New user and a few Classic 150 questions

[qrper]

Well this makes post number two!

A few quick Classic 150 questions.

New out of the box, and with 2K worth of power going to the batteries, the controller, well stinks. It smells like paint. Fan running, no errors, current within unit's range. Is that what I'm smelling? Hot paint?

When does the 'turbo' fan kick in?

thanks... QRPER

[Vic]

From your other Post under Lead Acid Batteries:

Morning QRP e

   ...    running strings of four 60-Cell PVs  creates an EXCESSIVE  input voltage for a Classic 150   ...

For 60 cell PVs,  strings of three PVs is ideal.

Use the MidNite Classic String Sizer,  to confirm:
http://midnitesolar.com/sizingTool/index.php

This excessive input voltage to the Classic 150,  creates excessive heating of the Classic.   And this is probably the reason for the aroma.

Strings of three 60 cell PVs is the key to good performance,   and long CC life.

FWIW,   73,   Vic

[qrper]

Interesting....

There is a good 100+ feet between the array and the controller even though it's wired with 1 gauge wire. That's why I went with the four in series to help with the voltage drop from the array to the controller/batteries.

I had been toying with the midnight sizing gizmo before I decided to go with the 4 panels in series. I understand what you're saying.

I can certainly re-wire the array, it's still in the building stage.

With 16- 60 cell panels, if I go three in series, I'll have five strings of three panels in series for 15 panels.  I'll have one odd ball panel left out.

I did notice something odd. At peak power the array should be sitting at 120 V dc. According to my meter, (A Fluke 77) ,and the classic, PV+ input is about 101 V dc while in bulk mode, well below the peak power point of the panels. Right now, the controller is in absorb mode and the PV+ input is 120ish V.

Currently 845 w/m2 @85º F

mike

[Vic]

Hi Mike,

Regarding the Vmp of the string of four PVs,   if the STC Vmp of each happens to be 30.00 V  (120 V STC string Vmp),   this is for a cell temperature of 25 degrees C (tested with a Flash Tube).   When PVs are exposed to the sun,   the cells heat,   which reduces the MPPT string voltage.

Bulk charging is often early in the day,   the  actual Max Power Point voltage also depends upon the Irradiance.  Low Irradiance in the AM,   reduces the cell temperature,   but,  also reduces the MPP voltage.   Also,   off-angle irradiance from the sun reduces the effectiveness of the PVs in capturing the maximum production,   vs the irradiance at Solar Noon,   which is the way that the STC PV testing rates the PV output parameters  (the flash tube/s are at right angles to the surface of the PV cells).   The tilt (elevation) angle of the PVs also affects PV production,   and so on.

Yes,   rewiring the PVs for three,  vs four per string,  will leave a spare.   But,  would bet that you will see more production from 15 PVs in strings of three,   vs  16,  wired as four per string,   (IMO).

FWIW,    73 (if you are a Ham),   good luck,    Vic

[qrper]

Vic,

I'm going to try and re-wire the array. I might have to wire up some extensions to reach the panels.

FYI... I am a ham... I wrote the "Emergency power for radio communications" handbook for the ARRL.

I'm quite aware of the issues with cell temperature and power/voltage ratings.

The old array, I had tilted at 48º for max winter power, but this time with the new array, I tilted at 30º to get the best (better) summer output.

the photo shows the new panels going up. The eight in the middle are the Trina solar, (another 8 went up after this photo was taken) while the ones to the right are the older Solarex MSX-64. It took a lot of labor to repurpose the old array mounting to hold the newer (and larger) panels. The ones on the pole mount, I don't know about them.

They are 17.6 V panels, ideal for use with the older Heliotrope General PWM controller. However, if I go with 6 of them in series, I'll have 105 V, yet 5 will only do 88 V. I'm leaning on going with 6 in series.

Your input?

I've been designing solar electric systems for decades, I'm old school when it comes to the newer MPPT controller.

Mike

[Vic]

Hi Mike,

IMO,   for a 48 V FLA battery,   and a Classic 150,  85-ish volt string voltage is essentially as perfect as one can get  --  high enough to EQ a cold battery,   tolerate hot PVs,   and keep the Classic as cool as possible.   Although,   that assumes a high EQ voltage of  66 volts   ...

So,   a string of five of the 17.6 V PVs  is as close as you can come to the above.   Five of the Solarex PVs and strings of three 60 cell PVs have an identical number of cells.   Modern PVs can eek out a bit higher Vmp than older PVs,   but the outputs are close enough.

We,   too,   will probably add some PVs,   with a 30-ish degree elevation angle for better Summer production.    Presently,   our PV elevation is about 50 degrees  (Lat plus about 14.5  degrees)   ...   just too steep for good Summer production.

You did mention that you had a long experience doing Solar system design   ...   sorry to kind of speaking down to you,   just hard to tell the depth and breadth of experience with a new member,   here   ...

OK   Good Luck,  73,  BTW,   there are quite a number of Hams here,   Vic

[qrper]

Vic,

Don't worry about it. Yup! I've been around this stuff for almost 40 years. Most of what I do now is for ham radio communications and such and smaller systems.  I let the larger systems to someone else. I"m also old school, so the MPPT controllers are an eye opener. In my time, you match the number of panels to the battery system voltage. Hooked up a PWM controller and life was good. So don't worry about 'talking down' I've gotten a rather thick skin after doing all those magazine articles and books. There's always a critic!

NOW!
Rewired the array to five- 3 panels strings. Open voltage is about 100 V.
Under load, I'm looking at 76ish V while the classic is doing 38 A into my 58.7 V battery bank.
Battery is floating now, and according to the classic, I pushed in 5.9 kWh hours of juice into the battery bank.

I did notice that the fan doesn't run all the time now, but that being said, the classic reports the temp inside at FETs to be 47ºC and 49ºC for the pcb. (can I change that to ºF?)

Running out of daylight now, and the instruments are reporting 610 w/m2. Battery bank floating with a hair over 2A.

BTW... My wife and I purchased an electric car. A chevy electric Spark. I plan on installing 6kWp grid tie array to help offset the car's demand on the grid. However, getting someone to install a array mount has been an issue. I've had estimates from $4200 to $6500....that's for the rack... no panels!

The photo shows 10kWp photovoltaic panels @ 250 W each. 4kW went to the battery back up, and the rest will go to grid tie.

Mike