Why such low amps from 150w solar panel? (1 Viewer)

[ddeezenuts]

I have to admit that I am an electrical idiot however with that being said I recently built a portable solar generator. It has been cloudy/rainy for the past week so once the sun popped out today I broke it out to see how it performed. Needless to say I am stumped...

I have a renogy 150w mono solar panel (Renogy 150 Watt 12 Volt Monocrystalline Solar Panel) connected via 10/2 wire to a waterproof trolling motor quick disconnect (rated at 16A I believe) which allows me to run it through my box and into my EPEVER 20A mppt charge controller (Amazon.com : EPEVER 20A MPPT Solar Charge Controller Tracer A 2210A + Remote Meter MT-50 Solar Charge With LCD Display for Solar Battery Charging : Patio, Lawn & Garden). Now there are a couple of sae 10 awg quick disconnects in line from the panel to cc to allow me to disassemble to generator/wiring with greater ease.

Today, it's 73* and partly cloudy. I broke out the panel and placed in direct sunlight but a tree blocked about 50% of the panel. At that time I was drawing .7A (the most I have seen). I moved it a moment later into 100% direct sunlight and was drawing .3A and 22ish Volts.

Why am I not see higher amps? You may need more info from me so I will be happy to provide what I know. Thought I would ask though...thanks mud

 

[e9999]

well, did you have a significant load? Is the battery fully charged? If the latter, the panel will not produce much power besides what the controller needs and the trickle charge. Then you'd see basically close to the open circuit voltage and little current on the panel side I imagine. 22V Voc sounds about right for a "12V" system. And 7W (0.3*22) sounds reasonable for the controller and a tiny bit of charging. The MT50 shows 14.7V on the battery side so that's not in the trickle voltage range though but still only 6W (14.7 * 0.4) .
Try discharging the battery and test again.
What I'm saying is that the panel will only produce whatever energy the load requires, not more than that, and with the MPPT controller errr well... controlling stuff..., it may be little.

Then again, I'm an electrical idiot also...

 

[LandCruiserPhil]

The good is ~22v output at panel. A fully charged battery with no load will yield low amp reading.

 

[ddeezenuts]

The good is ~22v output at panel. A fully charged battery with no load will yield low amp reading.

well, did you have a significant load? Is the battery fully charged? If the latter, the panel will not produce much power besides what the controller needs and the trickle charge. Then you'd see basically close to the open circuit voltage and little current on the panel side I imagine. 22V Voc sounds about right for a "12V" system. And 7W (0.3*22) sounds reasonable for the controller and a tiny bit of charging. The MT50 shows 14.7V on the battery side so that's not in the trickle voltage range though but still only 6W (14.7 * 0.4) .
Try discharging the battery and test again.
What I'm saying is that the panel will only produce whatever energy the load requires, not more than that, and with the MPPT controller errr well... controlling stuff..., it may be little.

Then again, I'm an electrical idiot also...

No load and batteries mostly charged. Let me go and discharge them tonight to some extent and retry the next time the sun comes out and I will report back. Thanks for the info gentlemen

 

[Cruiserdrew]

You'll need to discharge quite a bit, which is not all that easy.

When I'm looking at output, I'll have the battery run a small compressor for 20-30 minutes, then leave it running when I hook up the solar panel. That should show you max output of the panel.

With charged batteries, there isn't much current flow, as you found out.

 

[Rwhat]

I see almost 5 amps with full sun on a renogy 100 watt with a renogy view star controller. It's hooked to my aux battery.

 

[george_tlc]

Any solar charge controller that isn't a total POS will taper the charge off to the battery as the battery achieves a full state of charge. If it doesn't then it is damaging your battery.

Trying to measure output from a charge controller to see if you are getting the most it and the panel can provide presupposes a very discharged battery. You also need sun hitting the entire panel (not with some corners/edges shaded by leaves/tall grass etc). Panel should be pointed straight at the sun. Not a hazy day. etc.

cheers,
george.

 

[jonshonda]

Disconnect panel from everything else and put a multi meter on the output wires to measure output. Also, there is zero need for a mppt controller, and it is actually worse than a standard controller because it draws power from your system to work correctly.

 

[george_tlc]

Disconnect panel from everything else and put a multi meter on the output wires to measure output. Also, there is zero need for a mppt controller, and it is actually worse than a standard controller because it draws power from your system to work correctly.

Measure exactly what??

A 150W panel will produce quite a bit more than 10A Isc (in full sun), most any meter on Amp range will have at most 10A capability. Fuse = poof. Measuring the voltage tells you nothing much other than the panel isn't open circuit somewhere.

