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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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#109 ·
HA! After reading about these batteries allnight, I decided to get my soldering iron out (a 100w temp controlled iron) and solder together the A123's I jsut got int he mail, fresh from China! (side note: the dude who;s namewas on the return addy was Wo Hung Dong ! LOL!)
anywho, Im a cable guy, and i had a bunch of spare crap in a box in the garage, and as i set it down, I saw a battery pack fora cable phone/internet modem, andwith an A123in my hand alreadyI KNEW this sucker had tohave these cellsin them!
I cracked it open and YES!! ITs got FOUR of the 2200mah green A123'sin them! YES!!!!!!!

Now I got like 30 of these damn packs in my truck right now!!!
SWEEEEEEEET! Gonna make packs for every bike I got!


THey are these ones!

http://www.molicel.com/ca/pdf/ICR18650H.pdf
 
#112 ·
Ok, guys. I wanted to put a little note on here of what I have found.

Im a little obsessive compulsive so Ive spent a few days doing some heavy research on these battery packs. Ill share what Ive found.

1. If the cell is cheap, its a fake. Period. (ive bought 3 diferent ones cheap on ebay, plus some Ive found around my house and they all are crappy ones.)
2. They have to be fully charged before making the pack. That way you don't have to worry about balancing later on.
3. Be goddamed careful! The real ones will light your ass up if you get something crossed!

Thats it....

Just make sure your getting the REAL A123's and they are expensive. Pretty much anything your getting off ebay from china is gonna be a fake. you might get lucky, but for all the crappy ones Ive tried to get a deal on i could have made 2 or 3 good packs by now.
 
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#118 ·
I bought 10 of the small a123 1000mah cells for 10 bucks. The battery I made, bolt together, cranked my bike 5 times in a row. No more. a 650 single is hard to turn over though. Its an 8 cell.

These are the cheap low amperage ones. Im going to build a new battery with the larger cells.

 
#119 ·
I got swindeled then! mine cranked it a little, but died. Still had the voltage just not the amps.

All Im trying to turn over is a 450 twin.
 
#123 ·
OK so cheap solution time!

Based on the measurements of the cells. The OD is roughly 1.062"

1" PVC pipe is roughly 1.029" ID. So depending on batch tolerances it should be possible to use PVC to align the cells into a flashlight style stick. Or cut tubes of PVC and use PVC caps to press the contacts against the tops.

I like the idea of a PVC tube with 4 cells in a line. Get a quick disconnect and you have a baton under your seat!! heheh.

Bob
 
#124 ·
you may be on to something there... even if you did have to ream the pvc out a little..

stick style batteries or a 2x2 setup (two pieces of PVC side by side each w/ 2 cells) would work well in some builds..

-Jeff
 
#127 ·
It looks like they are just connected in parallel so that they push more amps at 3.3v. Then each 16 cell row is connected in series to hit 48v.

So they would need to be cut up and connected in series.

The part description is the correct model number.

Bob
 
#128 ·
that's the correct type of battery
 
#129 ·
also the pvc is a good idea but I wonder what the effect of holding the battery heat in will have on the cells

it might be wiser to use brass tubing (is available in 1/64" increments) or just drill lots of holes in the pvc.
 
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#136 ·
if you used brass or copper it would be a better heatsink like you said and could also be the ground side conductor... ie. have the negative go to you tube and then pull it back off where you need it and just insulate the pos from it... like the way a maglight uses the alu tube as a conductor


-Jeff
 
#131 ·
16 in parallel - A123 lifepo4 cell is 3.2v at 2300 mah

16 * 2300 mah = 32amp hours at 3.2v

I think you're right (or he is wrong)

I didn't know they came in lower amp hour ratings.

either way I think racing geek is right these aren't the ones we use for motorcycle batteries (although they would likely work if you used the right number of cells)
 
#132 ·
:doh: I never realized they may be wired in parallel. I just assumed it was series.

