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diy solar

Runaway Voltage ~ Growatt SC48120-MPV SCC

MrM1 said:
Agreed. And in speaking with Watts247 they are ok to refund so I will go that way and may try a replacement as I cannot find another SCC that will charge between 100-120 amps with a 250v max input AND has PV1 and PV2 inputs.

The Sigineer Power 120A (M48120) fits the bill ... but at least cosmetically it looks exactly like the Growatt SCC I already have, just rebranded.

The reason I need 2 PV inputs is that is how the system is already designed from the combiner boxes. Any ideas on a different SCC that has 2 inputs that fits this bill?

System as designed right now:
View attachment 123519
Click to expand...

Did you try slaving it to the AIO yet?

The sigineer link your provided said it will slave to their inverters, I would imagine your growatt would do the same?
 
So I had chimed in on this a while back and have gone over the entire thread again. My Growatt AIO is doing the exact same thing with its internal mppt charger. I have tried different settings and get no improvement. If charging only from the grid, the batteries will charge to the float level and sit there indefinitely. If the solar panels are connected, even when the charge priority of the growatt is set to utility only, and if there's even a little solar available, the voltage rises slowly until the BMS shuts off due to the first high cell hitting the trigger point.

And to a few prior posts saying it's just junk, pitch it and get something good, that's not a helpful comment at all. Please don't bother replying if that's your best advice.
 
Brett V said:
And to a few prior posts saying it's just junk, pitch it and get something good, that's not a helpful comment at all. Please don't bother replying if that's your best advice.
Click to expand...

The charger you describe is not functioning properly. If that's how they work, and this thread is the first time I've heard of it, saying it's junk is very helpful. I've personally helped configure a dual growatt system charging DIY 8S2P Eve 280Ah cells configured for manual charging. They performed exactly as they should. Charge to absorption, hold for a bit, drop to float. Done.

The OP and you are describing a malfunctioning MPPT.
 
sunshine_eggo said:
The OP and you are describing a malfunctioning MPPT.
Click to expand...

That's what I was figuring, and with my symptoms being exactly the same as the OP, thought it relevant since he's using a stand alone mppt and I'm using the integrated one in the AIO. I wonder if they're the same board inside?
 
sunshine_eggo said:
The charger you describe is not functioning properly. If that's how they work, and this thread is the first time I've heard of it, saying it's junk is very helpful. I've personally helped configure a dual growatt system charging DIY 8S2P Eve 280Ah cells configured for manual charging. They performed exactly as they should. Charge to absorption, hold for a bit, drop to float. Done.

The OP and you are describing a malfunctioning MPPT.
Click to expand...
So from what you can tell, am I missing anything in my set?

I plan to replace the charger from Watts 24/7 and see what a different one will do
 
Brett V said:
That's what I was figuring, and with my symptoms being exactly the same as the OP, thought it relevant since he's using a stand alone mppt and I'm using the integrated one in the AIO. I wonder if they're the same board inside?
Click to expand...
Seems to be kind of mixed. My understanding is the charger is exactly the same, but then I have been told by resellers that there are some differences but I don't know what that is
 
Brett V said:
That's what I was figuring, and with my symptoms being exactly the same as the OP, thought it relevant since he's using a stand alone mppt and I'm using the integrated one in the AIO. I wonder if they're the same board inside?
Click to expand...
The General consensus seems to be that the 120 amp charger, and the 120 amp built-in charger are mostly the same. Kind of like being mostly dead. As in "he's only mostly dead" (Billy Crystal - princesses bride)

 
MrM1 said:
One end is usb, the other is 9 pin.
Click to expand...
Have an unpowered usb hub and usb-a cables ordered to go between the GW spfxxxxt, GW scc48120, and Rasp Pi running Solar Assistant. Crossing fingers they will all play nice together.
 
MrM1 said:
Seems to be kind of mixed. My understanding is the charger is exactly the same, but then I have been told by resellers that there are some differences but I don't know what that is
Click to expand...

Well it seems yours and mine are acting exactly the same...so if the hardware is different, it has to be software. My guess is the hardware is the same and they both have a software issue.
 
I know to communicate with the software to calibrate the battery voltage, you use that cable that is USB to 9 pin. You plug the USB into the inverter or charge controller, and then you have to use a Serial adapter back to USB into your computer
 
I would think, with as many Growatt users there are on this forum who have also built their own batteries (aka DIY LFP) ... It would seem if this was a software issue or inherent in the SCC design, it would seem like it would be wide spread and be all over the forum.

It is for this reason I plan to try another Growatt SCC (replacement). Just seems like a faulty one to me.
 
But to be on the safe side, I also plan to set the charge cut off voltage in the Heltec BMS to 3.55v per cell. I don't like using the bms as the charge cut off, but better safe than sorry.
 
MrM1 said:
I would think, with as many Growatt users there are on this forum who have also built their own batteries (aka DIY LFP) ... It would seem if this was a software issue or inherent in the SCC design, it would seem like it would be wide spread and be all over the forum.

It is for this reason I plan to try another Growatt SCC (replacement). Just seems like a faulty one to me.
Click to expand...

I think the problem won't manifest itself until a user regularly charges more than the loads on the system. So it could indeed be widespread and we never see it.
 
Last edited:
Oddly, the only answer I am getting back from the manufacture and the seller is (basically) "you should be using a battery with BMS communications to the SCC or AIO scc" That just seems odd to me, and a cop out
 
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