Cell have arrived (8 x 280Ah, VariCore)

[Martijn]

After over 50 days in transit, my 8 cells have arrived, two boxes with 4 cells each.

No bulging, some scratches at the terminals, all cells measure 3.21 to 3.23V.

The 6mm holes are so tiny, need to be careful with that thread. It seems the shop now sells with modified terminals ( see photo there ) with deeper holes with longer thread.

Only thing discovered so far is in the 2nd photo below, any idea what it means? Looks like there might have been some fluid there?

I'll try to balance these this weekend.

 

[Steve_S]

I advise some careful checking of the threading & hole depth. Hand tighten the screws into each hole and check to make sure they are the same depth and straight, not on an angle. A good idea is to use a Q-Tip with rubbing alcohol to clean out the holes, the small cut material and cutting oil from they were taped can be problematic. Looks ok to my eye.

 

[Martijn]

Thanks Steve, I've cleaned the holes and removed some material. I've put grub screws in with loctite, worked fine.

At least 2 are somewhat angled. Any specific reason why you mentioned this?

 

[time2roll]

The 6mm holes are so tiny, need to be careful with that thread. It seems the shop now sells with modified terminals ( see photo there ) with deeper holes with longer thread.

Those are aluminum nuts that are welded on top of the terminal similar to adding a stud. Not as long as you think because the terminal is not drilled.

 

[Steve_S]

Thanks Steve, I've cleaned the holes and removed some material. I've put grub screws in with loctite, worked fine.

At least 2 are somewhat angled. Any specific reason why you mentioned this?

Well many vendors TAP their own holes (they do not come from factory that way unless it's an order of 5000pcs and NOT Bulk cells either). So they hire someone to do it and not very attentive, hence the cocked angle on some cells. If the busbar does not sit perfectly flat and flush with the "terminal face" there will be problems, so be certain it is full face contact between busbar & face, the screw being on slight angle is ok as long as contact is good. BTW: Loctite is NON-Conductive and can increase Resistance which is not good, a fact I won't argue, that mule was killed long ago and we are not going to excavate it again..

 

[Martijn]

OK, thanks for the explanation.

For this installation, I won't be using flat busbars, but braided copper with lugs crimped on, so I guess it's somewhat easier to pay attention to each separate terminal connection. The terminals will be cleaned of loctite.

I've attached each cell to a benchtop powersupply, so far I had to clean and adjust 1 connection because of some issues.

Next up, assembly, speed charge for a bit and then a top balance.