MPPT Controllers

Your energy survey, either actual use or desired use, indicates what AH use on an average day? That number (times 1.5 or 1.75) determines battery size. Then comes necessary panels at 1 solar watt (or 1.5) per battery AH, then an adequate controller. Why are you going backwards?

I’d stick with the display type, and add a Victron BMV state of charge meter to gain a complete understanding of your overall systems operation... But I’m not clear on your controller inquiry... If you add a second controller to an existing system the problem that often occurs is the two controllers compete with each other (often called ‘dueling controllers’) due to conflicting output voltages... Better to just have one controller when possible, else do a kinda workaround and try say a single-stage type as a possibility to minimize dueling...Others may have some experience with this malady as well.

But when adding panels, attention should be given to having like kind output voltages, else the higher voltage panel will default to the voltage of the lesser panels voltage...A minor difference won’t matter too much - just saying...

I was referring to changing out the controller, and upgrading to MPPT...BMV meter already acquired...

Or like kind amps for serial panels.

I find the MS MPPT 60 reasonably easy to use. But like various small electronic displays it usually involves a learning curve.

If you went with Victron battery monitor I would go Victron controller.

I am very happy with my Morningstar. I opted for no meter display and it requires a computer connected to do the programming but I really like the programming so well worth it to me.

MPPT all the way. Buy some room for expansion. You need a larger controller.

“If you went with Victron battery monitor I would go Victron controller” I can agree with time2roll as well - since you already have the Victron BMV, the Victron MPPT controller would communicate with it and with the Smart phone App you’d have all the info you’d ever need at the tip of your index finger... Also, unlike my former old-school (but otherwise reliable) Xantrex Linklite, the BMV is ‘designed for’ LiFePo4 as well, and I’ve found it’s Li SOC tracking to be quite accurate...

3 tons

Thanks, everyone, very helpful. Good tip on the Victron controller... hadn't seen this one yet... thanks!

obiwancanoli,

I would get a larger amperage controller. Why buy more than you need? Large amperage controllers "stack" the active components. A 60 amp controller typically has 3 20 amp devices. As the solar harvest starts "low" in the morning, on a 60 amp controller, only 1/3 is active. That means it runs more efficiently and more amp-hours get stored. then at solar noon the input wattage is shared between all three segments--allowing each one to run below maximum capacity. In a 50 amp controller there may only be 2 25 amp devices. So at solar noon they won't be as efficient as the 60 amp controller. These are NOT real numbers--they are just to give you the gist of what happens.

I, too, would highly recommend the Victron controllers. Just get the biggest one that you can afford. It is going to be the most expensive component, so then adding more panels is cheap to do.

Sizing should be 125% of the maximum harvest. So for a 20 amp harvest--the controller needs to be 25 amps. The reason for this is partly "cloud" effect. Essentially the clouds may act as a lens and temporarily increase solar irradiance.

About the only mistake I made was to have a controller that does not have enough capacity to add more wattage. This means, if I wish to add more panels--I have to buy an EXPENSIVE controller. My current system panels cost $5.50 per watt, in 2005. Now it is sometimes possible to find them for $0.50 cents per watt. The first system I had was from 1992. It was 30 watts. Cost was $56.67 per watt.

Do you know how many watts-hours you will be consuming?

One of the best, especially for the price, MPPT controllers is the Outback FM60. It will take input voltage up to 150v and can handle 60 amps. (It can actually be adjusted to 70 amps if you find the right spot in the manual.)
However, if your system components link together for control and monitoring (inverter, battery meter, charge controller, etc.) then I would certainly recommend getting all the same brand so they can communicate.