I wanted to launch a new thread because the current thinking is buried in other threads after previous values were determined to be incorrect.
TL;DR - use 4Nm max to torque your M6 bolts (or the nuts on your studs).
Explanation
Many of us were all mislead by the spec sheet of the EVE cells which says
We initially thought this meant the bolt torque max was 8Nm. We now believe this is the maximum rotational stress that the cell terminals can take -- in other words, don't pull on the cables that are attached to the cells.
Why are we thinking 8 is too high? Well, for one, I've stripped my threads using 7. Other have stripped at 6. So it warranted investigation ...
We found evidence of more appropriate torque values for an M6 bolt, standard pitch. There are different kinds of aluminum and we don't know which kind is used for the cells and thread depth matters, but, take a look here: - M6 is about the same as 1/4-20 and in the aluminum column we see 45.6 in/lb which is 5Nm. And here: Even SS M6 max is 60.3 in/lb. And these are values for bolts (not including thread depth)! So, even the bolts aren't supposed to go this high, let alone the aluminum.
While 4Nm sounds really low, it provides roughly 700 pounds of clamping force! https://www.engineersedge.com/calculators/torque_calc.htm
If 700 isn't enough, then your terminals/lugs/bus bars need cleaning
I welcome additional input/references -- but I would love to keep the thread size under control (e.g. no "me, too!" posts) so people don't get lost in here. Thanks!
References
https://diysolarforum.com/threads/x...ifepo4-cells-purchase-review.3850/post-178919 through post 2158 (and maybe beyond)
Some specific callouts: https://diysolarforum.com/threads/x...ifepo4-cells-purchase-review.3850/post-180590, https://diysolarforum.com/threads/x...lls-purchase-review.3850/page-105#post-179191
TL;DR - use 4Nm max to torque your M6 bolts (or the nuts on your studs).
Explanation
Many of us were all mislead by the spec sheet of the EVE cells which says
The anti-torsion of pole is 8Nm. The torsion should be less than 8Nm when used.
We initially thought this meant the bolt torque max was 8Nm. We now believe this is the maximum rotational stress that the cell terminals can take -- in other words, don't pull on the cables that are attached to the cells.
Why are we thinking 8 is too high? Well, for one, I've stripped my threads using 7. Other have stripped at 6. So it warranted investigation ...
We found evidence of more appropriate torque values for an M6 bolt, standard pitch. There are different kinds of aluminum and we don't know which kind is used for the cells and thread depth matters, but, take a look here: - M6 is about the same as 1/4-20 and in the aluminum column we see 45.6 in/lb which is 5Nm. And here: Even SS M6 max is 60.3 in/lb. And these are values for bolts (not including thread depth)! So, even the bolts aren't supposed to go this high, let alone the aluminum.
While 4Nm sounds really low, it provides roughly 700 pounds of clamping force! https://www.engineersedge.com/calculators/torque_calc.htm
If 700 isn't enough, then your terminals/lugs/bus bars need cleaning
I welcome additional input/references -- but I would love to keep the thread size under control (e.g. no "me, too!" posts) so people don't get lost in here. Thanks!
References
https://diysolarforum.com/threads/x...ifepo4-cells-purchase-review.3850/post-178919 through post 2158 (and maybe beyond)
Some specific callouts: https://diysolarforum.com/threads/x...ifepo4-cells-purchase-review.3850/post-180590, https://diysolarforum.com/threads/x...lls-purchase-review.3850/page-105#post-179191
Bolt Torque, Axial Clamp Force, Bolt Diameter Calculator
This fastener bolt torque calculator will Estimate the unknown torque, diameter, axial force applied and coefficient of turning friction for the given conditions.
www.engineersedge.com
Torque Table Standard Bolt Sizes SAE
The following suggested tightening torques provide an excellent starting point for determining torque requirements. Remember, you may need to vary these numbers somewhat based on the individual joint or the amount of fastener lubrication.
www.engineersedge.com
EVE LF280 (3.2V 280Ah) Product Specification (Version E)-2019.7.5
Most recent Spec Sheet for the 280 LFP cells as provided directly by EVE March-14-2020.
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