Solar charge controller

[Shadow Catcher]

OK I screwed, I did not do my home work to the extent I should have and how often do I say do your homework.
This is going to cost. The 180W solar panel I have is made for a grid tie system and puts out too many volts for the charge controller that I have efforts in using a DC to DC converter have not succeeded so I am about to bite the bullet and buy a Morningstar MPPT controller. The deciding factor is that it will take up to 75V input which means I can in series add in the 20W panel and still stay with in parameters.
Has any one seen information on MPPT vs PWM real world performance?
PMW is pulse width modulation (traditional) vs MPPT, maximum power point tracking controllers are basically able to convert excess voltage into amperage.

[Nathan N]

I'm interested in the answer(s) as well.

Nathan

[dreadcptflint]

Here is a head to head video:

http://www.youtube.com/watch?v=QpL4RR0_QyM

I did a bunch of looking at controllers last year and I don't remember finding anything bad about MPPts other than the cost.

[bdosborn]

Here's some links to discussions regarding the Morningstar MPPT. Bottom line, its good for 10-15% increase in harvest, depending on the weather conditions. Its also one of the most efficient controllers on the market.

Linky 1

Linky 2

Linky 3

Don't feel bad, I had to upgrade my controller too after I added too much panel. I have the Sunsaver MPPT and its a great controller. I can plug it into my PC and log values as well as add a meter for it. Check the specs before combining panels. You want the maximum current to be the same for panels in series and the maximum voltage to be the same for panels in parallel. You probably can't combine your 2 panels with the same controller as my guess is they wont be a good match. But, you can parallel controllers so maybe you use the old controller for the 20W panel?

Linky 4

Bruce

[Shadow Catcher]

Thanks bdosborn, I will be calling Backwood today and ordering the Morningstar controller meter and data interface.
The next question will be concerning the use of temperature compensation with an AGM battery. I am going to try and find the answer on Wind&Sun and will do some more reading.

[bdosborn]

I have the remote temp. probe and the meter. The meter shows two temperatures - the temp at the controller and the remote temp. I bought the remote temp probe after I noticed more than 10F difference between the two values, even when I knew they should be within a degree or two. The readings settled down after I installed the probe and started showing more realistic numbers. The probe isn't a must have item but it will result in the best battery charging voltages. I waited to buy one till my wallet wasn't so empty and I'd found the best deal I could.

Warning! Having the meter is a nerd test. If you spend more than a minute watching the solar output in real time, you might be a nerd.


Bruce (Yeah, I failed the nerd test)

P.S. The controller has a load terminal where amperage is logged so you can monitor the amp-hrs going to a load. Its only a 15 A output but you could use it to track your energy usage if you can get most of your loads routed through it. It also disconnects the load when the battery voltage gets too low.

I use one of these to track my amp-hrs -


Trimetric TM-2025-RV. Between the Trimetric and the Morningstar, I can track amp-hrs in and out of the battery and the PV panel performance. Its like having an instant battery gauge. Much more accurate than using a voltmeter.

[Shadow Catcher]

I just finished the order to Backwoods for the Morningstar controller remote meter and I added in the meter bus and remote temperature sender. Now all I need is the trailer to put all the stuff in!

[bdosborn]