The care and feeding of a123-based packs...

[Doctorbass]

Hey Gary.. What do you think about my idea combined with the idea of Fechter about the cell paralleling method?

see topic here http://endless-sphere.com/forums/viewtopic.php?f=14&t=8712&p=136809#p136809

I mean for high current!!! setup

ex:

Doc

 

[GGoodrum]

Interesting, Doc. The only problem is that there's no hole in the braid for the threaded rods used to hold the end caps on tight. Maybe using a smaller width braid would help.

 

[MitchJi]

Hi Doc,

Wouldn't the braid plus springs between the end caps and the braid (pushing the braid against the cells) provide a more reliable connection?

If you don't want springs Tubular Braid might work better than flat braid:
http://cgi.ebay.com/250'-BELDEN-866...1/2"-WIDE_W0QQitemZ120350851214QQcmdZViewItem

http://www.worldwidewire.com/copper-braid/copper-tubular-braid.htm

http://www.worldwidewire.com/copper-braid/copper-flat-braid.htm

 

[steveo]

Hey Gary.. What do you think about my idea combined with the idea of Fechter about the cell paralleling method?

see topic here http://endless-sphere.com/forums/viewtopic.php?f=14&t=8712&p=136809#p136809

I mean for high current!!! setup

ex:

Doc

Doc

This is a great idea ..

only problem .. the crystallite motor will blow LOL

-steveo

 

[GGoodrum]

I think the whole point is too lessen the workload. Adding springs, would not make it any easier to build the packs.

 

[MitchJi]

Hi,

I think the whole point is too lessen the workload. Adding springs, would not make it any easier to build the packs.

The fact that the springs wouldn't be conducting the current should make it easier. Using pop rivets to fasten them to the caps might only take a few minutes. Particularly using bowed washers or slotted cup washers:
http://hubbard.thomasnet.com/viewitems/washers/bowed-washers?&forward=1

Minimum load build up with maximum washer deflection – light thrust loads compared to other style spring washers.
Used to apply tension between two surfaces to eliminate “play” and prevent rattles.
The spring rate is approximately linear between 10% and 80% of available deflection.

http://hubbard.thomasnet.com/viewitems/washers/cupped-spring-washers-slotted?&forward=1

Slotted washer for less "load build-up" and more flexibility. The slotted washer provides soft, uniform friction between two surfaces and has a wide range of flexibility without creating heavy "load build-up". It is used for maintaining a uniform pressure between surfaces, not for repeated flexing.

 

[GGoodrum]

Mitch, the problem is what do you rivet the springs to? There are pretty big holes in the end caps already. For the middle 10-cell blocks in the pack I did, I put the copper strip in between two end caps, and had the springs go through these holes:

I like the wide braid idea, but that only works for putting 10 cells in parallel. Also, if you want to stack blocks of cells, like I did, and use threaded rod to compress everything together, you'd need to drill holes through the braid and use nylon standoffs, like I did:

What would be perfect is a plastic piece the same width and length with bumps/dimples at each cell position. This could go under the braid to push it up at the right spots. I'd worry that the holes would allow the braid to not have a great connection.

What does circular braid look like? None of the links you posted had any pics.

-- Gary

 

[dnmun]

the use of copper strap is in order to make the 5P, and maintain the springs at right angle to the strap. that could almost be as thin as copper ribbon since the current flowing from cell to cell in parallel is insignificant in relation to the current carried out of the top layer of 5P.

you could have sheet copper cut to fit the outline of the end pieces so it fit snug horizontally to prevent the springs from moving, but instead of the screw and nut attaching the 2 conical springs from each side, drill a small hole and insert an awl or nail at an angle to allow you to corkscrew a copper berylium spring through the sheet and the solder it midway through the hole so that the spring is then orthogonal to the end plates, but use the heavy straps at the end to carry the current. you could solder other types of springs than conical battery contacts, even have cylindrical springs and solder a cap on it so the contact is a larger surface where cell meets spring think soft metal for the contact surface. then these intermediate pieces would be modular to provide the sense line contact, and the big current would go out on the straps at the end. or you do something along the same lines at the end connector.

it even looks like the layout of the pcb was done to bring the outside poles of the 2 wide packs right up in line.

excellent thread. nice work too.