I know they also come as 1100mah but even that wouldn't make the 20Ahrs he mentioned. Isn't Trucker using 8 of the 1100mah cells on his Savage?

The other thing that is also confusing me is that after a quick search of the web, the 26550 number designates the cells used in the DeWalt battery packs which are 2300mah. Maybe he just doesn't know what has?
 
#138 ·
I asked the seller if he knew if they were genuine a123 cells and he said
"I do not know but they are the same size. Optimum Batteries made the packs but not sure about cell manufacturer. I can charge them and check that they have capacity. They cost me $520 per pack of 50 volts at 20 Ahrs. The BMS are not reliable and some of the cell became dead. I will make sure that your order is only with good cells.
Thanks ron"

He says 16 of them to make a 3.2Volt 20 ah pack, Which would mean that the cells are in parallel not series, meaning that the MAH goes up and not the voltage.
Even then though, 20,000/16=1250mah, which is way less then 2300mah which each A123 cell is rated for...Not sure if they are genuine cells, but looks like they might be just at a lower mah or the guy just got the mah wrong in his listing.
 
#139 ·
$520 is very very cheap for a 50 volt, 20ah EV battery.

Edit: actually the prices have dropped that sounds about right but cheap
 
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#140 ·
OK, here's the deal.

There are dozens of LiFePO4 battery manufacturers.

The one you want, is A123 Systems. A123 Systems batteries are Green. 50A max discharge, 2300mAh, 3.2V a cell.

ALL of the lightweight battery manufacturers, (Turntech, Ballistics, Full Spectrum Power, Carbonspeed, Maviryk Design) use cells manufactured by A123 Systems for their batteries.

The only other manufacturer that comes even CLOSE to the performance of the A123 Systems cells is K2 Energy. Those cells are manufactured in Finland. You can buy them from the factory with a dealer discount, but they are not nearly as reliable as A123 cells for powersports use due to higher internal resistance.
 
#141 ·
Um, doesn't a 1860 put out 2,200mAh @ 3.7V ????
The Ah ratings of these cells seems suspiciously low...
 
#142 ·
DEWALT CHARGER

For those that already have a dewalt charger for a drill here is how you can make a charger for your battery pack. My dewalt charger charges between 7.2v-18v.

I had an old dewalt pack that was no longer keeping a charge so I disassembled it and made my own charger for my A123 4 cell pack that I use on my bikes.

It's real easy. You remove the four screws from an old drill battery pack and clip the wires and solder new lines to the old pack.

White= Hot (red)

Flat metal=Negative(black)

I taped the terminals because I didnt have any round terminal clips.

I only let them charge for 15-18 minutes = 13.9volts





 
#143 ·
DEWALT CHARGER

For those that already have a dewalt charger for a drill here is how you can make a charger for your battery pack. My dewalt charger charges between 7.2v-18v.

I had an old dewalt pack that was no longer keeping a charge so I disassembled it and made my own charger for my A123 4 cell pack that I use on my bikes.

It's real easy. You remove the four screws from an old drill battery pack and clip the wires and solder new lines to the old pack.

White= Hot (red)

Flat metal=Negative(black)

I taped the terminals because I didnt have any round terminal clips.

I only let them charge for 15-18 minutes = 13.9volts
pretty dam cool!! I thought that 18v charge current was too high??

Also, anyone know what kind of tool to buy/use to get a professional crimp on the ends for an 8ga wire and quick-connect ends??
 
#144 ·
I didnt look at the real technical specs on the charger it just says it has a range on the front label between 7.2-18volts. My drill packs are 9.2volts. Either there is a voltage regulator inside the charger or drill pack. I kept an eye on it with the voltage meter and once my 4 cell pack had 13+ volts I cut off the charge.
 
#146 ·
Do we have any info on weight savings with an 8 cell in comparison to a lead brick battery? Just curious.

And for all this info, a single solid link to the right kind of cells (ebay auction or whatever) would be extreemely helpful. From someone who has made these batteries and have not had them fail.
 
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