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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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#337 ·
We have a spot welder at work, and we make NiCd, NiMh packs. And the guy, responsible for makin em now, claims that if you overlap nickel strips one over another they tend to explode. That i dont believe 100%. Thats why i asked about settings
 
#338 ·
Interesting! All my packs have at least 4 layer of nickel strips. Reason being, the first pack I made with nickel plated steel strips(crap) lit up like the 4th of July when I tried to start my bike.
That was 8 months ago and at the time I didn't have time or funds to devote toward the project(6 week premature baby).
Within the last month I've spent time researching and largely because of the "e-bike" scene there is tons of in-depth tutorials on building LiFe packs.
A couple of important points I picked up:
1. Use only a battery spot welder to affix battery tabs, this is what I got and it works perfectly.
2. Use only pure nickel strips and read carefully because most sellers will try and hide the fact that their steps are plated steel.
3. Depending on current requirements, use multiple layers of strips, again I used 4 between the main cells and 2 to tie the parallel cells together.
4. Don't forget the balance lines that provide the charger with the voltage of cells individually. This helps maintain the integrity of the pack as a whole by making sure each cell is at the same village.
5. Use a real Lipo charger to charge/discharge/balance and even determine the pack capacity, what I and many others have
6. Group cells with similar voltage/capacity in the same pack.
 
#340 ·
I guess one other thing to note is when welding the tabs, you want to keep the heat to a minimum. I went from cell to cell only doing one weld per cell until each cell had 3-4 welds. The welder should be adjusted so that a solid weld is produced but no more current than necessary to keep heat down.
 
#341 ·
Hey Guys sorry Ive been MIA. Does any want the 26650 cell pack? I bought a 100 cells because they were inexpensive. I dont give a fuck if I make a dollar. The non-disclosure will be dont sue me bitch! Ill be happy with breaking even. I have a battery welder now so non of that gay fucking soldering. I am using the 50 amp connectors. For the SV's I find out you need more cold cranking amps. I make a series of 2 parallel of 4 to get more mAH out of the cells. Hit me up if you want a 4 or 8 cell pack for your bike. Lithion ION is the way to go for batteries that pack a punch.
 
#349 ·
did you used it strictly for starting or for cycle use?

because i will make a pack for cycle use(no alternator anr starter on bike) and without management system it will be out of ballance pretty quick and die. cant remember the name fur we have a nice fella who built electriv vfr400 here. and he had the same problem on his system
 
#363 ·
I came >this< close to tack welding a battery pack with my tig welder... decided against it at the last minute. The thought of putting the juice through it made me a little queasy. If I had the proper soldering tool I would have done that.
 
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