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Old 12-25-2016, 02:01 PM   #1
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Charge controller?

If I have 8, 12v, 150w solar panels. Is would one or two of these charge controller that can handle all 8 Panels 96v in Series on a my Bus?

two of these?

or one of these?
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Old 12-25-2016, 03:18 PM   #2
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I'm not a reliable source, Jazty seems to be the electrical guru around here lately. But with 8x150 watt solar panels, that gives you 1200watts of electrical power. Which would be about 100 amps of power. So I would assume you would want enough charge controllers to support 100 amps worth of power (maybe 4 of the second link you posted?).

Also why would you wire them in a series to have a 96V system rather than parallel for a 12v system? I don't understand electric much but that seems wrong to me.
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Old 12-25-2016, 04:47 PM   #3
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If you put out 12 volts you will never charge a 12 volt battery. It takes 12.9 to 14 volts to charge a 12 volt battery.

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Old 12-25-2016, 05:19 PM   #4
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Those are good CCs, like all Victron products are. However, I think you're planning it wrong. Any MPPT controller will be most efficient when down-converting about twice the battery charge voltage from the panels, i.e. if it takes in about 30 volts to produce 14.7 for the batteries - efficiencies will be typically in the high-90s percent at that step-down ratio. If you're asking it to down-convert from 96 volts it will produce much more heat, and heat shortens the life of electronics more than almost anything else. And most "12 volt" panels typically produce about 18 volts Vmp if they have 36 cells - 144 volts (eight times 18 volts) is more than most single CCs can reliably handle, and an edge-of-cloud event can briefly push that voltage even higher than that.

Also, I'm guessing you had planned to have all your panels in series. That's a good idea for home installations to reduce cable losses where there could be a considerable distance from array to CC, but any mobile installation won't have to deal with such long cable runs. If one panel on a series-connected array is shaded, even slightly such as by leaves or obstructions on the roof, the entire array's output can be cut to nothing (especially if the panels have only series-wired cells). A parallel-wired array on the other hand will still produce usable power even if one panel is shaded.

If you split your array into two you can have a CC for each half, then you won't run into issues of too much power per CC, and you'll have redundancy to prevent complete system failure if one critical component fails. For example, I have eight grid-tie panels and two 60 amp Morningstar CCs: each CC charges its own bank of four batteries, then both banks are combined to power the DC loads. This way, I will always have at least half my power even if something bad happens. Having two CCs also means that if you tilt your panels to face the sun better, if one array is tilted at a different angle than the other and therefore producing slightly different power, then a single CC won't get confused trying to calculate the PV's maximum power point.

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Old 12-26-2016, 03:23 PM   #5
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I've studied different solar power configurations and what John outlines is what I'm going to do, it makes the most sense of the different layouts I've looked into.

Another factor to consider, if you build a 24V system you won't need as large of cables to connect everything together either. This is probably the way I will go.... 24v for AC inverter, with either a smaller 12v bank for 12v loads or a 24v-12v converter (depends on what the total 12v draw ends up being).
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