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paulz
Member
# Posted: 25 Jun 2020 18:55
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Yesterday I headed north to get some hurricane ties, and as I usually do, checked out Craigslist for stuff. I wound up a little further north to get a 1000/2000w inverter I've been wanting to have on my yard truck. Met a super neat 67 year old guy with a huge spread who was downsizing. Long story short, and being one of PT Barnum's greatest disciples, I came home with this solar array for $300, along with a couple of 12v controllers tossed in.

Yeah they are old, Seimens SP75,12 of them. Nice rack he made. He thought they were set up for 48v. There are two output pairs, each are measuring about 110vdc in indirect sunlight.

Isn't there another test I can do to measure what's left in these? And, being a solar slow learner, is it OK to leave them unconnected in any sunlight? Finally if these are still viable, what are my options for getting some use out of them?
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Nobadays
Member
# Posted: 26 Jun 2020 09:20 - Edited by: Nobadays
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Great score! My guess is, 6 series/ 2 parallel based on the panel specs.... you can find that HERE.

With a rated VOC of 21.7, 6 series theoretically in full sun light with the proper angle you should have 130 vdc. My guess is in indirect sunlight, 110vdc means they are in decent shape.

It won't hurt them to sit in sunlight but... tarpping them would probably be better... it may be DC voltage but those wires are still hot when sun is on the panels.

Get a SCC rated for the voltage/ amperage output and put'em to work. The only thing that seems odd to me is the amperage output is only 4.4 so in a 6s 2p arrangement you would potentially have 130vdc at 8.8amps which seems low on the amperage side for charging.

Bound to be somebody smarter than me that can shed more light!

paulz
Member
# Posted: 26 Jun 2020 10:17
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Thanks Nobys. The low amp rating may be due to old design, the guy was sure they are a decade old or more. They should get some full sun this morning, will measure volts again.

My cabin and shop are about 200 ft. apart. Cabin is 350 sf, shop is 2,500. Panels would be best put on the shop roof but would be nice to have the juice run to the cabin. I did a bit of reading, if I use them at 24 or 48v I can run a smaller line. Or invert to AC at the panels.

Lots to consider, luckily no rush.

FishHog
Member
# Posted: 26 Jun 2020 10:46
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I've got some of the same panels. Still working fine. I'm sure they aren't 100% but still lots of life left in them.
No issue with leaving them in the sun, won't hurt the panels as long as no one sticks their tongue into the contacts

Thats a good score for sure.

paulz
Member
# Posted: 26 Jun 2020 20:27
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Thanks Fish! Didn't get to test today but I'm sure they are workable.

My sunniest spot is unfortunately 200 ft from the shop and 400 from the cabin. I will have to do some research and see what the best way to set up.

FishHog
Member
# Posted: 26 Jun 2020 20:41
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You can use smaller wire for higher voltage, so might be best to have batteries close to the panels with an inverter then run standard 110 to your cabin.

Its really just the cost of the wire difference and line loss that you will gain on, but it might be significant.

paulz
Member
# Posted: 27 Jun 2020 05:22
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Ok thanks Fish. So I'm reading up on charge controllers...

I don't get the two 110vdc lines he has this wired up for.. wouldn't be hard to change.

I have 4 good matching group 24 deep cycle 12 volt lead batteries at the ready.

I have my 12v 5000w inverter I use in the shop now, hooked to two batteries in parallel and the 130 watt Harbor freight solar kit. It works well, ran a miter saw quite a bit yesterday but it does run the batteries down.

Simplest for me, I'm thinking, would be to get a charge controller with 12v output and connect those 4 batteries in parallel, put my inverter there, all at the panels, and run a 110 ac line to the shop.

Ok? So how do I wire the panels to input a charge controller for this? Don't they have input parameters for voltage and amps?

I would keep the Harbor Freight setup for DC in the shop, the LED lighting and usb powered stuff I have hooked to it now.

