A123 20Ah cells price down to 17.50$ per cells?

[megacycle]

Yeh thats it, sort of reverse to most designs, to facilitate the heavy current switches, obviously they will never have to switch heavy current only carry it. It's not a mock too, have actually charged it incomplete, using g clamps,
but was worrying about cell compression.

U bracket would be similar to this, but with a cut out in the switching area at the top.
Could also be 2x overlapping angle iron to allow for different size packs.
Guage of steel does not have to be heavy as bracket is to be fixed onto the skeleton frames, keeping some compression on, because don't want to pressurize the cells any more than just limiting their expansion.
The real pressure on tabs will be applied by the additional bolts or screws mentioned.

Almost come up with the switching and pressurizing arrangement.
It's been tricky because i'm predominantly electrically trained.
It will have to incorporate a snap action, as balancing currents could be in the order of 100A for a split sec.
dependent on alarm settings, eg 0.01V/0.0001 Ohm.
Checked this at start of project with disimilar voltage cells touched together and current clamp on peak current settings.
Though hard to see a spark, must have been extremely transient, hmm scope, anyone threaded this before

While it all probably may seem overly contrived, hope not going of in wrong direction ,can't think of any other method to create an almost instant balance function for fast charging.

I did consider single chargers for other setups, other doc, how you going with those, i was worried about BOM$$$ for fast charging my packs. What you planning on running
would be easy to couple with this design, is that what you're thinking could connect chargers to bar ends with a connector, good one, reverse arrangement, lateral, De Bono would love it.

Cheers for now.

 

[docnjoj]

Luckily, Megacycle, I don't need to charge fast. Overnight is fine so even the 2 amp Voltphreaks chargers will work. Anyways I'm only going for 12S. Don't ride that fast any more. Too old!
otherDoc

 

[megacycle]

Yours might be easier with a linked plugs and sockets rated for 25-30A continuous, if you're not gonna gunnit much doc.

Megacycle's looking for a mega charging system, trying to improve charge time & efficiency, expensive, lossy BMS's :?
and don't want to wait over night, charging on the fly, unless i'm camping out .
So got 3kW meanwell for onboard to charge to 21-24S @ 20Ah for now@ 20 odd mins charge time ,hopefull


PS. Where's the Aussie A123 buy, 170@17.50, hopefully about $3k's worth for a car

 

[megacycle]

Changd the frames for the 3mm and fixed some U brackets over the frames and painted neg one black for now,
Packs got to be black so i don't notice carbonising, pop .

Have shifted the switching area over slightly, more to one side, to allow for the seperators to sit in.
Chamfered one end of the - bars to tiny points to allow the seperators to push in.
Clamped the switching area with the little blocks in and got the 4mm2 shorting cable out.
Nice flash and warm insulation, not a good test, but had to be done
Then put some temp seperators in the switches and tested and balanced with shorts at end of bars, looking good.
Work in progress yawn, kids & missus are in bed.

Edit: Like spkpn's design page 8, someonebody did similar in another thread recent, tabs where overlapped through an insulating plate and bolted. Could do that with the phenolic panel too, me thinks, over large battery bus to help sink the heat, if the bat pack's to be hammered occasionaly. Would be good for a large pack for the car.

 

[ElectricS2000]

A little update...
After everyone's suggestions, I designed another prototype for the pack.
Compared to the older pack, this pack is a little smaller in length, but with the same amount of cells.

A big concern with the previous pack was the need for a huge amount of copper or aluminum for bus bars. I did the math, and anyway you cut it, I would be spending between $500 and $800 for copper bus bars. This is mainly because quarter inch, along with a couple of 3/8" were needed for the pack. You can see the amount of copper necessary in my previous post.

