Why such low amps from 150w solar panel?

[jonshonda]

You guys are too much. Not going play your games any more.

Cruiserdrew, I went with US batteries cuz they are local and when compared to other 155ah batteries, are very competitive price wise and here is a local retailer, otherwise I would have gone with Trojans, which are very popular w/ camping and more expensive then US batteries. Feel free to provide pricing for batteries that compare in ah. I also chose Bogart because it provides the only accurate method for measuring charging and discharging via a shunt. Any other systems do that? Didn't think so. I am a data freak, and the Bogart by far surpasses every system w/ regards to data provided. I agree regarding panel size and charging capacity, but haven't needed more yet, and unless I do a 4-5 day cold weather camping trip, I don't know that I would need more unless it was overcast every day.

George_tlc. Its a 12v panel, and needs to provide more than 12v otherwise it wouldn't be very good at charging a 12v battery...would it? On a cold day your charge controller (if you have a battery temp monitor) should be pumping out way more than 12v. Actually, even on a warm day my deep cycle batteries like just over 15 volts to equalize. Does your charge controller equalize your batteries, or compensate for temp? Mine does, that is why they state 17 volt max.

 

[george_tlc]

You guys are too much. Not going play your games any more.

Cruiserdrew, I went with US batteries cuz they are local and when compared to other 155ah batteries, are very competitive price wise and here is a local retailer, otherwise I would have gone with Trojans, which are very popular w/ camping and more expensive then US batteries. Feel free to provide pricing for batteries that compare in ah. I also chose Bogart because it provides the only accurate method for measuring charging and discharging via a shunt. Any other systems do that? Didn't think so. I am a data freak, and the Bogart by far surpasses every system w/ regards to data provided. I agree regarding panel size and charging capacity, but haven't needed more yet, and unless I do a 4-5 day cold weather camping trip, I don't know that I would need more unless it was overcast every day.

George_tlc. Its a 12v panel, and needs to provide more than 12v otherwise it wouldn't be very good at charging a 12v battery...would it? On a cold day your charge controller (if you have a battery temp monitor) should be pumping out way more than 12v. Actually, even on a warm day my deep cycle batteries like just over 15 volts to equalize. Does your charge controller equalize your batteries, or compensate for temp? Mine does, that is why they state 17 volt max.

No worries, we're only trying to educate you. And, no it is not a 12V panel. It is a panel that is sized to work 'ok' with a PWM controller with a standard 12V SLA battery. The maximum power point (17 - 18V) is well above a fully charged SLA voltage, so it still will work better with an MPPT controller and give a net gain over direct connection via a PWM controller. The decision again is purely $/performance. MPPT controllers are getting cheaper - after all the extra electronics cost over PWM is maybe $10 in components for something in the 10A range and $15 for 20A.

Yes, my MPPT charge controller has the full range float/bulk/absorb etc cycles and is temperature compensated. It monitors/displays the charge voltage/current and amp.hours etc etc.

I know a little about solar charge controllers and how they work. I know a little about SLA charging. I go out camping for 2 week stretches or longer and do monitor what my MPPT controller is putting into my aux battery that runs my fridge etc. This versus the original PWM controller. Real world comparison in a camping situation with various weather conditions.

We aren't being argumentative just for the sake of it, we are just trying to inform you how an MPPT controller will provide higher charge even with a smaller panel (I run an 85W panel typically, folding dual '12V' panels in parallel, though easy to configure for series connection). This works well to keep an ARB fridge running day in and day out even in 100F+ day time ambient conditions.

Anyhow, the OP has plenty of info to figure out what his setup is or isn't doing. The rest is documentation for anyone else coming onto this thread to use to make their own $/performance decision.

cheers,
george.

 

[Cruiserdrew]

Jon-Let me remind you that you are making the categorical statements here. In case you've forgotten here it is:

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.

But your statement implies a lack of understanding, which is what George and I are trying to correct. You have an excellent, if very expensive system. That's great. It sounds like you were not finished making categorical statements:

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.

You could make the argument that your entire system is a "waste of money", given you could duplicate it's function with a $50 Morningstar controller and a couple of Costco deep cycle batteries. But you still have a nice system. You made the decision to spend the big $$ on a nice system monitor and a battery you didn't need, but others might choose to use an MPPT controller. It's all ok. There is nothing wrong with that. Your statement "worse than a standard controller because it draws power from your system to work correctly" is farcically nonsensical, and is both incorrect, and silly because all charge controllers use system power to drive their electronics.

PWM controllers are nice because they are cheap.

MPPT controllers are nice because they are a bit more efficient, and a lot more flexible (meaning you are not tied to "12 volt" panels.)

I could duplicate the function of your entire system with your current panel, a $50 Charge controller, $200 in Costco Golf Cart batteries, and a pair of $10 voltmeters from Ebay. So be careful about what is or isn't a waste of money.

Does your charge controller equalize your batteries, or compensate for temp? Mine does,

So my $50 Morningstar PWM controller will equalize, compensate for temp etc. I guess the point is, there are many ways to skin this cat, all good. Making categorical statements in this thread and others that are either wrong or misleading is probably not something you should do. The funny thing is, once you understand things better, you will agree with us! I hope you'll come back and post up.

 

[jonshonda]

I could duplicate the function of your entire system with your current panel, a $50 Charge controller, $200 in Costco Golf Cart batteries, and a pair of $10 voltmeters from Ebay. So be careful about what is or isn't a waste of money.

