Newbie inverter/ Powerwall advice please :)

[Subjated]

Hi All, i hope this is the right place to post.

finally getting back round to my DIY solar system install after having to change my plans a bit. but anyway I have a few questions and would be grateful for any help

ill keep it short, my house consumes around 10kw a day and I'm looking at buying ex solar farm panels for around 6kw of panels; these are generally 30v @8.5A and fitting them on top of my summer house/ garage roof.

I have a supply of 18650 batteries so I'm currently in the process of testing and building a DIY Powerwall for around 11KW of storage, ill maybe at to this later. but I'm really stuck when in comes to inverter and BMS choices. with the rising costs of everything, I'm sure as with a lot of people my budget is limited, so cant really afford to make a mistake in my purchase.
does anyone have any advice as to what BMS would be able to be used with X inverter? any suggestions or anything i may be missing is greatly appreciated.

 

[MisterSandals]

does anyone have any advice as to what BMS would be able to be used with X inverter?

The BMS depends solely on the battery, not the inverter.
What battery config are you making?

You will need a BMS mostly based on the number of series connections.
If you are making 10P4S. (Aka 12.8V battery) you will need an 4S BMS.

Going forward you should try to use correct units for better communication. And using correct units often lets the answers just fall into place.

house consumes around 10kw a day

KWh

DIY Powerwall for around 11KW of storage

KWh

with X inverter?

So you are referring to inverting DC to AC, right?
These are specific to a battery voltage and sized in watts usually for the loads that they can support. There is not much “this working with that” otherwise.

And making batteries from little cells, from what I have seen, neither the easier or cheaper solutions.

 

[Subjated]

Sorry, kWh yes.

As for the battery sorry I should have been more specific, it will be 14s maybe 120p with the amount of cells I have . So essentially a 48v system. I understand the bms has to suit this, but does it not have to communicate with the inverter as I see so many with bms connections?
Also am I right in thinking that if I was ever to draw 5kw of power at any one time (whilst this would be unlikely and minimal) I would need a 104A bms (5000/48 = 104.16) but I’m guessing there should be a safety factor or something built it? Would obviously want this to be as safe as possible and I hear the word “shunt” used a lot but I’m not exactly sure what that is?

If the nominal voltage of a cell is 3.7v would a 4s battery not be 14.8v?

As for the inverter yes dc to ac and I know I’ll need a hybrid one. I may draw 5kw through it but this would be rare, I don’t know what a good cost effective options? Any suggestions?

As for battery cost I think I’ll be less than £1000 for the battery , didn’t think you could get anywhere near 11kwh of storage for that can you?

Many thanks

 

[MisterSandals]

but does it not have to communicate with the inverter as I see so many with bms connections?

No the BMS (nearly all anyway) just sit by and monitor the battery and cut off negative if safety limits hit. An inverter does not control it or vice versa.