Prismatic LiFePo4 without terminal connectors, what to do?

RHTizzy

New Member
So I received two of these cells and neither have connectors attached to the poles, they're just flat surfaces of apparently aluminium. The seller recommends not to tap holes into the cells but to laser weld some studs. That's not something I can do myself and represents an increase in the cost never mind the difficulty of actually finding the appropriate studs. Are there any other responsible solutions you guys know of?
 

smoothJoey

Ooga Booga!
So I received two of these cells and neither have connectors attached to the poles, they're just flat surfaces of apparently aluminium. The seller recommends not to tap holes into the cells but to laser weld some studs. That's not something I can do myself and represents an increase in the cost never mind the difficulty of actually finding the appropriate studs. Are there any other responsible solutions you guys know of?
Since you mention two cells I gonna guess there were others.
How were the others provisioned?
 

RHTizzy

New Member
No, just the two. They're Eve cells (or sold as) and shipped from Poland. They actually both also have a bit of a bulge even though they were shipped at 3.2V. The terminals themselves do look a little scratched which might have been a result of the shipping process as neither had any protection caps fitted. It doesn't seem possible that they are used cells without any way of connecting the poles, correct or is there some way of using them as is? I suspect I've actually received two good cells which I just can't use without some way of connecting them. These are my first two cells so I'm not sure about anything...
 

smoothJoey

Ooga Booga!
No, just the two. They're Eve cells (or sold as) and shipped from Poland. They actually both also have a bit of a bulge even though they were shipped at 3.2V. The terminals themselves do look a little scratched which might have been a result of the shipping process as neither had any protection caps fitted. It doesn't seem possible that they are used cells without any way of connecting the poles, correct or is there some way of using them as is? I suspect I've actually received two good cells which I just can't use without some way of connecting them. These are my first two cells so I'm not sure about anything...
I'm struggling to understand why you would buy just 2 cells.
Lifpo4 batteries are divisible by 4 modulus 0.
I would ask someone here with tapped terminals to see how deep they are tapped.
Do you have a tap/die set?
Are you proficient with it?
I'm not, but I know there are machinists on the list.
@ArthurEld may or may not be a machinist.
You didn't specify which eve cells you have.
That may be an important detail.
 

RHTizzy

New Member
Just two to test before buying a whole bunch.

Aluminium is really soft and can actually even be tapped by drilling undersized and threading a bolt. That's not a problem, but drilling is not really a responsible idea and all manufacturers say that, so I'm looking for another option besides laser welding and drilling.
 

ArthurEld

Photon Sorcerer
I'm struggling to understand why you would buy just 2 cells.
Lifpo4 batteries are divisible by 4 modulus 0.
I would ask someone here with tapped terminals to see how deep they are tapped.
Do you have a tap/die set?
Are you proficient with it?
I'm not, but I know there are machinists on the list.
@ArthurEld may or may not be a machinist.
You didn't specify which eve cells you have.
That may be an important detail.
Hi smoothJoey and RHTizzy. I was a machinist over 40 years ago. Those skills stick with me. Especially since I've been a CNC machine programmer since then. It is quite easy to add threads to your terminals.
If you practice on a piece of cheap aluminum you can get used to the process.
 

HRTKD

Boondocker
Just two to test before buying a whole bunch.

Aluminium is really soft and can actually even be tapped by drilling undersized and threading a bolt. That's not a problem, but drilling is not really a responsible idea and all manufacturers say that, so I'm looking for another option besides laser welding and drilling.

All of us with the early EVE cells have drilled/tapped terminals. Finding someone to laser weld a stud and base on is going to be harder than finding someone to drill/tap. What size (in Ah) are the cells? Someone with the same Ah size could measure the drilled depth to give you an idea of how deep you can go.
 

RHTizzy

New Member
All of us with the early EVE cells have drilled/tapped terminals. Finding someone to laser weld a stud and base on is going to be harder than finding someone to drill/tap. What size (in Ah) are the cells? Someone with the same Ah size could measure the drilled depth to give you an idea of how deep you can go.
They're 280Ah cells. I have a few milling bits around so could easily get a flat hole even though they're not meant for drilling. If push comes to shove I'm not afraid of screwing it up other than the unknown depth. Preferably though I'd like to test them without doing irreversible damage...
 

