How to optimize what I already have??

B3nn

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Oct 26, 2021
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So question about adding more batteries.
Is there a safe way to mix lithium in?
Run them on a different charge controller? Or don't even bother?
 

Hedges

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Mar 28, 2020
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8,397
Ya. On the charge controller it says there's 18v input. I assumed that was what it was reading from the panels at real time. But now I'm questioning if that's what it is, or if it's the max option for my config

18V means it had the PV panels at Vmp, and you were harvest all power available.
Or, 18V was as low as it could pull them, and lower voltage would have given more power? What amperage did they show?
 

Hedges

I See Electromagnetic Fields!
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Mar 28, 2020
Messages
8,397
So question about adding more batteries.
Is there a safe way to mix lithium in?
Run them on a different charge controller? Or don't even bother?

Don't bother. Different charge voltages and current sharing due to resistance. (Although, some people advocate it)

If you make a lithium system, max and min voltage are more critical (BMS should disconnect if SCC or inverter pushes to wrong voltage.)
They also can't be charged below freezing. And they have some fire risk.
But, they tolerate (thrive) not being fully charged.

I prefer excessive over-paneling, and having charge current regulated by SCC.
 

B3nn

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Oct 26, 2021
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18V means it had the PV panels at Vmp, and you were harvest all power available.
Or, 18V was as low as it could pull them, and lower voltage would have given more power? What amperage did they show?
Just looking right now. Volts says 14.6 (it's early morning hear and indirect sun.
Current amps is 0.34a
 

Hedges

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Mar 28, 2020
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8,397
I do recommends 2s2p.
Curious what voltage and current you'll see early morning with that.
14.6V sounds like pulled as low as it can given battery voltage and headroom, so I'm guessing higher PV input voltage helps (during this very low production time.)
 

B3nn

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Oct 26, 2021
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Man. This is actually doing considerably better then before.
I also ended up buying an automatic power transfer switch that I'll install this weekend.

That way I can run off the main house without issue, if anything ever happens or we get a crazy amount of rain/fog for a week straight again
 

vdub

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May 31, 2021
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Its a short form notation for 2 strings comprised of 2 panels in series
I always understood "2s2p" to be two in series with those two pairs then in parallel, that is, simply 2 series, 2 parallel. I've never heard of "2 strings", but maybe its just a different way of saying the same thing. 4s2p for 8 panels would be 4 in series with final out as 2 parallel. At any rate, you need to pay attention to the potential output of your solar array and the input capability of your mppt. You don't want your output to exceed the mppt's capability. You can juggle the series/parallel to make sure have a good match. Series increases your voltage and parallel increases your amps.

I'm no expert and you can see how much of a nob I am by going to my "sanity check" thread. At that point in the build of my system, I was really ignorant of what I was getting into. I have learned a lot since then, so I feel somewhat qualified to give advice. If you read thread, you will see a reference to a "string calculator". If you live in an area where the morning temps could be lower than freezing, then you need to run your panel specs against the string calculator to determine the highest possible output of your array.

Finally, the most important thing I learned in my struggle to get my system up was that I shouldn't have purchased anything until I had a good plan on paper. Unfortunately, you have made the same mistake I did. Your best bet now is to draw up your system in great deal and send it to this site and/or Renogy to make sure your system will work as you expect it too. Take pictures of of the specs on your panels. As you can see from my thread, there are lots of smart people willing to lend a hand. Best of luck! vw

On edit: Buy all the tools you will need. Get a GOOD crimper for each wire size you will be dealing with and get a kit of ends. Here is the stuff I bought:

And, most importantly, Will's book....
 
Last edited:

B3nn

New Member
Joined
Oct 26, 2021
Messages
18
I always understood "2s2p" to be two in series with those two pairs then in parallel, that is, simply 2 series, 2 parallel. I've never heard of "2 strings", but maybe its just a different way of saying the same thing. 4s2p for 8 panels would be 4 in series with final out as 2 parallel. At any rate, you need to pay attention to the potential output of your solar array and the input capability of your mppt. You don't want your output to exceed the mppt's capability. You can juggle the series/parallel to make sure have a good match. Series increases your voltage and parallel increases your amps.

I'm no expert and you can see how much of a nob I am by going to my "sanity check" thread. At that point in the build of my system, I was really ignorant of what I was getting into. I have learned a lot since then, so I feel somewhat qualified to give advice. If you read thread, you will see a reference to a "string calculator". If you live in an area where the morning temps could be lower than freezing, then you need to run your panel specs against the string calculator to determine the highest possible output of your array.

Finally, the most important thing I learned in my struggle to get my system up was that I shouldn't have purchased anything until I had a good plan on paper. Unfortunately, you have made the same mistake I did. Your best bet now is to draw up your system in great deal and send it to this site and/or Renogy to make sure your system will work as you expect it too. Take pictures of of the specs on your panels. As you can see from my thread, there are lots of smart people willing to lend a hand. Best of luck! vw

On edit: Buy all the tools you will need. Get a GOOD crimper for each wire size you will be dealing with and get a kit of ends. Here is the stuff I bought:

And, most importantly, Will's book....
Thanks for the knowledge drop. I'll check these out.
I'm happy with the choices I made for my system. My initial plan was to start small and scale up since my initial plan wasn't to have all of my 3d printers or laser cutter in my office.
I always understood "2s2p" to be two in series with those two pairs then in parallel, that is, simply 2 series, 2 parallel. I've never heard of "2 strings", but maybe its just a different way of saying the same thing. 4s2p for 8 panels would be 4 in series with final out as 2 parallel. At any rate, you need to pay attention to the potential output of your solar array and the input capability of your mppt. You don't want your output to exceed the mppt's capability. You can juggle the series/parallel to make sure have a good match. Series increases your voltage and parallel increases your amps.

I'm no expert and you can see how much of a nob I am by going to my "sanity check" thread. At that point in the build of my system, I was really ignorant of what I was getting into. I have learned a lot since then, so I feel somewhat qualified to give advice. If you read thread, you will see a reference to a "string calculator". If you live in an area where the morning temps could be lower than freezing, then you need to run your panel specs against the string calculator to determine the highest possible output of your array.

Finally, the most important thing I learned in my struggle to get my system up was that I shouldn't have purchased anything until I had a good plan on paper. Unfortunately, you have made the same mistake I did. Your best bet now is to draw up your system in great deal and send it to this site and/or Renogy to make sure your system will work as you expect it too. Take pictures of of the specs on your panels. As you can see from my thread, there are lots of smart people willing to lend a hand. Best of luck! vw

On edit: Buy all the tools you will need. Get a GOOD crimper for each wire size you will be dealing with and get a kit of ends. Here is the stuff I bought:

And, most importantly, Will's book....
Just went through your amazon links and looks like I got pretty much the same stuff as you. But I already had all the tools and terminal connectors
 
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