MPPT Charge Controllers

[cal40john]

Originally Posted by Joe Simmons

Moreover, if you are using an MPPT controller with your panels wired in series, you will get superior low-light power generation.

As to the person earlier who has their panels in parallel- If you have a MPPT controller, why are you doing this?

Series(high voltage) is always more efficient(esp. in low light), if you can use it of course.

I don't think Chucksp ever got back with his real world test, but I questioned whether series wiring of panels has any gains in low light.

From #41 in this thread:
http://www.cruisersforum.com/forums/...r-42602-3.html


With almost any amount of light the voltage of a single panel rises to a level above that of the battery, so the battery would charge. The current output though is what decreases significantly.

Diagram from:
Electrical Characteristics of Solar Panels or PV Modules - AltE

[sailorboy1]

Are we saying that solar panels operating at lower voltage (say 12 volts) instead of 18V, that the current does not increase for the same power output? We keep talking about current but the panels are rated in power. To make it simple for me are we just saying that solar panels are more efficient at the 18V and therefore provide more power at that voltage, and that the efficiency difference is like 30%?

[daddle]

Your understanding is correct. The chart shows that the current is somewhat constant for a given amount of solar energy. Since power is the product of current and voltage (W=VxA) it is most productive to arrange the load so the panel can produce the voltage at the peak power point.

[blahman]

Low-voltage panels (12-13) aren't a good choice for boats if wired in series as they will often not reach a high enough voltage to charge your batteries correctly. If you have 12v panels, it's better to wire them in series-parallel to have a 24v array that your controller will reduce to the appropriate level.

Voltage can be easily reduced, but it's tough to boost (without significant loss).

~Aaron

[witzgall]

Yep, and this is one of the reasons I installed 2, 24v panels on Jubilee. They are wired in Parellel, so 24v into the controller, and the controller "bumps" it down to 12v for charging. This way, if light is hitting the panels, they are doing something, and shading of one panel does not cause and issues. Also, with 6 gauge wire, coupled with the lower amps of 24v, we are loosing less current in the wiring.

The other reason I installed 24v panels is that we have a Torqueedo 24v dingy motor, and I wanted the option of charging that from the panels in the future, with a mod in the wiring to divert to the dingy battery and a flip of the output dip switch.

Chris

Originally Posted by blahman

Low-voltage panels (12-13) aren't a good choice for boats if wired in series as they will often not reach a high enough voltage to charge your batteries correctly. If you have 12v panels, it's better to wire them in series-parallel to have a 24v array that your controller will reduce to the appropriate level.

Voltage can be easily reduced, but it's tough to boost (without significant loss).

~Aaron

[Larry]

I am only running 170 watts of panels. I use this mppt controller and it works great. It's limit is 15 amps though. I also mount it on a chunk of aluminum for better cooling and longer life.



List Price: $278.00 Our Price: $232.75 Save: $45.25 (16%) Model: SUNSAVER MPPT Brand: Morningstar Corp


What I like is that it has a modbus serial port output to your pc so your panel performance is logged constantly with free software from the company.

I run my panels in series for the reduced voltage drop and slightly better performance. But this is not a huge gain in performance.

Cheers
Larry

[Yohelah]

Originally Posted by richardhula

...cope with these higher input voltage to charge 12 volt batteries - I'm curious

Outback MX60 will accept up to 160VDC. We have one with a 24 volt array, 3 sets of 12 v panels in series-parallel. Works great, you start charging earlier in the day, and it's more efficient. This configuration allows us to use pairs of solar panels of different size.

Rob
Yohelah

[Tellie]

A little thread drift and quick quiz for you MPPT whiz kids. Every now and then I get stupid. I usually shut off all power when I leave the boat. I forgot to do this about three weeks ago. I had shut off the breaker from the panels and the batteries went dead after a week. I thought all I had to do was turn the breaker back on and the panels would take over and start re-charging the batteries. No such luck. My Blue Sky MPPT was showing nothing, no read out nada. I checked the input at the MPPT and got a strong 18+Volts from the panels, but nothing coming out and going to the batteries. For two days I figured my MPPT was shot. Any guesses as to why I was wrong?

[colemj]

Originally Posted by blahman

Low-voltage panels (12-13) aren't a good choice for boats if wired in series as they will often not reach a high enough voltage to charge your batteries correctly. If you have 12v panels, it's better to wire them in series-parallel to have a 24v array that your controller will reduce to the appropriate level.

Voltage can be easily reduced, but it's tough to boost (without significant loss).

~Aaron

This isn't correct. Nominal 12V panels have an actual output of 17-18V. Also, solar panels are constant voltage devices and will reach their voltage output rating as soon as light hits them. The amperage is the variable output. Any panels wired in series will have a voltage output equal to the sum of the series. Wired in parallel, the output voltage will equal that of a single panel, but the current will be additive.

It is just as difficult to reduce voltage without significant loss as it is to boost it. The same electronics are used for both purposes. However, it is easier to convert voltage to extra amperage than to boost voltage without losing amperage

Mark

[senormechanico]

Tellie,

The Bluesky runs on battery voltage, not panel voltage.
The quick and dirty way to recharge from solar in that case would be by jumping solar + to battery + .
I don't think you would need to jump solar - to battery - as there's a shunt in the electronics on the - side.

Of course, you would need to monitor your battery voltage while it's in this "manual" mode.



Steve B.

[Tellie]

Originally Posted by senormechanico

Tellie,

The Bluesky runs on battery voltage, not panel voltage.
The quick and dirty way to recharge from solar in that case would be by jumping solar + to battery + .
I don't think you would need to jump solar - to battery - as there's a shunt in the electronics on the - side.

Of course, you would need to monitor your battery voltage while it's in this "manual" mode.



Steve B.

Bingo!
...and I was a commercial electrician for years. It took me two days to cave in and finally pull out the manual and read it. I was about to order a new one. Sometimes I feel so foolish.

[mtnsapo]

Hey guys! Great discussion! I have a quick question. As long as the combined input power/amps/voltage of the combined system is not over the specs of the mppt controller, can i hook up my wind gen to the same mppt controller? I am thinking of the blue sky 3024 and have 310 watts of solar and a wind generator. Can I plug this all in on the same input terminal?

thanks!

[witzgall]

No, you cannot do that. Blue Sky will tell you so either in their manual or if you call them. As I understand it, the voltage of a wind generator changes so much as the wind speed changes, that the controller can never get a good read on the Maximum Power Point, which is how they do their magic.

Chirs

Originally Posted by mtnsapo

Hey guys! Great discussion! I have a quick question. As long as the combined input power/amps/voltage of the combined system is not over the specs of the mppt controller, can i hook up my wind gen to the same mppt controller? I am thinking of the blue sky 3024 and have 310 watts of solar and a wind generator. Can I plug this all in on the same input terminal?

thanks!

[senormechanico]

Think of the MPPT controller as an automatic transmission on a car.
With a wind generator, you're constantly changing the available power and the controller must constantly be "changing gears".
They're not made to do that as quickly as the wind load changes (in most areas).
The power available from the sun is generally more constant.

[Extemporaneous]

Originally Posted by senormechanico

Think of the MPPT controller as an automatic transmission on a car.
With a wind generator, you're constantly changing the available power and the controller must constantly be "changing gears".
They're not made to do that as quickly as the wind load changes (in most areas).
The power available from the sun is generally more constant.

Wonder if you could run it into a capacitor and then somehow bleed power off the capacitor more evenly. It would still have to adjust up/down so as not to go outside the capacitors capacity. Perhaps it would take enough oscillation out of it so that an MPPT controller could cope??

Anyone?
Extemp.