Pyrofx

Flux capacitor builder
Beware of using the correct size end mill. It needs to be smaller than the bolt he. If you have a mill , I'm sure I dont need to mention this. .
But you could plunge a smaller cutter, then drill with proper drill bit and end up with a flat bottom.
 

RHTizzy

New Member
Almost convinced I need to drill now but still hoping for some clever solution that's non-destructive. I'll have a look for the tapping thread (no pun intended), thanks.
 

smoothJoey

Ooga Booga!
I just found this, inspired by @Sanwizard.


I have not tried it, if it didn't work you would have a mess so suggest you try it with a couple of bits of scrap first.
 

fafrd

Solar Addict
They're 280Ah cells. I have a few milling bits around so could easily get a flat hole even though they're not meant for drilling. If push comes to shove I'm not afraid of screwing it up other than the unknown depth. Preferably though I'd like to test them without doing irreversible damage...
I’ve tapped mine to 7mm depth which is the abolute deepest you should drill (slowly, by hand) - the copper surface of the lower terminal plate just starts to show at 7mm.

5mm is a much safer depth to tap Eve 280Ah terminals.

It is pretty easy to drill slowly by hand - use a tap handle. The trick is getting a guide in place to assure that you are drilling (and later tapping) normal to the terminal surface (ie: straight).
 

JMc

Solar Enthusiast
Their advice about laser welding the terminals is correct. If the aluminum is only 5mm thick, tapping for a M6 bolt is going to be sketchy because even with a bottoming tap you will only have 2-3 threads. Good luck applying torque to that tiny mechanical connection in aluminum.
 

Jordi

Solar Enthusiast
Dear people, for a noob like me, what would you reply If I propose welding some copper strips to it by using a significant amount of alloy and a spot welder? Risky option? Could detach easily?...?
 

JMc

Solar Enthusiast
Dear people, for a noob like me, what would you reply If I propose welding some copper strips to it by using a significant amount of alloy and a spot welder? Risky option? Could detach easily?...?
That would be soldering, not welding. There are aluminum-zinc alloys that can be used to join aluminum parts, but heat is the issue. Aluminum conducts heat very well and by the time the terminal is hot enough to accept the solder, the battery electrolytes underneath are way past their intended range. Great looking solder joint, damaged battery. Copper to aluminum? Soldering copper would first require tin plating the aluminum…
 

RHTizzy

New Member
Perhaps conductive epoxy in combination with minimal thread tapping could provide a strong enough terminal connection? So perhaps drill and tap a minimal hole and use the epoxy to fix a washer (for surface area) and the bolt in place to the existing terminal pad..

The epoxy is rather expensive but seems like a viable option when used with aluminium and steel, and adding the washer and the shallow tap (even 2 or 3 threads) would provide a much better base for torquing down thick lugs...?
 

Rednecktek

Solar Addict
Call up your local jewelers and ask if they can laser weld aluminum. Worst case they say no but their equipment is designed for very small surfaces and very controlled heat. Their stuff could probably weld a lug right on there and they'd know how to prep the surfaces.

If you find a place that says they can do it ask them which metals would be best and find some bolts in that for them to weld on.

Really it seems you've got 3 options for dealing with these:
1: Convince the seller to supply NON busted cells
2: Find a local jeweler who would be willing to laser weld a bolt onto the spots
3: Try your hand at hand tapping threads very carefully
 
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smoothJoey

Ooga Booga!
Perhaps conductive epoxy in combination with minimal thread tapping could provide a strong enough terminal connection? So perhaps drill and tap a minimal hole and use the epoxy to fix a washer (for surface area) and the bolt in place to the existing terminal pad..

The epoxy is rather expensive but seems like a viable option when used with aluminium and steel, and adding the washer and the shallow tap (even 2 or 3 threads) would provide a much better base for torquing down thick lugs...?
It sounds like you want to put a washer under the lug, confirm?
That sounds like a bad idea.
 
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