# James Rosenberger's posts

#### Posted by James Rosenberger on May 20, 2008 11:49 am

#1 -
Thank you for the detailed response!  This all makes much more sense now.  I agree, knowledge can't hurt you    It can only help to make better decisions moving forward!

thanks again!

#### Posted by James Rosenberger on May 16, 2008 11:22 pm

#2 -
I do understand now, thank you.

I realize now what was throwing me off. In the SunSaver MPPT manual it says on p.18:
"The SunSaver MPPT can accept 12v, 24v, or 36v nominal off-grid solar module arrays."

I think when I read this, 24v was stuck in my head.  It didn't occur to me that an odd nominal voltage between 12v & 24v existed.

Knowing the Evergreens are 18v nominal, I understand 2 wired in parallel would produce an 18v nominal array.  That won't work for a 24v system.  But 2 wired in series would produce a 36v nominal array, which would be fine for a 24v system.

One Final question on "Nominal" voltages.  How do you determine what a panel's nominal voltage is?  For example, the high wattage Sanyo panels have Vmp in the range of 52-56v.  Nowhere in the spec sheets does it mention its nominal voltage.  If it wasn't listed in the altestore "basic stats" of the panel, I would never know it's a 42v panel.  I might have guessed it to be 48v nominal.

Thanks for the education!

#### Posted by James Rosenberger on May 16, 2008 05:37 pm

#3 -
Thanks!  That does make perfect sense.  I should spend more time in the "learn" section

Seems like "nominal" is pretty obsolete these days.  I tend to always reference Vmp.

Glad to know I was on track using the Vmp for my voltage drop calculations!

#### Posted by James Rosenberger on May 16, 2008 03:12 pm

#4 -
Hmm... now I'm confused..  I guess what does "nominal" really mean??  Is that the actual output voltage I'm going to see in real life?

This will really mess up my voltage drop calculations if that's true.  I have a 80ft run between my panel and my MPPT charge controller..  I thought I would get about 24v out of the panel during peak sun.  If I'm only going to get 18v that is a big difference.

Maybe we are just talking semantics/terminology here because the calculations don't make sense with 18v.
Evergreen ES-170:
18v x 6.72a = 120.96 Watts  vs. 25.3v x 6.72 = 170.016 Watts

I guess the "nominal" term makes sense looking at my controller capacity.  If the Evergreen was 24v Nominal, I would never be able to use 2 panels since I would exceed the 36v max input.  If it's 18v I can run 2 in series and not exceed any spec (as long as I have 24v battery).

Morningstar SunSaver MPPT:
Max Voc: 75v
36v PV Nominal Max
Nominal Max Input Power (solar array)
with 12v battery - 200 watts
with 24v battery - 400 watts

#### Posted by James Rosenberger on May 15, 2008 10:49 pm

#5 -
These panels are really 24 Volts.  Why are they listed in the store as 18v?

thanks

#### Posted by James Rosenberger on May 9, 2008 09:38 pm

#6 -
Thank You!  I would have never been able to figure that out myself!

#### Posted by James Rosenberger on May 9, 2008 04:52 pm

#7 -
Can anyone tell me the difference between these two panels?

The only difference according to the spec sheets are the number of cells per module.  With all other factors equal, is there any advantage of a solar panel having more cells?

My only thought would be maybe more cells would be able to better handle partial shading?

KC85T = 36 cells per module
KC85TS = 72 cells per module

http://www.kyocerasolar.com/pdf/specsheets/KC85T.pdf
http://www.kyocerasolar.com/pdf/specsheets/KC85TS.pdf

#### Posted by James Rosenberger on May 8, 2008 10:57 pm

#8 -

What type of "volt meter" do you want?  a simple analog or digital volt meter that does nothing but show voltage?  Or do you want something that will show other battery data like; capacity in amp hours, watts, amps, % full?
Doing a quick search on this site will show you some of the options:
http://search.altenergystore.com/search/?w=volt+meter&p=Q&ts=v2

For your second question.  Simply speaking, the less you discharge your batteries the more life you will get out of them.  For example, If you constantly discharge your battery beyond 50% of its capacity, it will have a shorter life span.  If you only discharge it to say 90% of it's capacity, it will have a much longer life span.

For your last questions, to determin how it would affect your charge controller, first you need to know what your current charge controller specifications are.  Then I would need to know the specific wattages of your panels, would you wire them in series or parallel?, how many amps will your new solar array produce, how many amps is your load drawing, etc...

#### Posted by James Rosenberger on May 8, 2008 12:20 am

#9 -
Not sure what type of charge controller you have, but you could upgrade to a charge controller that supports data logging to a PC.

The best cheapest option I have found so far is the Morningstar SUNSAVER MPPT controller for \$244.  It requires an optional PC interface that can't be expensive since it's just a RJ-11 to Serial adapter (Which I can't find anywhere for sale..  Alt-E staff... are you going to carry this??)

I have read the documentation, but I'm still not clear of every parameter it logs though...

Morningstar has a free download of their software that interfaces with the controller (MSView):
http://support.morningstarcorp.com/item.cfm?ItemId=8

http://store.altenergystore.com/Charge-Controllers/Solar-Charge-Controllers/MPPT-Solar-Charge-Controllers/Morningstar-MPPT-Charge-Controllers/Morningstar-Sunsaver-MPPT-Charge-Controller/p6185/

If your looking for something less expensive, The Morningstar TRISTAR-45 is \$147.  It is non-MPPT, but offers data logging to a PC.

http://store.altenergystore.com/Charge-Controllers/Solar-Charge-Controllers/Pwm-Type-Solar-Charge-Contollers/Morningstar-Charge-Controllers-Pwm/Morningstar-Tristar-45-45A-Chg-Ctlr-Without-Display/p806/

#### Posted by James Rosenberger on May 7, 2008 11:50 pm

#10 -
Personally I use X10 devices to control loads on a timer basis.  I use an appliance module which has a relay to switch the 120V device.  The only power draw is the controller unit.  Depending on the controller unit you get it can draw almost nothing.
I use an alarm clock type of control unit which I just checked with my "kill A Watt" and it reports 1 Watt.  This can control up to 8 modules on different on/off time schedules or many more than 8 modules if you want to switch at the same time.

www.x10.com or www.smarthome.com  Radioshack used to sell them under the "Plug 'n Power" brand,  but not sure if they do anymore.

#### Posted by James Rosenberger on May 7, 2008 11:32 pm

#11 -
I know what you need.�  Get a Doc Wattson at www.powerwerx.com for about \$60.

Here is the link to the manufacturer's website:
www.rc-electronics-usa.com

They have two models, you can compare the specs here:
Model R102 - "Doc Wattson":
http://www.rc-electronics-usa.com/ammeters/r102-amp-hour-specs.html

Model WU100 - "Watt's Up":
http://www.rc-electronics-usa.com/ammeters/amp-meter-specs.html

If your battery capacity is less than 65Ah, you will probably be fine with the WU100.  I'm considering getting one for my small 12V stuff.  I think the TriMetric is much better off for keeping close track of your batteries though.  I don't believe these units above will give you the "Net" usage on your batteries, but they will give you the basic stats like watts, volts, amps etc of your DC loads.

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