Binding lifepo4 batteries? tape/pipe clamps

jofred99 · Jun 21, 2020

I'm in the process of putting my first battery together in a static location (non-moving) and wanted to know about binding the cells. Everyone seems to bind the cells together using vinyl tape/vhb tape, pipe clamps, etc.

Why do I need to do this? Are the +/- posts that flimsy or are we trying to keep the battery innards from blowing out?

Ampster · Jun 21, 2020

The cell expands when charged all the way to 3.6 volts.

Fred S · Jun 21, 2020

Just binding with tape is not as good as clamping, and the clamps don't have to be fancy. I'm cheap so I just used wood 1x4s as a frame around the center of the cells. I screwed the 1x4s together with 3 long drywall screws per corner, and used washers on the screws on one side to prevent countersinking. The screws can be adjusted in and out slightly to vary the pressure on the long horiz. side of the cells.

Skull_Leader · Jun 22, 2020

Ampster said:
The cell expands when charged all the way to 3.6 volts.

Yeah, but why do you want to prevent that?

Ampster · Jun 22, 2020

Skull_Leader said:
Yeah, but why do you want to prevent that?

It puts a strain on the terminals and the manufacturer says the batteries will last longer if clamped.

mrdavvv · Jun 22, 2020

Check: https://diysolarforum.com/threads/e...e-clamped-tight-or-spaced-for-expansion.7892/

sremick · Jun 22, 2020

I've always viewed the tape as a temporary thing while building. I cannot imagine it providing any "clamping" whatsoever if the batteries started to expand.

Those of you who use threaded rods/bolts: what diameter do you use?

mrdavvv · Jun 22, 2020

sremick said:
I've always viewed the tape as a temporary thing while building. I cannot imagine it providing any "clamping" whatsoever if the batteries started to expand.

Those of you who use threaded rods/bolts: what diameter do you use?

1/4 for the threaded rod, feels good enough.

I was thinking in using packaging straps for a simpler build, the plastic its very sturdy and they can be crimped very hard, but havent tested yet:

sremick · Jun 22, 2020

mrdavvv said:
1/4 for the threaded rod, feels good enough.

That'd be good. 1/4" would fit fine in the design I have in mind. I might use 6 for good measure, instead of just 4.

I was thinking in using packaging straps for a simpler build, the plastic its very sturdy and they can be crimped very hard, but havent tested yet:

I'd be worried about the straps "biting into" the batteries since all the force would be directed at a narrow amount of the battery casing. Something like Winston or CALB might hold up, but perhaps not the aluminum "blue" cells that don't have a thick plastic shell.

mrdavvv · Jun 22, 2020

I posted some photos of my build at the end of this thread, keep in mind that i have plenty of pressure with 4 rods and my battery its a very long one, think 6 might be an overkill but havent seen your design

EVE-280 cells should these be clamped tight or spaced for expansion?

I working on my 4s 280ah battery plans. I thinking of my battery box. should these cells have a air space between them or be bonded tight together with a hose clamp or something similar.

diysolarforum.com

sremick said:
I'd be worried about the straps "biting into" the batteries since all the force would be directed at a narrow amount of the battery casing. Something like Winston or CALB might hold up, but perhaps not the aluminum "blue" cells that don't have a thick plastic shell.

Forgot to mention the addition of 4 aluminum angle strips for this purpose!, or maybe use some rectangular aluminum extrusions and pass the plastic strip inside them!, ill do some testing in the future.

sremick · Jun 22, 2020

mrdavvv said:
I posted some photos of my build at the end of this thread, keep in mind that i have plenty of pressure with 4 rods and my battery its a very long one, think 6 might be an overkill but havent seen your design

I'm going to use an aluminum plate (thickness TBD) that clamps one end of 4 batteries against the side of the box, which will also be aluminum. If I can get by with only 4 bolts, all the better, since they are a special-order and expensive.

AussieSim · Aug 16, 2020

mrdavvv said:
1/4 for the threaded rod, feels good enough.