As per the other thread, MPPT is technically WORTH it. The quiescent draw is a few mA (with no sun) and a PWM controller will be similar. Whether one wishes to spend the additional $$ of a decent MPPT controller versus a PWM controller is end user's choice - and that's a financial decision.

MPPT conversion efficiency is likely around 95% (for a reasonable design), that 5% loss is conversion loss AT the provided power level (depending on battery SOC). PWM will be quite a bit less efficient since it is not keeping the panel at its maximum power point, it can't.

MPPT becomes an even better choice if the panel you have as quite a higher voltage at its maximum power point since the DC DC conversion of the MPPT will give a better system output than a PWM that forces the panel voltage to be at battery voltage.

I assume you know how a PWM controller works versus the DC DC conversion of an MPPT controller and what maximum power point means?

cheers,
george.

 

[jonshonda]

Measure amp output. Not a very good chance at a 150watt panel putting out 10a. I had the exact panel OP did and in direct summer sun the highest I measured off the back of the panel was just over 7 amps. Ask someone who knows, and they "should" tell you that for a small setup like 150watt system, a MPPT is a waste of your money. I had a conversation w/ morningstar and that was the answer I received from them.

 

[george_tlc]

Waste of money doesn't mean it technically doesn't output more power. If you are out and NEED all the power you can get during an extended camping trip etc - then the 'money' is less of an issue versus the getting more power from the panel.

7A max from a 150W panel - umm, not if that panel is a 12V panel. I get at least 6A from an 85W panel... A 150W panel will certainly put out 10A+ in full sun - unless your full sun in at a high latitude...

Glad you got your answer from morningstar and are happy. I have both a PWM and MPPT controller that I've used on the SAME panel and MPPT puts consistent higher power into a somewhat discharged battery in the real world - camping a couple of weeks away from civilisation. Like I wrote before, the benefit of MPPT is when the maximum power point voltage is higher (the higher then better) than the battery voltage. Run a '24 panel' to reduce voltage losses in longer cables and MPPT makes even more sense - but that's a separate plus.

Many of us have been using solar for decades. Some of us even know a little about what we write about... I'd hazard a guess I've been using solar panels for possibly longer than the fellow at morningstar you talked to has been out of diapers

cheers,
george.

 

[jonshonda]

^george, maybe just look at the renogy link in the orig post before you argue with someone who owned the same exact panel at the OP and was able to measure its output. It states right on their spec sheet that optimum amp output is a little over 8, and that is a stretch.

This is what I love about the internet, people are more than willing to argue against OEM specs AND someone who has first hand experience with the item in question.

MPPT vs PWM

PWM vs MPPT Solar Charge Controllers | Solarcraft

More info, also indicating Morngingstar is one of the best in the business and might know more than you think george.

MPPT charge controllers vs PWM for very small systems?

 

[george_tlc]

Well, it's not a 150W 12V panel if the output is around 8A (Isc). That's barely a 100W panel. AND again, full output would need full sun at a lower latitude. Solar panel ratings typically assume 1kw/sq metre.

Isc will be higher than 'rated' output. Do NOTE that the 'rated' output is at the maximum power point (that is how solar panels are rated)...

I'd suggest that the 8A (at maximum power point) will likely be around 18 - 19V (typical for a so called 12V panel).

Hmm, 8A a 18V ~ 150W.

cheers,
george.

 

[jonshonda]

did you reference the link?

 

[Cruiserdrew]

did you reference the link?

@jonshonda - just for grins I did look at your links and unsurprisingly they agree with @george_tlc and myself. I think the disconnect is that you do not understand how either type of controller works and thus are giving erroneous information about misunderstood concepts that you read about on the internet. The fundamental thing I think you misunderstand is that the power generating capacity of a panel, varies based on the voltage at which it operates. So any panel with a PWM controller (since it's basically a fast on off switch) will operate at battery voltage, somewhere around 12-14 volts. The same panel if allowed to operate at it's maximum power point will typically run at higher voltage where it can produce 10-30% more power.

In the example of 12 volt panels the MPPT is usually around 17.5 volts. Only an MPPT controller can operate the panel at a different voltage from the battery. A PWM controller during a "pulse" connects battery voltage directly to the panel and so the panel has to run at a lower and less efficient voltage.

These differences are small (but real) in our small vehicle based systems, and only you can decide if it's worth double the price to harvest a few more watts off your panel.

I, too, have PWM and MPPT controllers, and have done the experiment with my 160 watt panel using a power meter. MPPT makes more power over time in virtually all conditions, but the PWM does well enough, and costs half as much. It's an economic decision which one to use. I suggest you repeat the experiment and decide for yourself.

