Rogue 20A MPPT Controller Question

[mena661]

Maybe Marc will chime in but maybe this question is generic enough that others might answer. I was perusing the Rogue 20A manual and saw the 320W limit for 12V systems. I'm wanting to put two 150W panels in series to up the volts and reduce current in an attempt to be able to use more panels on the controller at a later date. If my total amps is well under 20, can I go beyond the 320W max for the controller?

[mena661]

Thanks Almot. I'm just going to use one of the built-in presets for the time being. No need for the data converter just yet.

[Almot]

mena661 wrote:
I was perusing the Rogue 20A manual and saw the 320W limit for 12V systems. I'm wanting to put two 150W panels in series to up the volts and reduce current in an attempt to be able to use more panels on the controller at a later date. If my total amps is well under 20, can I go beyond the 320W max for the controller?

You can, and you should. What you should also do, is get Rogue 30 instead of 20, especially if you go beyond 320W :)...

Rogue 20 will clip the output amps at 20, maybe 21A.

300W array under ideal conditions will output about 10A @30V. After the conversion to 13.5V, 10A becomes 22A. Ideal conditions don't happen at sea level, so you are OK with Rogue 20, but pretty close to losing some power. If you increase the wattage beyond 300 or 320, you will likely lose some power at peak sun (compared to if it were Rogue 30), but you will still get more power than with 320W, because most of the day there will be no clipping as your amps will be below 20.

Rogue 20 requires data converter or remote display to change any settings because it has no interface display like Rogue 30. So the difference in price is not that big.

[BFL13]

mena661 wrote:

BillyW wrote:
Does anybody know how (well) the Tracer temp compensation feature works?

Not sure, I was that mysterious someone that BFL was talking about would post his findings on the Tracer.

Mena the guy said he went ahead and bought a Tracer and would test it for us sometime early this year. From back east somewhere ISTR. I will do a search.

It was hmknightnc

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27359688/srt/pa/pging/1/page/2.cfm

[mena661]

BillyW wrote:
Does anybody know how (well) the Tracer temp compensation feature works?

Not sure, I was that mysterious someone that BFL was talking about would post his findings on the Tracer.

[TurnThePage]

Does anybody know how (well) the Tracer temp compensation feature works?

[mena661]

If the Tracer works well then it's a good deal IMO.

[BFL13]

Yes, quality assurance is worth a lot and the price difference is little more than a tank of gas for the truck which nobody blinks at. Also it's only a one time thing soon forgotten, while the truck keeps wanting more 😞

One of the members ISTR on the East Coast said he would report on the Tracer. That 100Voc gives it a big advantage over the 20a EcoW at 42Voc if you wanted to use two 12s in series which you can't with the EcoW.

[mena661]

smkettner wrote:
300w and 20a controller will serve you well.

If you expand in the future... cross that bridge when you get to it. It might be a second 20a controller or a replacement 60a controller. Might be higher open circuit voltage MPPT needed or high amp PWM depending. Expansion system may not series or parallel well with existing panels. Too many future what ifs. Load that 20a with 300w and enjoy.

Good points smk! I just might need more than 10A for expansion next go round and a second controller may just make more sense. And it will save me $100 towards panels.

BFL13 wrote:
I was thinking cheaper MPPT too like the Tracer if you don't want all the fancy data stuff and laptop connections etc which have nothing to do with feeding the batteries but do provide geek entertainment 🙂

A 20a, 100Voc Tracer is about $140

You know I didn't think I wanted all the fanciness but at $275 for the Rogue 20A, it's not too much considering what you get plus Marc is really helpful here. I'd like to support his company. Plus I worry about the cheaper units shutting off in the summer like the Iota converters do.

[time2roll]

300w and 20a controller will serve you well.

If you expand in the future... cross that bridge when you get to it. It might be a second 20a controller or a replacement 60a controller. Might be higher open circuit voltage MPPT needed or high amp PWM depending. Expansion system may not series or parallel well with existing panels. Too many future what ifs. Load that 20a with 300w and enjoy.

[BFL13]

I was thinking cheaper MPPT too like the Tracer if you don't want all the fancy data stuff and laptop connections etc which have nothing to do with feeding the batteries but do provide geek entertainment 🙂

A 20a, 100Voc Tracer is about $140

[mena661]

BFL13 wrote:
In the manual above the 320w recommended limit guide it says:

"....... Conversely, an array that is oversized will constantly push the MPT-2024 to its maximum limit of 20A. At and beyond this limit the power from the array is constrained and the MPPT algorithm is overridden so that the controller does not exceed its maximum current output. To avoid wasting available power, follow the guidelines given in Table 4.4.1 when sizing your array."

Maybe I should read the whole manual next time. 🙂 Thanks all, I'll get the bigger controller. And, yes, BFL I could get a cheaper (with higher amps) PWM Morningstar but I'm not sure if I'll be adding anymore panels. I'd have to do some more measuring on the roof to see if I could get more up there.

[CJW8]

Mena,
I live in AZ. I have checked my controller when it was 100+ out and the sun directly overhead many times with no excess heating observed. My son is a solar installer and I have watched him size many systems including two of my home systems. It is very common to size the PV array larger than the inverter.

[KJINTF]

Hi mena

MPPT controller rating = Input Power (w/ a max voltage limit) & Output Current

When the input power rating is exceeded (on quality controllers) typically the integrated "Processor controlled TRACKING function" is used to reduce the input power level, which then limits the output current to within the system specifications.

Many folks run a higher power array than the controller is rated for with out issues.

I suggest you do NOT
Instead oversize the controller
This oversize allows for -
Future array expansion
No wasted energy when the "clipping" occurs, wasted $ on power that is not used
Reduced heat - higher the current higher the internal heat generated
Longer life from running cooler
Generally just a better system design

[westend]

Mena, if you call them, there's a real good chance you'll get Marc on the phone. He's a good fella' and may take the time to answer all your questions. That was my experience, anyway.