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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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#2 ·
Excellent, thanks for posting that I've been meaning to look into making those, a couple of them would be usefull, for my bandit and for the cafe conversion I want to do for my 250
 
#5 ·
It's not hard. Most of the hardware can be found online for less than 40 bucks.

..............

BTW try to get a really hot iron. I bought a cheap iron and had a difficult time soldering my points. If you dont have a good HOT iron you will just sit there trying to melt the solder on the batteries and eventually damage the batteries. Make sure you have a super hot iron to melt the ACID core wire. Of course I wasnt going to sit there and damage my batteries. My wire's melting point is set at 450 degrees F.

..............

It's really fucking easy.

..............
The price is much more than the $40, when you factor in the additional TOOLS, (high heat soldering gun), and time. Most people only have 25 watt soldering irons. You want at least a 100watt soldering iron, and a 400 watt soldering iron would be even bettery.

I just wanted to mention that no battery manufacturer recommends soldering to their cells.

You may not see it, but every cell that has been soldered is damaged internally. The high heat of the soldering flows through the aluminum and into the cell where it vaporizes the lithium into lithium gas. Soldering the batteries also risks soldering the Over Pressure Release Valve (OPRV) shut, causing a danger for explosion since you've now disabled the manufacturer's built in safetey mechanism. See Speedcell's notice.

Suppose your high power soldering iron costs $40, that brings your total costs to $80. That is still $10 more than my 4cell unit (shipped!), AND you still have to spend an hour putting everything together.

I have over $1500 worth of tools and equipment to properly assemble these batteries. In addition to the warranty, you get my expertise. All of my cells are built with a Capacitive discharge welding, an manufacture approved process.

I have also assembled more than six units for people who initially thought that they could build it themselves, but in the end it was not worth their time and effort.

The picture below show's my $70 4cell unit on the right:



And here's a parts list of what you get for your money:

 
#7 ·
#11 ·
Ahh quit the debate guys, this is a great info thread..leave the bickering to the bitch section. ;)

One thing I would add is that the hyperion bars can be a bit better because they arch up over the cell and can be less prone to arching.

here is a link on where to get them
http://www.aircraft-world.com/shopexd.asp?id=5085

they used to sell the bigger ones but changed because people were plugging up the vents in the batteries with solder

The little hole in the top of the battery is the vent..dont plug it up! :D
 
#15 ·
Holy shit Mavyrick, relax, no one is stepping on your feet. :doh:


We are intelligent people, (for the most part), and understand the risk/benefits/cost of doing something ourselves vs. buying an experienced person's unit with a warranty, etc.



So, thanks again to stephen for posting good info.
 
#16 ·
lets be fair here, there is definitely a risk of damaging the cells while soldering. I don't think it is unreasonable for maviryk to point out the advantages of how he makes them. Welding IS the correct, manufacturer approved method of building these batteries.

Now we have some instruction on how we can DIY, we know the risks of diy and the benefits of buying one allready made. Now, anyone have any other tips on building them?

Here's one, you can buy the quick disconnects cheap on ebay. They are listed as fork lift battery quick disconnects, made by anderson, I think. I haven't added quick disconnects on my batteries yet, but I have thought about it :)
 
#17 ·
lets be fair here, there is definitely a risk of damaging the cells while soldering. I don't think it is unreasonable for maviryk to point out the advantages of how he makes them.
+1, but the way he approached it was pretty dick.





So help me understand this guys...

Difference between using "capacitive discharge welding", and a high powered soldering iron, is just that we will degrade the lithium some because of the heat applied, right?

Stephen and Emanarasi, how long have you guys been running your homemade units? How are they holding up?

What was the wattage of the soldering irons you used?
 
#23 ·
Capacative discharge welding = spot welding. Arc passes from one electrode to another w/ the workpiece in between. Welding happens very quickly and puts minimal heat in the workpiece. We do a lot of it here on aircraft parts.

Short burst of intense heat that cools quickly is less harmful to the battery than the prolonged heating and cooling of solder. Not to say that soldering can't work well, but anyone attempting this should have some practice before trying to learn on the battery!
 
#24 ·
I'm someone who is pretty skilled with electronics. I've been soldering and making or modifying electronic things for years now, and I know what I'm doing. I chose to buy my own battery pack because I didn't like the risk involved with DIYing it. Yeah, it cost me a lot more, but I knew the pack was made correctly. If you choose to undertake this, be sure you know what you're doing, know all the pros/cons and do it at your own risk, that's all I have to say.

PS: Can't we all just get along? :D
 
#25 ·
Why not just build this to go with em....

Home made spot welder, complete with 2x4 handle.


 
#26 ·
LOL. I think you might just blow up the battery with that. You want much lower current and the ability to control the duty cycle.

There's a bunch of tutorials on DIY CD battery tab welders online, but they're not very reliable for long term use, especially with cheap capacitors and power supplies. (Power supplies can't put out enough current, capacitors explode from too much voltage)

You'll have to be able to control your voltage, current, and duty cycle. Too much current you'll blow out the metal, too little and you won't get a good weld.

I designed my own dual pulse welder using laboratory grade power supplies and computer grade capacitors.

Here's an example of a DIY CD Battery tab welder:

 
#28 ·
some goodies to add

One of the A123 cells in the last batch I bought was defective.
Got very hot while charging 57 degrees C and wouldnt hold a charge.
SOOOO i took it apart....
Its pretty simple in there.
What interested me the most was the cross section of the negative end plate and what effects applying pressure to it would have. Which is what happens when I clamp the cells in between the nylon plates.
The end plate comes almost to the center and a narrow rivet goes through the terminal and inside to the copper strip. The terminal is insulated from the end plate by a plastic material.
















 
#29 ·
Wonder if flint could whip some of these up? :D


Good to see your thread going well SSS
Heres a new concept for A123 cells
Solderless framing. Just started a 09R1 engine with this battery.
Theres no solder or paste between the cells and connector plates
heres the design process
3d modelling Inventor



Inventor drawing which makes DXF files



AutoCAD which doctors the DXF file so the tool path progy can use it



Tool path progy (comes with router) to program contours and depth of cut.



3D visualization of the cut.



And watch the chips fly
http://www.youtube.com/watch?v=OEHEmlBgBM4



 
#34 ·
yes you correct that is fucken cool
 
#36 ·
That's what I was asking about! That way if one of the batteries goes south, you can swap it out. FYI, a small diode-isolated LED indicator could show if the battery was good or bad.
 
#38 ·
I'd kick in for one. I'm not feeling the bolts to connect it together. I'd rather see those counter-sunk.


EDIT - I'd want a 6-slot though.
 
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