# ThunderSky battery straps?



## EVfun (Mar 14, 2010)

I need to make some new Thundersky battery straps for the original end plates. They packaged the cells in blocks of 4 or 6 and I want to regroup them into rows of 10 (4 rows of 10 are going under the hood of my '66 Datsun.) I'm looking for the material to make new straps at a decent price. The straps are 1/2 inch wide and pretty thin (how thin depends on the material.) 

I will need 40 straps with a few extras get learn to get the 90 degree bends on each end just right. The cell blocks use 8 straps of thin stainless steel from China. I want to add 2 straps that go under the cells for a total of 10 straps per block. My options at this point seem to be:

1. Get extruded flat aluminum in the 1/16th by 1/2 inch size. That is not a commonly stocked size. The best price I've found online is $2.60 per 6 foot strip and since the bands need a minimum length of 27 inches it would take 20 strips. I'm also a bit concerned about using aluminum as it would be placed in tensile load, not a strong point for aluminum. 

2. Get a sheet of material, either aluminum or stainless steel, of the appropriate thickness (about 0.060 for aluminum or about 22 gauge for stainless is my estimate) and have a shop shear it into 1/2 inch widths. I would need a sheet metal shop that regularly handles small jobs. Depending on the cost to cut it this could be a better deal.

3. Get the cell blocks banded like they do pallets. Most banding seems to be more than 1/2 inch wide and I think metal banding would be needed. 1/2 inch is the max width so the banding sets into the channels in the plastic battery cases. There is potential steel on aluminum corrosion issues (the end plates are aluminum.) I'm not sure if any type of plastic banding would resist stretching enough to prevent battery swelling.

I'm looking for any input on these idea or any alternative ideas. Thanks!


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## RKM (Jun 9, 2008)

I used SS strapping, clips and purchased the tensioning tool as well. Works well. The strapping comes in a roll, cut to suit. I used clear poly tubing to protect the corners of the strap where it breaks around the top of the cell. The tubing also helps to insulate the strap from the cell posts. The bottom of the batt boxes have 5/16" round iron welded in place to soften the radius of the strap.

Having a metal shop shear to 1/2" width would be tricky to do (too narrow) and would leave razor sharp edges that you won't want to handle.

Rob


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## azdeltawye (Dec 30, 2008)

I just used standard 1/2" wax coated cold rolled banding steel. I bought 300' for $40 at Grainger:
http://www.grainger.com/Grainger/items/3CTU8?Pid=search

Then re-configured the cells and compressed them with pipe clamps while I fabbed the longer straps. Piece of cake...


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## RKM (Jun 9, 2008)

Piece of cake...


A tedious, time consuming piece of cake!

Rob


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## JRP3 (Mar 7, 2008)

If you use a solid end piece instead of the segmented end plates you could get by with only one or two straps. That's what I'm doing, and using ratcheting cargo straps with a barrel adjuster bolt between the hooks to add more tension.


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## dtbaker (Jan 5, 2008)

I have not built my strapping/boxes for the incoming TS cells yet because they haven't arrived and I am still squeezing juice out of the FLAs.... BUT I am planning....

In my existing battery boxes, it may work best for me to stack sets of cells horizontally. I am thinking this would allow a combination of tie-down and cell compression with one plate on top, and all-thread down thru the bottom of existing boxes to compress.

any problems with this approach?

From what I saw of the internals of the cells, they shouldn't mind being horizontal instead of vertical... unless the Li goop between cells might migrate out the top of the wrappers? Does anyone have any input on the long-term effect of mounting cells horizontally?


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## major (Apr 4, 2008)

dtbaker said:


> Does anyone have any input on the long-term effect of mounting cells horizontally?


This was a topic a while back. Some of us have been told by cell suppliers that they need to be installed vertically.


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## dtbaker (Jan 5, 2008)

major said:


> This was a topic a while back. Some of us have been told by cell suppliers that they need to be installed vertically.


any mention of WHY they have to be vertical?


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## frodus (Apr 12, 2008)

Its because the vents are on top. if they DO need to vent, its better to vent gas than hot liquified battery goop. They don't vent very often, its only a safety thing. EVComponents recommends mounting them upright to avoid these dangers.


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## dtbaker (Jan 5, 2008)

frodus said:


> Its because the vents are on top. if they DO need to vent, its better to vent gas than hot liquified battery goop. They don't vent very often, its only a safety thing. EVComponents recommends mounting them upright to avoid these dangers.



AHA...
well that makes sense then.