I was thinking in using packaging straps for a simpler build, the plastic its very sturdy and they can be crimped very hard, but havent tested yet:

View attachment 15935

I considered options of plastic/PET straps with a metal clasp,

Plastic straps with a heat welded join

Electric/pneumatic stap machines

Metal straps

But in the end I thought all of the manual machines were likely to crush the cells underneath and would leave too much slack after removing the machine. I wanted something with adjustable tension that was removeable, so for my 8s * 280Ah 24V "square pack" I will use 2 linked 700mm hose clamps to encircle the pack (plus tape)

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toms · Aug 17, 2020

I think the key to pack strapping is to have rigid end plates that protrude slightly wider than the pack width.

I have used this method with 10mm plywood and 3 plastic straps.

The plywood extending 5mm past the end of the cells stops point loading of the straps on the corners of the outside cells, as well as any loading from the strap ratchet on the side cells.

Even if i was using hose clamps (which i think will work well) i would use end plates as described to stop point loading of the straps on the cell corners.

AussieSim · Aug 17, 2020

100% agree, the hose clamps at the top and bottom will take tension off the terminals/bus bars, but will not load compression on the centre of the flat side.

Rigid plates/plywood at both ends are required.

AussieSim · Sep 13, 2020

An update on the Aliexpress hose clamps. They ship in pairs, so i now have 4 pieces.

The "700" size represents the diameter of a circle, because the hose clamps are each a bit over 2 meters, with the smallest clamped circumference of about 1 meter.

Fortunately that covers 8s 280Ah 24V square pack (about 1.27m) and 16s 280Ah 48V (about 1.85m)

Oldtoad · Oct 3, 2020

What size would you suggest for a 4s 280AH set?
Aliexpress says about a month to ship here, is that what you experienced? Australia is a bit closer, so I would expect you got them quicker than to the USA.
I'm thinking hose clamp bands for compression, heating pad, insulation with a plywood box for securing the battery in the van.

Ampster · Oct 3, 2020

Oldtoad said:
I'm thinking hose clamp bands for compression,

I prefer thread rod and a plate at each end to distribute clamping force. Hose clamps, even with corner protection put too much pressure in wrong direction.

Steve_S · Oct 3, 2020

Clamping, Binding, Prep for installation into a Plywood Casing. This is with my 175AH Cells recovered from the ShunBin Disaster.

Step ONE: align the cells and apply even clamp force (good hand tight squeeze). Having them well "squeezed" prior to taping/clamping/strapping will ensure a good solid "block".

Step TWO: Apply our Binding. ALSO, If installing into a box, Pull Strings is smart, to help you IF you ever have to pull the cells out. OR would you rather curse & swear while tipping the box upside down while whacking the bottom in hope to free the cells ? The old saying is applied "Be Prepared" and of course the first step in crisis management is prevention... "Blue Air" can be prevented.

THE BOX: (This is my 280AH cell box), the ones I'm making for the 175's are identical except for overall dimensions as the cells are a different size altogether. The space between the cell blocker & front, is where the QNBBM Active Balancer slips into. As I use Chargery BMS the main module will be external to the case.

Hope this info helps, Good Luck & Have Fun !
Steve

AussieSim · Oct 3, 2020

Oldtoad said:
What size would you suggest for a 4s 280AH set?
Aliexpress says about a month to ship here, is that what you experienced? Australia is a bit closer, so I would expect you got them quicker than to the USA.
I'm thinking hose clamp bands for compression, heating pad, insulation with a plywood box for securing the battery in the van.

The 8S square pack should be fine with the 400-500 or the 450-550 diameter hose clamps. In my case delivery took about a month, tracking was pretty useless.

Edit : For 4S it would depend on the pack configuration

They do need a plank of wood, you can't use them on the raw cells as the metal band will cut into the cells, and as the undersurface of the winding buckle is designed for a circle, and will protrude into the wood. (This is a temporary setup, once all of my cells have arrived, I'll IR match them in packs)

There is increasing resistance winding down the hoseclamp as it becomes tight. This leads to the buckle twisting, meaning a slotted power drill bit tends to fall out of the slot and used a 7mm open end spanner

I've ordered hex shank drill bits, AWG 20 M6 crimp rings, TR1035+, kapton tape and double sided tape.