Best way to configure?

sprintman
sprintman Registered Users Posts: 16 ✭
in Solar Beginners Corner #1
After reading many of the great posts on this forum I am intrigued with the Rogue MPPT controller. I am not sure I adequetly understand how much panel it can handle---60 volts 30amps. Can some of you give me some examples of ways to configure panels (size and voltage, parrallel or series) to get the most out of this system. My anticipateded battery bank is 4 6v golf cart batteries wired for 12v. What I'd like to cover is 1200-1500 watt hours per day....am I anywere close to being able to do this using this controller and battery bank? If not how many watt hours can I cover with a discharge rate on the batteries of no more than 50 percent. I also realize I can use 24+ v panels.......is that advantageous in this situation? Thanks!
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Best way to configure?

    Look at it this way: the batteries provide the Watt hours you need, the panels recharge them. So the first question is: how much battery capacity do you need for 1500 Watt hours per day on a 12 Volt system?

    So 1500/12 (note: no loss allowance) = 125 Amp hours. The most you want to draw down golf cart type batteries is 50%, so you need a minimum of 250 Amp hours. If these batteries are like the standard Trojan T105's they are 225 Amp hours, so one set would be borderline for 1200 Watt hours, two sets in parallel would be more than enough for 1500 (450 Amp hours could supply up to 2700 Watt hours, not including losses).

    That means your battery choice would work. Now take a look at recharging them. Assuming they will be charged while in use and you want to make the minimum 5% net charge rate (Trojan recommends 10%) shoot for 10%: a peak potential current of 45 Amps.

    Right there we have a problem: the Rogue will only handle 30 Amps, which is roughly 6% charge rate. It will handle one set of these batteries which would be charged at 22.5 Amps, but that will limit your Watt hours to a maximum of 1350. This may work for you if you can do load shifting and keep draws to a minimum.

    Either you can up the charge controller to a 45 Amp or larger unit and use an 865 Watt array (rough calc) or you can scale back usage and use the Rogue with about 432 Watts of array. Which would suit your needs better?

    Also, unless the new Rogue unit has increased its input Voltage you can't feed them 60 Volts. I believe the limit is 36, so they're not a particularly good fit with a "24 Volt" panel. But they have just come out with a new model and I haven't seen the specs on it yet so I could be completely wrong here.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
    Re: Best way to configure?

    the new one is rated to 60 voc. this means that under no circumstance shall the voltage from the pvs exceed that voltage.

    the controller has a current limit of 30a output and at 12v this is 12vx30a=360w so much more than this in pv would not do. yes, pvs have deratings and there are other losses, but there are times when they could output more than their rating, although rare, and you won't get more out of the cc than what it is rated for. as was said 30a is 30a/(225ahx2)=6.66% and is marginally doable only when running the controller full tilt.
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