Seplos Mason DIY Kit - Ancillaries - Advice

Makia2023 · 2023-10-17T07:27:26Z

Hi all and thanks in advance for any assistance, I wondered if someone with experience of the Seplos Mason 280L or 280 could offer advice on what ancillaries I should purchase for my planned install. Although Fogstar (the retailer I am using for the Mason) have been helpful with general questions, it has been difficult to get an exact list of what I need to buy (and from where) alongside their systems. The inverter I plan to use - Sunsynk 8K-SG01LP1-EU 8.8kW Ecco Hybrid 1Ph Inverter (tradesparky.com) I believe for my planned system of 3x SEPLOS 15.2kwh packs all I need is the following: 150 amp - fused isolation switch between batteries and inverter 4* Positive Copper Cables 95mm2 (M8 lugs or seplos connectors? How long should they all be?)4* Negative Copper Cables 95mm2 (M8 lugs or seplos connectors? How long should they all be?)Earth between all sets A diagram of how to wire these would be useful as I can't find one as yet!? Can anyone link me to the cables with the correct "ends" assuming i go for the 280L on wheels? If somebody has a diagram or picture with explanation of their system then that would be very useful to ensure I get the correct bits. I plan to order later this week subject to having all of the required information. I do have a professional electrician stood by to do the final install of the system to include commissioning however I plan to have everything built and set up ready for just a check over and final connection to the board.

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27/12/2023 8:49 pm

Posted by: @makia2023

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I'm told 48v as the cut off is the best options as that is approx 10% soc. Is this your view and can you provide any advised values for me to confirm what I've read (or not).

Also, I'm assuming Pylontech setting for the inverter should work with the seplos BMS?

Let's deal with the BMS settings first.

Very few people seem to question what is meant by an assertion that a BMS or inverter is somehow compatible with a product from a different manufacturer.
It might be referring to the voltage settings which are required for the connected devices...
... or it might be that data is being transferred across a CANbus or Modbus communications link.
That would enable measurements made by the BMS get reported/recorded by the App issued for the Inverter, or vice versa.

It may have nothing to do with protecting your precious batteries.
So beware!

There are also many views across the internet as to the 'best' parameters which you should apply to your LiFePO4 cells.

Will Prowse, who has been publishing hundreds of You Tube tutorials on inverters, solar panels and batteries over the years, currently suggests:

48V LiFePO4 Battery w/ BMS

Absorption: 58V
Float: 54.4V
Inverter Cut-off: 42.8V-48V

Individual 3.2V LiFePO4 Raw Cell (for individual cell capacity testing)

Absorption: 3.625V
Float: 3.4V
Low voltage disconnect for capacity testing: 2.5V

Whoever you choose to believe, the basic principle remains the same.

The Inverter/Charger parameters are those which you set to define the voltage envelope within which your batteries are charged and discharged.

The BMS parameters are set outside of those.
The BMS acts rather like a fuse. If there's a fault, or an error in configuring the inverter, then it will step in and disconnect the battery before any damage is done.

Putting it the other way around; The inverter parameters are inset from those of the BMS.

Here are the absolute maximum and minimum voltages you should consider using: with a LifePO4 cell.

The inner pair of voltages are those which are set in the inverter (or charger) per cell.
A cell should not fall below 2.6v, nor be charged higher than 3.55v
which equates to a range of 41.4v to 56.8v for a 16S battery (sixteen cells in series).

The outer pair of voltages are applied to the BMS.
If the charge/discharge system fails, then the BMS prevents any cell falling below 2.35v or rising above 3.65v

You might suppose that equates to a maximum voltage of 16 x 3.65v (58.4v) for a 16S battery.
But that's not so.
Remember, the BMS has sense wires across each individual cell.
It will cut off the charge-current as soon as the first cell in that battery rises to 3.65v.

In practice I wouldn't configure my inverters and battery BMS units to these absolute minimum and maximum values.
But everyone will have their own opinion on how much they wish to inset from those extremes.

Save energy... recycle electrons!

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MisterB

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16/03/2024 9:57 am

@robl when i assembled mine last year around June time i think it was, i used a piece of 18mm melamine (kitchen cupboard shelf) in the bottom, i used EVE 280AH cells and ignored the plastic strips but used the foam between the cells. Using 18mm melamine meant that i could then hold the cells in compression.

some others have 3d printed a mesh type support that fits neatly in the bottom of the case. i have also recently heard that Seplos have now sorted the issue ....?

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