90ah EVE cell terminal screws

[wakepics]

I bought some 90ah EVE cells from Basen with the intent of making two 4s batteries for my fishing boat trolling motor. They finally got delivered and I was a bit surprised to see the M4 terminal screws. I should have looked at the specs more closely before ordering, but here we are. I'm a bit concerned that the tiny screws won't stand up to waves while fishing. I plan to strap the cells together well, and then house them in a watertight gun case (secured with foam), which will also be strapped down to the boat, so they should be pretty secure, but it still worries me. I thought of getting M4 to M6 adapters and threadlocking them in, but that isn't resolving the issue of the small threads. I also thought about trying to retap to M6, but I don't want to risk damaging the cells.

Any thoughts on this situation? Should I just focus on securing everything really well and stick with the original screws? Maybe get M4 studs and loctite those in, then use a nut on top of the terminal rings to make sure I have full thread depth inside the terminal? Any input would be appreciated!

Thanks
Josh

 

[Browneye]

What is your planned current draw with them? Which BMS are you going to use?

They should be fine, use nylocks on tinned lugs. The threads isn't really what carries the current, and M4 is strong enough. The terminal base contact surface is what carries the current.

The terminals on the 230A EVE cells are m6, which is pretty small for 120A's as well. Lots of replies on a thread on the subject, we finally determined that proper aluminum washers to increase contact area was a good solution, and tinned not copper lugs as copper and aluminum creates a lot of galvanic corrosion action.

Here's what I did on the 230A cells - the two terminals at the lower left have the washers, compared to the rest:

 

[wakepics]

Thanks for the response and photos Browneye. Max draw from my motor is 56amp, but typical will be <20-30. I'm using a JBD 100amp BMS. My cells have the terminals as shown - so they have a fairly flat mating surface to begin with. Would aluminum washers still be advisable?

 

[Browneye]

No, no washers needed. Notice how tiny the pads are on my cells. Supposedly they're good to about 120A, but didn't want to take a chance - resistance = heat and voltage loss. One of the forum members found aluminum washers with a perfect hole size for the studs - increased the lug and bus bar contact substantially. The electrical connection is on that pad, not the terminal stud.

SS studs, aka grub-screws, red-locktited in is recommended. Every time you screw in and out on those wears the threads. They have an allen socket on one end, just snug them up. Your torque is applied to the top nuts.

Apply tinned lugs directly on terminal flats, use nylocks, torque to spec. You'll be good. Clean the pads right before with fine sandpaper, then apply Ox-Gard or nolox or similar on the aluminum pads. A split-washer and nut would also work. You just want a pure and clean connection to those pads with your connect cables/lugs. Many cells come with tinned copper bus bars - they work fine for this application.

Proper torque is critical, as too much could strip out those sockets, and then you've got big problems. Those pads are pretty thin and fragile. The manufacturer will have a terminal torque spec. Get a inch-pounds torque wrench.

I tapped my bus bars for the balance leads as I didn't like the idea of those small ring terminals under the terminal stud nuts.

 

[S Davis]

If you use lock tight make sure you use the primer for dissimilar metals, the grub screws are probably stainless steel.

 

[Ampster]

Maybe get M4 studs and loctite those in, then use a nut on top of the terminal rings to make sure I have full thread depth inside the terminal?

That is what I have done because the full length of the stud in the terminal top was the most important part of the mechanical connection. In my case I used M6 but the concept is the same.