Questions about Siemen panels

Posted by Michael B on August 20, 2009, 10:39:23 PM

Re: Questions about Siemen panels (Reply #5)

sorry. thats a sharp 224 watt module. a pair of those with a tracker and a roll of 00 wire would only set you back 5 grand or so. mostly just joking. mostly.

Posted by The other Michael B on August 21, 2009, 12:02:43 AM

Re: Questions about Siemen panels (Reply #6)

Gottcha.

Posted by Thomas Allen Schmidt on August 23, 2009, 09:12:03 AM

Re: Questions about Siemen panels (Reply #7)

It would appear that you are reading open circuit. But it looks good.
Typically speaking, ones power usage is the starting point and the PV array and battery storage are factored from there.
http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/
If you go here and choose; Average, Annual, Flat Plate Tilted South at Latitude, you will see that the area you mention receives the equivalent of 6 to 7 kW hrs. per square meter, per day, based on those parameters.
This is a fair assessment, in my opinion, of the the number of hours of equivalent full rated power from a PV module if the lower value, in this case 6, is used based on those same parameters listed above. So -
2 x 48 x 6 = 576 watt hours or .576 kW hrs.
In terms of battery storage that would be -
576 / 12 = 48 amp hours
I like to multiply that by a factor of no less than 5. This would help to keep what is used from the battery over night in the top 20% of discharge and maybe give a few nights of reserve power.
48 x 5 = 240 amps hours of battery storage.
For example: Trojan T-105's are advertised as having 220 amp hours of capacity at the 20 hour rate.
I agree with Michael B that a charge controller is essential and that a battery monitor such as the Bogart 2020 is very helpful in understanding the "ebbing and flooding" tide (metaphorically speaking) of power flow within your system.
Plan for the future.
http://www.bogartengineering.com/2020.htm
Oh, there is lightning surge protection to consider as well!

« Last Edit: August 23, 2009, 03:00:40 PM by Thomas Allen Schmidt »

Posted by The other Michael B on August 24, 2009, 12:58:05 AM

Re: Questions about Siemen panels (Reply #8)

I was wondering if you were going to show up.

Yes, that was 18V open ckt with the panels pointing almost directly at the sun at 3pm.

I uses my toy hauler about 12 - 4 day weekends between Oct an May.

I just fired up my trailer and these are my ~amp draws with different appliances turned on.

Fridge + two air sensors = .5A
+ Inverter = .8A
+ 1 light = 1.7A
+ Heater, no inverter = 5.0A
Heater, + Inverter = 6.0A
Heater, Inverter, +1 light = 7.0A

I'm sure it would go over 10 amps with the heater and TV on.
I guess it would be hard to figure my amp-hours with the heater coming on and off during the night.

When camping, I have been leaving my trailer plugged into my truck with two 12V batteries and it does draw down the truck batteries, but there have been times when the solar panels did bring it up to full charge as shown by the lights on my battery test panel.

Tomorrow, I will try it with the fridge, inverter, and TV on to see if the panels keep it at full charge.

Where would be a typical place to mount the Bogart 2020? The plastic battery box is on the driver's side so I'd have to find a way to access where ever I mounted it. Are there less expensive monitors. These solar panels were given to me several years ago.

So, aside from this meter, would I also need a charge controller. Are the $30 ones good enough for my 96W solar panels?

Thanks for the reply.

Mike B.

« Last Edit: August 24, 2009, 04:55:55 AM by Mike Beatty »

Posted by The other Michael B on September 03, 2009, 10:35:48 AM

Re: Questions about Siemen panels (Reply #9)

Being someone who likes to know what is
happening all the time, I ordered the Trimetric
for my two 48W panels that are wired in parallel.
I do not have any plans to expand my setup.
Just trying to run the trailer genny as little as possible.

I did some testing yesterday and came up with:

1:00 PM, 19V and 6.06A with a clear sky and cold panels.

I then fired up the trailer off grid and got these readings.

CO2 + Propane = .18A
+ Fridge ==== .51A
+ 1 Lite ==== 1.46A
+ Inv/w TV === 6.06A
+ Heater === 11.00A
Got inverter alarm. 11 amps doesn't like going through meter leads.
The inverter is 300W and is enough to run my 15" LCD TV and digital
converter. I rarely have the heater and light on during the day.

Will my panels keep up if I charge the batteries with the genny in the morning?
I should be pulling < 5A with just the TV and inverter on. During the day, I am
away from the trailer for an hour or two at a time, so it gets the full charge minus
the fridge, CO2 and propane sensors.

Should I disconnect my truck batteries when I get to camp and run on
the Trojans alone?

« Last Edit: September 04, 2009, 06:17:41 AM by Mike Beatty »

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