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Old 25-11-2016, 21:46   #1
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Solar panel differences?

Hi all, is then any real world differences between various brand dollar panels regarding current generated ie. Amps going into batteries?
On my last boat I had 300w monocrystaline, cheap chinese panels.On a good day after 6 years they would produce approx 14 amps/hour in full sun, this is in the tropics. Will I see higher amp reading on the xantrex display using Kyocera or equivalent compared to lesser know brands?



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Old 25-11-2016, 23:07   #2
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Re: Solar panel differences?

Quote:
Originally Posted by daletournier View Post
Hi all, is then any real world differences between various brand dollar panels regarding current generated ie. Amps going into batteries?
On my last boat I had 300w monocrystaline, cheap chinese panels.On a good day after 6 years they would produce approx 14 amps/hour in full sun, this is in the tropics. Will I see higher amp reading on the xantrex display using Kyocera or equivalent compared to lesser know brands?
(First, that's just amps not amps/hour. Please use the correct units - it avoids confusion as the discussion gets more complicated. )

If the panels are correctly rated, a cheap chinese 300w panel will produce about the same amps as an expensive Sunpower 300W panel und the same conditions. The difference is that the SunPower panel will be considerably smaller.

I assume that 14 amps was at midday. From a 300W panel at midday in the tropics, that is lower than I would expect but important factors are:

What sort of batteries?
What was your SOC% at midday
What voltage was going into your batteries?

What sort of controller, PWM or MPPT?
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Old 25-11-2016, 23:30   #3
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Re: Solar panel differences?

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(First, that's just amps not amps/hour. Please use the correct units - it avoids confusion as the discussion gets more complicated. )

If the panels are correctly rated, a cheap chinese 300w panel will produce about the same amps as an expensive Sunpower 300W panel und the same conditions. The difference is that the SunPower panel will be considerably smaller.

I assume that 14 amps was at midday. From a 300W panel at midday in the tropics, that is lower than I would expect but important factors are:

What sort of batteries?
What was your SOC% at midday
What voltage was going into your batteries?

What sort of controller, PWM or MPPT?
Ok, should not of added the 14A bit. I realize controller and soc have a bearing.
My question was do cheap panels put out the same as expensive panels. Thanks for your answer.

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Old 26-11-2016, 01:45   #4
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Re: Solar panel differences?

We have been seeing 23 to 24 amps regularly on fine days around mid day from our Sunpower 327w in the tropics of Oz. Going through a Morningstar Tristar 60 MPPT controller.

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Old 26-11-2016, 02:17   #5
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Re: Solar panel differences?

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We have been seeing 23 to 24 amps regularly on fine days around mid day from our Sunpower 327w in the tropics of Oz. Going through a Morningstar Tristar 60 MPPT controller.

Dave
Wow! That's fairly impressive. Theoretically they can put out approx 27amps, yours is very close. In my experience generally 60% of the theoretical maximum is normal, but I haven't used a mppt.
Thats one for the more expensive panels.

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Old 26-11-2016, 15:49   #6
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Re: Solar panel differences?

Quote:
Originally Posted by daletournier View Post
Hi all, is then any real world differences between various brand dollar panels regarding current generated ie. Amps going into batteries?
On my last boat I had 300w monocrystaline, cheap chinese panels.On a good day after 6 years they would produce approx 14 amps/hour in full sun, this is in the tropics. Will I see higher amp reading on the xantrex display using Kyocera or equivalent compared to lesser know brands?



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I'm a solar tech. Most solar panels are rated at about 16% efficiency, sunpower gets to 21% but cost a lot more. For a house the efficiency may not matter but on a boat the extra efficiency can be a big advantage.
There are three tiers of panel manufacturers. Tier one is used for solar farms where bankability is essential, the warranty had to be insured.
Tier two are the high quality large manufacturers.
Tier three are the smaller shops, generally good but check reputation, warranties are worthless when they go out of business.
There is some very cheap garbage out there. You'll get power from them but they will get water ingress before long because the backing film is cheap junk.
Reputation is everything.
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Old 26-11-2016, 16:11   #7
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Re: Solar panel differences?

