System upgrade/expansion

msgieser · February 2014

After several years of successful off grid living, I'm building an addition onto the house and therefore need to expand the solar system. I presently have 3 280 watt 24 volt modules , max power current (Imp) = 7.63 amps, max power voltage (Vmp) = 36.72V each. After going thru an Outback combiner box, they feed into a Morningstar TS-MPPT-60 Controller and charge 6 Trojan T105-RE batteries (675 amp hours total at 12 volts.) I want to add another 800-900 watts of panels ( possibly 3 more of the same I have now). My main question.....how much more will the TS-MPPT-60 handle? If I need to expand the controller, can I tie in another TS-MPPT-45 or 60 into the present one and if so.....how? I will also add another 4 batteries for an additional 450 amp hours. Thanks everyone...you all have been a great help in the past and have helped make off grid solar power living a success

Cariboocoot · February 2014

Re: System upgrade/expansion

At 12 Volts? 60 Amps * 12 Volts = 720 Watts / 0.77 = 935 Watt array.
With three 280 Watt panels on it already, you're basically at the limit for the controller. You can parallel another controller without much difficulty, but only MidNite Classics actually 'talk to each other' and achieve full co-ordination (the "follow me" function).

Frankly this would be a good time to ditch that 12 Volt system and move up to 24 Volts. Sure you'd need a new inverter and probably have to replace the batteries as well (but it may be time to do that anyway). If you can get more of the same panel you could double the array size on the same controller, and you'd be improving the efficiency by lower current for the Watts drawn.

westbranch · February 2014

Re: System upgrade/expansion

You may have to look around to see if you can get exactly the same panels again, sizes change quickly it seems. Then the decision as to how to assemble your new array(s). The closer the specs the better depending on what you want to do.

msgieser · February 2014

Re: System upgrade/expansion

Coot...so, if i purchase a new 24 volt inverter, and add two more 6 volt batteries and rewire all 8 of the six volters to get 24 volts, I should be able to double my array size and use my existing 60 amp controller???? The 6 volt batteries I have now are in excellent shape...not any heavy use, so don't want to pitch them.

Just how would I parallel another 60 amp controller....if I decide to go that direction and stay with 12 volts?

Cariboocoot · February 2014

Re: System upgrade/expansion

Yes you could double the array on the same controller if you go to 24 Volts: 60 * 24 = 1440 Watts.
The controller's current output rating is the same for 12, 24, or 48 Volts and as such becomes more Watts as you go up in Voltage.

When you say your batteries are in excellent shape - how old are they? It makes a difference for adding new ones. Years, number of cycles, quality of maintenance ... all becomes "aging". Within 1 year there usually is no problem, but even if kept up well the years will have an effect.

As for paralleling another controller, you just hook it to the battery the same as the first. With the numbers programmed the same it will work as well as can be. No special tricks required.

newl · February 2014

Re: System upgrade/expansion

I'd recommend using the string calculator which will give you pretty much what you're after http://www.morningstarcorp.com/en/strings/calc.php

System upgrade/expansion

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