sunshine_eggo
Happy Breffast!
116.07V was the peak of the day while there was no charging?
Wiring 2 Victron Smart charge controllers in parallel on PV side
- Thread starter martan
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116.07V was the peak of the day while there was no charging?
No this was with charging. You think charger is getting even higher voltage than that and not reporting it? Why would they build it that way?
sunshine_eggo
Happy Breffast!
No.
"They" are subject to the laws of physics.
If you pull a current from a voltage source, the voltage drops. I provided you with a chart showing that above.
That's the reason there's a Voc and a Vmp.
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Checkthisout
Solar Wizard
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No. The limit on the charger is OPEN CIRCUIT voltage. Panels that are hooked to a charge controller that is charging are in a CLOSED CIRCUIT.
Open circuit voltage is listed on your panels. You'll add each panels voltage if in series.
What Eggo man is trying to teach you is that cold panels can exceed the open circuit voltage listed on their label.
You do DO NOT want to exceed the CC's open circuit rating. Over-watting is tolerated, over voltage is not.
RoadTurtle
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I'm seeing my 24V panels exceeding rated VOC at 70F
I understand what VOC is, and if charge controller is capturing and logging the highest voltage during charging, then my method of measuring should be correct. Where I lost you is when you're telling me I should measure the highest voltage disconnected from the charger. What do I achieve by it if the controller is telling me the VOC already when panels are connected and measuring happens under real "charging" operation. What am I missing?
Checkthisout
Solar Wizard
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What happens when your battery is full?
I'm not sure I understand your question, or the point of it. Can you elaborate?
Checkthisout
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When the charger begins to taper the amps flowing out of the array because the battery is approaching full, the array voltage will climb up.
I wish my battery was ever full after a day of charging. But regardless, it only climbs to a point. And that's what the this whole discussion is about, finding that point of max VOC. With 5 and 6 panels.
Checkthisout
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Well, not best or worst practice. Just total up the panels and don't go over that in the faith that your battery will never be full or that the CC can tolerate some abuse.
This is all more-less theoretical stuff, I know what I'm supposed to do and what I shouldn't. Just trying to see where I can push it to the limits. Doesn't mean I will. My battery and inverter can feed what I need to feed with power, the panels are the weakest point. I need to squeeze as much as I can out of them and find ways to add more of them. It's all good.
sunshine_eggo
Happy Breffast!
Does your method account for peak voltage when there is no charging?
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There is always charging.
But let's say there wasn't, controller is reporting Vmax, isn't that the highest voltage of the array ? You answered previously there is no higher voltage than the one reported by Victron. We might be going in the circle here.
sunshine_eggo
Happy Breffast!
@martan
Let's try another more obvious example. This was an OVERCAST day that was so cold, my MPPT was shut off:
At the indicated position, I had a peak voltage of 143.03V with 0A charging. Later in the day, it warmed up enough to allow the PV to power the loads but not charge the battery.
You need to plan for the time that the charger is offline for one reason or another. It's not safe to assume that any time you have sun, the MPPT will be able to pull power. These systems require maintenance or upgrades. Unless you're willing to shut the PV off before there is any potential way to see max Voc under all circumstances, and you'll never forget or make a mistake, then sure. Go ahead. Push the envelope. What you see is too close for comfort for me on my 150/100, so I upgraded to a 250/100. Yes, I could have increased my Vmp by adding another panel in series, but my array is a fixed size and expansion isn't an option.
Let's try another more obvious example. This was an OVERCAST day that was so cold, my MPPT was shut off:
At the indicated position, I had a peak voltage of 143.03V with 0A charging. Later in the day, it warmed up enough to allow the PV to power the loads but not charge the battery.
You need to plan for the time that the charger is offline for one reason or another. It's not safe to assume that any time you have sun, the MPPT will be able to pull power. These systems require maintenance or upgrades. Unless you're willing to shut the PV off before there is any potential way to see max Voc under all circumstances, and you'll never forget or make a mistake, then sure. Go ahead. Push the envelope. What you see is too close for comfort for me on my 150/100, so I upgraded to a 250/100. Yes, I could have increased my Vmp by adding another panel in series, but my array is a fixed size and expansion isn't an option.
sunshine_eggo
Happy Breffast!
You're certain there will never be a case in the future that the MPPT won't be charging? Maintenance? Troubleshooting? BMS intervention if using LFP. I've had my system completely offline several times over the past couple years for one reason or another.
I did not say that. I think you heard what you wanted to. If you're always pulling current due to charging availability, the MPPT will never see the maximum Voc of the array.
I'm not.
Turn the charger off tonight. Leave it off for the first hour the sun is up. What is your Vmax?
In case of maintenance, or troubleshooting etc. I always disconnect the panels first, at least in my setup.
If I always pull current and MPPT never sees the maximum VOC, then the maximum VOC is not a problem for the controller, correct?
By "leave the charger off", do you mean turn it off in the menu in the app? Or physically disconnecting from the array and measure the voltage of the array manually?
sunshine_eggo
Happy Breffast!
This is a very romantic notion that things will always work as you expect. Plan for when things go wrong. Don't expect them to never go wrong.
I can't imagine a benefit of 6S that buys you anything worth the risk. higher Vmp PV is actually less efficient due to the larger DC-DC conversion gap.
menu switch in app. That way it's still active and logging. You'll be able to confirm it at the MPPT PV terminals.
Correct, and that's what we're doing, romantically speaking, I always plan for when things go wrong and there always better be a plan B.
Just wanted to see if you agree when in this one specific scenario I'm describing, the max VOC wouldn't be a problem. Of course there are many variables and real life out there. That's why I'm not going to end up with 6S array as my regular setup, perhaps I'll experiment with it, or maybe not. Just for my own amusement.
I'll test the VOC with charging 'off' tomorrow on the 5 panels and see what I get.
I'll add a 6th panel and then split it into two 3S in parallel, this will lower the voltage and perhaps I'll lose some power on voltage drop over the distance, but still safer than risking the controller that I might sell for a bigger one.
sunshine_eggo
Happy Breffast!
30-60 minutes after sunrise should suffice. The panels will warm up, and the voltage will drop.
What's the distance?
BTW, what are your daytime lows?
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