My First Solar Panel

[metrologist]

I bought a 100W solar panel off ebay (http://www.newpowa.com/v/vspfiles/downloadables/NPA/NPA100-12.pdf). I then bought an Anself CMTD solar controller based on a video I watched before the one below.

I'm not sure what I'm going to use this for, it was just an impulse after experiencing a camping trip with friends who had the 45W Harbor Freight solar kit. I thought this would be a better setup and hoped to use LiION cells. I might take an appliance - like a TV or computer - or maybe just a few room lights off the house circuit and put it on this solar system. We pay about $0.2/kWH.

The video explains that the charge cycle and voltage cutoff seem good for a 12V LiION system, except the controller goes into trickle charge with around 70mA. I was wondering if I just put a switched load of that amount on there it would more or less solve the issue (or a TV might even have that much standby load), or is it not that much of a concern?

[metrologist]

Too cheap?

Next, I have a lightly used Subaru alternator and one of those 48" shop fans that is destined to become a...windmill?

[metrologist]

The solar panel arrived today. I ran it outside at 7pm pointed at the sun with a DMM and was getting 22.4v and 2.94A direct from the panel. Inside in subdued lighting it was 10v and 100ma.

[metrologist]

This solar charge controller is disappointing because it seems they could just open up the settings and have a more useful product.

I mean, it seems to work as designed, but this particular model, the Li-ion version, has locked all of the settings except a timer, which I have no idea what use is a timer? What would I be setting?

The other versions of this controller let you set the PV and load on and cut-off voltage, and the battery type. The Li-ion version is fixed at lower values, and that sucks!

It may also have a problem because I've not been able to get current from the PV above a trickle, even when there is a 400ma load. One qualifier is that I am using a sealed lead acid battery until my Li-ion packs come in, so maybe the controller is doing what it should? I think that if the battery voltage is 12.6V that the PV is shut off no matter what the load is drawing. I need to play with it more to understand that.

Edit: I played with it more and hooked up a 3s RC li-ion battery pack. There wasn't enough sun to get a reading because the current reading for the PV is 400 ma lower than reality, so it was showing 0.0A. 

[metrologist]

I haven't been able to figure anything out.

I found an 11.1 V li-ion laptop battery that its own self test indicator shows 50% charge. It's been sitting for at least a year, but has more than 10V open circuit.

When the load is off, my DMM shows ~0.1 to 0.2 ma into the battery. Why would't there be more current into the battery to fully charge it? Maybe the battery is bad and wont take current?

The controller shows voltage jumping from 10.5 to 12.6V, and a battery bar indicator shows full with the last bar toggling on/off. That seems weird.

I turn on a 400 ma load and my DMM now says there is ~200 ma discharge from the battery; the controller voltage is jumping more rapidly in the range of 10V to 12.6, and the battery bar indicator is also jumping from max to min or in between... The controller also occasionally indicates some current from the PV, it can flash over an amp (1.2).

I'm confused. 

The PV alone measures about 22V open circuit and 5.8 amps short circuit. I'm happy as that seems like well over 100W, which is the panel's rating. I like that panel.

[fourtytwo42]

I think this is my point, if you just buy random things like this "charge controller" you have no idea what to expect it to do, maybe sometimes you get lucky and it does something you want it to do but I suspect often people are disappointed. At least if you design and build something from scratch you know exactly what its going to do and what to expect.

[metrologist]

My experience is not the same as Adam Welch from the video. Also, the video of the standard version did not behave like mine.

I can accept it being a questionable, cheap import product. I'm not sure it is just my own ignorance, however.

I appreciate the reply and as I now started looking at (equally suspect) MPPT units on ebay, I had considered how much more satisfying building my own Arduino based controller would be.

[fourtytwo42]

People never seem to get real with there expectations, IMOP 99% of the cheap stuff on Ebay is FAKE, it's churned out in some factory somewhere, not tested using fake components to a design copied from somewhere but not understood and altered to suit local supply and manufacturing issues and somewhere down the line somebody buys it expecting it to do something useful ummmmmmmm....................
If you want something that probably works find your LOCAL solar supplier with good old "made in the USA" or "made in the UK" stamped on it. I am a strong believer in you get what you pay for

[metrologist]

Yes, you mean like SunEdison or Solyndra? Our choices are somewhat limited and sharks are sharks after all.

I could not have built or bought a more bang-for-buck panel at least, and what I learn through this will be so much more valuable...

[james_s]

Laptop batteries are "intelligent" with internal control and protection circuits, you usually can't use them directly without either communicating with that control circuit or bypassing it. You can buy simpler protection boards for Li-ion packs.

I've actually had quite good luck with cheap ebay modules. Some of them are junk but most work as advertised.

[metrologist]

I continue to be horribly mystified by my observations with this solar controller. It seems like a popular model and can be bought on Amazon, so it has to be good, right (kidding)?

Maybe I have it hooked up wrong? I now have wired 3 individual 18650 cells in series to the battery connection on controller. These are good name brand cells.

