Terminating the 15Ah and 20Ah Cell-Man cells

I've used my feeble word skills to try and draw my idea of a purpose made tab clip.

Can someone give me the exact sizes for the tabs please.

Comments and ideas welcome. Thanks

Peter

SpringClip.jpg
 
hi Peter
these are the dims of the tabs, 45mm w x 25mm h, (thickness is less than a 0.1mm, my accurate vernier gauge is not handy ) I was just playing with a trial connector this morning, so had a cell on the table.
I am going for a clamp system to give greater pressure, so the only comment I have, which is not very constructive, is do you think a spring will give enough pressure to make contact well enough to allow 200A?
btw, there is 35mm between the tabs, and 18mm tab edge to cell shoulder, I have only just worked out how to put pix up on the board, so give me a bit more time before I do drawings!
hope this helps
Charlie
p.s. just seen cell man's post as well, there is confirmation for you!
 
I get the tabs at more like 0.22mm for the negative and about 0.35mm for the positive alloy tab. Sorry my info was a bit incomplete as Charles quite rightly stated it's about 34-35mm spacing between the tabs.

I don't know the actual pressure required to get a good contact. I use toggle clamps to clamp the tabs on my test system and they seem to be sufficient but could be better. If you are using the spring clip it should be pressing down onto a clamping block to spread the pressure over the tab.

I'm going to revise my 1p connection method and use 6 or maybe 8mm square brass bar on the rear, clamped to a non conducting material. Similar to my previous effort for the 1p termination but narrower conducting clamps. I feel this will give a lightweight, compact, easy to assemble/construct termination method with no compromise in performance. That's the plan anyway :mrgreen:
 
sjoerdvdd said:
peter,

arent't you worried about vibrations? i can imagine tabs can vibrate a lot more with a loose connection, than when they are fixed..
Click to expand...

I agree that's a consideration i need to look at when all on the bench. I would use some heatshrink over the clips to insulate them once clipped onto tabs.

Perhaps some foam/plastic strips pushed inbetween tabs to keep it all steady with a lid over the top.

This may not be best suited for very high currents but in my system i'm looking at 100A max for short periods.

It should be possible to have clips which give full tab face to face contact so that's a lot of surface area call it 45 x 20mm.

Just an idea.
 
allright, i like the way you look at terminating them though.

another question.

the 20Ah cell is 165*227*6.9 if i'm correct. the height (227mm) is it from bottom cell to upper tab, or effective cell chemistry ( bottom cell till upper hard part), or is it measured from bottom cell till end insulation, since the pictures show some unused insulation above the chemistry before the tab connections begin...
 
The 227m is the distance from where the insulation finishes and the tabs start, to the end of the cell. If that makes sense. The actual cell chemistry part as you said is about 200mm by 155mm or so. The actual width is more like 160mm and it really just depends on how the edges have been folded over.

JRP3 said:
You might want to try a thin layer of this stuff on your connections: http://www.sanchem.com/aSpecialE.html I'm using it on my Skyenergy cell connections.
Click to expand...

Thanks that's great info. Will have to try and get hold of that or something similar. The only thing that occurred to me just now is if this is conductive it might not be ideal if it's used on 1p terminations that are in fairly close proximity to each other. I imagine if used sparingly it would be ok :?:
 
JRP3 said:
Yeah you aren't supposed to glop it on, just rub a thin layer into the surfaces so they are all sealed. It helps to warm the stuff up a bit as it comes out of the tube almost like a wax if it's cold.
Click to expand...

It's looks like good stuff. I've sent an enquiry to the manufacturer so see what they come back with.
 
how about alternating which end the cells terminate ie one right side up one upside down. This would mean that there are two conduction sides, but would allow larger contact areas.

Could the pack be placed on it's side? as i think having conductive material on the bottom would be bad.
 
