MisterSandals
Participation Medalist
The good news is that in Alaska (AK in your name?), you were not getting 900W from you array so 20A SCC not as bad in reality as on paper.
But yes: 20A x 28V charging = 480W
Which charge controller should I buy?
- Thread starter WillAK
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But yes: 20A x 28V charging = 480W
I have two exact same charge controllers, one is 20a and one is 30a. I just happened to double check and noticed the box for the 20a controller was empty and then realised i'd had the 20a connected all summer and wondered why my 900w panels were only ever putting out 600w.
I thought that was just the efficiency of the solar panels!
You would have to post the model number for us. Some of those EPEVER had an load output that was a bit lower then the battery charger output. I went from epever to victron. The victron worked much better.
Hedges
I See Electromagnetic Fields!
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Are your 2x 450w PV panels in series or parallel?
If they are in parallel, or if voltage is high enough that you can put them in parallel, try orienting them one toward morning sun, one toward afternoon.
With a 90 degree angle between them, trig or in the case of 90 degrees just the Pythagorean Theorem will indicate the maximum area presented toward the sun is about 0.7 x 900W = 630W.
You should get the same 600W but for more hours of the day (given long enough days)
Besides fitting more panels on a given charge controller, this may help avoid curtailing production due to full battery middle of the day, keep battery full later in the evening and begin recharging earlier in the morning - less depth of discharge used at night, more usable power for you.
At least in the summer (when you may not need it as much) because sun sweeps a larger angle.
If they are in parallel, or if voltage is high enough that you can put them in parallel, try orienting them one toward morning sun, one toward afternoon.
With a 90 degree angle between them, trig or in the case of 90 degrees just the Pythagorean Theorem will indicate the maximum area presented toward the sun is about 0.7 x 900W = 630W.
You should get the same 600W but for more hours of the day (given long enough days)
Besides fitting more panels on a given charge controller, this may help avoid curtailing production due to full battery middle of the day, keep battery full later in the evening and begin recharging earlier in the morning - less depth of discharge used at night, more usable power for you.
At least in the summer (when you may not need it as much) because sun sweeps a larger angle.
4mm² solar cable is rated for 55amps, 6mm² for 70amps ...
14a panels X 4 = 56amps ... so normal 4mm² is not suitable, 6mm² would be correct
No, im not in Alaska. The AK is the beginning of my surname.
I'm in South of Spain 36°N so we get a full 10-12 hours of direct sun every day. So I'm sure the panels would have easily put in around 900w.
As I said the most i've ever seen it put in is 630w at 3pm July 31st. The 20A CC explains why
Ok now im really confused! I didn't have the 20a charge controller connected. I have a 40a connected.
So why do my solar panels only ever put out about 60% of their rated power? They are supposed to be 900w and I only ever saw 630w maximum.
The 2 panels are connected in parallel and were pointed directly at the sun at 2pm on july 31st.
So why do my solar panels only ever put out about 60% of their rated power? They are supposed to be 900w and I only ever saw 630w maximum.
The 2 panels are connected in parallel and were pointed directly at the sun at 2pm on july 31st.
Hedges
I See Electromagnetic Fields!
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Which panels?
Does the data sheet give NOCT power? Can you find them on CEC website, and what PTC power is listed for them there?
Rated STC watts are under conditions of 1 full sun and 25 degree C cell temperature.
Under realistic conditions, they typically produced 70% to 85% of that, but occasionally conditions are ideal and they may hit 100%.
Off season, the sun is filtered through longer atmosphere path. Summer, they are at elevated temperature. As they get older, they produce less.
It does sound like you should have gotten more than 67%.
Was battery near full at that time? Could have charged most of the way in the morning, and battery was accepting less at that point.
Data sheet page 47, looks like 24V battery and relatively low PV voltage should be 98% efficient and 600W
(Good they provide these curves, not seen for many brands.)
What voltage are the panels putting out when operating at maximum power point in hot weather?
Try two in series (so long as Voc would not be too high, nominal and adjusted for freezing.)
If battery is at elevated charging voltage, in hot weather Vmp could be lower, and SCC needs some headroom.
Page 41 it says battery voltage +2V, doesn't need much. If the specs are done well, that would even be at full current.
But try higher PV voltage (which should only decrease efficiency 1%.)
If that doesn't help, go back to lower voltage, because 2% loss is 2/3 the temperature rise of 3% loss, better for reliability.
Does the data sheet give NOCT power? Can you find them on CEC website, and what PTC power is listed for them there?
Rated STC watts are under conditions of 1 full sun and 25 degree C cell temperature.
Under realistic conditions, they typically produced 70% to 85% of that, but occasionally conditions are ideal and they may hit 100%.
Off season, the sun is filtered through longer atmosphere path. Summer, they are at elevated temperature. As they get older, they produce less.
It does sound like you should have gotten more than 67%.
Was battery near full at that time? Could have charged most of the way in the morning, and battery was accepting less at that point.
Data sheet page 47, looks like 24V battery and relatively low PV voltage should be 98% efficient and 600W
(Good they provide these curves, not seen for many brands.)
What voltage are the panels putting out when operating at maximum power point in hot weather?
Try two in series (so long as Voc would not be too high, nominal and adjusted for freezing.)
If battery is at elevated charging voltage, in hot weather Vmp could be lower, and SCC needs some headroom.
Page 41 it says battery voltage +2V, doesn't need much. If the specs are done well, that would even be at full current.
But try higher PV voltage (which should only decrease efficiency 1%.)
If that doesn't help, go back to lower voltage, because 2% loss is 2/3 the temperature rise of 3% loss, better for reliability.
I pretty much plan on 60% from my strings in the summer. Welcome to solar.
At least it's not just me then. I presumed I'd done something wrong.
Clear, cold winter day in full sun, you should see full power. Good time to make some waffles with all the power.
In the summer it's 30c/100f in the shade so the panels could easily be 60c/140f so that makes sense. I'll test it over the next few months as the colder weather comes.
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