Thanks greatly Stuart, an isolated centre bolt mounting would make all difference to the layout of my battery bank, I don’t know on your thinking allowing for a 5mm 2P or 3P PCB terminal blocks, as they are handy for take offs from the battery bank, if there is enough room left on PCB ?, I just thinking out loud, The setup that I have would do away with the 3 fuse banks on the right, 6 termination blocks on the bottom, the tall BMS stand, and lots and lots of cabling between everything, and give me more room in the cabinet.
This is what I have at the moment, the idea would be to connect a wire to the centre bolt (ring connector) and that is then soldered/connected to either + or - terminal.
You would also connect the other site of the cell to the opposite terminal - there is a SMD fuse on the positive side of the PCB.
How does this look? Can you also check that the hole at 13.5mm is large enough?
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I’d actually prefer the previous version for myself…fewer connections that can fail.
@stuart if you would like to keep/maintain this version could I still get the files for the other version and order that one?
@Ross do I understand correctly that the weight of the battery+bussbar is supported only by the bolt on the backside? Since + and - bolts must be separated, I expect there to be quite some torque at the center of the cell…isn’t that a bit a risky design?
I’ve messaged you both with the respective versions of your LTO boards, Happy Christmas!
Let me know how you get on.
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They arrived!
Thanks so much again @stuart! I’ll solder them up and program in the next weeks. Just need to order the USB connector thing and board expansions. Then I’d be happy to send you yours.
On a side note: I noticed that the positive connector hole is quit big. What was your intention there? Big cable directly into the hole? Are there standard connectors for this size which I don’t know about?
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I have allowed a nylon flat washer either side of board with a M12 nylon nut and each terminal to battery has a M3 stainless screw
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Its large enough to solder a cable to, or bolt or a ring crimp terminal (which is what I’d do)
The boards look great, I don’t think I’ve ever created a “round” thing before 
These do have a larger 1.2amp balance current as well - hopefully the bolt hole can act as a heat sink for it, there’s also more copper on the slightly larger PCB.
Just noticed the optional J1 header on the PCB I haven’t noticed before, what is it’s purpose?
I’ve ordered 150 yinlong cells for a 22S 4P build.
I’m wondering if I really need a BMS if I dont stress these cells.
I was going to set my SolArk 12k Inverter so it doesn’t go anywhere near the high or low voltage cutoffs of these cells.
Thoughts?
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Wow super cool, be sure to post some pictures of the setup once you’re ready.
The LTO cells go up in voltage really rapidly once they are close to being fully charged. Even if cells are slightly (<10mV) out of balance around 2.4 V, they can be super out of balance at >2.6V. This is what I’ve observed with my pack (I have to admit though, that I did not top balance them e.g. at 2.7-2.8 V).
But, even if you top balance, the fact that the voltage raises very rapidly towards the end of the charge, still requires good balancing if you want to use the entire voltage range of the pack.
Now, should you get a BMS? Well, look at it from this perspective: You just spent 3000-4000$ on a battery that could last for 30+ years. The DIY BMS+shunt trip etc will cost you 10-15% of that but you’re not at risk of having only 5 years life time.
The best part out this and all the diyBMSs that Stuart has designed is you can data log the voltage, it is the most valuable tool one can use to catch a battery before it goes high, the voltage of the LTOs that I have in my 22S bank, and they do vary across the banks, this bank has been running for about 3 months, I have noticed from the start of building that one bank continuously losses voltage over a week or two and have to put a charge into that bank of about 5amps over 3.5 hours, without this data logging i can’t keep track, as I know one of the batteries in the set of 3 have failed and need swapping out, I am waiting for a few spare Yinlong batteries to turn up, if you look at this graph you will notice the bank that is responsible
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Just starting to set out the DiyBMS boards to my bank, being an insulated hole in the centre of the board allows me to not worry about which polarity or bank to place the boards
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Its just exposing a couple of spare pins from the ATTINY, doesn’t do anything at the moment. Normally the temperature sensor would also be at this spot - although on the boards I made for you, I’ve moved this to a JST connector
Did you try programming the code? do that before you connect up to the cell !
Yes I have programmed them all to the LTO branch of github
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I have all the boards connected to the batteries and tx and rx cables connected, the blue LED is double flashing every 8.5 secs, but as yet i can’t get the controller to talk to the boards, this controller was not re-flashed, but was flashed about 3 months ago with then the latest code, I have tried single boards only on the controller, and have a known good controller from my other battery banks to test on a few single boards but seems to not want to talk to any of the boards, any way to fault find what might be going on?.
Note<> just noticed that when i connected a single pair cable from the controller TX to the RX of a single module the blue LED doesn’t flash at all.
Hi @Ross, @stuart
Thanks for developing and sharing these developments - especially the BMS for LTO’s. I have a few of these cells and would like to get 6 or so of the circular boards, but I can’t see an easy path to ordering from JLCPCB. I’ve not ordered and PCB before but have started playing with Kicad. Can you help?
Thanks
Tony
I might have worked it out, Have new code into controller, just starting to see cells