 

[jonshonda]

You guys are too funny. Bogart Engineering is considered the best when looking at solar charging. Their SC-2030 system is one of the best and most well regarded systems used for home, camping, and expedition use. Guys who live off the grid and depend on solar charging for 100% off their power (not just weekend use) consider Bogart to be THE authority on solar.

Guess what type of controller they use and hundreds/thousands of customers depend on? PWM. Take a look at their FAQ, click on section C, then C1. It will explain their (American engineers btw) decision to use PWM vs MPPT. If you can honestly tell me after reading that info that you still feel MPPT is worth extra money over PWM, you cannot be helped!

Frequently Answered Questions - Bogart Engineering Click on section C, then C1.

 

[Cruiserdrew]

@jonshonda

You are misrepresenting what was directed at you. I don't think anyone said "it was worth it" or "not worth it" for that matter. Only that it was a choice you had to make based on how much you wanted to spend or if you want to maximize the output from your system.

You said MPPT was not needed. Some times it is. For instance, let's say you have a standard solar panel instead of a 12V panel. The VOC of a standard panel is in the 40-60 volt range. So if you tried to run that panel with a PWM controller, you would be forcing that panel to operate in a very inefficient voltage range(12 volts) and likely throwing away 1/2 or more of your panel's output.

I'll tell you I use the PWM controller most of the time because I like the charging profile better, and because I have surplus power off my panel. But if I was operating at the limit of the panel's capacity, I would use the MPPT controller to maximize the output of the panel. On my 160 watt panel, I see about 1 additional amp of charging current in similar conditions. So that's 1amp x 13 volts = 13 watts additional power harvest. It's about 10% more. (agreed it's not the 30% claimed by some).

I also get the impression that you are just posting things you read, vs actually having any knowledge or experience with what you're talking about. Have you ever used a solar panel to charge your truck battery in camping conditions?

So post up a picture of your system in use.

 

[jonshonda]

You forget the OP is using a 12V panel, so in this case there is very little/zero value for your money if choosing a mppt controller. Did you read the info in the link? Yes, I have done a lot of research on the subject (in this case reading), and get my info from people who know more about the subject then me.

My system is the Bogart Engineering SC-2030 and TM 2030, with a Renogy 150watt panel w/ 30ft of 8 gauge wire and two US Battery 12V XC2 155ah batteries wired in parallel for our Jayco 12HW camper. I run our water pump, heater, radio, lights, and fans off our system. I really don't need to get into battles over solar controllers, as you guys are correct, both will do the job. But as you will read in the link I provided from an industry leader, mppt might not be as great as most people "think".

 

[Cruiserdrew]

@jonshonda

I think it's ironic that you're making an economic argument for PWM and yet you bought needlessly expensive batteries, charge controller and monitoring system where a $50 Morningstar PWM charge controller and your DVM would have done the same job. IT isn't a matter of better or worse as you seem to want to play it based on your reading. It's just a choice based on your needs. I'm not biased either way, but can say based on my experience, that MPPT is more efficient. Only the end user can decide if the additional expense is worth it.

Your system sounds nice but "under paneled" to me. You have nice, large, expensive batteries and a max charging rate of 10 amps. So if 50% discharged, it would take 15 hours (about 3 days) of good sun to recharge your system. I'd add a second panel, or even switch to a 250-300 watt house type panel to get the best use out of those expensive batteries. But then you'd need an MPPT controller so nevermind...

 

[george_tlc]

Yeah, there seems to be a confusion by @jonshonda. The OP panel is NOT 12V, it has a maximum power point around 17V - typical of a "so called 12V panel". MPPT will work fine a most of the time provide better system efficiency than a PWM controller.

Andy & I have tried both MPPT and PWM. We have practical results that show MPPT provides higher overall power delivery (charge) to the battery (and that is what counts) versus a PWM controller.

He has stated and I have stated that the decision is a monetary one. There are many $100 or less TRUE MPPT controllers out there if you sort through the fake Ebay ones. They are proven to deliver better performance than PWM. PWM at its most can only connect the panel direct to the battery (that is what PWM does - pulse width modulation). It is clear from solar panel datasheets that current delivery from the panel will be LESS at 12 - 14V range than at the panel's maximum power point. Therefore it is clear that an MPPT controller will be putting higher current into the panel than if the panel was connected directly to the battery (that is what PWM does).

The choice for the OP and any other is whether to spend the money on an MPPT controller or a PWM.

cheers,
george.