Dow-Kokam (NMC) vs. A123 (LiFePo4) comparative analysis...

I'm very interested in these cells at a great price. I still would like to see different ways of connecting this cells. I see the bar clamp method, can they be solder. And what kind of solder ? Gestalt I bet your finger prints are all over the glass. Did they have to ask you to leave so they could lock the door ? It's after 5pm.
 
Connecting cells...my idea....Use nylon bar ripped to about 1/4 thick( not exact for these cells, but .240 thousands was corredt size for the FFR 25a cells) . The length is the width of the top of the cell. Set these in a jig, drill three holes , left middle right side of tabs . 1/4 or 5/16 through so a threaded rod goes through all pieces, nuts on the end and your done.
Balance wires of course between the tabs ( i'm thinking small wires like on the lipo packs) No need for soldering. Easy to take apart etc . I have this nylon bar in 3/4 and 1 inch thick. Think it's called hi-density polyproplene, comes in different size sheets from McmasterCarr.
Tell me whats wrong with this idea. Cass
 
Do you have pictures of the nylon bar. I have some PTFE that also might work and is easy to get. Cuts with a table saw or jigsaw.
otherDoc
 
I just watched Jack Rickard's video on how to make connectors and a polyurethane case for the cells. He uses common materials like alloy bars drilled and fastened with nuts, Nordlocks and bolts and then showed how to make a poured polyurethane case for the 6 cell battery! Very clever and fairly easy to do. I have never seen his show before but he does seem to know what he is doing. Check it out in the thread just above this one! He is using A123 20 ah cells.I am not sure alloy is the best material to use for connectors because of oxidation but it does look easy to make with a drill press! Cool stuff.
otherDoc
oops! The thread is just below this one now. Hugues made the post with the link.

For those who have not seen it:
http://www.youtube.com/user/marionrickard?feature=mhum#p/u/0/wlDJhpiqL_Q

demonstration starts at about 27:00
 
Without having had a cell in my hands, I'm just guessing. I'm thinking a small jig, fit a tab and use a paper punch, or maybe something similar. Make a couple holes in each tab to match all the cells. Fold the tabs over in pairs, maybe, put a clamp type fixture over the fold, insert 2 small bolts with nuts, after smearing the tabs with No=oxide grease, and bolt tabs up tight. Have a durable tab sticking up from the clamps and use that for connecting wires I'm so damn limited down here. I may have to go to Florida and make up what I want.

Need to get some stuff shipped down, anyway. :roll: :lol:

Need to watch that Video, now. Thanks for the link, whoever posted it. 8) 8)

Well, that ain't gonna work. My high speed DSL gets about 3 second bits played at a time, between buffering :shock:

Gott find another video. :roll: :roll:
 
bigmoose said:
Justin of ebikes.ca turned me on to DWOLLA for funds transfer. It takes a few days to set up the accounts but it was like $0.25 to transfer any amount. Does not have pay pal refund capability however.

Just checked DWOLLA:
With Dwolla, transactions under $10 are free and everything else is just 25 cents per transaction.
Click to expand...
Click to expand...

dwolla shaking up the banking industry. if you want free transfers you can open a us bank account and use popmoney and send money. a new free service from them.
http://usbank.com/en/advertising/popmoney.cfm?redirect=popmoney

EDIT:
just found out other banks off pop money. here is the list:

https://www.popmoney.com/popnet/faces/popmoney/common/about.jsp?name=partners
 
I've been trying to hold back here, but i can't anymore.
Hate to dump on sangeSF but i've seen him explode on people more than once over what appears to be minor things ( to me ) and display a negative attitude in other ways.
He also did tell the forum to screw off basically and that he was done helping people. That was about a month ago.

There has also been no apology. Instead, when someone brings it up, they are labeled a troll. Seems a little sociopathic to me IMHO.

I even offered to do testing on the NMC cells you were trying to do a group buy on.. i tried to highlight the positives that most people wouldn't see since naturally everyone here compares it to RC Lipo ( battery sellers love that! :lol: ). I crunched some numbers for you. you even snapped at me and i'm not sure why.

This is not acceptable behavior for someone you are going to trust hundreds of your dollars with.

