10kWh LifePO4 DIY Battery Addition..... Here is my write up.

munsterfan2 · 25-08-2022 12:51pm

https://www.boards.ie/discussion/comment/119517789#Comment_119517789

Will probably have to do that, although it was by no means the worst when I tested capacity. Will look at restricting input / output current in the meantime

BTW, does anyone know where to set a charge / discharge limit, is it the BMS or the inverter ?

Thanks

garo · 28-08-2022 5:42pm

Depends on which BMS/Inverter you use. It could be either/or. The BMS typicaly sets voltage limits and the inverter SOC limits.

noelocon · 29-08-2022 5:20pm

"I also sourced some 25mm2 cable for the battery wiring. I had some lying around and bought a couple of lengths with lugs connected but as I discovered that I needed different sizes of lugs on each end of cabled I would advise to make your own cabled up.".....

I watched the WIll Prowse video on wiring and it got me worried in case I used the wrong rated cable. I've was looking at getting Bolatus 2Pcs Battery Inverter Cable 1m 3AWG/25mm² from Amazon but it's rated to only 100amps and I have 16*200amp batteries.

Is it better to get copper welding cable ?

great write up BTW

championc · 29-08-2022 6:30pm

The batteries' charge and discharge are restricted to the lowest common denominator, so I expect the limit of the inverter to to 100Ah, and likely lower

unkel · 30-08-2022 2:39am

@noelocon - you'll be fine. Your battery is 200Ah, but your inverter is unlikely to even charge / discharge your batteries at anywhere near 100A. Your 25mm2 cable is fine

Now the lesson you should take from this is to use the correct units. Your batteries are not "16*200amp". You have 16 cells in series and each has a capacity of 200Ah. So your total battery pack has a capacity of 200Ah also.

noelocon · 30-08-2022 9:15am

https://www.boards.ie/discussion/comment/119540355#Comment_119540355

yea good call, better safe than sorry ;-)

aleesi · 02-09-2022 3:03pm

Hi,

Apologies if this is been already answered (or if it doesn't make sense at all). I see many are opting for the Seplos BMS, can this BMS work either in parallel or as a master with any other brand like Puredrive, Pylontech or Dyness?

aleesi · 02-09-2022 3:06pm

https://www.boards.ie/discussion/comment/119560228#Comment_119560228

I will answer myself, found some info in their official website as per below. Has anyone tried to parallel a Seplos based battery with Puredrive or Dyness by any chance?

The default is the Pylontech CANBUS protocol

Goodwe

Growatt(The default is SPF(off-grid) protocol. If your inverter is SPH(on-grid) , please contact the sales person)

Victron

LUXPOWER

Sofar

Deye

Sermatec

Renac

TBB POWER

Solis

SMA

Foxess

IMEON

slave1 · 02-09-2022 4:21pm

What do you mean? Are you thinking of pairing say, a Dryness battery with a DIY setup?

championc · 02-09-2022 5:11pm

https://www.boards.ie/discussion/comment/119560228#Comment_119560228

A BMS is for building a pack from RAW cells.

Each of the bundled solutions like the Pylontech, Dyness, Puredrive are pretty much the same thing, but packaged in a fancy box.

With a DIY solution, you can actually see the physical cells and see the busbars joining them together.

If you saw the inside of a Pylontech, you probably wouldn't buy one

aleesi · 02-09-2022 6:03pm

https://www.boards.ie/discussion/comment/119560678#Comment_119560678

Exactly, for those who already has a battery (in my case I ordered a puredrive that hasn't been delivered yet), let's say a pylontech, per Seplos datasheet it appears that the BMS is compatible with pylotench canbus protocol which means (in theory) you could parallel a pylontech with a diy with Seplos BMS over canbus, they should be able to act as master / slave and talk to each other...

So it would be great to know if anyone has tried this setup as surely many people would have bought a PV system with battery in the past (pylontech / dyness / puredrive) and would be looking to expand capacity, the DIY approach would be a great option to add more battery storage to an existing PV + battery. In my case the battery is still on its way and I would consider cancelling the order (specially if both puredrive and DIY were not compatible at all) and go straight for the DIY solution. If I was to bite the bullet and stick to the puredrive (5KWh) I still would be interested in adding another 5-7 KWh to my system at a later stage, but rather from a DIY battery pack. So any feedback would be much appreciated as I think I could still cancel the puredrive if the seplos is not compatible, surely with the current demand and backlog the provider wouldnt have any problem at all to give my battery to the next in the queue...

Thanks in advance

slave1 · 02-09-2022 7:09pm

Oh, not sure about that, others more knowledgeable can kick in….

unkel · 02-09-2022 8:03pm

Technically it's possible, but it makes no financial sense to add a DIY battery to a premade one. Just sell the premade one. Even second hand it will pay for most of the cost of the DIY battery that's 4 times as big 😁

aleesi · 03-09-2022 11:34am

https://www.boards.ie/discussion/comment/119561692#Comment_119561692

Fair enough! since I haven't received mine yet I'll see can I cancel the order and go down the DIY route. If not I'll see I seplos tech support can shed light. Thanks for the feedback

poker--addict · 03-09-2022 2:07pm

https://www.boards.ie/discussion/comment/119560940#Comment_119560940

But would i be misinformed to say that the bundled solution wont leave someone having to consider concepts like balancing ? (which is probably easy if you understand it).

Reading posts from spose about the alarms he got too, and munsterfans dead cell, sort of supports my concern that a lot of time is involved in this?

championc · 04-09-2022 1:28pm

Well these bad boys got me through the night without needing to charge them from the grid, after the sh1te day yesterday 😀

slave1 · 04-09-2022 3:35pm

Have you two Seplos there? I just went with 2P16S (not sure of proper expression)

championc · 04-09-2022 3:52pm

https://www.boards.ie/discussion/comment/119569752#Comment_119569752

Yes, possibly overkill, but I had a spare Seplos, which I know I could have sold.

But I have full control now over each string. I have the marine knobs on the + and - cables, so I can have strings 1, 2 or 1 + 2 active

unkel · 04-09-2022 5:12pm

A BMS lead can only manage one cell. So strictly speaking if you have 32 cells, you should have them as two strings of 16SP1 each with their own BMS. Like @championc has.

graememk · 04-09-2022 6:42pm

https://www.boards.ie/discussion/comment/119570257#Comment_119570257

although a paralled 200ah cell electrically becomes 1 400ah cell. None of these bms's have much of balancing power anyway, 100ma at a push..

Im running a 16s2p. There would be no reason a 16s4p wouldnt work. Just dont rely on the bms to do much balancing, would be important to top balance first!

spose · 04-09-2022 8:30pm

https://www.boards.ie/discussion/comment/119569855#Comment_119569855

Where did you split the battery cables…1 from inverter to fuse/breaker and then 2 out, further down the line or using the bus bar on the first bms to feed the second?