Will it work? Bluetti & solar panels

Firebrand

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GreAtHings. I am unsure, but I do dare to ask a question here, if I may ;-)
And I want to know if I do get it right.

Q: Can I add these 2x solar panels in series to my Bluetti AC200P (and will it work fine, of course)?
AC200P specs: Voc 35-150V

( A )
SPR-MAX3-400 specs: Voc 75.6V, Vmp 65.8V, Imp 6.08A => 2x 75.6V = 151.2V
That equals to overvoltage (by the numbers at least), so this is a no-go. Right?

( B )
SPR-MAX3-375 specs: Voc 74.9V, Vmp 62.5V, Imp 6A => 2x 74.9V = 149,8V
Close call. But this ought to work, right?

Anyone?

Thx
 

DaGoose13

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B would work until the temperature dropped enough to send the VOC over 75v and then it wouldn't work. According to STC, real performance will be about 80% or so.

You might be able to put them in parallel though and get them to work for B. A would be close.
 

MisterSandals

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You might be able to put them in parallel
What is the reasoning behind wanting them in series? Parallel seems like the obvious choice; amps will be low and easy to fuse/wire. You will gain if there are shading issues too. You will only need a pair of $15 Y connectors (Amazon has several).
 

Firebrand

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B would work until the temperature dropped enough to send the VOC over 75v and then it wouldn't work.
So, my reasoning "(2x 74.9V = 149,8V) < 150V" is not enough ... What am I missing here?

The idea is to add (SunPower) solar panels to power my AC200P efficiently, with the most solarpower yield possible.
 

MisterSandals

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So, my reasoning "(2x 74.9V = 149,8V) < 150V" is not enough ... What am I missing here?
The 150V is usually a hard, catastrophic limit. The Voc of your panels is rated at 25 deg C (77F). When it gets colder, the voltage increases.

And, I would bet the optimal MPPT range is a bit lower than the max input voltage. And, running the electronics at the red line is likely not going to be good for longevity.

I do not know the MPPT algorithm of your system, but many who have experimented have found that having array voltage closer to battery voltage is more efficient (but well within the input voltage range of course).

I used to think 80% of max input voltage was best but have since accepted repeated results indicating lower is better. If you have any results, similar or contradicting, please share.
 

MisterSandals

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The idea is to add (SunPower) solar panels to power my AC200P efficiently, with the most solarpower yield possible.
And with rereading this, it sounds like you are considering “volts” to be the unit of power. You should be looking at watts (volts x amps), the true metric for charging.
The MPPT charger is designed to optimise the charging my massaging the volts and amps for optimum yield. Supplying power in the sweet spot of the MPPT range for input voltage will allow the MPPT function operate as designed.
 

Firebrand

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Thank you, MisterSandals, for your kind reply.

Maybe 2x SunPower P3 375W then (series) ’d work? Voc 42.9V, Vmp 35.5V, Imp 10.56A
(solar panels are for a Bluetti AC200P Voc 35-150V)

(2x 42,9V = 85,8V) being much less red line I guess
 

MisterSandals

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Maybe 2x SunPower P3 375W then (series) ’d work?
Sure but probably exactly the same as 2x 75V panels in parallel. Your SCC will see voltage and amps, it has no idea or care about how your array is configured.

I am still wondering about your aversion to parallel? It’s usually only a problem when amps of the array get higher than you can wire. Neither of your proposed systems are anywhere near that.
 

Firebrand

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Okidoki then ...

Which (probably 2x) SunPower solar panels would you add in parallel for maximum gain with the AC200P?
 

MisterSandals

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Don’t get my comments wrong, I am a huge fan of series connected panels. But with 75V panels (and therefore very low amps), parallel make more and more sense.

Besides, if you consider high vs low voltage panels, thir difference is how the individual cells are connected: the higher voltage will have a greater series configuration, a lower voltage will have more cell strings in parallel.
 

Firebrand

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Thank you again. But it remains difficult. Sorry! You say the cheapest (best) solution works. Maybe I'm looking at the specs all wrong. Which solar panel specs are the most valuable then, you’d say?

I was focused on the AC200P’s Voc specs being 35-150V (I know now, that these are 'hard' limits.) and was looking at the solar panels Voc specs to check those fit in that range. Obviously I'm doing something terribly wrong here ...
 

MisterSandals

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I am not sure what you are struggling with. Either of the panel pairs in your OP are good choices. They NEED to be wired in parallel to keep the volts in range.

The 42.9 V panels will work equally well. I think series would be better but parallel would be sufficient, especially with shading issues.

It won’t start charging until it sees 35V so if you put 42.9V panels in parallel, is will take nearly full sun to start. Not the best for cloudy days either.

If either of the three workable solutions is significantly cheaper, personally I would choose the cheaper. All are fine, actually quite good for what yet sounds like you are doing.
 

Firebrand

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I think I kinda get it now, hopefully ;-)


AC200P Voc 35-150V

2x SPR-MAX3-400 "in series"
Voc 75.6V ... BUT (!) in winter that number may go up, e.g. 85V
So (2x 75.6V = 151,2V being already >150V hard limit) becomes (2x 85V = 170V being >150V hard limit).

2x SPR-MAX3-400 "in parallel"
Voc 75.6V ... BUT (!) in winter that number may go up, e.g. 85V
So 2x solar panels equal Voc 75.6V (or 85V in winter), staying safely <150V hard limit.
Keeping in mind that – in real use – at least 35V (or perhaps better 37V) is needed to start charging. (a 75.6V solar panel usually drops V, weather)


This was an example. I may choose to go with another type of solar panels (undecided), as Bluetti states: "We suggest connecting at least 3pcs BLUETTI SP120 (120W) solar panel or 2pcs BLUETTI SP200(200W) in series. The open-circuit voltage of AC200P is between 35V-150V. Would you mind making sure solar panels' open-circuit voltage is in the range? Otherwise, it may cause low voltage/overvoltage protection. In addition, considering the loss of solar panels during conversion, the effect of 2 panels is not good." I guess that's because a solar panel usually drops V (weather) and 35V (or 37V) is needed to start charging. And a solar panel set-up of 360W appears to be a minimum.
 

MisterSandals

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I guess that's because a solar panel usually drops V (weather) and 35V (or 37V) is needed to start charging. And a solar panel set-up of 360W appears to be a minimum.
The Bluetooth 120W solar panel Voc is 24.4V and the working voltage (Vmp), is 19.6V so they need to be in series to get to just belowmiddle of the input voltage range.

I suspect the voltage for the 200W panels is similar.

So the key is getting the array voltage to meet the SCC range. Still.

 

Firebrand

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There are multiple solutions. But for me, now, I believe 2x SPR-P3-375’s ought to work if my calculations are right. That's what I wanted to know.

Definitely going to try and learn more. No urgency.

Thank you all for your input.
 

MisterSandals

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I believe 2x SPR-P3-375’s ought to work
They will be perfect in series. A 43V panel is more standard and adaptable than a 75W panel so a good choice in that matter too.

Be careful, solar is highly addicting. Check back in when you get this up and running. We will help with your next solar project too if you need it.
 
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