 

[Roy Von Rogers]

Let me chime in here cause I have been looking for a solutions to mounting my M1 cells. I originally thought the springs and the plastic ends were an exellent solution. The question I have is this...how thight are you making the spring connection ? I'm assuming once you tighten the assembly, there will be some spring space in there, but since those cells can move between the springs, I wonder if its a good idea for that type of movement of cells, especially if used on an ebike with all the vibrations.

My visualisation keeps comming back to mounting the cells in to a holder that holds the cell tight, and then soldering the ends to something flexible.

Btw, has anyone looked at desoldering braid for such connections, not sure how many amps those could take, but one can soak it beforehand with solder. I know it comes in different sizes, I dont have any here to test with, since I use a desoldering pump...just wondering.

Roy

 

[GGoodrum]

Actually, there's no way the cells can move at all. The caps themselves are a very tight fit, and they are compressed down very tight, so the springs are fully compressed. This is a very solid pack.

 

[Roy Von Rogers]

Ok so when you tighten the assembly, what is the end stop when you tighten the assembly, the screws in the middle of the springs??. And if so, how much pressure is being applied to the ends of the cells. I cant tell from the pictures what is holding the cells tight. If the cells are torqued down on the end of the cells, how much pressure can the cells handle.

I'm trying to tell by your pictures if the spring area is resessed and the plastic end holder is what tightens down on the casing of the cells, or your tightening down on the spring area.

Roy

 

[GGoodrum]

Ok so when you tighten the assembly, what is the end stop when you tighten the assembly, the screws in the middle of the springs??. And if so, how much pressure is being applied to the ends of the cells. I cant tell from the pictures what is holding the cells tight. If the cells are torqued down on the end of the cells, how much pressure can the cells handle.

I'm trying to tell by your pictures if the spring area is resessed and the plastic end holder is what tightens down on the casing of the cells, or your tightening down on the spring area.

Roy

I'm using two threaded rods that go through the gaps between the cells. Tightening down a nut on each of these compresses the two end caps together, which also compresses all ten springs on each end against the cells. Here's a couple pics to illustrate:

For the blocks in the middle, I bolt two of the end caps together, back-to-back, with the copper strips/springs sandwiched in between:

Each "layer" is tightened down, before assembling the next layer. I use lock washers, and a bit of blue loctite to make sure everything stays put. Usually I tighten them down until the springs don't compress anymore, and then back off just slightly.

Anyway, the whole assembly is pretty solid. I put two of these 8s5p sub-packs one on top of the other, and taped them together using black duct tape. The LVC board is sized to bolt directly to the front of the "stacked" sub-packs. I then covered the completed assembly in shrink wrap.

I need to do another couple of these 16s5p packs, but I really dread having to do a whole pile of the copper strips and springs again. I'm definitely going to look into some sort of compressable braid or tubing. That could save a ton of labor.

-- Gary

 

[MitchJi]

Hi Gary,

What does circular braid look like? None of the links you posted had any pics.

Search for Belden Tubular Braid.
http://www.takefiveaudio.com/mall/shopexd.asp?id=289

http://cgi.ebay.com/Belden-cable-ti...und-strap_W0QQitemZ280317900916QQcmdZViewItem

Buy It Now price: US $7.99
2 - 18' pcs. of Belden cable tinned copper tubular braid approx. 5/16" diameter. The looser braid is expandable up to about 1/2". You'll get one 18' coil of each type braid.

Mitch, the problem is what do you rivet the springs to? There are pretty big holes in the end caps already. For the middle 10-cell blocks in the pack I did, I put the copper strip in between two end caps, and had the springs go through these holes.

