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DIY: A123 Lightweight Battery Pack

196K views 364 replies 90 participants last post by  lukemike 
#1 ·
It's not hard. Most of the hardware can be found online for less than 40 bucks. I found the cells for $5 a piece. I just ordered more cells to build another pack for my track lady. Most of this information has been generously generated by the RC hobbyist. A lot of those guys build extensive battery packs.

The A123 4 Cell pack (12 volt) was plenty for my SV650. I used a 60W Iron with a temperature control box. I soldered at 600F. My 60watt box goes up to 896F. It worked without a problem. The solder works best if you have a fat tip. They are a few bucks at the electronic store. (Fry's for me)


I already had some Gorilla glue in my tool drawer so that worked to glue the linear side of the batteries together to prevent them from moving.



# Nominal voltage: 3.3V
# Nominal capacity: 2.3Ah
# Core cell weight: 70 grams
# Internal impedance: (1kHz AC) 8 mΩ typical
# Typical fast charge current: 10A to 3.6V CCCV
# 70A continuous discharge
# 120A, 10 sec pulse discharge
# Cycle life at 10C discharge, 100% DOD: over 1,000 cycles


It only takes 5 seconds to melt the solder.

Here was my cost.

Cost $5/ea Cell
Shrink Wrap $1.50
Battery 8 gauge cables $1.50 + Terminals $1.50 (local car audio store)
Battery bars $0.99
Total: $25.50

I have a lot of shrink wrap and 2 cells left if anybody wants to buy them. $11+shipping (let me know)









8 cell pack (Jacked from R1 forum)


The battery bars can be made by anybody. This is just an example of Hyperion making battery bars. I found a pack of ten the other day for a $1.

DEANS - IDK maybe thats the name of the guy that made the bars.




Videos:





It's really fucking easy.

"When in doubt just google it." :D

Update:
Note there are a few cock blockers on the thread. I already know that you know this is a home made battery pack. I dont need to warn you that you need the right tools to accomplish this small task. Obviously anything we do at home we are responsible for our own liabilities.

I just bought a set of A123 batteries for $4 bucks a piece on ebay. So if you look diligently you will find deals. The small roach clips I got them at an electronic store for $3 bucks a pack.

Charger: Venom they are about 40-60 on ebay. The refurbished charger is okay.

 
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#39 ·
i clicked on this thread and started reading the end and wanted to know what all the fighting was about so i read through the whole thing.

first, mad props for the DIY great write up for us on a budget life style do-it urselfers

sec, mavrik (or how ever u spell it) dont be such a money hungry butt hurt (cuz he showed everyone how easy it is to make) dickhead. this is what this site is here for should all the mechanic get all bent out of shape cuz someone did a DIY on adjusting carbs or a fabricator sue someone cuz they did a DIY on SSSA swap. jeez man not everything in life is about trying to ring ur friends dry DONT BE SUCH AN ASSHOLE
 
#40 ·
While he did get a little enthusiastic, pointing out the safety ssue of covering the releif valve was a stand up thing to do. He could have sat back, let him make something that was possibly dangerous, and done nothing. He opened his mouth and pointed out a safety issue.
 
#42 ·
Yeah, either needs the connecting bolts countersunk, or a rubber boot to sit in, or both.
 
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#44 ·
I'm in a hurry and didn't read this all that carefully, but my friend's dad owns a plastics machining company. This is exactly what they do.

If you guys all want some, get me a file and I'll ask him how much for a bunch of them.
 
#47 ·
I have some cells at home I'll check, but mine are the lower amperage yellow cells. I'll start workin on this. I'm gonna see how much I can simplify it. Lookin like an 8 cell pack is the way to go or is there still interest in the four cell pack?
 
#48 ·
Might as well go 8. Can't hurt.
 
#49 · (Edited)
BTW, WTF ever happened to Ripperton? He just vanished.

EDIT. Was thinking of someone else. He vanished too.
 
#54 ·
yes yes i like the direction this is taking.
 
#55 ·
Anyone have a good hit on where to buy the green cell. I'm seeing some retailers on ebay but the one guy is offering them in 6, 12 or greater quantities and they average 8 dollars a cell.

Better price???
 
#60 ·
Diagram for stephen. It's BASIC and doesn't take into account the balance wires and other such oddities, but it does show how the voltages work. He was confused on how the batteries accounted for the 13.2VDC when you had 8 3.3V batteries.

 
#62 ·
Yours was more of a hookup diagram. This is an explanation of how the 3.3V turns into 13.2V. Sorta the same.
 
#64 ·
You will also want to put each pair of cells in parallel. It makes it nearly impossible for the cells to become unbalanced.

Without it, the adjacent cells can be 3.6v and 4.1v, but by the time they get to the end it balances out to 13.2v.

You must fully charge each cell to the same state of charge before final assembly.

You must fully charge each cell to the same stage of charge before final assembly.
 
#67 ·
Hey so where are we with getting some of those solderless housings produced? I'd be down for for a couple 8 cell ones, maybe a 4 cell one or two as well...

Also just asking if they're going to be machined or if we could get them vacuum molded someplace?
I'm sure if more people on the forums knew about them we could get a bunch of interest in them and get them done for really cheap.
We could possibly do flat 4 cell design that would be "stackable". That way there's only one mold to make, if designed properly the top and bottom pieces could be the same. then if you want to do an 8 cell battery you'd just get 2 of the kits and set them up in parallel

We do have a rapid prototyping machine at work but our resin is retardedly expensive or else half of my bike would be one off prototyped pieces :p
If we did figure out the stackable 4 cell design I could print one off. Anybody have hookups with a vacuum form manufacturer?
I think there may be a couple around Vancouver here but I'd have to ask around.
All of the manufacturers I deal with do collectable figures/toys. I some how don't think polystone resin or vinyl would be appropriate for this application...
 
#72 ·
Vacuum formed plastic might not have the stability to contain the battery and hold the contacts in positive contact. Worth trying though.
 
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