In order to combat this, I needed to design a pack that didn't rely on the cells connecting directly to each other, since that would call for thick copper to space the cells. I had always wanted to do something along the lines of the white zombie's pack, having the tabs bend over a copper bus bar, and then another bus bar being clamped down on these tabs. However, this wasn't practical using 4 cells in parallel. After a little finicking with my A123 test cells, I figured I would cheat, and treat two 20ah cells as one 40ah cell. Now I need 2 parallel (which is 4 cells), which would allow me to use the clamping system.

With the new clamping design, I can use 1/8 copper bus bars, with more surface area. The total for all eight packs will be around $223 (according to onlinemetals.com).

Take a look, any criticism will help!

BTW the silver bus bars will be copper, I just made them silver to show contrast. Also, there will be two 3/16" holes securing the bus bars. I only made one in the CAD drawing due to simplicity.

 

[megacycle]

Can't view your images Elec
Are you thinking laminating and clamping the bus, so multiple tabs can be sandwiched with the 1/8" bar and come out of the packs clamped together at 1/8" x n parallel. Then maybe use flex cables lugged to the sandwiched bars between modules?

I got 162 x 25mm bus sections cut from a 450mmx 900mm sheet, enough for 10 packs.
Was cheaper than bus here and i did'nt want it in a roll.
A$108 for the sheet and $45 for cutting, they are fairly well cut no bent edges.


The smaller modules 265x165x70mm, i'm putting together,It's now 8S to standardise.
the prototype of is nearing completion, i only know this because the amount of black tape needed is getting less .

 

[ctirad]

Hi, is there any source of the cheap A123 20Ah cells in Europe?

 

[999zip999]

China is the cheap source. That's why a group U.S. buy

 

[nieles]

Hi, is there any source of the cheap A123 20Ah cells in Europe?

i would be interested in a europe groupbuy

 

[poirot89]

me to

 

[schabo]

i also interested

 

[megacycle]

Aussie group.

 

[Wheazel]

Also interested in a Europe buy.

 

[adam78]

+ Europe group buy

 

[Dauntless]

http://www.smooth-on.com/catrequest.php

http://www.smooth-on.com/

Not to join in the bashing, but I do want to redirect your thoughts where casting and molding are concerned. It's an easy enough process for you to think you really can make your own cases and containers, the whole reason I studied this in school is for the sort of R&D activities you're engaged in here. If you have cast a part but it didn't completely setup, (Harden) DON'T go sticking your batteries in there, for the reasons you saw in the video. (I wanted to scream "NOOOOO!!!!") And DON'T forget the MOLD RELEASE! Especially if you decide to work with urethane. Don't know what to think of what problem he had, but I'll say make sure you get a good MIX! When you have 1:1 or 2:1 ratios for mixing A:B, they are very unforgiving, slightly more or less of what you were supposed to put in there can ruin everything. I should think it goes beyond molding technique to say you don't want your electronic parts touching anything while it's still wet.

I like the Smooth On I have posted here, look at all the how-to videos they have for you, as well as technical bulletins. Urethane is a tough material, but unforgiving. Silcone is forgiving, I guess because it's life is so short and it wants to go out on your good side. Scientific crowd here shouldn't have much trouble getting going with this.

 

[dangerzone]

+ Europe group buy.

 

[spkpn]

I am also interested in eu group buy. But also consider that from a123rc it is possible to get the cells for 32$ shipping to your door included for any number of cells...

 

[nieles]

I am also interested in eu group buy. But also consider that from a123rc it is possible to get the cells for 32$ shipping to your door included for any number of cells...

is that with or without import duties for your country?

in the Netherlands they will add 19% +12,5 to "all" imported goods over 22 Euro

 

[boppinbob]

All this talk about group buys and building modules and battery management systems yada yada yada lipo doesn't sound that bad.

 

[spkpn]

is that with or without import duties for your country?

of course without (how could the price be invariant under different duties for different countries otherwise ). However, they offer a "workaround" I wont be to specific about it but I guess u can imagine..

 

[cwah]

So many people interested in the europe group buy but nothing happened?