Inverter and custom battery compatibility

[cajocars]

I plan to buy 16 280Ah LiFePo4 cells to build a ~14kWh battery with BMS from basengreen.com
I won’t have solar for the moment as I’ll just buy cheap energy overnight, but I want to future proof for solar (I have space for 10 panels, so around 4kW)
I was thinking about the Growatt SPH3600, which was also in one quote I had for solar panels installation.
How do I make sure this inverter will accept a custom build battery?

 

[sunshine_eggo]

Given that the inverter will work with all flavors of lead-acid, building an equivalent 48V 16S LFP battery means it will "ACCEPT" it.

If you mean to have the two communicating, that's purely a function of the BMS you choose.

 

[shavermcspud]

Given that the inverter will work with all flavors of lead-acid, building an equivalent 48V 16S LFP battery means it will "ACCEPT" it.

If you mean to have the two communicating, that's purely a function of the BMS you choose.

Incorrect, the SPH series has to be stipulated for either LA or Lithium, it will have a tick on the outer box to state which model you have. Although you can set the Lithium SPH to a default battery mode its has big issues and ends up with an error and falls back to grid mode. The off grid Growatt SPA series however work fine both ways. I have fitted a few SPH using custom packs and the Seplos BMS flashed with the Growatt firmware, two years in and working fine still.

 

[brum]

Does Seplos offer custom firmware for different inverters? If yes - where do we find these?

 

[cajocars]

Is an on grid inverter the right choice for my use case (charging overnight and discharging during the day)
Also, am I right that the difference between on and off grid is that the former is connected in parallel to the grid, while the latter is connected in series?
Would an off grid inverter limit the amount of power I can draw (i.e. not allowing me to draw 10kW even if that’s available from the grid)?

 

[shavermcspud]

Does Seplos offer custom firmware for different inverters? If yes - where do we find these?

Only if you have the Can BMS and need to use a Growatt SPH inverter.

 

[shavermcspud]

Is an on grid inverter the right choice for my use case (charging overnight and discharging during the day)
Also, am I right that the difference between on and off grid is that the former is connected in parallel to the grid, while the latter is connected in series?
Would an off grid inverter limit the amount of power I can draw (i.e. not allowing me to draw 10kW even if that’s available from the grid)?

The grid tie option you have is exactly whats needed in your situation

 

[cajocars]

The grid tie option you have is exactly whats needed in your situation

Does it have an option never to export to the grid and charging on a timer? or can I tell it when to charge the batteries via a serial port input or similar?

 

[time2roll]

will the system be subject to local government permit and inspection? DIY battery may not be on the list of approved products.

 

[shavermcspud]

Does it have an option never to export to the grid and charging on a timer? or can I tell it when to charge the batteries via a serial port input or similar?

It does have this option yes, zero export.

 

[cajocars]

It is often heard that the inverter power should be equal or slightly lower than the PV installed power to make it work efficiently
Does it apply to the ‘rated power’ or ‘max DC power’?

 

[shavermcspud]

will the system be subject to local government permit and inspection? DIY battery may not be on the list of approved products.

Probably not in the EU or UK

It is often heard that the inverter power should be equal or slightly lower than the PV installed power to make it work efficiently
Does it apply to the ‘rated power’ or ‘max DC power’?

We overpanel the Growatt systems when we install by 20%, as long as you stay within the max permitted MPPt voltage of 550v you'll be fine.

 

[cajocars]

Probably not in the EU or UK


We overpanel the Growatt systems when we install by 20%, as long as you stay within the max permitted MPPt voltage of 550v you'll be fine.

Is that rated power or dc power? See my previous post

 

[shavermcspud]

DC power i.e from the MPPT inputs the 3600 is nominal 3600Watts but will take 6600Watts Pv input for winter time and clip during the summer.

 

[cajocars]

DC power i.e from the MPPT inputs the 3600 is nominal 3600Watts but will take 6600Watts Pv input for winter time and clip during the summer.

Would having a 4kWp array and an inverter with max DC rating of 6600kW make the system work less efficiently?

 

[shavermcspud]

Would having a 4kWp array and an inverter with max DC rating of 6600kW make the system work less efficiently?

Its much better for the winter months and in the summer you'll just see clipping at the top end when the inverter maxes out. You get much better efficiency when the inverter runs at the upper most end of its rated input.

 

[cajocars]

Its much better for the winter months and in the summer you'll just see clipping at the top end when the inverter maxes out. You get much better efficiency when the inverter runs at the upper most end of its rated input.

So the inverter I’m looking at is too powerful (as in DC input) for a 4kWp system?
This is the inverter a company wanted to install with 10 x 400W panels

 

[shavermcspud]

So the inverter I’m looking at is too powerful (as in DC input) for a 4kWp system?
This is the inverter a company wanted to install with 10 x 400W panels

No the 3600 is an ideal match, it just means that it can accept up to 6.6kWp. Overpaneling is very common.

 

[cajocars]

No the 3600 is an ideal match, it just means that it can accept up to 6.6kWp. Overpaneling is very common.

So again I have to look at the ‘rated power’ instead of ‘max DC power’

 

[shavermcspud]

So again I have to look at the ‘rated power’ instead of ‘max DC power’

exactly. its a good match for your system