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So, I'm building my first LiFePO4 pack. 4S2P from new 105AH EVE cells, Overkillsolar BMS. Pretty standard stuff. Then I get to the whole compression topic... I read the EVE data sheet, and I think we need to be a bit more pedantic about what it says, and more importantly what it doesn't say...

Closing this out... I've added a copper washer between each cell terminal and the busbar above. The three terminals in the middle stack that had both a busbar and three lugs on top (left and right balance wires, plus the BMS sense wire) got new longer bolts in order to assure enough "bite"...

A necro-post, but perhaps this would be of some use... I'm planning to mount my OverkillSolar BMS on the wood-based battery box using 3D-printed plastic clips. Set of 6, one for each post, should hold things well, and with a bit of space under the bottom for a little airflow. Not sure if I...

ACK! I just noticed that EVE *does* indicate a compression spec (same 300 kgf) under "Cycle life" in their datasheet. Missed that. So, please excuse the dust. Is there a similar spec for the 305 AH Envision cells? I wonder how universal this is. I haven't found it in their datasheet.

Yeah, I'm wondering the same. I've only had the battery on-line for 2 days now, and so far the balance has remained good. We've got a massive storm coming tomorrow (I'm in California), so this could be interesting on a couple of fronts. Typical load is about 10 amps, with a "floor" SoC that...

As Yabert notes, the top row of cells are paralleled by the cross-connect wires at their bottom, and the three heavy wires that go to the Battery Positive terminal. Same for the bottom row, which have a set of cross-connect wires at their top, and the BMS B- input at the bottom.

Essentially true, hence my conclusion that the busbar to terminal connection isn't working properly. Actually, the connection between the terminal and the bottom of the busbar is in parallel with the connection between the top of the busbar and the bolt head, so some current will flow through...

Hi folks, I've done some digging, but haven't found an answer. I'm building my first battery pack, so have a lot of questions... The battery is going to be built from a dozen 105AH EVE cells, 4 in series to make 12v. I have a single OverkillSolar 4S 120 amp BMS. With 12 cells total, the...

Ok, thank you both for the details. But to clarify slightly, two cells at 3.3v may indeed have different SoCs, but two cells at 3.300v should be pretty closely matched. I am counting on this with what I have done. Sounds like the "balance when not charging" option in the BMS is less than...

I honestly don't see the difference; electrically, what I've done should be the same. The cells are fully connected in parallel through the sideways-running wires, and in series with the usual bus bars. The sideways-running wires are certainly lighter gauge (they're #12) than the bus bars, but...

I understand and agree that many of us may not live long enough to wear out these batteries. But what surprises me is that the battery cell manufacturers themselves seem to be mute on the basic parameters to actually build a proper, safe, multi-cell battery pack using their cells. Is this...

Well, yes, there are more parts involved when the wiring terminal is inserted in there. But the thing is that I'm seeing several mv between the screw that holds everything together and the busbar that sits directly under it, and essentially no drop between the screw head and the terminal itself...

Thanks for the feedback! Diagram attached, below. Not to scale, of course, but relatively close. The three thick black wires would be the same length on each side of the battery; planning #6 or #8 wire here. The medium thickness light green are the inter-stack balance wires as discussed in...

Right, but that imbalance in currents can be created in more than one way. Instead of a high impedance cell, for example, imagine that all the cells are exactly matched but the connection between one cell and its busbar has some resistance. In that case, that same "sideways" current would...

I'd settle for what the automotive folks have to design to. At least it could provide a baseline.

Reviving this with a nit follow-on. What should one do with the mid-point of the two series strings? Leave them alone, or cross-connect them? In other words, two parallel strings of two panels each, or two sets of two parallel panels wired in series? I'm thinking that under some shading...

To close this out, I went with the plan above. The iCharger was used with "fast" balancing enabled to do the initial full charge at 15 amps rate. You could see the balancer working to keep everything in line. After the full charge I ran a balance-only pass, followed by another charging pass...