Can i ask a question? If the cells are so difficult to solder because the tabs are so large, couldn't you just snip them so the tab is divided into 3-4 or four smaller sections and solder it that way? It seems like a good way to solder on a wire to them as well.

beware, here comes some bad ASCII art. Imagine you are looking at a couple stacked cell tabs from the end of the battery.

cell tabs before:
_______________
_______________

after snipping:
___ ___ ___ ___
___ ___ ___ ___

Next, the mini-tabs are bent away from each other a bit so they can be soldered individually. I don't know know how the deep the cut needs to be perhaps, to the start of the pouch? It may even be possible to do a second round of soldering to reflow the tabs back into a single long tab now that they have been "tinned" this way

after soldering round 1(ignore the dots, I needed them for space holders):
_______.........._______...........
......... _______.......... _______

soldering round 2 possibility?:
______________________________

soldering a power wire in between tabs turns into a spot soldering job maybe? you could join a small balance wire to the mini-tab as well(ignore dots again):
_______ .......... _______ ..........
======================================
.........._______ ............ _______


OK, is this possible?

I'm just thinking of a way to turn those big tabs in to something more manageable. These mechanical fasteners are neat, but I just want a big honking capacity lipo that's packaged like an R/C battery, not something that needs cabinetry.

I have also seen lipos that look like they were crimped in some type of device that fused or soldered the tab under pressure and/or heat. What is that thing?
 
http://www.albert-roller.de/go.aspx?lid=2&tid=15&pgid=4#l1 check out the pulsar soldering setup, it's an electrical resistance setup which sounds like a bad idea for soldering a battery, but it's the form factor that I like. It's like a big pinching, soldering claw heated from both sides.
 
will_newton said:
Can i ask a question? If the cells are so difficult to solder because the tabs are so large, couldn't you just snip them so the tab is divided into 3-4 or four smaller sections and solder it that way? It seems like a good way to solder on a wire to them as well.

<snip...no pun intended>

I have also seen lipos that look like they were crimped in some type of device that fused or soldered the tab under pressure and/or heat. What is that thing?
Click to expand...
Interesting idea!
I'm wondering if what you saw was a "resistance soldering" device. They're capable of soldering very, very heavy gauge materials.
 
Well Liveforphysics reckons using LiPo solder works just fine, except you need to be quick so as not to damage the cell. As I am likely to be needing to get at the odd cell, mechanical connections will suit my 8 x 3p 4S packs. Lots of mucking around, but the risk of short-circuting the cells while soldering is very real :shock:
 
Luke was looking at a tool that could be clamped onto the tabs to heat the hole tab completely and quickly. I have actually got a pack that I soldered together but it just seemed so difficult and messy that I abandoned it. Most people seem keener to have a mechanical method that could be worked on more easily as well. Cutting the tabs maybe could make the soldering a bit easier I think but given the choice of a mechanical or soldered termination, I'd pick the mechanical. It offers lots of advantages and if it can be done in a compact/lightweight way with minimal losses I think it's definitely the way to go. If the soldered pack was really quick and easy then yeah it would be tempting but it hasn't been.

I've got a 3p pack and a 1p pack both mechanically terminated that I'm currently working on and I'll get some pics up later. It's still more time consuming than I would like but it's better. If the parts could be made fairly cheaply instead of machined by myself, I think it's a very viable option.
 
Peter's idea of a simple clip got me thinking. In our office, we have these neat little clip dispensers that quickly clip a few sheets of paper together without making any holes in them

I reckon that these (maybe two or three per tab) would work well if the tabs were cleaned, coated with conductive paste and then folded over each other first. The clips are stainless steel, or plated/painted spring steel, but I don't think this matters. Taps for the BMS connections could be just AMP 0.25" long tags clamped inside the "sandwich".

The clips are put on with a little plastic dispenser, that opens the ends out a bit so that they slide on easily. Here's a link to a site with pictures of the little clips;

http://www.internet-stationers.co.uk/Shop/istationers_shop/index.asp?deptID=1570&ptype=2

Each clip is around 1/2" to 5/8" wide.