Maybe deep down, you are a super good guy, but so far the first impression is not looking good. You do not sound like an ethical person. I hope you prove me wrong, but i am only here to warn others about what i've seen.
 
Since I am planning on a 6s2p pack for a 48v 40ah pack I'm thinking that I will use two copper bars with bolts to make a tab sandwich to parallel two of the cells together. Then run the series connections from the copper bars. Should make it pretty simple to take cells out if they ever need to be replaced or worked on. Some simple rubber or plastic caps to cover the connections and there you go.

I like the idea of encasing them in resin, it would insulate the cells but would make it impossible to do repairs. You would have to just scrap em. Plus, dont these cells like to have a bit of compression?
 
999zip999 said:
Gestalt I bet your finger prints are all over the glass. Did they have to ask you to leave so they could lock the door ? It's after 5pm.
Click to expand...

Oh no, a123 is a great company. They directed me to one of their "private viewing booths" where I could get as "comfortable" as I wished. Even a tissues and a trash can were provided :twisted:
 
gestalt said:
Since I am planning on a 6s2p pack for a 48v 40ah pack I'm thinking that I will use two copper bars with bolts to make a tab sandwich to parallel two of the cells together. Then run the series connections from the copper bars. Should make it pretty simple to take cells out if they ever need to be replaced or worked on. Some simple rubber or plastic caps to cover the connections and there you go.

I like the idea of encasing them in resin, it would insulate the cells but would make it impossible to do repairs. You would have to just scrap em. Plus, dont these cells like to have a bit of compression?
Click to expand...


Supposedly we should not need compression but the cells need to be protected somehow. I like the copper sandwich idea but there would have to be some good insulation, perhaps Coroplast to protect adjacent electrodes. I would probably use lexan or regular acrilic to protect the sides from puncture. Maybe even Choroplast. Anybody got a drawing of the connectors that they want to use?
otherDoc
 
So how about borrowing a bit from ol witty jack and cast just the copper parts in the resin. Drill out the holes for the bolts to go through. I think you would need to use hex key bolts so that you could use those "L" shaped ones to get in that tight space between cells when tightening. Probably would even need to shorten the key a bit.
 
Hmmmmmm.......Gestalt, that does seem like a possible way to do it. The resin is messy stuff and one still has to make a mold but.....Could you elaborate on this method of yours?
otherDoc
 
I still stand by my original statement...

A TROLL, IS A TROLL, IS A TROLL...

I have done NOTHING to warrant the CRAP I'm STILL getting.....

(I have NOT asked for, (nor received) even one penny yet from anyone! - So giving out my PERSONAL information OR Pics OR even my shoe size, is NOT WARRANTED, NOR IS IT RELEVANT, AS OF YET (and actually, isn't relevant at ANY time, because when dealing with Paypal on large orders, you need to give so much information, and the checks they do are crazy at times, so IF someone sent me money on Paypal, they would get my personal information anyways) AND putting ANY of that out yet, (ON A PUBLIC FORUM), in MY OPINION, is considered a form of harassment and/or an attack and/or childish!!)
Anyone? Anyone / everyone, chime in, if I've asked for ANYTHING as of yet?!?!?
(More on that in a bit..)

Remember me saying..
Let's call it a "feeler" thread, for a while...
Once all the particulars are worked out, THEN we can move it to the for sale section, if you so wish..
(There is still some figuring out of shipping size/costs/boxes/etc BEFORE we confirm we can go ahead with pooling everyone together)
Click to expand...
(Apparently some people didn't see that post..)

I HAVE spent my time, sending numerous emails to numerous vendors trying to get these cells. (at a good price)

I HAVE spent my time trying to organize the group buy.

I HAVE spent countless hours answering PMs about cells, shipping, timing. Etc.

I HAVE been "trolled" on for no other reason expect for the timing of this thread.
(Makes ya wonder if anyone/someone had a true vested interest {i.e. Money} in the NMC group buy and may lose out because of this thread, now doesn't it?)

Do I NEED or WANT anyone to TRUST ME?
NOPE!!! And let me explain why...
IT'S CALLED "PAYPAL BUYERS PROTECTION"

I HAVE already declined ONE offer from someone that wanted in on the buy, because they wanted 400+ cells and I wasn't taking the chance that if that one particular group of cells was "bad" for some reason, and there was a Paypal reversal, there was NO way I would be protected, because, in order to get MY money back, I would have to ship 400+(lbs of) cells back to china and shipping FROM USA TO CHINA is a whole lot MORE expensive than to here. (AND I would have to pay that OUT OF MY OWN MONEY! (as Paypal doesn't give you the money to ship the item back out to the vendor/seller))..

