Additional MPPT for a All in One Growatt. Is it possible?

[MrTrevino]

Hello All,

I have a Growatt 3000 All in one inverter and I have max out its MPPT Capacity. Because of the Battery Bank size it never reaches full charge in one day.
It is possible to add a second solar array using an external MPPT to the system without damaging the Inverter internals? The attached diagram shows two possible
point on where to connect the second MPPT. My guess will be point A so the shunt registers the current coming into the batteries. But the main question is if it
might damage the Growatt in any way.

 

[rmaddy]

Use point A so the shunt can measure everything. As far as the Growatt is concerned, any point along that wire is effectively the same thing. It makes no difference. It's not uncommon for people to hook up multiple charging sources. It's fine.

 

[Prefersdirt]

Use point A so the shunt can measure everything.

My brain must be fried. What is the Shunt in this setup?

My setup is like the OPs and the shunt part has me boggled. Thanks

OP - great question.

 

[DThames]

My brain must be fried. What is the Shunt in this setup?

My setup is like the OPs and the shunt part has me boggled. Thanks

OP - great question.

Meter shunt like Victron Smart shunt should have all current both to and from the battery running through it.

Yes you can connect a second charger. Normally one will dominate when the battery gets close to full charge voltage. Not a problem, just don't be surprised.

 

[MrTrevino]

Use point A so the shunt can measure everything. As far as the Growatt is concerned, any point along that wire is effectively the same thing. It makes no difference. It's not uncommon for people to hook up multiple charging sources. It's fine.

Thank you for your quick response. I am planning to make it happen soon and I just wanted to make sure my assumptions were correct.

 

[MrTrevino]

Meter shunt like Victron Smart shunt should have all current both to and from the battery running through it.

Yes you can connect a second charger. Normally one will dominate when the battery gets close to full charge voltage. Not a problem, just don't be surprised.

Thanks DThames for a double confirmation.

 

[Prefersdirt]

Meter shunt like Victron Smart shunt should have all current both to and from the battery running through it.

Ok, the fog clears a little. So the shunt is simply a monitor. Sort of like the BMS I have on my homebuilt batteries. My brain had it as a charger unit.

 

[mrzed001]

Hello All,

I have a Growatt 3000 All in one inverter and I have max out its MPPT Capacity. Because of the Battery Bank size it never reaches full charge in one day.
It is possible to add a second solar array using an external MPPT to the system without damaging the Inverter internals? The attached diagram shows two possible
point on where to connect the second MPPT. My guess will be point A so the shunt registers the current coming into the batteries. But the main question is if it
might damage the Growatt in any way.

It is called DC coupling.


You can add as much MPPT (, inverter, charger, ...) units to the battery as you like.

Do not forget the battery C rate.
A lead-acid battery can be charged only at 0,1C. A lithium at 0,5C.
So 400Ah lead-acid can be charged only by 40A.
400Ah LiFePO4 at 200A.

 

[MrTrevino]

It is called DC coupling.
View attachment 67763

You can add as much MPPT (, inverter, charger, ...) units to the battery as you like.

Do not forget the battery C rate.
A lead-acid battery can be charged only at 0,1C. A lithium at 0,5C.
So 400Ah lead-acid can be charged only by 40A.
400Ah LiFePO4 at 200A.

Oh. Very Interesting. Thank you very much. It give me a much clearer view.

 

[rmaddy]

Do not forget the battery C rate.
A lead-acid battery can be charged only at 0,1C. A lithium at 0,5C.

That's not universal. For LiFePO4 it depends on the BMS. I have a drop-in 12V 206Ah battery with a recommended charge current of 40A. That's only 0.2C.

 

[mrzed001]

That's not universal. For LiFePO4 it depends on the BMS. I have a drop-in 12V 206Ah battery with a recommended charge current of 40A. That's only 0.2C.

LiFePO4 cells can handle 1C charge and discharge. For longer life we recommend to use only 0,5C.
Yes. If you use a weaker BMS that can handle only 40A then the limit/bottleneck is not the battery, but that small BMS.
And you should scale for that.
But if you ask me, that is a bad design.