weber, I've sent a non populted BMS PCB for ease of postage. (actually I don't have any others spare). It should allow you to run some thermal tests.
coulomb, re Jack Richard's post on diy forum.
"You can see this best not at the cell level, but across the pack simply because the voltage swings are larger and easier to measure." ??
0.4V x 20 = 8V which voltage is hard to measure ??
The thoughts re 2.0Vpc under short term load I agree with.
I don't know what sort of BMS Jack has worked with but ones that involve multiple wires back to a central system from each cell surely went out with the ark (and wet lead acids !). Yes they are dangerous.
Rod Dilkes' BMS and my poor cousin for instance run one optically isolated wire around the whole pack.
Jack quite rightly points out that you should buy a few spare cells as some are likely to fail for one reason or another. My confusion comes when he discounts BMS value yet expects to find the said faulty cell in the pack ???? Do consider that without BMS you WILL KILL cells.
True, if TS cells are safe when abused then BMS may not be required to save a fire but at the same time, BMS WILL BE REQUIRED to get the max life out of a pack and diagnose problems.
I note Jack is all uptight about matching cells in a pack (as he doesn't use BMS ?). Chill out man. If you have a meaningful BMS coupled to a smart charger then you can run any size / age or chemistry cells / batteries in a pack. Try it. Ah is just Ah as long as you have enough ! The Ah of the weakest / smallest cell will determine pack Ah.
This reality unfortunately pours water on the "no BMS required" idea.
I have long said that the BMS really comes into its own as a pack ages since cells do not age equally.
The "spare cells" argument also falls apart (re matched cells) when you consider that a cell from storage with no cycles on it will of course have a different capacity to the rest of the pack that may have 1000 cycles on it !!!!
Sorry, bit of flame throwing there !
edit: pack is spelt pack