FishHog
Member
# Posted: 27 Jun 2020 07:36
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I'm not sure about his wiring either, but if you want to keep a 12v system, all the panels should be wired in parallel to a 12v charge controller. Might have to trace his wiring back to see what is going on.

Not to confuse things, but many charge controllers can take higher voltages (panels run in series to 24 or 48v), and then still charge 12v batteries. So I'd be tracing his wiring to figure out what he has before you pull it apart, and buy the right charge controller.

ICC
Member
# Posted: 27 Jun 2020 09:45
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If you were to place the batteries and inverter close to the panels, how many amps maximum of the 120 VAC power would you need to use at any one time at the cabin, 400 feet away?

A 400 foot run of copper wire to deliver 120 VAC at 5 amps would need 8 AWG wire. Ten amps at 120 VAC would need 4 AWG. Fifteen amps at 120 VAC would need 3 AWG. Aluminum wire would need 6, 3 or 1 AWG.

ICC
Member
# Posted: 27 Jun 2020 09:53
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I don't understand how the previous owner used those CC with these panels. There doesn't seem to be much info available on those CC, but they would appear to be old enough that they are PWM, not MPPT and likely can not handle high voltage. But I'm guessing. Or were these just laying around, not actually in current use and he just tossed them in to get rid of them?

ICC
Member
# Posted: 27 Jun 2020 10:09
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You could use them wired as 2 strings of 6 in series, each set of six wired in parallel, with something like a Midnight MPPT CC. They have ones that can handle 150 VDC input as well as 200 VDC and 250 VDC input and charge into a 12, 24 or 48 volt battery bank. If you don't have an inverter that will do what you want, I would seriously consider 24 or 48 volts instead of 12.

paulz
Member
# Posted: 27 Jun 2020 10:41 - Edited by: paulz
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I have opened up a couple of the junction boxes. It's wired in two separate series runs, 6 panels each, which makes sense since the 110-115 vdc I'm getting on each run is about 18-19 per panel.

He said he lent this to a friend to use it, who rewired it to suit his needs. Is there a controller that takes that much input? Or did his friend wire it up for some odd situation?

I have to go to the city Sunday to pick up a lathe so have been browsing around.. My panels are rated at 4.4 amps (thanks Noby for the link), so in parallel with 12 panels that's 53 amps. There are a few controllers for sale but rated at 30 amps, seems like a common rating, maybe for RV or boat systems. I need to step up to something bigger right?
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Nobadays
Member
# Posted: 27 Jun 2020 10:51
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^^ what ICC says.... your issue is distance and small voltage. The Midnite Solar "The KID" SCC would work with these panels in a 6s 2p arrangement. It will handle 150vdc 30amps and output can be 12,24 or 48vdc. This would allow you flexibility on how you wire your battery bank. (I would add though that everyone I know that starts out with a minimum SCC ends up buying a bigger one down the road as they add panels. Food for thought)

I would agree with ICC and suggest you keep your eyes open for a 24.... preferably 48vdc inverter... pure sine wave. An inverter/charger would give you the option to hook your generator (one of the many ) to the system and when you are running the generator you will also be charging your batteries.

Keep watching craigslist for some heavy wire to get power up to the cabin... 400' is a long run as ICC points out. If you can get an inverter with a 220vac output you can reduce your wire size. An 8AWG wire will get you 212vac, a 3.43% loss at 15amps (I think 4% is considered acceptable... ICC ? ). If you want 220vac at the cabin, to feed a load center, you would likely want a minimum of 30amps, so minimum of 5AWG for an under 4% loss but way better if you ran 2AWG.... less than 3% with aluminum, less than 2% with copper.

I'm pretty sure you can scrounge up some wire! You won't regret doing it right the first time!

Nobadays
Member
# Posted: 27 Jun 2020 11:05
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Paul... jump over to diysolar forum HERE look under the DIY Solar Blueprints. There are a bunch of options for different low cost SCCs. Kind of poke around there as the site owner does a lot of videos to help folks like us understand what we need... he makes it pretty easy to grasp. He did a video comparing charge controllers.

