200 watts of rich solar polycrystalline panels and 20a epever charge controller

[jonyjoe303]

You have the panels connected correctly for maximun performance. Connecting in series will result in better results with your mppt controller. The mppt controller converts the higher voltage into more amps to your battery.
There is a post with 200 watt panels, https://vanlivingforum.com/showthread.php?tid=41071 , that shows the difference between parallel and series connected panels. They got double the output by connecting in series.

In full sunlight you should be getting 10 amps when the sun is overhead.  If your battery is going into absorption too soon especially in cloudy weather, you need to verify the battery voltage at the terminals (with multimeter) and bounce that with the mppt controller voltage on lcd screen. Both should be reading 14.4 volts.
All the solar controllers I used mppt and pwm were off, they all read .5 volt higher then what the battery read. This results in the battery never getting a full charge.
If your battery is only charging at 4 amps with solar and going into absorption then floating that might mean its not fully charging at the right voltage.

 

[XERTYX]

The 4 amps was when I initially hooked it up at 4pm with the battery fresh off of a charger. It was fully charged and in float. I was seeing 4 amps in to the battery but that was just the loads I was running (12v compressor fridge set to 27°F and a 5w usb fan). I need to connect some more loads to it, but I dont have anything else rn. I have an old inverter somewhere...

 

[PlethoraOfGuns]

Yes, as HDR said, there is some serious confusion going on here. With a MPPT controller, it doesn't matter if your panels are wired in parallel or series, the batteries will be seeing the same amperage from the same number of panels when there is full sun. At low light, the series method will make more power because the voltage will still most likely be higher than 12 volts and the controller can still be dumping some power into the batteries. That's the magic with MPPT controllers.

If it helps you to understand the electric wizardry, do the calculations in watts. If the two panels are making 140w wired in parallel at 18v, that's 7.8a going into the controller. The controller will step down voltage to 14v, the 140w will be 10a going into the battery. If the two panels are making 140w wired in series at 36v, that's 3.9a going into the controller. The controller will step down voltage to 14v, the 140w will still be 10a going into the battery.

Yes, the higher voltage of series setup will make less amps, but the volts are also higher. The wattage is the same across the board, across the different voltages. Sometimes it's better not to use amps as a reference when talking about different voltages.

 

[XERTYX]

Yeah that's one reason why I went with series. Yesterday was cloudy all day. I was seeing 14v at 1030am. There was almost no light, no direct sun all day and it got fully charged. Still running my fridge from Friday.

 

[PlethoraOfGuns]

Yep. If it was wired in parallel, you wouldn't be charging at all in those conditions. But series does thave it's downsides. But I think the upsides outweigh the down. But that might not be the case for everyone.

 

[XERTYX]

Yup. That was one reason I went with series. And also I used 10 gauge wire to replace the supposedly 10 gauge MC4 cables. So there should be practically no voltage drop from the panels to the CC.

 

[XERTYX]

At 10:15am. Just saying.








The thumbnails are upside down for some reason but just click on them.

 

[PlethoraOfGuns]

Right there is the math shown as a real life example.

 

[XERTYX]

Yup. It's not even 11 yet and it's almost fully charged. I've seen 9.7a to the battery but now its slowing way down cuz the battery is already up to 14.1-14.4v. A few clouds in the sky so its bouncing.

 

[PeterPiper]

So it's not easy to admit when you're wrong but.......

It seems I was wrong.

I have some research and information exploring to do.
Specifically, I'm apparently confused about the amperage available between series and parallel.
Since series increases voltage and parallel increases amps.

I think somewhere in here the law of conservation of energy applies and I must have missed the relevance or connection here.
My apologies to anyone offended.

I do know that my Xantrex PWM controller does a superb job of topping up my battey in my minivan.
And I've seen more than a few reviews on Amazon where people also said their Xantrex C40 outperformed higher end MPPT controllers.

Since I have a new Epever TRIRON 4210N MPPT controller on hand, I'm now going to move it to the car and do some testing.
I hadn't even considered it before.

