Some Preplanning

Hello again!

Ok I have tried several times to type this but failed without making a mess. So very badly used paint to show you what I am doing with my house build. Its not easy for me to get my head around all the details so thought make it basic first and then worry about the little details after.





Mistake with the VMP in picture should read 58v

So My plan is to be free from the grid for my use, I plan on running all house appliances from this, So I need to spec my powerwall right. Appliances here in the UK are all 240v AC. Should I spec my powerwall to be around 240v DC or Should I use the many methods out there and go with around 60v with a decent inverter?

Potentially have enough roof space for around 90-100 solar panels. 1 Wind Turnine. My plan is any power that im not using to export to the grid to feed back into the local community otherwise priority is me.

Appliance and heating are:GSHP, Double Oven, 2xInduction Hob, 2x Washing Machine, 2x Tumble Dryer, Dishwasher, Kettle, Toaster, Microwave, Coffee Machine. Obviously there will be phones, laptops, Tv's but the list above will be the big hitters on power.

There are so many different arrangements I seen Im left confused.

My powerwall is going to be ongoing so I want to nail the arrangement of series and parallel pre build.

So First Does my excel sheet to calc batteries packs and potential powerwall designs look correct?




If so ignore the figures Could anyone recommend a good series parallel configuration to use to manage potentially the draw in Amps and Watts to make this a safe Design.

I am so sorry this is a little all over the place!

James

You start in wrong end if you ask med

* How much do you use currently? What is your peak current?
* The voltage of the solar panels is decided based on inverter you going to use
* The size of the inverter and type of inverter is decided on your wallet and how much you use
* Size of battery bank is most likely 48VDC nominal. Thats the most common
* Size of battery bank depends on how many days you want to last in bad weather depending on how many panels and your current daily average is.

So how you arrange of your panels is irrellevant currently. You need to set all other stuff first but I do recommend HVDC system for the panels where you have 500-800VDC instead. THen you dont need as thick wires. That is what I run on bigger part of my system.

If you havent checked out my system start there because I think you can find some interesting points on that system.

Grid-tied also demands a bit more in terms of what gear.

daromer said:

You start in wrong end if you ask med

* How much do you use currently? What is your peak current?
* The voltage of the solar panels is decided based on inverter you going to use
* The size of the inverter and type of inverter is decided on your wallet and how much you use
* Size of battery bank is most likely 48VDC nominal. Thats the most common
* Size of battery bank depends on how many days you want to last in bad weather depending on how many panels and your current daily average is.

So how you arrange of your panels is irrellevant currently. You need to set all other stuff first but I do recommend HVDC system for the panels where you have 500-800VDC instead. THen you dont need as thick wires. That is what I run on bigger part of my system.

If you havent checked out my system start there because I think you can find some interesting points on that system.

Grid-tied also demands a bit more in terms of what gear.

Click to expand...

Hi Daromer

Again your help is happily received.

Firstly I not currently a home owner or renter. I house sit saving moneyso have no access to my current data. This is what is making this so hard to work out!

I guess I've started my plans with the above as its going to be part of my planning application for this build. Creating a selfbuild sustainability home which harness green energy only.Back when I was a home owner I ranged from 10kwh-30kwh a day depending on what I use to do but this also was before I wasn't educated on LED lighting, A rated appliances basically smarter use of electric.

I've started get watts of all appliances I hope to use or as as close to so I should have some figure soon to go on. If my list of appliances seemed big I am building this house as a house for life and looking to get a lot right at the very beginning to reduce cost in long run.

Your YouTube channel is awesome by the way!

I do understand answering the Peak Current is the key! I have spreadsheet and getting close! Some of the info is hard to get hold of though!

You could answer me this question though: Say I had 444LG ICR18650D1 cells in 7S74P, This would give me around 48V nominal with roughly 190Ah ish due to being recycled laptop batteries from my work at around 2600mah. I think if I have calculated right this pack would be around 3.8kwh? Next when I start building the powerwall on this configuration how would I decide on the fuse to use on each pack? (not cell) As each cell has a 2A max discharge rate which I believe makes the cell 2c in rating? however I dont understand truly what happens when you start creating battery packs and the using them in series and parallel.

I am starting to get my head around some of this but I do need help!

