Rogue MPT-3048 now available

Hi lorelec,

I'm glad it has finally arrived!

... and it's a better kit than was supposed to be. Voltage sense cables that were about to become optional, are now included.

Got some questions/comments on the spec.

1. Spec is 97.5% efficiency at (17V/13.6V). What's the power level?

2. More important, what's the efficiency at 480W, 68V/13.6V?

3. From spec: typical operating power consumption is 0.98W. Max power consumption is 1.5W. That doesn't make sense. Max PV power is 480W. At 97.5% efficiency, you're dropping 12W into the charge controller.

Sal

#3: Salvo, your arithmetic is correct. 2.5% losses from 480W = 12W, not 1.5W.

#2: They have a well written manual. There are efficiency curves on the page 43. I believe, it's 98% up to 30A point. When there is 30A clipping, all bets are off. This is 30A unit. The current is clipped at 30A (or 30.5A according to tests). When the battery is 13.6V, 480W panel won't be utilized fully because the output can't be 34.5A (480*0.98/13.6).

13.6 is the float stage, right? Battery doesn't need a high current at that point. But if you are running high loads at this very moment, then yes, you need more current (and bigger controller). The closest one is MS45, 40-50% bigger in terms of amps and dollars. Or ... you can use this one, with 15% "losses" (4.5/30A). These 15% are not actual controller losses, they are losses due to exceeding the controller limit, which is in turn caused by high loads. Like Microwave maybe. I would rather get a cold one from fridge than run a MW on a hot sunny afternoon (when batts are in float), but tastes differ ;) ...

Looking at the Efficiency Graph on page 43, the specified 97.5% efficiency at (17V/13.6V) is actually peak or maximum efficiency. It occurs around 5 or 6A. As current increases (from the peak of 5A, efficiency drops down to 94% @ 30A.

Essentially, the controller is losing 3.5% power as a result of (I'm assuming) copper losses located primarily in the magnetics and some fet on-resistance losses. This is the best the controller can accomplish (MPPT = 17V). At MPPT = 85V and 30A, efficiency losses are 8%, or 38W when applying 480W.

Sal

I think self-consumption power and the efficiency are two different things. If you look at MS45 graphs, at 98V /13.6V is has same 92-93% conversion efficiency as the Rogue, but in specs MS45 says "self-consumption 1.3-2.7W". 92% = 8% loss, this is 38W from 480W panel, not 2.7W, right?

In summarized specs they all provide very basic information, and Rogue is playing by the same rules as others. In retailers sales pitch - that Rouge doesn't have since there are no retailers other than factory - you can find things like "the industry’s highest peak efficiency of 99%" (for MS45), but they forget to tell that this is only if you use 48V bank and charge it with 52V. In real life MS45 can have 92-93%, but for this info you have to read the graphs. Or things like "significant less power loss than other MPPT controllers" - since when 2.7W is less than 1.5W, I wonder...

Salvo wrote:
Got some questions/comments on the spec.

1. Spec is 97.5% efficiency at (17V/13.6V). What's the power level?

2. More important, what's the efficiency at 480W, 68V/13.6V?

3. From spec: typical operating power consumption is 0.98W. Max power consumption is 1.5W. That doesn't make sense. Max PV power is 480W. At 97.5% efficiency, you're dropping 12W into the charge controller.

Sal

1) 97.5% efficiency with a 17vin and 13.6vout is at ~70w input.

2) You're unlikely to see 480w in with a 13.6v output. At maximum output (30a) and at 68vin (92.8% efficiency), (13.6 * 30) / 0.928 = 440w. Unless you have 40w of losses in your wiring, you won't see 480w.

3) Power consumption is what the controller uses for powering its electronics, and does not consider losses from power conversion.

Specifications should be accurate. Car manufacturers can't get away with advertising fuel efficiency of 50 mpg and not mentioning speed is only 20 mph. That's crap! The charge controller manufacturers are counting on the average person not able to interpret the spec correctly.

You just about need a degree in electronics to REALLY know what you're getting. Take for example the Rogue controller ampmeter accuracy.

Ammeter Accuracy: 1.0% at full scale (100a)
Ammeter Resolution: 0.1 amp

If the display reads 12.5A, what error do we have?

The meter accuracy is 1% of 100A, or +/- 1A. Add the resolution error and total meter error is +/- 1.1A.

When the display reads 12.5A, the error is 1.1A/12.5A = 8.8%.
When the display reads 5.0A, the error is 1.1A/5A = 22%.

Sal

Salvo wrote:


Ammeter Accuracy: 1.0% at full scale (100a)
Ammeter Resolution: 0.1 amp

If the display reads 12.5A, what error do we have?

The meter accuracy is 1% of 100A, or +/- 1A. Add the resolution error and total meter error is +/- 1.1A.

When the display reads 12.5A, the error is 1.1A/12.5A = 8.8%.
When the display reads 5.0A, the error is 1.1A/5A = 22%.

Sal

You're not reading the spec correctly. It says 1% AT full scale, not 1% OF full scale.