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dj61636goblin avatar image
dj61636goblin asked

Mppt synchronized charging

So to start, my set up is I have 2 mppt 100/30 controllers hooked up to 600 watts of solar panels in parallel. Now, when i have one mppt controller on, it's stable wattage readings, a nice steady 200-250 watts on a slightly cloudy day. The usual smooth fluctuations as clouds pass. But the moment I turn on my 2nd charge controller the wattage fluctuates greatly. Like the controllers are fighting over the electricity rather than working together.

Controller one drops to 0w while controller 2 spikes to 200 and then they keep swapping back and forth, sometimes seeing spikes of 600 watts. And the readings just jump all over the place. if I I turn one charger off and it stabilizes again. With either or charger, it will stabilize. It will even effect the reading of my DC readings labeled "heater" which is only powering led lights and nothing else at the moment.

Is this normal? Because it doesn't seem like they're synchronized charging. And it happens whether or not I have them synchronized. Nothing changes. The only change that occurs is when I completely turn one off or on. I even disconnected all the ve direct cables and it does the same swapping in the Bluetooth apps as well.


MPPT Controllerssmart solar charging behaviour
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ingo21 avatar image ingo21 commented ·
you should connect each controller to it own set of solar panels....
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dj61636goblin avatar image dj61636goblin ingo21 commented ·
Yea, it seems this is what I will have to do, I was trying to avoid running another 200 feet of heavy gauged wire from the solar panels to the cabin. I was under the impression that the synchronized charging function would have both the mppt controllers work as though it was one large mppt controller. Was assuming it would like automatically sense the PV current and split the workload between them since the 100/30 maxs out around 400w and having 600w of panels and two mppt 100/30 with the "synchronized charging" would mean I could just slap two controllers on the same panels and they'd act as a one.

Oh well...maybe I'll return the second mppt and just buy a 60 amp mppt controller if that'll be the cheaper option after pricing out 200 more feet of wire

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ingo21 avatar image ingo21 dj61636goblin commented ·

if you add another 200W of solar and a new wire

you could run 400W solar on each controller.

you would have a redundant system , if one fails or need service the other is still charging......

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seb71 avatar image
seb71 answered ·

I have 2 mppt 100/30 controllers hooked up to 600 watts of solar panels in parallel

This kind of sounds like both MPPTs are connected to the same panels.

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And it happens whether or not I have them synchronized.

Synchronized using VE.Smart Networking?

You should not use that when you have a GX device.

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If the the load+battery charging are less than your panels can produce, it will make the MPPTs to reduce the power.

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What device is set as battery monitor in your system?

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dj61636goblin avatar image dj61636goblin commented ·
Yes, both mppt's are hooked to the same panels. I was under the impression that "synchronized charging" meant I could use both the solar controllers in parallel as though it was one large mppt controllers. It seems I should split the panels and run them separately to each mppt controller. I was just trying to avoid this as my system is off grid for a cabin and the solar panels themselves are about 200 feet from the cabin and that's a lot of heavy gauge wire to purchase and run.


I was using only the gx device at first with shared voltage and current sense turned on. I turned on the synchronized charging after I seen this happening, and tried every combination of having the gx device on or disconnected.

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I have a victron smart shunt 500a as the battery monitor.

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