Being wrong sucks.   But if learning and improving is the result.....

 

[PeterPiper]

However, I may not be totally wrong either.......
Actually, depending on your source, your goals, and especially your location I may be right after all
If nothing else, it seems that stating "MPPT is always better" is also incorrect.
I live where it's hot and sunny year round. This probably affected my initial opinion.

Another source.....
https://solarcraft.net/resources/articles/pwm-vs-mppt-solar-charge-controllers
PWM vs MPPT Solar Charge Controllers
► Comparing the Two
If maximizing charging capacity were the only factor considered when specifying a solar controller, everyone would use a MPPT controller. But the two technologies are different, each with it’s own advantages. The decision depends on site conditions, system components, size of array and load, and finally the cost for a particular solar power system.

► Temperature Conditions
An MPPT controller is better suited for colder conditions. As solar module operating temperature goes down, the Vmp1 increases. That’s because the voltage of the solar panels operating at their peak power point at Standard Testing Conditions (STC is 25C°) is about 17V while the battery voltage is about 13.5V. The MPPT controller is able to capture the excess module voltage to charge the batteries. As a result, a MPPT controller in cool conditions can produce up to 20 – 25% more charging than a PWM controller.

In comparison, a PWM controller is unable to capture excess voltage because the pulse width modulation technology charges at the same voltage as the battery. However, when solar panels are deployed in warm or hot climates, their Vmp decreases, and the peak power point operates at a voltage that is closer to the voltage of a 12V battery. There is no excess voltage to be transferred to the battery making the MPPT controller unnecessary and negating the advantage of an MPPT over a PWM.

► Array to Load Ratio
In a scenario where the solar array is large relative to the power draw from the batteries by the load, the batteries will stay close to a full state of charge. A PWM controller is capable of efficiently maintaining the system without the added expense of an MPPT controller.
► Size of the System
Low power systems are better suited to a PWM controller because:

• A PWM controller operates at a relatively constant harvesting efficiency regardless of the size of the array
• A PWM controller is less expensive that a MPPT, so is a more economical choice for a small system
• A MPPT controller is much less efficient in low power applications. Systems 170W or higher tickle the MPPT’s sweet spot

 

[PlethoraOfGuns]

It's ok to be wrong sometimes. If I had a nickel for everytime I was wrong, I'd be the next Elon Musk! This electrical stuff is confusing. I've been an electrician since highschool and it still scares me. I just want to help people understand it a little bit. Sometimes we get wrapped up in opinions, but this is a numbers game, leave opinions in your back pocket. Nobody is offending anyone, we just all need to slow down and ask more critical questions in order to understand this mess.

 

[XERTYX]

One of the things I found researching videos with this specific MPPT controller is that when the panel voltage is near the battery voltage it seems to mimic PWM charging.

In the video using an ebox-wifi com port dongle and the graphing software from his computer he printed a graph of his daily charging with a single 100 watt panel. When the voltage was at like 15 volts the curve on the graph seemed similar to the performance of a PWM controller. Once it was above 16 volts he saw true MPPT charging.

My last solar array was a teeny 20 watt array and a 10a PWM controller. On cloudy days I noticed the panel voltage wouldn't get to 14 or thereabouts until noon or 1pm. That was part of the reason I wanted to go series. Higher panel voltage on cloudy days so even though the amperage would be less due to the clouds the voltage would be high enough to charge the battery.

Another reason I wanted an MPPT controller is that i have an amateur radio license (ham radio) and I've read that PWM controllers create noise in the radio when its charging the batteries. Also the cheap PWM controllers often have a very inaccurate voltage display, and there do not seem to be a lot of choices of decent PWM controllers.

 

[XERTYX]

It seems like I'm now fully charged. Hella sunshine and I'm seeing 53 watts with my fridge cycling (45 watts) usb fan on max (5 watts) and charging a tablet (probably rated around 5 watts not sure) 12:36pm

Edit:

Maybe not quite. The fridge switched off as I posted that and I'm seeing 22 watts. So the battery is probably still in absorption.

