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diy solar

Solar pv voltage too high

Dooski3

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Jun 29, 2021
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Ok so I recently got my setup all done only to find out my voltage is a bit too high. The first few days of operation were pretty cloudy and falsely made me think everything was ok. When the sun is out I'm at 120v ish and the mppt on my growatt is only good for 60-115v. I was running a 3s3p configuration. Am I going to have to run a 2s4p setup? Or is it possible to leave it 3s3p but basically just make 1 string 2s to drop the overall voltage? Which would be a lot easier to rewire and give a higher voltage?
 
Ok thanks guys. Is the second wiring configuration possible until I do the rewire? If so would the voltage be about 107 if my math is correct? I'm going to have to order some stuff to do the rewire.
 
go with the 2S4P, Which will put your voltage within limits, and the four parallel panel arrangement will give you more current to play with. - remember, panels in series, the voltage will be additive. Pannels in parallel, the currents will be additive.
 
What is the current limit on the SCC? Going to 4P might provide too many amps. And the higher amps of 4P over 3P means you need to revisit your wiring sizes and fuse/breaker sizes to be sure they can handle it.
 
go with the 2S4P, Which will put your voltage within limits, and the four parallel panel arrangement will give you more current to play with. - remember, panels in series, the voltage will be additive. Pannels in parallel, the currents will be additive.
Ok thanks. I'm new and this is my first setup so bear with me but I was thinking you wanted to be higher in the voltage range (but within limits) to account for cloudy days and shading? Or do people just not do it because of longevity reasons as the first guy mentioned? Do voltage and amperage drop together? (I was assuming it was mainly the voltage)
 
What is the current limit on the SCC? Going to 4P might provide too many amps. And the higher amps of 4P over 3P means you need to revisit your wiring sizes and fuse/breaker sizes to be sure they can handle it.
It's good for 80a so 4p will be ok. But I will be having to do a rewire (including breaker) as you mentioned.
 
The solar panels will only produce what the load is asking for. For example, my 6 panels operate on average 65 volts only put out 12 amps to run my house. I have 2S3P with the maximum voltage Vmax 70 volts and SCC of 24 amps. But where my panels are located and how I wired them, I only get 19 amps of available current at 68 volts and an air temperature of 80 F. - But my panels run my whole house during the day and from the battery for 5 hours at night before the Utility kicks in for the rest of the night. - So I'm not going to lose sleep of losing a few amperes.
 
Basically like an alternator in a 12v system does? At least in my situation I will need all of the amperage they can give all of the time though. So the load would always be max. Just the battery charging by itself should handle all they can give, but I'm also running a "tiny house".
 
I found my answer to the second wiring option question. I was way off in how I thought it worked. It would only end up being a overall voltage of 80v. (the lowest voltage in the parallel string)
 
When the sun is out I'm at 120v ish and the mppt on my growatt is only good for 60-115v. I was running a 3s3p configuration. Am I going to have to run a 2s4p setup?
If 3S is 120V, then 2S @ 80V will be perfectly fine for your Growatt.

With MPPTs the voltage is generally kept within an operational band and doesn't vary a huge amount, while the current drawn will be varied based on available light and what loads the inverter needs to supply.

It's also wise to leave a bit of headroom between the rated voltage of a string and the inverter's Voc limit.

I have a similar issue with mine, except it's a 105V Voc limit. 3S just ain't suitable.
 
Am I missing something, what Growatt only accepts 60-115vdc panel input?
What model Growatt do you have? Whats the specs on panels VOC? ISC? joe.
 
Am I missing something, what Growatt only accepts 60-115vdc panel input?
The one in this other thread has that MPPT spec:

SPF 3000TL LVM-24P

More recent ones have a Voc of 145V
 
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