I was actually thinking of using the Schneider Conext XW+ inverter, anyone had experience with these? On paper you can expand, prioritise power over exporting, smart functions seems a good fit. Probably get what you pay for.

Schneider tend to do good stuff!

7s is only 24V nominal. 14s is 48V nominal (51 actually)

44cells with 2,6Ah would give you a total of 2,6*3,7*444= 4,2kWh.
74p would yield = 74*2,6 = 192Ah
To calculate the C rating max if its max 2A continous and the cell is 2.6Ah= 2/2,6 = 0,77C

You really only need to fuse 1 string and not each pack. Since you have max 2A on the cells and if this is continous then you got a total of 148A max continous. i would go with 200A fuse if you plan to run it up to the continous. If you dont go above 100A instead to save some on the cells then fuse it 120-150A.

Individual fusing then around 5-10A is more than enough. With 74p you have plenty of juse to burn of a 10A cell-fuse.

When you paralell cells you get more capacity. Ie Ah * number of cells. You also get more current that you can use ie A * number of cells in paralell.
You dont add upp capacity per pack when adding them in string. Ie a 2s10p of 2Ah is only 20Ah and NOT 40Ah.

For each set of those packs in series your Voltage goes up. Ie 1 pack is 3.7V nominal and 2 packs in series is 3.7*2.

daromer said:

Schneider tend to do good stuff!

7s is only 24V nominal. 14s is 48V nominal (51 actually)

44cells with 2,6Ah would give you a total of 2,6*3,7*444= 4,2kWh.
74p would yield = 74*2,6 = 192Ah
To calculate the C rating max if its max 2A continous and the cell is 2.6Ah= 2/2,6 = 0,77C

You really only need to fuse 1 string and not each pack. Since you have max 2A on the cells and if this is continous then you got a total of 148A max continous. i would go with 200A fuse if you plan to run it up to the continous. If you dont go above 100A instead to save some on the cells then fuse it 120-150A.

Individual fusing then around 5-10A is more than enough. With 74p you have plenty of juse to burn of a 10A cell-fuse.

When you paralell cells you get more capacity. Ie Ah * number of cells. You also get more current that you can use ie A * number of cells in paralell.
You dont add upp capacity per pack when adding them in string. Ie a 2s10p of 2Ah is only 20Ah and NOT 40Ah.

For each set of those packs in series your Voltage goes up. Ie 1 pack is 3.7V nominal and 2 packs in series is 3.7*2.

Click to expand...

Dude you are amazing with your speedy replies!

Have to apologise as normal I suffer from delivering half the information as I jumble my thoughts into text!

What I meant to type: I was thinking of making each batterymodule with a configuration of 6s 74p. Clearly is only 25.2v which I think is 22.2v Nominal? You have correctly pointedout my calculation errors asthis is still not going to get me 48v Nominal.I did also mean to addmy intentions with themodules are to arrange them in a2s4p but the 6s74pis only going to achieve 44.4v Nominal If my calculations so far are correct.

I am sorry for the way I type stuff! I should proof read hahaha

So could this be a better plan in this case: 7S74P for each pack. This would give me the same AH but rectify my mis calculation on voltage when I then for example take each module and wire them in a 2S4P giving 58.8v, which should be around 51.8v nominal? with around 769ah if the cells all have a capacity above 2600mah? Think my calculation is right I would achieve 45.25Kwh with a usable 36Kwh and a grand total of 3108 Cells used.

Does that sound a good estimate so far?

Daromer thanks for your patients and hope the above reads a lot easier! And thank you for demonstrating calculating the C rating! All your help is appreciated!

So if I now have got my calculationsright and please don't think this happening straight away this is still planning stage.


Is this right? Where on this design should Ihave fuses?

I will be fusing each cell on with the 7s74p design like others have done on to a copper or brass strip.

From this I will be taking it to a Schneider Conext XW+ or Conext SW as per schneiders off grid design. Would I need any additional parts before it connects to the Schneider inverter i.e would it be go practice to incorporate more isolating switchs to allow maintenance and disconnection, anymore fuses etc?

I've seen some people use elctromechanical relaycontactors but is this because you are feeding power from solar panels directly from charge controllers in to the batteries and then pulling power out and Is this something the Schneider Inverters I am looking do as you wire the schneider mppt in this inverter?

Once again all input is welcome and thanks for taking the time to read and help!