I've seen the comparison that show a roughly 20% advantage to Sunny Boy on the pre-upgrade ST2500. Does anyone have any information about the total energy harvest of the upgrade ST2500 vs. the Sunny Boy? Has the gap been closed?

There is no gap anymore with the current version thanks to Henry!

arnold

In the real world , there is no difference and there are MANY limitations to using a single string inverter. Hot weather and maximum output performance of the Suntie is much better than the Sunnyboy, just to name a few.

Solar panels have output variances , even if all the panels are the same ratings. Most manufactures only warrenty to +-10% when new ....

Did you have an Suntie first and Ugrade or always have an upgraded unit.

Thanks for your reply.

I had an original SunTie in operation for 2 years, so I'm quite familiar with it's shortcomings. I received my upgrade unit in July. The SunTie upgrade operates much, much better than the original unit: much quieter fan, no shutdowns in the middle of perfectly sunny days, much better MPPT, accurate power readings,... The energy harvest of the upgrade unit is definitely better than the old unit.

I could use more power output -- should I add another string of 4 panels or switch inverters (if the SB is that much better)?


The upgraded Suntie is a good product and works quite well. From what I've read, the Sunny Boy's specs show it 4% higher efficiency and possibly a couple more percent due to lower wiring losses due to shorter wire runs and higher voltages. So I wouldn't be surprised to see the Sunny Boy 6% or so ahead. Also, the
Sunny Boy design may have some shading advantages -- losing panels one by one to shade rather than in groups of 4. However, if the difference in power generation is in the 10-15% range it's much easier and cost effective to replace the inverter than to add more panels. It would be nice to see someone do an up to date semi-scientific comparison of the energy harvest of the upgraded SunTie vs. Sunny Boy inverters from 2 identical side-by-side pv arrays.

I've already done the tests ...

Its real world 0-2% different net generation delievered to the grid Suntie XR-UPG compared to Sunnyboy 2500U. This was on my dual KC-120-1 (24) panel system(s) as shown in HP91 artical

The shading can be better for the sunnyboy if you just cover a single panel but in most systems if theres something causing shading it will cover multi-panels.

The Suntie can handle THIS better since it can run with as little as 4 panels , on the Sunnyboy anything more than 4-6 (out of 24) shaded and your going to drop below the minimum input voltage. This is not a guess , I have seen this on my dual arrays running side by side tests

As for wiring , you should have 6 AWG for the 48 volt strings and 10 AWG for the Sunnyboy string. No big deal and the cost differance is like 200 bucks for the whole array to wire it correctly. Sure if you use the wrong wire type you will lose power , but what does that have to do with the Suntie or Sunnyboy?

In your array , you have NO INVERTER OPTIONS ... since you have arrays at different angles , the sunnyboy won't work and might not even power up until late morning since alot of the panels are west facing ..

And you are completey missing the fact that solar panels are not all the exact same in current (power) delivered even if they are the same name plate rating from the same manufacture. The allowed tolerance is +- 10% and when in a single string , you only get the current produced by the WEAKEST panel. This is not as big a deal in the Suntie since it will only limit 4 panels , but it will limit all 24 in the Sunnyboy

Have I explained this so you understand ? this is a very importaint issue to understand. one has no control on the panels , they are what they are and you cant send them back unless they exceed the +-10%

As for more power , you can add 4 more panels to the Suntie and be operating near the power limit more often. With your mixed angles , it should work well.

So there's a 0-2% difference between a upgrade Suntie and a Sunny Boy in a side-by-side comparison. That's what I wanted to hear, and not from the manufacturer. Thanks!

Xantrex has a marketing problem because there's a whole lot of people out there, including people who sell large volumes of these products, who think the Sunny Boy is 20% better than ANY Sun Tie today. The upgrade Sun Tie really is night and day better than the original. Thanks Xantrex for making it right.

The upgrade Sun Tie handles my mixed orientation panels quite well. Another advantage of the Sun Tie is that grouped-by-4 panels are much easier and safer to troubleshoot. Due to a bad manufacturing run I've had 6 panels out of 24 suffer 50% failures in the last 8 months (6 of the panels lost power from 1/2 of the cells). When my system power output started to fall off it was fairly easy to measure the amperage of the 6 strings to narrow down which panels went bad. If I had a single string of 24 panels, I would have had to measure all the panels one by one to find the bad ones -- which would be pretty scary with 400+ volts running through the system. I know first hand that all PV panels are not necesarily perfect for 25 years -- troubleshootability is an important aspect of a good PV system design.

Xantrex has done a poor job in getting out the message the new Suntie is just as good and in many ways better than the Sunnyboy

Just to be clear though , it was ME , under contract with Xantrex, that did all the redesign for the Suntie XR-UPG.

I redesign the Hardware and Software, Xantrex Engineering were my support for PC layout , secondardy verification and pushed it thru UL to be re-certified (required when there are any design changes)

My performance testing was over 6 months with lab quaility power analyzers (Yokogawa 1030wt.

The Software is all new and Xantrex is in process of applying for 4-5 patents based on my work.

I spent many long days watching the Sunnyboy and Suntie work Side-by-Side and came up with some cleaver ways to make the Suntie be a equal performer even though the raw efficentcy is lower.

In Dynamic conditions , the Suntie Tracks better and faster than the Sunnyboy and on days with lots of clouds the Suntie can actually out perform the Sunnyboy by a percent or two ..

The Start-up message , by the way enhanced with GP Technology , GP = Guppy Powered.

The 20% poorer performance number is from my HP91 artical and for whatever reason , the dealers don't want to believe The Suntie is an excellent performer now.

When I wrote the HP article , the Sunnyboy seemed like the perfect choice. Having now worked woth both inverters for over 18 months and understanding ALL the issues , I run my arrays with the Suntie Now.

If your running a large array , the Suntie is a TRUE 2500 watt inverter .. the Sunnyboy reports about 2-3% high on its power generation and this limits it's maximum output to 2425 watts. The Sunnyboy will thermal derate on my 2880 STC array in summer weather.

SMA now offers the Sunny Breeze (my suggested name by the way) which is an external fan and wallwart. But the power comsumed by this fan is not calculated into the effientcy numbers where as the Suntie fans is.

So sit tight , add more panels and tell a friend what YOU think of the Suntie-UPG

I didn't realize you did the actual engineering work on the UPG. Nice job!

I'm a software engineer myself. Many times I wished I could get my hands on the Sun Tie source code as I watched the old firware MPPT algorithm flop around! Though from reading your paper I see there were hardware issues that contributed to the problem which I don't have the expertise to fix.

The Key Point in all of this is that there is more to life than efficiency! MPPT performance and thermal derating are really the keys. Add the advantage of shorter strings of PV modules -- I actually tested my modules and wired them in matched groups of four -- can't do that with the Sunny Boy.

Gordon