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## EVfun (Mar 14, 2010)

I've asked here, and on a couple other lists, about repackaging my 60 amp hour TS cells and have been weighing the different advice. What I am going to do will look like the pictures Darren attached except I'm going to use Stainless Steel banding. I will cut the strapping, bend the ends to the correct length, and punch holes for the screws, then put the cells back together into larger blocks. 

Is there any preference on the type of stainless steel? I found that 1/2 inch banding is available in several thicknesses and grades of stainless. I found a couple of pretty good deals, one on 304 stainless at 0.025 thick and another on 201 at 0.020 thick. 

My under hood battery pack is evolving. My original plan was 4 rows of 10 for a block of batteries under the hood, a block of cells 24.5 inches wide and 18.125 inches deep. I have a bunch of cells sitting on the new battery tray right now and discovered that won't quite fit between the inner fenders. I will have to go with 5 rows of 8, for a block of cells 22.625 inches wide and 19.75 inches deep. It is nice to see a battery pack taking shape in the car.


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## Frank (Dec 6, 2008)

Do you mind divulging your source for strapping? I would imagine any type of stainless would have longer life than plain steel although it's probably not critical. I need to repackage some of my 100AH cells but am concerned that 1/2" is too wide for the "slots" on the side of the batteries, and am thinking of using 3/8".


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## tomofreno (Mar 3, 2009)

> If you use a solid end piece instead of the segmented end plates you could get by with only one or two straps.


 I received the Sky Energy standard threaded rod and small end plates with my cells from evcomponents, and only enough end plates to use two per cell group (one on each end), rather than the 3 on each end shown in some photos in the vendor forum from Steven of SE. That is what I am using, with the plates centered on the side of the end cells. I have seen no sign of swelling so far, after about 50+ cycles, despite overcharging one cell to 4.2V. I recently swapped out some cells that had been over-discharged and the sides of all cells in those groups (including the 4.2V one) were all very flat and fit flush against adjacent cells. This indicates to me that swelling is only an issue for more severe overcharging, but dunno.


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## gdirwin (Apr 7, 2009)

I am at the same stage with my TS 200AH cells - I will have 2 boxes, each with 2 rows of 12 batteries (48 total).

Is there a limit to how many cells you can strap together?

The stock cells came in blocks of 5... I am thinking of strapping all 12 together (the full row) - this would eliminate the aluminum end-plates in the middle (valuable space I would rather use for insulation!).


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## JRP3 (Mar 7, 2008)

I did 12 together, I don't see any limits to how many you could do.


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## azdeltawye (Dec 30, 2008)

gdirwin said:


> I am at the same stage with my TS 200AH cells - I will have 2 boxes, each with 2 rows of 12 batteries (48 total).
> 
> Is there a limit to how many cells you can strap together?


I would worry that at some point the bundle would be too heavy for those little straps on the end plates to handle. Not to mention unwieldy and requiring another person to help lift.
My 6-cell group of TS180AH cells weighed in at 79lbs.


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## EVfun (Mar 14, 2010)

Frank said:


> Do you mind divulging your source for strapping?


I ordered the banding from Net-Tech on Friday. I will post again when UPS has it in their possession and I have a tracking number. I ordered a 100 foot roll of 1/2 inch by 0.025 thick 304 Stainless. Other types of Stainless are available as well as different thicknesses and widths. 

If you are making a long string of cells you could run 2 bands off of each bottom screw, one on the side of the cells like they are shipped and another band under the cell because the grooves are on the bottom of the cells too. I was planning to do this when the plan was to use 4 banded blocks of 10 cells each. The current plan is for 5 blocks of 8 cells each so I don't think it will be needed, especially since I'm using the small 60 amp hour cells.


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## EVfun (Mar 14, 2010)

An update for Frank on the banding for the TS cells.

I ordered a 100 foot roll of 304 stainless steel banding, 0.5 inch wide by in 0.025 inch thick from Net-Tech on 3-19. The total, including shipping, was $49.92. It was shipped by UPS ground one week later (3-26.) The banding arrived on 4-1 (typical 4 day shipping time from Nebraska to Washington.)


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## Frank (Dec 6, 2008)

Thanks - I ended up ordering a roll of 316 (3/8" * .025") after discussing with the nettech folks. My order was a bit more money but shipping was expensive.

FYI, it seems there's a chance that the good folks at EV Components might have miscellaneous straps available. I called and they promised to research it but it seems to me that they're out straight most of the time and I'm not holding my breath. I had already ordered the strapping anyway. What's interesting is that it takes a lot more than you would think! I have to reband four packs and that will take 32 pieces. I'll probably make a jig to facilitate the process.


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