Testing A Suspect 24V Solar Panel

[kando]

G'day mates,

I'm new to all this solar power stuff so don't be to hard on me for asking, what may be to some of you, dumb questions.
Okay, I won/bought a, supposedly, 24V 200W panel from a seller on eBay.com.au, I plan on installing a off-grid 600W (3 x 24V x 200W panels) on my workshop roof, I already had two 200W x 24V panels sitting in my workshop, so I got the third, suspect, panel. The first thing I noticed on unpacking the panel was, it is not the same dimensions as my other two 24V 200W panels. (I have most of the other gear I need, controller, Inverter, batteries and what-not but this question is on the suspect panel so I won't muddy the water...I hope) And there is no spec label on the back of the suspect panel so it could be anything.
Anyway, I set the three panels in full midday sun facing North (I'm in Australia) and used my multimeter to do a quick Voc test. With my two older 24V 200W panels, one gave a Voc reading of 38v, the other gave a Voc reading of 37.2v. With the suspect new panel, I got a Voc reading of 21.1V. So I'm guessing the new panel is a 12V panel and not a 24V panel. Am I right or am I missing something?

Thanking you in advance for any advice you can provide.

Bill
Australia

[Mike90250]

21Voc is most certainly a 12V system panel. Useless on a 24V system.

Is it a home made panel, or a factory reject ? Most factory panels will have a spec sticker on them

[kando]

Sus 24V panel

21Voc is most certainly a 12V system panel. Useless on a 24V system.

Is it a home made panel, or a factory reject ? Most factory panels will have a spec sticker on them

G'day Mike,

The panel was/is not on any system,I did the Voc test on the panel while it was sitting in my backyard, facing the full midday sun on a beaut clear sunny day.
The seller is selling the same panels on eBay.com.au He states on the sales page, Quote from sales page:
FEATURES

Peak Power (+/- 5%)
Rated Voltage: 24 V Also available in 12 V
Rated Current: 5.56 A
Open Circuit Voltage: 36 V
Maximum System Voltage: 1000V
Diode Protection Fitted
Front Glass: 3.2 mm (1/8 in) tempered
Junction Box: IP-65 rated with diode
Frame: Anodized aluminium alloy type
End Quote

From his text above, I assumed all sales are for 24V 200W panels unless the buyer requests a 12V 200W panel. I'm trying to get the seller to exchange the panel for a 24V 200W panel so we'll see how things work-out.
He replied to my email with the following response.
Quote:
Due to the nature of importing these items, the manufacturer will from time to time provide variations of the panels we order. We request you set them up and provide photos of any measurements that you take readings of.
End Quote.

I'm guessing the Voc reading will be enough info' for him to exchange the unit. I'm also guessing the importer/seller knows less than I do about solar...And I know just enough to be classed as dangerous

Cheers Mike,

Bill
Australia

[russ]

Bill - Sounds like he selling whatever junk he can get his hands on - typical of fleabay

[FloridaSun]

G'day mates,

I'm new to all this solar power stuff so don't be to hard on me for asking, what may be to some of you, dumb questions.
Okay, I won/bought a, supposedly, 24V 200W panel from a seller on eBay.com.au, I plan on installing a off-grid 600W (3 x 24V x 200W panels) on my workshop roof, I already had two 200W x 24V panels sitting in my workshop, so I got the third, suspect, panel. The first thing I noticed on unpacking the panel was, it is not the same dimensions as my other two 24V 200W panels. (I have most of the other gear I need, controller, Inverter, batteries and what-not but this question is on the suspect panel so I won't muddy the water...I hope) And there is no spec label on the back of the suspect panel so it could be anything.
Anyway, I set the three panels in full midday sun facing North (I'm in Australia) and used my multimeter to do a quick Voc test. With my two older 24V 200W panels, one gave a Voc reading of 38v, the other gave a Voc reading of 37.2v. With the suspect new panel, I got a Voc reading of 21.1V. So I'm guessing the new panel is a 12V panel and not a 24V panel. Am I right or am I missing something?

Thanking you in advance for any advice you can provide.

Bill
Australia

just read your intro thread and noticed you said, " I already have most, if not all the gear I need, including six x 6V x 225AH batteries, controller, inverter and what-not to set-up the small off-grid system."
So you are planning on a 12V, 675Ah battery bank??

[kando]

just read your intro thread and noticed you said, " I already have most, if not all the gear I need, including six x 6V x 225AH batteries, controller, inverter and what-not to set-up the small off-grid system."
So you are planning on a 12V, 675Ah battery bank??

