*Outback MX60 MPPT 60 amp charge controller*
A Review
By: Randomthoughts
02 October 2007

The Outback MX60 MPPT 60 amp charge controller, $483 US, a review.

I purchased a MX60 because after I received my 24 volt solar panels, I realized that their peak power point when cool was also 24 volts. this meant that when exposed to sunlight on a warm day that the peak power point would be below the normal charge point of my batteries.

The MX60 is much higher than the price of simpler charge controllers, but in many ways is worth every penny, matching system voltage and tracking the peak power point of the panels.

The MX60 will auto configure to most battery voltages, 12 to 60vdc. Maximum array sizes per MX60 are 800W@12v, 1600W@24v, 3200W@48v. The real beauty of this is that it can take input voltages up to 135vdc (150v absolute peak) and drops them down to you battery voltage. Practical applications are that the array can be run at higher voltages/lower amps for less line loss. This means you can run smaller wire or longer distances. Assume your retreat cabin is tucked away in dense tree cover, and the nearest clearing with good solar access is a hundred yards away. Wire the panels at 120volts, run a longer, small wire to the MX60, then thick wire to drop to battery voltage.

Another reason, the peak power point of solar panels changes with temperature. The MX60 extracts all the potential power available, example a typical 12 volt nominal panel will have it's peak power point at 18volts/25 degrees C. This is so that when you put it out in the sun when it's 40C out, and being black, it climbs to 60C, that it well still put out 14 volts to charge a 12v battery. If it's a cool winter day, when you really need the extra power, this extra voltage is unavailable with a regular charge controller, you need a MPPT (Maximum Power Point Tracking) controller.

In my home system, nominal 48v, actually operates while charging at above 50 volts. I tied each set of 3 panels, nominal 24 volts each in series for 72 volts nominal. The peak power point during the summer is about 63volts (21v per panel). A conventional C40 type controller would force the panels to operate at battery voltage, (25 volts/panel) and only accept two panels in series, so I would lose potential power input.


Wiring compartment MX60


Display MX60


Remote control Outback Mate

It comes standard with a 4 line LCD display, and optional remote control/display and optional remote temperature sensor for your batteries.

To expand a bit on some of the advantages of this controller for me, the solar panels I purchased (best $/watt I could find) are by a company called Grosolar. All other panels I have, had the extra voltage at STP, so that at real world temperatures they would still put out sufficient voltage to charge batteries. These Grosolar panels have Vp=24v, I am assuming at STP as well. This was an oversight(screwup) on my part, but I didn't notice it until after I had taken delivery of 1850 watts worth. My intention was to wire the panels in series, 2x24v for input to stacked Outback GTFX 3048's controlled with a C-60 type charge controller (battery bank is 24x 2000Ah@2v Excide brand batteries). Actual real world Peak Power Points of 20-21 volts per panel show my fears were right.

The MX60 takes higher voltage/ lower amps and converts to lower voltage/ higher amps. The final output is limited to 60 amps, and the MX 60 is a 5 stage charge controller, so the batteries should not be a limiting factor. There is some conversion losses, but the internal fan cooling dosn't seem to come on much below 1200 watts, so it's not loosing much.

The Outback inverters internal controller is for grid/generator interactive use, and does nothing for solar inputs if the grid is not available to dump excess energy into.

For specific jobs the cost of the MX60 is worth it in increased power output from MPPT, lower line losses from increased transmission voltages and flexibility when upgrading (panels above 130 watts are only available in 24 volt I found out, as I wanted 12/24 volt panels I could take with me when bugging out, yet these bigger panels now have the best $/watt) The MX60 allows 24 volt panels to be used with legacy 12 volt systems, such as RV's and existing inverters.

One other point, if you have other outback products, the MX60 is designed to integrate with the rest of their product line, where all inverters/charge controllers plug into a single hub, and communicate by cat5 cable to a single remote control, the Mate, suitable for mounting in the safe room.
Randomthoughts



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