Off the top of my head I can think of two or three options:
1. Use big washers on the other side of the plastic caps.
2. Use a piece of plastic or two strips of plastic on the other side of the plastic caps.
3. Rivet bowed washer springs or slotted cup washer springs directly to the copper straps. They should be much easier to fasten to the strap than regular coiled springs.

I need to do another couple of these 16s5p packs, but I really dread having to do a whole pile of the copper strips and springs again. I'm definitely going to look into some sort of compressable braid or tubing. That could save a ton of labor.

I have some misgivings about the braid. First the amount of compression is very limited. Second the braid will tend to compress rather than spring.

I think you have come up with a very good solution. Using the end caps, bolts and springs are all excellent ideas. The result is excellent. I think if someone can figure out an easier way to use some kind of spring in conjunction with braids or straps that will be the best solution.

I like the idea of springs fastened to the caps, pushing something flexible (braid or thin copper strap) directly against the cells. I also like the idea of pop riveting springs directly to the plumber tape (copper straps with holes). I think straps (if someone figures out an easy way to use springs) will be easier to work with than braid.

 

[Doctorbass]

Hi Gary,

What does circular braid look like? None of the links you posted had any pics.

Search for Belden Tubular Braid.
http://www.takefiveaudio.com/mall/shopexd.asp?id=289

http://cgi.ebay.com/Belden-cable-ti...und-strap_W0QQitemZ280317900916QQcmdZViewItem

Buy It Now price: US $7.99
2 - 18' pcs. of Belden cable tinned copper tubular braid approx. 5/16" diameter. The looser braid is expandable up to about 1/2". You'll get one 18' coil of each type braid.

Mitch, the problem is what do you rivet the springs to? There are pretty big holes in the end caps already. For the middle 10-cell blocks in the pack I did, I put the copper strip in between two end caps, and had the springs go through these holes.

Off the top of my head I can think of two or three options:
1. Use big washers on the other side of the plastic caps.
2. Use a piece of plastic or two strips of plastic on the other side of the plastic caps.
3. Rivet bowed washer springs or slotted cup washer springs directly to the copper straps. They should be much easier to fasten to the strap than regular coiled springs.

I need to do another couple of these 16s5p packs, but I really dread having to do a whole pile of the copper strips and springs again. I'm definitely going to look into some sort of compressable braid or tubing. That could save a ton of labor.

I have some misgivings about the braid. First the amount of compression is very limited. Second the braid will tend to compress rather than spring.

I think you have come up with a very good solution. Using the end caps, bolts and springs are all excellent ideas. The result is excellent. I think if someone can figure out an easier way to use some kind of spring in conjunction with braids or straps that will be the best solution.

I like the idea of springs fastened to the caps, pushing something flexible (braid or thin copper strap) directly against the cells. I also like the idea of pop riveting springs directly to the plumber tape (copper straps with holes). I think straps (if someone figures out an easy way to use springs) will be easier to work with than braid.

Looking on the picture when i bought mine i was expecting getting somethink like that.. But that was alot bigger!!! and i have now 10 of them

They mentionned 4gauge.. lol.. the cross sectional abount of cooper is more like gauge 1 or 0- !!

That's why i posted these pictures.. to show some replacement idea i had to be able to make them usefull for me... I mean for high curent demand..!" lol

 

[leamcorp]

I have a question regarding the Dewalt pack. After taking the cells out of Dewalt pack and cut the soldered tabs... can I just pull those tab with a plier or should I trim them. I don't know if pulling those tab will also pull something else.

 

[GGoodrum]

I guess one thing that might work is to use this tubular braid, and put five ball bearings, or maybe hard rubber balls, inside spaced about an inch apart, to create "bumps" in the braid. I could then sandwich the bumpy braid in between two back-to-back end caps, like I did with the copper straps and springs:

If it would work, it would certainly be a lot quicker. Any option requiring individually attached springs, in whatever form, is a non-starter for me, as it will simply take way too long.

 

[MitchJi]

Hi Gary,

I guess one thing that might work is to use this tubular braid, and put five ball bearings, or maybe hard rubber balls, inside spaced about an inch apart, to create "bumps" in the braid. I could then sandwich the bumpy braid in between two back-to-back end caps, like I did with the copper straps and springs....

