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Author Topic: Solar panel  (Read 2670 times)

s2man

  • Guest
Solar panel
« on: May 30, 2013, 01:22:19 AM »
I snatched a 200W/24V solar panel off of craig's list, today.  New, 1/2 price of retail.  No, I don't think I'll be backpacking with it. I have so many projects going, right now, this will just go in the basement along with cables and a charge controller, for now, as a SHTF backup power source.  Once I get caught up (I've bought materials for three more projects, this week!) I'll mount it on the roof , connect a micro grid inverter, and let it start paying for itself.

What was I thinking when I bought the Easy Digi kit?  I have so much on my plate right now... <deleted long list>

KC9TNH

  • Guest
Re: Solar panel
« Reply #1 on: May 30, 2013, 08:05:15 AM »
Recently picked up a little 12w foldable panel that I like quite well. Ran some tests taking 5aH gel-cell down to the level it would be after 6 QSOs with the 817 (simulating healthy SITREPs x 2 x long weekend) and compared the time needed to bring the battery back up on the house charger vs. the panel, presumably operating on the other battery if needed. Quite pleased. I wanted to get the little ice-cube sized controller (for its form factor & being very well-potted) but they seem to have issues with either working great, or being DOA.  I had a DOA one & wasn't going to continue to be a postage-guinea-pig, so went with a different one, but quite small.

Makes the 817 w/little Elecraft tuner and baby paddle or key very sustainable.

ETA: I did pickup an extra 12.5' SAE extension cable so that, if needed, I can get the panel itself into the sun while "chilling out" inside a tree line (or staying warm in a bag).
« Last Edit: May 30, 2013, 01:25:05 PM by KC9TNH »

s2man

  • Guest
Re: Solar panel
« Reply #2 on: June 05, 2013, 10:27:37 AM »
I haven't been around for a few days.  I spent two days researching and purchasing components for my solar system.  The 24V panel I bought will be a great start to a home PV system.  But for an emergency, lets-charge-a-battery scenario, not so good.  It will either need two 12V batteries, possibly harder to find in a SHTF situation than one battery, or a charge controller capable of reducing panel voltage to charge a 12V bank.

After much research I had almost talked myself into a 45A Morningstar MPPT controller.  That would handle all the panels I could ever mount on my roof.  But then, I would not have controller redundancy;  Not a good prep.  So I ended up getting an inexpensive Chinese 20A MPPT controller which will take up to 100V input and charge a 12V bank.  Being a newish Chinese model, there is not much feedback on the reliability/longevity of these.  So as a backup I got a good, brand name, 8.8A controller which will handle either 12 or 24V systems, with panel voltage = bank voltage. 

In case I end up with a 24V bank I ordered two DC to DC converters. The first is a 20A 24 to 12V model, which should handle anything which could be plugged into a cigar lighter.  The second is a 3A variable output model.  Most rechargeable gadgets are rated in mA, so that should suffice for little tasks.  I chose the variable output in case I have some device which wants to be fed something besides 12V (For example, the Baofeng charger wants 10V, 400mA input). The converter supports 4.75-35V input and 1.25V-26V output, so will work on whichever bank voltage I am running. 

Cables are ordered, and I think the only other thing I need is fuses.  Then I should all set to assemble the system in an emergency.  DW and I agree that we wouldn't want to face TEOTWAKI without a bit of electricity ;-)   Most components will go in a Faraday cage. 

Then I had to spend another day working out my roof mount (commercial mounting systems are insanely expensive).  With the permanent home PV system in mind, I also ordered a 500W grid tie inverter.  So, on or off grid, I should be good to add another 350Ws of panels before I need to upgrade the controller and cables.

Frosty

  • Guest
Re: Solar panel
« Reply #3 on: June 06, 2013, 09:58:41 AM »
After much research I had almost talked myself into a 45A Morningstar MPPT controller.  That would handle all the panels I could ever mount on my roof.  But then, I would not have controller redundancy;  Not a good prep. 

Charge controller redundancy is my problem here.  I've read good stuff on the MPPT ones, I'm using a pulse width type now and would like to upgrade and put my current one away as a spare.  In a pinch, my battery bank is large enough that I could bypass the controller and dump the panel current straight to the batteries, but not really good except for bulk charging.  24 or 48v systems are usually used in whole-house systems, with 6v or 8v batteries in series.  I went with a 24v system and 6v batts (4 in series, and a second string in parallel). If needed, I can get 6, 12, 18, or 24v just depending where I tap off from. 

s2man

  • Guest
Re: Solar panel
« Reply #4 on: June 09, 2013, 12:43:15 AM »
That is a nice size battery bank. Yeah, you can hook panels straight to the batteries; You just gotta play charge controller with a DMM. :-D 

I am kinda torn on the battery bank, right now.  For mere emergency use, two 12V deep cycles would more than suffice (LED lights and charging batteries, phone, etc.).  But for future PV system growth I want to start with four 6V in series/parallel, like you have.  I think I just talked myself into golf cart batteries...

Careful on tapping a bank.  I've read nothing good about doing that.  A dead battery after TSHTF won't be easy to replace.  The battery balancers are mighty costly and will just give you 12V off of a 24V bank;  Look into the DC converters I mentioned.  You can get variable-output converters in much higher amperage than the 3A I ordered.

My grid-tie inverter arrived, yesterday. The cables arrived, today, and I ordered breakers and L feet for mounting.  Even DW is excited about getting the panel mounted and hooked up.  I'm using the PV system as a carrot; Put the car port up and I can play with solar.  I told you I have too many projects going...

I was looking into LED lighting and found most of them (cheap ones) cause EMI/RFI interference.  Of course, the complaints came mostly from ham radio operators.  I think I'll stick with CFLs.  Just gotta decide whether to go with 12 or 120V.  That's fodder for another discussion.

Nice weather coming for the next few days.  So ALL projects may be put on the back burner while I rework the quickie chimney installation I did when we moved in, two years ago.  Its not unsafe, but its ugly and leaky at times.

Frosty

  • Guest
Re: Solar panel
« Reply #5 on: June 09, 2013, 09:29:32 AM »
Careful on tapping a bank.  I've read nothing good about doing that.  A dead battery after TSHTF won't be easy to replace.  The battery balancers are mighty costly and will just give you 12V off of a 24V bank;  Look into the DC converters I mentioned.  You can get variable-output converters in much higher amperage than the 3A I ordered.

True.  Keep meaning to add a backup 24v DC-AC inverter to the faraday cage, so I wouldn't have to rewire the bank or tap off it to use our spare 12v backup inverter in the event our primary 24v inverter failed.  We've got related but opposite problems, I use 12v panels to run a 24v system.   

On golf cart batts, make sure you don't pull a Frosty.  My first system was 4 Trojan T-105's in series/parallel at our weekend cottage.  I destroyed the batteries pretty quickly by allowing them to drain too deeply too often, a combination of too small a bank for what I was trying to power and the newb learning curve (plus a bit of laziness).   Sounds like you got a great plan though.