As a matter of fact, now that I think about it..
I AM still at risk, (re: MY OWN RISK), IF I ACTUALLY go through with the final Group Buy, as if I send the final order and in comes the cells and they don't live up to spec.. I'm then stuck with 500+ cells which I couldn't ship back to china for less than $3,500!?!?
So what happens?, I get 30+ Paypal reversals.. And I'M in the hole for $1000's of dollars..
And let me reiterate.. OUT OF MY OWN MONEY!!

How many of you guys would take that risk?

It seems as if (SOME) people think I'm untouchable, should something "go wrong" or all hell breaks loose. It's the exact OPPOSITE..

And I still stand by the following.. Let me re-iterate ONE more time
(As it seems some people don't read certain things)..

I am done with "help me fix this" posts as apparently some people on here, just know everything, and why do I need to waste my time helping, if "those" people can do it for me... (As long as it has NOTHING to do with something I've bought or sold).
Click to expand...

I also find it completely abhorrent that even a moderator is chiming in with "conjecture", personal opinions, etc.. WITHOUT EVEN A PM to me FIRST..

Now can anyone tell me, WHY I would want to even THINK about continuing with organizing/leading the group buy as it's an incredible risk to me, while I'm getting crapped on, trolled, berated, etc..?!?
Would any of YOU guys want to?!?

Just an FYI... I WAS ORIGINALLY only "organizing" the group buy and THEN would have been asking for HELP from whomever has experience with group buys, but it seemed as if it just "fell into my lap" as more and more people (BEFORE I said I would do anything) started PMing me about cells and organizing/leading a/the group buy..

So, troll, harass, berate me, if you wish.. I'll just stop with the entire group buy and just deal with those that are mature enough and intelligent enough to see through all the childish crap (and, in my mind/OPINION, the "cliquey - behind the scenes "why should sangesf do this group buy (and get fantastic/cheap cells to people) when we can make a really good profit on here while making people think they're getting a 'good deal'", goings on here..

Sheesh! I even HAVE SPENT OVER TWO HOURS, JUST to write this post!
(I guess I'm just a glutton for punishment!)

End of line.
 
In the spirit of deplomacy and of progress I think we ought to start a new thread that relates to the group buy and whatever technical info that might be tossed about in that kind of thread. That way any arguing about ettequet and whatever else can stay here. I would rather that anyone that doesn't want to contribute or start their own group buy just let it go, but I'm not everybody.

I can only speak for myself and say that these cells have been in my imaginary dream bike for over two years. So I would like to see this group buy work out and would help in any way I can. But pretty much all I can do is contribute twords getting to that 500 mark.

We all know batteries is sometimes the hardest part and it's great that we have more large format options out there. Surely we must explore this source that hopefully can supply us into the future. With prices like this building an electric motorcycle, or even a car is more in the reach of many of us that have to really scrape by to keep our hobbies alive. Combined with rising gas prices, lower priced batteries capable of decent performance could be a boon to our cause here at E-S.
 
docnjoj said:
Hmmmmmm.......Gestalt, that does seem like a possible way to do it. The resin is messy stuff and one still has to make a mold but.....Could you elaborate on this method of yours?
otherDoc
Click to expand...

I'm thinking something like this. You take the two cells, bolt them together with the copper bars. Then solder on your series connection wires and on two ends of the pack the battery leads. A short piece of a straw or tubing big enough to go around the hex bolt. You put a mold over all that, I was thinking of making the mold from an ice cube tray. The straw would keep the resin from covering the hex bolt and giving you a path to loosen it. It would look something like the recessed screw holes you often see on portable stereos.

If you ever needed to swap out cells you would just have to loosen the bolts and slide the cell out. Might look cool too.
 
So reading a lot of these post, are we guaranteed these will live up to the specs? i.e. is all the "fake A123 cells" campaign just to keep the price of the A123 battery high?
 