I know you are trying to keep it low cost, but be careful as some of the cheap charge controllers nd inverters are just junk.

When we were planning our cabin system I had been choosing equipment by price trying to keep it cheap. I ended up on a solar forum that is frequented by a lot of professionals, installers and other folks in the business. They persuaded me to go with name brand equipment and though it was pricey, it functions well and will likely do so for many years to come.... I don't have to fiddle with it... I just flip the light switch.

paulz
Member
# Posted: 27 Jun 2020 11:09
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Hmm, ICCs post weren't there yet when I put my post up this morning. I have seen that happen on occasion for some reason. Yes, ICC, those controller were just thrown in the deal, not used with the panels.

Still digesting it but doesn't sound like I need to hunt down anything that's around on my trip tomorrow, and I am not in a hurry.

Thanks guys!

paulz
Member
# Posted: 27 Jun 2020 11:47 - Edited by: paulz
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Quoting: Nobadays
I know you are trying to keep it low cost, but be careful as some of the cheap charge controllers nd inverters are just junk.


Thanks, good to know. Actually buying used stuff I sometimes get lucky and get better quality stuff than the new stuff I buy (as in HF, lol). It's not that I'm cheap, which I am, but, as you've seen photos of my 7 acres of paradise, there ain't much sun, so solar has always been a back burner idea.

Here's an overhead shot. And a shot of the shop and the 'sunny' area.
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Brettny
Member
# Posted: 27 Jun 2020 12:06
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Paulz with 110v output you will want a 150v input CC. There. Bit more money than the 100v ones usualy but you can run further distances with 150v with less line loss.

I have two 30v output pannels and am still going to get a 150v input CC. I can comfortably get another pannel and wire in series.

ICC
Member
# Posted: 27 Jun 2020 12:50
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One potential problem when series connecting to obtain higher DC line voltages is that PV panels put out higher voltage when cold. So if you have some cold weather the output can be higher than what the CC is rated for. Conversely, panel voltage falls when the panels are very hot. In very hot weather the panel can get hot enough to have the voltage drop too low to be able to charge a 12-volt lead-acid battery.

The big name brand charge controllers all have string size calculators online. You input the specs for the panels, the weather extremes and it will inform you how many panels can be in series and how many in parallel.

When deciding on the battery bank voltage keep in mind that CC are output amperage limited. The aforementioned Midnite solar The Kid CC, for example is limited to a 30 amp output. So with a 12 volt battery bank that limits the total panel wattage to 30 x 14 (the rounded value for the charging voltage) = 420 watts. a 24 volt battery at 30 amps charge rate = 840 watts. A 48 volt battery at 30 amps charge = 1680 watts maximum.

I only used The Kid as an example. I have one on a trailer setup, but there are other brands and they will all have similar limitations to amps and watts. Read up before you buy anything, or experiment with stuff you may find as bargains on CL or wherever.

ICC
Member
# Posted: 27 Jun 2020 12:52 - Edited by: ICC
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Also, BTW, if mixing panels of different sizes and wanting to use one charge controller, the voltage outputs and the amperage outputs of the panels should be matched fairly close; 10% maximum variation will keep you more or less in line for best efficiency of the CC. I just mention that in case you think of adding some other panels at some point.

FWIW I have an almost 400 foot run from PV to CC and batteries. That uses a 600 volt charge controller input (max) to reduce the wire gauge size to something more affordable.

ICC
Member
# Posted: 27 Jun 2020 15:24 - Edited by: ICC
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Quoting: Nobadays
I think 4% is considered acceptable... ICC

3% is what my solar installer friend aims for. Me too. But don't get too carried away as most DC systems, unless they have a tracker, hardly ever put out the maximum rated power. However, mine does go over spec in the summer for an hour or so on a bright sunny day. Two possible reasons. (1) the panels are still relatively new and may have been slightly under rated so as to better keep to the rated output many years down the road. (2) We are at 9000 feet. Higher elevation = less air, as well as very clean air, and that increases the amount of sunshine that hits the panels. The amperage goes up a little with increased altitude.