You actually have more experience than %95 of the people on this board...

However.. Our experience over the last 10 months is that our Chinese solar panels put out EXACTLY what they are rated for at peak sun (about 12:30pm in the summer, in the tropics). Our 300W (we have 3, 300W chinese arrays) array will put out 300W if our batteries can take it. Our 3 300W arrays are about %15 bigger than a comparable big name array. Same power, just more space and WAY WAY less money!

Now here is the secret.. If you are running lead acid batteries, and an array bigger than 600W, you are probably saturated anyway. Unless you are burning power charging other devices (laptops, tablets, ect) you aren't making use of the extra power. Lead acid batteries can only accept so much power due to internal resistance (about 50-60A is it. closer to 50).

We have a cat, so we have ample space for panels. So for our setup, cheap Chinese panels are perfect. If we had a monohull with limited space, then it may be worth it to get more power in less space.

Back to your initial question.. Do the big name panels make more amps.. Absolutely if they are rated higher (and are probably smaller).
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Old 26-11-2016, 16:27   #8
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Re: Solar panel differences?

I agree with the fact that charge acceptance is inversely proportional to SOC , but if you can get that absorbtion completed early in the day by having efficient (and more) panels then you will get closer to full by the end of the day. Realistically im going to be limited to 400-500w, which is plenty for my needs.
Thinking of several small mppt regulators rather than one big one, thoughts?
I obviously have my own views regarding my questions but are interested in others opnions.
Thanks for the above responses.

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Old 26-11-2016, 17:00   #9
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Re: Solar panel differences?

The ratings on solar panels are basically minimum ratings for a standard condition. Panels that are designed for say 200watts might be sorted off the manufacturing line. Ones that only give off 193watts might then get labeled and sold as 180watt panels.
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Old 26-11-2016, 17:52   #10
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Re: Solar panel differences?

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Originally Posted by daletournier View Post
I agree with the fact that charge acceptance is inversely proportional to SOC , but if you can get that absorbtion completed early in the day by having efficient (and more) panels then you will get closer to full by the end of the day. Realistically im going to be limited to 400-500w, which is plenty for my needs.
Thinking of several small mppt regulators rather than one big one, thoughts?
I obviously have my own views regarding my questions but are interested in others opnions.
Thanks for the above responses.

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I have found that multiple controllers (MPPT) tend to fight each other ie one will drop to float well before it should due to sensing the charging volts from the other controller.

Depending on how you can do your wire runs to batts this can be an issue in the real world vs paper. Ill be moving up to a single larger controller next season to avoid this so if this can be an issue for your run(s) I would avoid multiple controllers.

Also on the efficiency thing the panel temps play a huge role especially with the thin semi flexible panels. I found that in turkey vs greece for example where panels got way hotter due to less wind cooling the panels the efficiency was down to nearly half what I was experiencing in Greece (25 amps peak in greece vs 16amps on a hot still day in turkey)

I have older german panels on one string and newer chinese panels on a second string and saw no real difference in the heat caused efficiency drop for whats that worth also.
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Old 26-11-2016, 18:39   #11
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Re: Solar panel differences?

Hi Barra, ok that's interesting. Theory vs real world, my using multiple smaller mppt's was theory, which is always trumped by real world.....

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Old 26-11-2016, 19:14   #12
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Re: Solar panel differences?

If you have an MPPT controller controlling say 4 parallel and one gets shaded, the MPPT tracking will not be optimal. If you had two controllers on two sets of two panels, if one gets shadowed the other set will still get tracked optimally. Its all a tradeoff. The other advantage to multiple controllers is back up if one dies.
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Old 26-11-2016, 19:49   #13
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Re: Solar panel differences?

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If you have an MPPT controller controlling say 4 parallel and one gets shaded, the MPPT tracking will not be optimal. If you had two controllers on two sets of two panels, if one gets shadowed the other set will still get tracked optimally. Its all a tradeoff. The other advantage to multiple controllers is back up if one dies.
That was my thinking and the reason I was thinking of 2 or 4 smaller genasun controllers.

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