So I am going to be in on the group buy if I can pull my funds together in time. My plan is to make modular trays out of 3/8 ABS plastic similar to what eig and a123 does with their cells. Inside of these units the cell are flipped to create the series connection and balancing leads could pass through out to the ends of the cell blocks. I think I will machine pieces of aluminum that will sit against the tab and carry current from cell to cell and will be crushed together when the whole thing is screwed together. I wanted to completely in-case my cells with these modular parts so that it serves as a hard case too. The whole thing will bolt together with all thread or similar. Hey maybe at some point if I get the design down right I can move to have them injection molded instead of cnc'd.

Oh and I wasn't going to worry about heat. I was considering putting a .5mm air gap between cells in which air could flow but that would also open it to the elements.

moble_big.jpg


auto_x600.jpg


I gotta get a cell in hand to start the design.
 
mvly said:
So reading a lot of these post, are we guaranteed these will live up to the specs? i.e. is all the "fake A123 cells" campaign just to keep the price of the A123 battery high?
Click to expand...

From what I can tell, a lot of the "fake a123 cells" campaign where/are based mainly on cylindrical cells being rebranded..
 
magudaman said:
So I am going to be in on the group buy if I can pull my funds together in time....
Click to expand...

I wouldn't worry about that.. We're still 100-124 short and then we still have to create the thread in the for sale section, get all the members involved to be ready to add funds, in a timely manner, (which will probably be the longest wait), etc, etc...

So you/I/we have time yet...

I'm still figuring out for myself, how I'm gonna connect these..
(I'm looking at everyone else's ideas and see what would work the best for me.)
 
magudaman said:
My plan is to make modular trays out of 3/8 ABS plastic similar to what eig and a123 does with their cells.

Oh and I wasn't going to worry about heat. I was considering putting a .5mm air gap between cells in which air could flow but that would also open it to the elements.
Click to expand...

Don't overlook the requirement for compression bands (as noted in EIG's proof image). The majority of the tinkers buying these cells do not realize that until it's too late.
 
So it doesn't get lost, let me note here the sources Jack used for casting his battery shells. I had to watch a couple of video's to completion to catch the spec's of the materials and their source.

Silicon rubber mold is Mold Star 30 Platinum from Smooth On $173/gallon unit
http://www.smooth-on.com/Platinum-Cure-Sili/c1115_1341/index.html?catdepth=1

Onyx Black Urethane for hard shell is Smooth Cast ONYX from Smooth on $94/gallon unit
http://www.smooth-on.com/Urethane-Plastic-a/c5_1120_1325/index.html?catdepth=1
 
Seriously guys, don't worry about heat; just make sure your terminations can sink it. This is the biggest single factor in battery longevity and performance in my opinion.

Think about it - the tab is the bit that gets hot. Whatever is attached to this tab will sink it. If you have a nice big lump of copper block there to sink it and take the current, great. If you don't, the cell itself will sink the heat - not good. Air gaps are unnecessary and only introduce an opportunity for dust, water, crap and vibrations. Just don't skimp on the terminations and you'll be fine :D
 
Hi,

gestalt said:
Since I am planning on a 6s2p pack for a 48v 40ah pack I'm thinking that I will use two copper bars with bolts to make a tab sandwich to parallel two of the cells together.
Click to expand...
I think brass is less subject to corrosion and I think brass is quite a bit cheaper than copper.
Harold in CR said:
Need to watch that Video, now. Thanks for the link, whoever posted it. 8) 8)

Well, that ain't gonna work. My high speed DSL gets about 3 second bits played at a time, between buffering :shock:

Got to find another video. :roll: :roll:
Click to expand...
You could download it (who cares how long it takes if you are not watching it) and watch it later. The easiest way I know of to grab YouTube videos is to use the Firefox Browser and using DownloadHelper:
http://www.downloadhelper.net/
DownloadHelper is also a free Firefox extension for downloading and converting videos from many sites with minimum effort.

Video DownloadHelper is best installed from the Mozilla Add-ons site. Go there and just click on the Add to Firefox button and follow the instructions.
https://addons.mozilla.org/en-US/firefox/addon/video-downloadhelper/
The easy way to download and convert Web videos from hundreds of YouTube-like sites.
Click to expand...
Click to expand...
If that doesn't work with your DSL maybe someone else will download it for you.
 
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