You guys are fun. I am questioning why they even make pwm controllers if the are such underdogs compared to mppt, and I wonder why so many people continue to buy pwm controllers? Educate me, in your own words how much more efficient a mppt controller is, during what conditions, and why. Also, tell me why I should trust you more than the people who engineer products for solar use. I guess I will be open to saying what I have researched isn't correct, but believing random people on the internet vs manufacturers written statements is difficult.

You might want to look up the specs on what exactly I am able to monitor and program with my system before you make such a categorical statement. No one would buy the system if it could simply be duplicated by $10 worth of equipment.

 

[george_tlc]

You guys are fun. I am questioning why they even make pwm controllers if the are such underdogs compared to mppt, and I wonder why so many people continue to buy pwm controllers? Educate me, in your own words how much more efficient a mppt controller is, during what conditions, and why. Also, tell me why I should trust you more than the people who engineer products for solar use. I guess I will be open to saying what I have researched isn't correct, but believing random people on the internet vs manufacturers written statements is difficult.

You might want to look up the specs on what exactly I am able to monitor and program with my system before you make such a categorical statement. No one would buy the system if it could simply be duplicated by $10 worth of equipment.

They make PWM controllers since they are cheap and simple. Basically a microcontroller and a large FET and some firmware. Simple to make, simple to program and cheap. VERY cheap. Most people are cheap, most people will just do what various manufacturers write. PWM are CHEAP to make - LOTS of profit in them. MPPT cost more and often can't be marked up by the same factor and still have a cost effective selling price. Consider... it is a lot easier for a manufacturer to state that a $100 (pick a number) PWM controller will do a good enough job than to convince folk that a $200 MPPT controller will provide better efficiency and return on investment.

An MPPT controller is much more complicated since it has a DC DC converter core inside and also a much more sophisticated algorithm that computes maximum power delivery in real time and adjusts the DC DC converter output to remain at the maximum power point of the solar panel. There are various algorithms in use, some proprietary some in the public domain/hobby to perform the tracking. The rate that the power point is tracked and output conditions adjusted is dependent on the hardware design of the DC DC converter and the algorithm. Some track in real time, some perform a 'sweep' every so often.

An MPPT controller will be MORE efficient whenever the operating conditions (sun, battery state of charge) would have the maximum power point power deliver about 5% higher power than if the panel was directly connected to the battery (as per PWM). That 5% is roughly what the MPPT controller losses are in the DC DC conversion. Simply put, the MPPT will attempt to extract the maximum power from the solar panel (with a 5% energy conversion loss). That 5% is not constant since the duty cycle of the DC DC conversion will vary depending on input/output voltage differential, so the converter can essentially go 100% duty cycle when the panel output drops (due to clouds etc) and so the conversion loss can go to essentially 0% at that point.

Do you understand how an MPPT controller can provide higher output power than a PWM controller and what the voltage vs current curve of a solar panel is?

We (Andrew and I) never stated a PWM controller is an underdog (with the implied negative connotations), it was you that stated an MPPT controller is useless for a smaller system such as 150W. We are saying that an MPPT controller is certainly not useless and will generally outperform a PWM controller. It is a financial decision whether to spend the extra $ on an MPPT based on the increased power that is provided for those $. For some, that money can be spent on a larger panel system - but for some that additional panel size/volume may not be a viable choice.

Again it was you that stated an MPPT controller requires power from the system and so a PWM controller is better. This is false, they BOTH require power from the system.

cheers,
george.

 

[Cruiserdrew]

PWM controllers are good. You seem to want to believe that we have been putting them down. That isn't the case, and infact I stated I mostly use my Morningstar PWM controller over my Chinese Ecoworthy MPPT controller. They work great. But in my hands MPPT controllers are 10% more efficient. Some have reported even more, especially in low light conditions.

As to why do people buy PWM controllers?-it's because they are a solid practical choice. They are cheap to buy and work great in the right circumstances. They practically give them away on Ebay.

The real question you should ask, is why does Bogart continue to use PWM circuitry? My guess is it's because they always have. They have a robust design, they are 100% familiar with it, and their customers love it. Why change? But there are other high end companies too-Morningstar, Midnight Solar, Outback, Blue Sky etc, and their upper end is all MPPT, mainly because they are designed to utilize larger more efficient panels that are "24 volt" or "36 volt".

Anyway, I'd recommend you borrow (or buy) an Ecoworthy or Epever MPPT controller to experiment with. They are about $100 on Amazon. Then do your own test and see which one provides more power to the battery during bulk charging. In a small system it isn't a big difference, but it's a difference that you will easily be able to see.

And one other thing to muddy the waters: When not in bulk charge mode, most MPPT controllers revert to PWM charging!

Regarding your system, I'm not putting it down. At all. It sounds like a great system. But not an inexpensive one. With regards to my hypothetical example of duplicating your system's function for much less-It's just a thought exercise/example. You give up the monitoring function of the Trimetric monitor, but you would have roughly the same amount of stored power ie functionality, for much less. Again, that's just another choice. Believe me if I had a huge system, with 1000 amp hours of stored capacity, and multiple $300 batteries, I'd have a monitor like the Trimetric. But in a small 160 watt system, and 300 amp hours of stored power that monitoring system is massive overkill in my view. But in your view, you need that. Cool. I monitor my 2 batteries with a volt meter. It's not as nice, or as accurate, but it's enough to keep tabs on our simple vehicle based systems.

Some additional reading with some posted data if interested:

Rubicon Solar Power Experience

Camp Solar Setup