I don't like to undersize AC wiring as voltage drop makes motors run hotter.

My electrical system calculator app uses 3% as a default for max voltage drop. I always figured that was a good number to set as a max drop. BUT, the NEC allows for 5% max drop at the outlet furthest from the service panel. So, take your choice, remembering when the NEC, like all codes, states a minimum allowed "something" that is the least good allowed. Never hurts to better.

paulz
Member
# Posted: 28 Jun 2020 07:02
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Thanks guys, I really appreciate the help. Still trying to grasp all the input and output voltage and amp parameters and options, hard on my old noggin'.

But it sounds like I'll be spending $500 to $1,000 on a controller. There is this one advertised local on Craigslist for 500, sells for 900 new. Good one?

https://www.magnum-dimensions.com/pt-100-mppt-charge-controller

FishHog
Member
# Posted: 28 Jun 2020 07:41
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The people I've talked to with Magnum components have been happy with them. Did a 3 week off grid stay in Hawaii house sitting and that is what they used. that is my only experience with their products but the owner was happy 2 years in and we had no issues.

Nobadays
Member
# Posted: 28 Jun 2020 09:37
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Magnum is good equipment.... that one would give you a lot of room to grow!

paulz
Member
# Posted: 28 Jun 2020 11:01
Reply 


Hmm, maybe I'll cal the guy..thanks! So would it take the two 110v inputs the panels are wire for now or would I reconfigure? The specs are in the link above.

ICC
Member
# Posted: 28 Jun 2020 11:51
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Have a look at the detailed specs to check what watts it can use at the different battery voltages. That will help guide you to choose 12, 24 or 48, though I still recommend 24 over 22.

Also look to see if Magnum has monitoring that can tie their inverters together with this CC. Most big names do that within their own brand.

Are you still thinking of running AC power the 400 feet? I would be careful of that choice.

paulz
Member
# Posted: 28 Jun 2020 20:23
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You mean 12 not 22 I assume. No I'm not convinced on running AC the 400 ft.

I don't see anything about specific wattage at different voltages, in this image or in the spec sheet
https://www.magnum-dimensions.com/pt-100-mppt-charge-controller

He is selling inverters with the CC but wants quite a bit. He says this stuff is not lithium battery compatible. I wasn't planning it but could happen in the future.

Here is the ad.
https://sfbay.craigslist.org/eby/ele/d/alameda-magnum-off-grid-100-amp-solar/71369104 50.html

ICC
Member
# Posted: 28 Jun 2020 20:44
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Quoting: paulz

You mean 12 not 22 I assume

Yep. Big finger tips on a small screen and no proof reading

ICC
Member
# Posted: 28 Jun 2020 20:48
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Myself, I wouldn't spend serious money if it was not usable with lithium. I'm going to look at magnums site , I haven't looked in years. Data signal iffy right now. We may have to hop over the ridge. Fishing good though, no another soul about. Just me and the Cub

paulz
Member
# Posted: 28 Jun 2020 20:58 - Edited by: paulz
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I went fishing yesterday, off the pier in San Quentin, next to the prison. Got nothing, guy down the pier caught a big ray. Really windy, big whitecaps. Still good to relax.

Thanks ICC.

paulz
Member
# Posted: 30 Jun 2020 17:43
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Quoting: ICC
Myself, I wouldn't spend serious money if it was not usable with lithium.


Catch anything? Poking around on forums I found at least one guy using the pt-100 with lithiums, LFMP whatever that is. I called the seller of this one, nice guy, says yeah with a BMS is can be used with lithium. Do other SCCs have built in BMSs?

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