Maybe soft rubber balls would work like springs. How about putting rubber tubing inside the tubular braid? It would have more spring than the braid.

Any option requiring individually attached springs, in whatever form, is a non-starter for me, as it will simply take way too long.

http://endless-sphere.com/forums/viewtopic.php?f=14&t=8660&start=30#p132349

i took the springs from the a 123 and reversed them to be able to use a pop rivet for 2 spring takes less than a minutes to do the 6 that are on top of the pack...

The springs he used are probably not heavy enough but his post leads me to believe that its possible to quickly fasten springs to either strap or the end caps, with the right springs and the right method.

On the other hand your idea of using rubber inside tubular braid makes me think it might be possible to get equally good results with even less work.

 

[Doctorbass]

I have a question regarding the Dewalt pack. After taking the cells out of Dewalt pack and cut the soldered tabs... can I just pull those tab with a plier or should I trim them. I don't know if pulling those tab will also pull something else.

I would suggest to not pulling on them. the positive one have a nickel disk glued on it... some had problem when it just peled off... My suggestion is to cut them and them to sand a bit the resting spotweld.

Doc

 

[GGoodrum]

Mitch -- The springs in the DeWalt end caps can only handle about an amp, I think. Besides, I tried rivets, but the tool I got from Lowes made my hand hurt like hell after only 15-20 rivets. I didn't find it much faster, and using the good springs ws difficult with rivets,because they wouldn't always hold.

Rubber balls may be the solution, as I want those portions to "poke through" the holes in the end caps, but the rest of the braid needs to flatten, as it would be sandwiched between two end caps.

-- Gary

 

[leamcorp]

I have a question regarding the Dewalt pack. After taking the cells out of Dewalt pack and cut the soldered tabs... can I just pull those tab with a plier or should I trim them. I don't know if pulling those tab will also pull something else.

I would suggest to not pulling on them. the positive one have a nickel disk glued on it... some had problem when it just peled off... My suggestion is to cut them and them to sand a bit the resting spotweld.

Doc

Thanks - I'll try to clean it off a bit. I won't be using the tabs and just wanted to clean it off.

 

[leamcorp]

Mitch -- The springs in the DeWalt end caps can only handle about an amp, I think. Besides, I tried rivets, but the tool I got from Lowes made my hand hurt like hell after only 15-20 rivets. I didn't find it much faster, and using the good springs ws difficult with rivets,because they wouldn't always hold.

Rubber balls may be the solution, as I want those portions to "poke through" the holes in the end caps, but the rest of the braid needs to flatten, as it would be sandwiched between two end caps.

-- Gary

Gary, what about the snap clips that I'll be using for 18650 holder. The contact point is much larger than the spring you're using. Do you think thats enough to push 48v?

 

[GGoodrum]

Gary, what about the snap clips that I'll be using for 18650 holder. The contact point is much larger than the spring you're using. Do you think thats enough to push 48v?

Actually, I forgot about those, but that might be an option as well. Just clip those on the the copper straps. The compression should hold things nice and tight. Do you have the part number for those clips handy?

 

[leamcorp]

Actually, I forgot about those, but that might be an option as well. Just clip those on the the copper straps. The compression should hold things nice and tight. Do you have the part number for those clips handy?

Part # - 534-204

Just got 500 of those. Take a look at the 18650 holder thread. I'm making same thing for A123 - adjustable.

By the way, do you have the LVC board? I need one soon.

 

[GGoodrum]

Part # - 534-204

Just got 500 of those. Take a look at the 18650 holder thread. I'm making same thing for A123 - adjustable.

By the way, do you have the LVC board? I need one soon.

Found them, thanks. Hmm... I see there's a slightly larger version as well (5209...). I might have to get some of both sizes to try.

The new 16-channel LVC boards came today. I'll put them up on my site in the morning.

-- Gary

 

[leamcorp]

edit - Wrong thread.

I got those thick ones too.