Yes mate, I have six Trojan 6v 225AH Deep Cycle Golf Cart Wet Battery T-105's set-up as three 12v banks. (Parallel & Series Connections) At the moment I keep four of the batteries charged using three American made smart battery chargers, Genius G3500, I change the charger from one battery to another as the charger reports full charge on the battery. I also use one 40W solar charger/controller (The British designed and built PWM5 Solar Charge Controller) wired to one 12v bank, it does a great job. When I get around to putting things together, I'll wire the three banks as one 12v bank. I also have one 30A MPPT 12V/24V 380W/760W Solar Panel Regulator Charge Controller and a 2.500W pure sine wave inverter (5000 max) I plan on adding six more T-105 batteries, if I need them, wired the same way. I'll install a second lot of three 24v 200W panels and another 30A MPPT Controller to feed that second bank but that's only if I need the extra.
I plan on setting everything up using the KISS principle 12V, plus the 12/220v inverter to run any power-tools when needed, just as though I was working on a boat, but you know what they say...The best laid plans of mice and men Whatever, the first order of the day is to sort-out this bleeding solar panel gaff, exchange the 12v panel for the 24V 200W panel, which was advertised, then set things up and see how everything works-out.

Cheers,

Bill
Australia

[Mike90250]

.... I plan on adding six more T-105 batteries, if I need them, wired the same way. I'll install a second lot of three 24v 200W panels and another 30A MPPT Controller to feed that second bank but that's only if I need the extra......

You already have more batteries [12V, 675Ah] than panels [600w : 40A] that can keep them charged.

For your nearly 700A of batteries , you NEED about 70A of charging, to recharge after a cloudy day. Or plan on running a generator to charge them. Just add the PV panels to keep the current batteries healthy. And you should consider a 24 or 48V system with all that amps at 12V.

[FloridaSun]

Yes mate, I have six Trojan 6v 225AH Deep Cycle Golf Cart Wet Battery T-105's set-up as three 12v banks. (Parallel & Series Connections) At the moment I keep them charged using three American made smart battery chargers, Genius G3500. When I get around to putting things together, I'll wire the three banks as one 12v bank. I also have one 30A MPPT 12V/24V 380W/760W Solar Panel Regulator Charge Controller and a 2.500W pure sine wave inverter (5000 max) I plan on adding six more T-105 batteries, if I need them, wired the same way. I'll install a second lot of three 24v 200W panels and another 30A MPPT Controller to feed that second bank but that's only if I need the extra.
I plan on setting everything up using the KISS principle 12V, plus the 12/220v inverter to run any power-tools when needed, just as though I was working on a boat, but you know what they say...The best laid plans of mice and men Whatever, the first order of the day is to sort-out this bleeding solar panel gaff, exchange the 12v panel for the 24V 200W panel, which was advertised, then set things up and see how everything works-out.

Cheers,

Bill
Australia

Understand you will not be getting full use of your batteries with parallel connecting. You will need at least a C/12 charge rate as well so with your present sent of 3x225Ah .. a minimum of 56Amps.
here's a good read on battery connections;

http://www.smartgauge.co.uk/batt_con.html

[kando]

Battery Charging

You already have more batteries [12V, 675Ah] than panels [600w : 40A] that can keep them charged.

For your nearly 700A of batteries , you NEED about 70A of charging, to recharge after a cloudy day. Or plan on running a generator to charge them. Just add the PV panels to keep the current batteries healthy. And you should consider a 24 or 48V system with all that amps at 12V.

G'day Mike,

I would have liked to have gone 24v but the 2500w (5000w max) inverter I have is 12v/220v, all my other gear, apart from the batteries, is 12/24v. Could I reduce the battery bank to four T-105 batteries? Then, if needed, buy two more T-105 batteries to make-up a second 4 x 6v bank, fed from a second lot of three 24V 200w or 250W panels. Chances are I will seldom use that much power to deplete the four T-105 batteries as I'll be running ten or twelve 12V 42 LED lights, as required, power-tools as required (they would pull the highest load) one 190W water pump, about six or eight hours per day. I have yet to test the water pump to see just how many watts it does pull but the label says 190W.
I've already got solar power with grid tie inverter on my home, it was installed by the pro's back in Feb' 2009, so basically I'm setting-up this stand alone small solar plant in my workshop as a test...Just in case I ever sell-up and move to living of the grid in the mountains or the bush.
Thanks for sharing your knowledge Mike.