 

[jonyjoe303]

If your running a fridge and the battery is getting charged up by 11 am with 200 watts I suspect the controller does not have an accurate voltage of the battery.

For instance I have a 365 watt panel and with cloudy weather its only putting out about 6 amps at 10 am, even if the clouds clear up and I get maximum amps from the panel (about 21 amps), the battery won't be fully charge for another 3 to 4 hours. It might get up to 14.6 volts (lifepo4) but it needs to go through the absorption, which takes at least an hour where it cycles back and forth from max amps to zero amps.

The controller has to hit at least 14.4 volts (with lead acid) stay there for a while (hours) then maybe go through the absorption where it will cycle back and forth for around an hour, then it will go to float. If its not doing this, it means the controller thinks the battery is full because of voltage drop.

Since you got full sunlight I would check the voltage at the battery terminals and see if you got the same voltage as the controller. If the controller is at 13.7 volts you should have the same on the terminals.


picture of my 220ah lifepo4 being charged with mppt/365 watt panel at 10am. The coulombcounter shows 93 percent  204ah (out of 220ah). On this picture the LED and the coulombmeter show the voltage at the battery terminals. The mppt controller voltage on the LCD screen was actually .5 volts off due to voltage drop. I had to raise the bulk voltage on the controller by .5 volts to compensate otherwise the controller would go to float too soon and battery never reaching full charge.

 

[XERTYX]

I thought it was nearly done. Displaying 13.9 and measured 13.96. I'm seeing 19.5w right now with a 5 watt fan running and a tablet charging.... actually tablet is full. I'll disconnect it.

13 watts with the fan on and tablet disconnected. So it's still in absorption at 1:12pm

9.1 watts if I turn the fan off. Still 13.9v

 

[XERTYX]

An interesting feature of the EPEVER charge controller....

It cycles thru PV voltage, PV amperage, temperature, battery voltage, etc etc etc.

It also displays PV Kwh. I would have assumed it would be a daily watt hour total but it's not. I thought I would mention that as I just noticed it's up to 0.5kwh measured since Friday afternoon around 4pm.

So in less than 48 hours and one of those days having been completely cloudy its generated over 500 watt hours of power. Pretty nifty.

 

[jonyjoe303]

when its reading 13.9 volts (terminals 13.96), its still in bulk trying to get back up to 14.4 volts. In absorption it would be reading 14.4 volts steady and the amps would be cycling back and forth from max amps where it stays for a few seconds then back to zero amps.
When in float it would be reading about 13.4 volts and charging at 1 to 2 amps (depending on what the voltage setting is) and the only thing that would happen is the amps would increase everytime you added a load.
The cloudy weather might be a reason it hasnt got to 14.4 volts. My battery also at almost 1 pm is still not fully charged, its right at 14 volts (7 amps charging) , but of the 7 amps , 3 amps are diverted to the laptop/lights.

 

[XERTYX]

Earlier today it was up to 14.4 14.1 14.4 and the amps were swinging up and down like mad. For the last few hours it's been at 13.8v and a steady 0.7a very strange. The battery is still under the return period. Maybe I killed it yesterday with no direct sun and a deep discharge after dark on friday trying to get the fridge down to temp.

 

[XERTYX]

So I'm at 13.9v I have been enjoying some cold because of the sun adult beverages. Anyway. Roughly 48 hrs 1 full day of clouds and 0.6kwh of power.


What was my point?! Not sure. But my beer is cold because the sun was out today. Maybe I'll return my 27DC battery. I have learned this much. . . I can run a fridge AND other loads on the rich solar panels. It's almost 5pm and I still have yet to pull more amps than the solar itself can power. Maybe I murdered a battery. I hope not. That was $100 but my next build WILL be more than 300w. Probably around 500w. Cuz I like using a rice cooker. Floating an electric heating appliance off of the sun seems super awesome.