I measure the load output voltage is ~12.6V and I connect a Wagan 150W AC inverter to the load and the inverter does not turn on.? I take the inverter inside and connect it to my variable power supply and it turns on with less than 12V, and will sound a low voltage alarm around 11V. I cannot figure out why it will not turn on with 12.6V from my controller? Perplexing to me...

I get a 400W inverter that has active cooling and it seems to work just fine on the solar controller, so I'm using that to draw about an amp.

My solar panel measures 22V and if I short it I get 5.85 amps, and I measure about an amp going into the controller. Everything is looking good, except the inverter occasionally trips off. I discovered that the controller often uses the power from the batteries rather than using the plentiful power from the solar panel, so the batteries are going dead.

I had this hooked up yesterday with passive loads and was getting 3amps from the solar panel and drawing as much into the loads. Now I am back to confusion and about to contact the controller seller.

[metrologist]

No more head banging. I just hooked up a 400ma load and I measure 200ma draw from the li-ion batteries. The solar panel is in full sun and was charging the batteries until I turned on the load.

The controller is either defective or just a bad design. I do not know which.

[metrologist]

I have a question about sizing my battery pack for this portable 100W solar panel, because I already bought a bunch of 18650 cells and I'm assuming I'll be able to find a suitable solar charge controller for them...

My area appears to get a 4.5 solar rating, meaning I can expect 450 Whr/day out of my panel.

The cells will be wired 3 in series and I am expecting to need 36 cells, or 12 parallel banks of 3 cells in series. That is with an efficiency derating of 0.8.

However, since this is a small portable system, I wonder if I should expect more like 1kWhr since the panel will track the sun and instead build 27 parallel banks of 3 cells in series? I can actually get 12hrs of direct sunlight now, but I could not find how much the solar energy is attenuated with the sun near the horizon vs straight up.

I know what you're thinking. I should just scrap that idea and buy a deep cycle FLA battery and another flavor of that cheap solar charge controller.

[fourtytwo42]

However, since this is a small portable system, I wonder if I should expect more like 1kWhr since the panel will track the sun and instead build 27 parallel banks of 3 cells in series? I can actually get 12hrs of direct sunlight now, but I could not find how much the solar energy is attenuated with the sun near the horizon vs straight up.

You don't say if your using one or two axis tracking, then you talk about straight up as if on an RV roof! well anyway here is a useful site for estimating the effect of trackinghttp://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php, otherwise the best angle to the horizon is the same as your latitude. I am lucky I have a 51deg roof slope and live at latitude 52deg north

[metrologist]

Wouldn't you use single axis like a German equatorial mount (oh, I guess you'd still have to adjust the elevation over the season)? The panel would always be perpendicular to the sun's rays. The pointing straight up comment comes from my dabblings in telescopes, where I remembered objects high up are brighter than when they are near the horizon because there is more atmosphere the light passes through. I guess the sun's light isn't attenuated very much.

If I can use that site properly, it looked like there is roughly 10% increase in using dual axis tracking vs optimal static placement. (although this wiki article indicates that sun at 30 degrees from horizon spreads the same light over twice the horizontal area of when straight above: https://en.wikipedia.org/wiki/Solar_irradiance#Absorption_and_reflection.)

When I was considering putting this panel on the roof to power an appliance, I was considering pointing it directly at the sun when overhead, but tracking on one axis to follow the sun slightly. I may not bother now.

I'll have enough batteries to build three 480Whr packs. I actually don't have much of a use for them now though.

Another thought I had was to buy another cheap lead-acid battery charge controller and use it with a small SLA, and then get a RC balance charger and run that off the load side to charge the bigger li-ion pack I described above.

[fourtytwo42]

If I can use that site properly, it looked like there is roughly 10% increase in using dual axis tracking vs optimal static placement.

That does seem quite a small gain but then for all I know your in Iceland or Antarctica

[metrologist]

OK, I picked Spain as that is about the same latitude, and it was ~25%.

[metrologist]

I found a description and joined that forum for more general answers about solar systems. I was wondering if my expectation for the equipment I bought are correct or not. Since my charge controller is not working the way I'd expect nor the way it's explained in the linked graphic, I need to do two things:

1. Figure out why, and that is the most important because it has strong influence on 2. If I find a manufacturing defect in my device and I can fix it, I will do so. If I cannot find a defect or failed part, I will have to assume there is something wrong that I cannot fix and it may be a design problem with the hardware or software, and that will make me avoid anything that remotely resembles the device that I already have... It may be better if I start a new troubleshooting thread in another forum if I need help on that...?

2. Find a suitable charge controller for what I want to do, and that is to use a 100W solar panel to charge Li-Ion batteries so I can have portable power for USB charging and an AC inverter.

I complained to the ebay seller of the charge controller and they sent me a link to a similar, but incorrect manual for the product. My complaint was reiterated and we will move from there.

Umm, yeah, the linky: https://www.solarpaneltalk.com/forum/solar/the-pros-and-cons-of-solar-energy/329053-charging-or-discharging-buying-or-selling