Bill
Australia

[kando]

Battery Charging

Understand you will not be getting full use of your batteries with parallel connecting. You will need at least a C/12 charge rate as well so with your present sent of 3x225Ah .. a minimum of 56Amps.
here's a good read on battery connections;
http://www.smartgauge.co.uk/batt_con.html

Thanks for the tips and the link FS, good information there.
How about if I go with 2 x 225AH battery banks, (4 x 6V x 225AH batteries) would the three 24V 200W panels be enough?

Bill
Australia

[Mike90250]

Minimum battery charge rate - flooded cells, 7 -12% of battery capacity ( C7-C12) This allows for enough time in absorb to bubble the electrolyte and stir it up, to prevent it from stratifying.

A couple more stickies to read
Solar Off-Grid Battery Design

http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design

http://www.solarpaneltalk.com/showthread.php?2144-How-Many-Batteries-amp-Why-Tutorial

[FloridaSun]

Thanks for the tips and the link FS, good information there.
How about if I go with 2 x 225AH battery banks, (4 x 6V x 225AH batteries) would the three 24V 200W panels be enough?

Bill
Australia

A minimum C/12 charge, 450Ah/12= 37.5A, rate allows for proper bubbly while a maximum of C/8, 450Ah/8=56.25A will charge sooner but still gives the FLA battery enough time to accept the charge so you're looking for 500W to 750W of panel for your 450Ah battery bank. Yes, 600W would work fine with MPPT controller.
Planning for a 24V bank now might save you some costs. You would be able to use your existing MPPT controller, smaller wiring-cables and be able to connect batteries in series for longer life.

Inverter thoughts... 450Ahx12V= 5400Wh Pulling even 1000W from your batteries would only give you a few hours use before 50% discharge. You could invest in a much smaller (than 2500W) 24V inverter for better efficiency at less cost... not only inverter cost but for cables too.

[kando]

12V - V - 24v Set-Up

A minimum C/12 charge, 450Ah/12= 37.5A, rate allows for proper bubbly while a maximum of C/8, 450Ah/8=56.25A will charge sooner but still gives the FLA battery enough time to accept the charge so you're looking for 500W to 750W of panel for your 450Ah battery bank. Yes, 600W would work fine with MPPT controller.
Planning for a 24V bank now might save you some costs. You would be able to use your existing MPPT controller, smaller wiring-cables and be able to connect batteries in series for longer life.

Inverter thoughts... 450Ahx12V= 5400Wh Pulling even 1000W from your batteries would only give you a few hours use before 50% discharge. You could invest in a much smaller (than 2500W) 24V inverter for better efficiency at less cost... not only inverter cost but for cables too.

G'day FS,

I went with a 12V set-up because I have several items in my workshop already. I have four 12v to 220AC inverters, one 300w, two 1200w and one 2500w, six x 6v T-105 batteries, one 12/24v 30A MPPT controller, solar panels and some other gear. I guess I could still go with a 24v system, I could sell all four of the 12v Inverters, buy one 24v to 220AC x 500w Inverter to run the water-pump, buy one 30A 24V volt to 12V DC-DC Power Converter to run the 12v LED lights, or run the 12v LED lights straight from the 12/24v controller, if that's possible, and run any power-tools I may want to run as they are now, from the 220v AC grid. I seldom use my power-tools these days so that would be no biggie.
Thanks for your advice FS, looks like I have some decisions to make.

Bill
Australia

[kando]

Set-up Rethink

G'day mates,

I have all the gear to do the work below, nothing to buy...I hope
I believe I will set-up two 12v systems, system one (1) will consist of three 24V x 200W solar panels, one 12/24 30A MPPT controller, four x 6V x 225AH batteries wired as 12v and one 2500w Power Inverter, (5000w max) pure sine wave DC 12V TO AC 240V. I have almost half a roll of 6mm tinned cable in my shop, and as I would only have a short run, about 5 or six meters overall, I believe that cable will be heavy enough. What do you think, will the 6mm tinned cable be good enough for the job, if not, what size should I use? While I'm asking, what size fuse should I use between the panels and the controller and the 12v battery bank to the inverter? This system will run a 190w water pump.

The second system (2) will consist of one 12v x 135w solar panel, one 12v 10A controller, two 6v x 225AH batteries wired as 12v. I'll use this system to run 10 12v LED lights as needed in my shop. I would use the same 6mm tinned cable in this system, would a 10A fuse between the panel and the controller be enough?
I'll set-up the light switches to light two LED's when switched on and each switch will be protected by a 10A fuse. So what do you think, will that work?

Thanking you in advance for your advice.

Bill