Jeremy
 
thats a golden idea jeremy,
here in oz ive got 24 of these cells to join up, and i just got some of them little clip type jobbies that you speak of.

theres 3 sizes of "nalclip" made by esselte and marbig that ive checked out, and it looks like you would get 4 of the small on a tab with a bit (4mm) of overhang over each side, (3 of them would be about 8mm shy of covering the full tab).

these small ones give about 2kg of clamp each fully spread out to 3mm, so 4 of them is 8kg, like jeremy said you would sandwitch a pair of metal blocks (maby just alloy?) of about 1-1.5mm each to spread out the pressure with some conductive grease on the folded over tabs.

and if your after more clamp force, then you can add 3 mediums over the top of the 4 smalls and 2 larges over that and you would get about 15kg total -plenty i would have thought, as it will hold this clamp force for good even after vibration, settling etc -its similar to how (and why) manufacturers clamp rubber hoses on cars seemingly without massive force but a constant pressure spring clip.

you can solder to the clips themselves with sanding and flux for bms connections so all in all seems like a neat, simple, repeatable and kinda "production" type of method.

hopefully theres nothing ive missed? so ill probly go with the method shortly.
 
Hi Guys I've made some progress on some new termination methods and have also found a company that can start machining the parts for me :D Not too many more days spent cutting, drilling, tapping etc....

The clips sound like they will work just fine as well. I really need to get myself some of the special grease for the terminations. If there's a source for this I'd like to order a little to give it a go. I spoke with a manufacture but minimum order was kind of big and needed to ship from US. If I can just get a small quantity ordered from somewhere that would be great.

Anyway here is a 1p pack that I've come up with:

View attachment 3

CIMG0588.JPG

Basically I've gone with brass terminals and decided to abandon the no holes in the tabs restriction I had placed on my self. I was hoping to mount the BMS balance wires on the rear of the clamps but it's a bit tight for space (difficult to get a spanner in there even if the connector was small enough) so I'm thinking of extending the terminal a little and bolting onto the front face of the brass terminals, or even the end. I'm going to just fit the ring crimp for the BMS sense wires under the bolts for now till a better solution is found. I'm also thinking that I will add grooves to the insulating material so that each brass terminal has a raised section of insulator between it and the next termination. The whole thing sits square which is made possible by a little tool I knocked up that ensures the tabs are folded over equally and square.

Here's a few pics of a 3p termination I've been working on but this will change quite a bit:

CIMG0559.JPG

CIMG0562.JPG

The terminals will not be countersunk as per the pics and they will be located with a non-conducting sheet/sections that sits over the clamps and positions them accurately and prevents anything shorting etc. This non conducting sheet still needs to decided upon exactly but the basic copper and brass terminals for the 3p pack are pretty much as they will be in the end solution and are now in small production.
 
Looking great Paul! Please to hear you have a firm on board with the brass terminations. Like I said, I have decided to go with Rod's BMS units which can bolt onto the terminals above the insulating material, provided nicely conductive bolts are used ;)

I have got a quote from an Australian plastics company for making boxes to house the 3p4s packs. Once I have confirmation of a few details I will send it your way. Australia is far from a cheap place to get things made, but it might give you some ideas.

Catch you soon,
CHRIS
 
regmeister said:
For the "grease", maybe something like PENETROX or NOALOX would be suitable?

http://www.galco.com/scripts/cgiip.exe/wa/wcat/itemdtl.r?listtype=&pnum=P8A-BURN

http://www.idealindustries.com/products/wire_installation/accessories/noalox.jsp

Oh, may I suggest not putting labels onto the tabs? The ones I have tried so far, have been difficult to peal off.
Click to expand...

Thanks, sorry about the labels, that's how i receive them. If you're going with a mechanical terminations I'd recommend a few mins polishing the tabs prior terminating anyway, that will soon shift those pesky labels :)
 
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