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[marshman]

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[nowty]

32 cells gives me around 28kWh of storage. I currently have 6 x US3000C Pylontechs which I will be selling very shortly, once they have gone I will get another 32 cells to give me 56kWh - which based on recent performance of the 21kWh of Pylons - will work nicely in the dark winter months. Removing the need to do some crystal ball gazing trying to predict how much PV generation I will get the following day and deciding how much overnight charging to do. Frustrating when I get it wrong and it is sunnier than expected and excess generation then goes to the grid.

Totally agree with that, I used to do daily calculations but now I use generalisations based on time of year and it 99% works when you have a large battery bank. Also makes charging the EV easier too, not worrying about sun popping in and out of behind clouds.

[Stinsy]

Nice work. That is some SERIOUS storage capacity.

[Joeboy]

Having observed what others have done and done some "back of fag packet man maths" type calculations I took the plunge and procured 32 LF280K cells. They arrived in early December but life (and xmas) got in the way and I have only just finished sticking them all together. Part of the hold up was having to shift the 6 Pylontechs as they were "in the way" and then building a shelf to carry the 170kg of cells. Whilst I was at it I put in two shelves to allow for "future" expansion.

32 cells gives me around 28kWh of storage. I currently have 6 x US3000C Pylontechs which I will be selling very shortly, once they have gone I will get another 32 cells to give me 56kWh - which based on recent performance of the 21kWh of Pylons - will work nicely in the dark winter months. Removing the need to do some crystal ball gazing trying to predict how much PV generation I will get the following day and deciding how much overnight charging to do. Frustrating when I get it wrong and it is sunnier than expected and excess generation then goes to the grid.

I haven't switched over to the new stack permanently yet as I am still "top balancing them" - long process with some 560AH of capacity! With a collection of power supplies and a couple of car batteries I can just about get 10A at 50 odd volts to charge them. I did use the inverter and some of the precious sunshine a couple of days ago to do some of the heavy lifting and charge them to around 95% S.O.C. but at that point at least one cell was pretty much fully charged, so I am now proceeding with caution and allowing the balance circuit to do its thing.

I went for a 16S2P format - i.e. 16 pairs of cells in series rather than two "packs" of 16 in parallel. Main reason is it only requires one balance circuit and one BMS. It did mean I had to fabricate a load more bus bars. I made those out of some "handy" copper strip - in fact a length of old lightning conductor - suitably drilled and sleeved with heat shrink. Hardest part was making the elongated holes. The pack is sitting on the shelf as 2 stacks of 16 cells. I spent ages looking at the "clamp" / "don't clamp" debates and in the end decided to clamp them between end plates. The length of 16 cells is approx 47" and standard threaded bar only comes in meter lengths - and works out quite expensive when you need 8 lengths - so I fabricated the side bars from some ali sheet I had "saved" from somewhere. The end plates were 1/4" thick ali plate. The cells were separated using some "Corex" (corregated plastic sheet), again from my "it'll come in useful one day" pile. I still need to box it all in and cover the top.

The 6 US3000C Pylontechs are less than a year old and still showing 99% S.O.H. I will be selling those shortly, hopefully as a job lot including 6 pairs of Pylontech brackets and set of long leads. I have all the original packing and documentation and also the Battery view software and lead. They are "plug n play" and have never missed a beat. If interested send me a PM.



6 x US3000C, 6 pairs of brackets, long leads, battery view s/w and lead - for sale soon!


Some pics below: will add more later.

Holy jamoley! What a set up!

[sw25481]

Hi Marshman

My cells just turned up from Colin and I am about to start the same. I have a couple of questions if you have a moment this week.

How are you planning to perform the switch? You now have a 16S battery that you want to introduce to a 15S stack so the voltages required for charging will be different. Are you going to have a big bang day where you disconnect the current stack and plug in the new? Are you going to leave the old stack at 50% for shipping and box them up. Perhaps you have two inverter / chargers and can support different battery stacks at the same time.

When you do swap in the new stack are you concerned about your Inverter talking to your new BMS? I can't decern exactly which of each you have. Perhaps that is not important for you

Others on this forum have built 15S batteries and left one Pylontech in parallel communicating with the inverter assuming (not unreasonably) that what it reports back will be relevant to the DIY battery. I was considering doing the same and leaving one of my cells as a spare but ideally I would love to get my SunSynk to talk to my JA BMS (both support CAM and RS435) and then I can just deco my Pylontech and sell those. My PylonTeck are only a few months old so I am not ready (or confident enough) to try and upgrade those to 16S

I am not the only one with the same idea https://diysolarforum.com/threads/sunsy ... 728/page-2 references https://github.com/maxx-ukoo/jk-bms2pylontech which is attempting Pylontech emulation for JK BMS

[Caesium]

When you do swap in the new stack are you concerned about your Inverter talking to your new BMS? I can't decern exactly which of each you have. Perhaps that is not important for you

I have a 16S setup now with no Pylons left. My inverter isn't talking to them, I'm not overly bothered about it. I've set charge voltage to 55.2v (3.45v per cell) and low voltage cutoff to 49v (3.06v or so). This is widely accepted as a very conservative safe range which isn't working the cells hard at all. You still get to use 95%+ of the capacity of the cells in exchange for a longer working life.

I lose two main things by doing this; the inverter doesn't know an accurate SOC, but I have JK BMSes that tell me this instead, so no loss there. And secondly the inverter can't currently be told to ramp down the charge amps as the battery approaches full, but since I'm already working in a very conservative voltage range, I don't really care about this either. If I was trying to push the batteries right up to 3.65v per cell then I'd be a lot more worried about overshoot and hence needing to ramp down the charge amps.

So yeah, it works for me having no coms.

[Swwils]

Take a look at the RS 485 communication protocol from Voltronic from 2020 and for Pylontech Ver 3.3 2018. These are documented online.

You might find it's not stable as Pylontech 15 cell will see a 16 cell higher voltage bus as either too high or as an additional (whole) battery.

Pylon CANBUS converter for JK BMS already exists.but it doesn't mean your inverter will be happy without appropriate settings.

[marshman]

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[Joeboy]

If the aftermarket BMS is robust and reliable why not? I'm looking forward to seeing the end results.

One benefit of the extra storage capacity is EV top up in this colder weather. I can chuck quite a lot of range into the car and still be operating the whole house right through to next charge window. Its a nice place to be.

[Caesium]

One "problem" with leaving just one Pylontech battery "communicating" with the inverter is that I think the BMS will limit the charge/discharge current, which is not what you want.

Yes good point. One Pylontech will set limits of 25A on the inverter, so about 1200W.

These 280Ah batteries can be charged/discharged at up to 0.5C I believe, so you can push 140A through them. And I have two sets paralleled so 280A would be fine. My inverter can only take/supply about 70A so no chance of breaching the limits.

I'd need a significantly more powerful inverter before this became a problem I think.