died after while of 24h on time - i tried to test how long it last till battery dies - i hoped for full none stop power as they take only take couple of Watts.
So i disconnected load(fans) and tried to charge the battery, there is a setting on controller how low the battery can go with load - so i have that set up at 11.3V
so 3 days later battery still not charged - display on controller shows 11.8 now

So i thought something must be wrong, so i took my meter and started testing
1. The voltage provided by the panel itself is 18.3 V - GOOD
2. the voltage on batter is shown as 11.8V - same as on controller - GOOD
3. so checked the Amps now, with controller connected it shows 1.2A current which is the same if i connected panel directly to the battery- GOOD
4. when i connect panel to the controller without battery connected - it shows me current voltage as 14.4 V in the moment i connect the batter voltage goes down to 12.2V - dont know why ?
5. Last thing, looks like battery is not getting charged


I know its not very common question here but maybe someone had similar experience.
Appreciate any help on this,
My water pump is on the way and need to get this up and running quickly.

 

[Shibui]

Last time we talked you told us you did not want to know all the ins and outs. I believe you said you were happy to wing it and design by the seat of pants. How's that going?

Lower volt reading when battery is connected shows the battery is absorbing some of the energy That's fine and normal when it is not fully charged. No load V and battery V will only = when battery is full.

There are many different controllers. Some taper the current into the battery so the closer to full it senses the battery the less it allows in. This actually means the battery will never really be absolutely full and the last few % takes ages to put in.
Other controllers have different ways to control the charge and can do a better job but also usually cost more. Some also monitor battery condition and can do special charge/discharge cycles to maintain battery health.

Usual reason for batteries not keeping up is power out is greater than power in. 20 W panel may never produce 20W in the real world, only on the test bed under controlled conditions. Even a good panel will only produce rated power under the best conditions - clear sky, strong sun right overhead so max power is only achieved for a few hours each day unless you have tracking and will not achieve max power most days. Your figures show 1.2 A x 12.2 V = 14.64W - obviously way below 20W
All these things are normally allowed for when sizing solar system.
Battery size is also critical to allow for the power draw and expected solar insolation and for battery health. Undersize batteries wear out quickly by charge/charge cycles and even quicker when they are not fully charged. Oversize batteries do not get proper charge/discharge cycles and can also suffer problems.

 

[eryk2kartman]

Cheers,

Ahh what can i say, ive connected everything and it seems to be working, system is designed correctly, 20W panel should charge 14Ah batteries with no problem, but since i moved solar panel into spot with a lot of direct sunlight, so batter will get charged pretty quickly, now its showing around 13.4 on the display, no load at the moment.
Also did a bit more testing and researching my panel angle was wrong, even it looked ok, so i adjusted that as well and its better charging already.
I think panel can produce 20W, without controller in full direct sunlight on the meter it showed 20.4V with 1.2 A, i believe controller is the weakest part, might need to be change in future we will see
I will play with new panel position and see how it goes.


Thanks for advice.

 

[CourtneyGonzales]

I guess the time has come to give this thread a bump. I'd like to install a few solar panels to power my house, but I absolutely have no idea how to make it real. I'd be grateful for any help.

 

[Shibui]

I'd like to install a few solar panels to power my house, but I absolutely have no idea how to make it real. I'd be grateful for any help.

There are many companies down here that specialize in household solar design and installation. Most offer free advice and planning. I guess there are also businesses in your area that do the same. Just look them up and get expert advice from several different sources to see what options you have.

You will probably need more than a few panels to power the house. Check current power bills to find out how much you actually use in order to plan how much PV will be needed to offset all electricity use but you don't need to generate all your own power. We have 1.5KW of PV on the roof. We use way more electricity than that but the solar definitely reduces the electricity bills. I'll be upgrading soon and possibly adding battery storage too.

 

[ABCarve]

I had a 22Kw array installed last May and I’m still learning. The array is running my house and my studio. Pennsylvania has “net-metering”, which means when you produce more power than you use the power company banks those extra KW for you so you can draw on that when you use more than you make. Essentially the power company acts as a giant battery for your output. At the end of the year they buy any excess energy in your account at much lower price than you would pay for the same power, $.025. That leaves me with nothing in my account for the worst months of our cold, gray, short days of winter, so I’ll have some electric bills. Not good but I understand their position. I still have to pay monthly for being connected to the grid.
My array does not track. At the height of summer, on a clear day, the max I’ve seen it make was 16.3KW. Given net-metering and my current usage it’s a pretty good match (not much left over at year end). I figure the pay back is about 8 years.