Another newbiew looking for pearls...

[WU9B]

Greetings one and all!

I have recently acquired a number of panels from an estate sale. I paid $20 for most of these and no more than $40 for the panels that appeared to be newer and in a box and probably in the neighborhood of $350 for all of these "gently used" items, which I believe are in the about of 10 or so years old. They were all in a warehouse so I don't know how much sun they have seen. I have the following: (and I think the ratings are fairly accurate, I don't guarantee my work)

8 Solarex VLX70 rated at Pmax=70 watts; Vpmax=16.5V; Ipmax=4.24A
4 PhotoWatt PWX500 rated at Pmax=50 watts; Vpmax=17.0V; Ipmax=3.2A
1 Siemens M75 rated at Pmax=48 watts; Vpmax=15.9V; Ipmax=3.02A

and

2 Sharp NTR5E1U rated at Pmax=175 watts; Vpmax=35.4V; Ipmax=4.95A

I also scored a Trace Engineering C40 charge controller and one

Samlex PSE-1260 600 watt inverter.

It seems to me that the first 13 panels are very similar but I don't know if I can mix and match them. The Trace C40 charge controller is jumpered still at the factory 48V setting. I have downloaded and read the C40 manual and it all looks very straight forward. I do understand that a 48 volt system my get a way with smaller AWG wiring as far as losses go. I also understand that a single bank of batteries in series might be better than a 2 or 3 banks batteries a series/parallel configuration... I have questions on setting the system up for use as 12VDC and 120VAC.

I am a ham radio operator and I have some radios and other equipment that runs on 12 V (13.8 would be better). The main radio draws .85 A (Let's call it one amp) on receive and about 18 Amps on transmit.

On a day where I would use the equipment a lot, I figure 10 amp hours on receive and 2 amp hours on transmit for the main radio for a total of 12 amp hours/day . To that I could add maybe (big maybe) 3 amp hours of accessories and smaller radios for a total of 15 AMP HOURS/DAY AT 12 VOLTS. All of these items currently run off of existing 120VAC power supplies so I can go either AC or DC on the radio stuff. I think the Power supplies will introduce some inefficiencies, right? So the system will pull more than 15 AMP HOURS if I use 120 VAC power supplies as opposed to running 12 volts into the room.

My computer consumes 280 watts per the Manufacturer so I calculate that to be 2.333 amps... call it 2.5 for grins. The computer tends to be on at the same time that I run the radios. I do not know what it consumes while it sleeps, I forgot to look at that. So if I turn it off when I am not using it I now need about 15 AMP HOURS for the radios and 30 AMP HOURS for the Computer (I think) which would be coming from the inverter (more inefficiencies). Looks like 45 AMP HOURS PER DAY being pulled 12 volts. Add all the unknowns and inefficiencies and looking for long battery life how much battery do I need? Will say two 110 AH AGM or golf cart style batteries fit the bill?

If I go this route I am looking at a 12 volt system so I need to change the jumpers in the charge controller, right (to 12 V)? and use heavy 8AWG minimum everywhere, right?

I also have no problem reconnecting these items to AC mains if needed. I do live in the Phoenix, AZ area so we get a lot of sunlight and I know the panels won't be so efficient at 110+ degrees F but there will be a lot of sun, even in the winter.

My questions are about the proper jumper settings on the charge controller if I go with a combination of 12 volts DC and 120VAC via the inverter for the computer. 12 volt setting right?

Maybe it would be wiser to contact an installer and just connect as many of the panels as I can to the grid instead and try to save $5 or $10/ month on my electric bill.

Thanks for taking the time to read this. I appreciate any and all opinions.

-Steve-WU9B-

[Mike90250]

Lots of thoughts there.

You can place panels in parallel +- 10% of their Vmax power Panels in parallel will go to the lowest voltage panel in the string.
(PV panels are current sources)
Panels in series, need to match +- 10% of the Imax power. Series limits the current to the lowest current panel of the string.

What you can run off 12 -15V is good, and skip the inverter stage. Problem is, PV & batteries recharge not at 13.8v like in a car, but closer to 15V, which some gear does not like

And it's better to have 2, 6V batteries in series, than 2, 12V in parallel.

Lets get some more thoughts and ideas.

Generally, Grid Tie arrays, need to all be the same matched panels.

[Sunking]

WU9B you can power all your field equipment no problem at all. A suggestion quit thinking and working in battery AH for now as it makes things more complicated when working with solar PV, use watt hours. Last step is to convert to battery AH

So add up all the watt hours you need in a day, multiply that by 2 and you know how much power your panels need to generate in a day. From there all you do is factor out watts by dividing the sun hours out. So if you need 1000 or 1 Kwh per day,byou need to generate 2 Kwh at the panel terminals, and with a 4 sun hour day you need a 500 watt panel. 2000 wh / 5 h = 500 w

As for the battery capacity there are two ways to go. If this is for occasional field work, multiply your daily watt hours usage by 2, then divide by the nominal battery voltage. So if you need 1 Kwh x 2 = 2 Kwh/12 volts = 167 AH minimum battery at 12 volts.

If using daily multiply daily watt hours by 5, and then divide by nominal battery voltage.

[Naptown]

I don't know about the other modules but those solarex modules are ancient. I don't think Solarex has been around as a brand name producing panels for 15 years. They were sold to Arco then to BP and BP just closed the plant and moved to China.
(I pass the plant about once a month in Frederick Md.)