Joined: 01 Jun 2005
Posts: 220
Location: Melbourne, Victoria
Update on my A123 batteries. Cycled every cell in the 4 cell pack and found 3 are ok (~2170mA), but one is pretty much had it (<1600mA). The dead one has been cycled 4 times and still not increased in capacity, although its now not dropping straight from 3.6V to 3.15V when I discharge it.
I've also found that most of the time an A123 is being discharged (~1.25A) the voltage is around 3.1-3.2V.
The 4 cell A123 pack from RMP uses the flexible braid, but the 3 cell pack uses solid bars.
"Summary: The new (green plastic sleeve) A123 cells available at www.battlepack.com/a123.asp are of a much higher quality build than the older (white cardboard sleeve) A123 cells that we're all used to getting. Their IRs all meet spec., as do their nominal and peak voltages; however, (here is the BIG bonus) out of over 2700 cells obtained and sold through battlepack.com, they have reported that NONE have been found to be substandard/defective vs. 4-5% of the old version A123 cells. These new cells also appear to be a little lighter (by about 2.5g/ea) than the old M1 cells, and also seem (in my opinion) to solder more easily than the old style cells. Am I happy with these new cells? You bet...and I'll be buying more of them."
Sun Aug 09, 2009 9:24 pm
Spockie-Tech Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
Yes, I got 2 out of 10 cells from a new DeWalt pack that were about 1750-1900, compared to the rest at 2100+, which I thought was pretty dodgy matching.
Hopefully the new ones are better and they actually start selling them through a variety of channels so we can stop raiding dewalt packs _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
They cost more so its nice to know they are better. _________________ Satisfaction is proportional to effort and results.
Mon Aug 10, 2009 6:38 am
assassin
Joined: 27 Jun 2004
Posts: 1105
Location: SunshineCoast
How are people going soldering onto the end of the original A123 cells? It looks like some sort of flux is needed/recommended. _________________ Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world.
Albert Einstein.
Mon Aug 10, 2009 7:34 am
dyrodium Experienced Roboteer
Joined: 24 Aug 2004
Posts: 6476
Location: Sydney
I had no issue with a hot 80W iron and some big normal solder, i think the ones with subtle fluxes don't work all that good. Also i dremeled the ends to help the solder flow in better.
EDIT: that's not a bad price for 10, I paid that much for mine a few years back, and to be honest, these other bargain used ones just seem crap XD _________________ ( •_•)
Joined: 20 Jul 2004
Posts: 2523
Location: Victoria
quote:Originally posted by assassin:
How are people going soldering onto the end of the original A123 cells? It looks like some sort of flux is needed/recommended.
s39 solder flux i got it for $6 a bottle from a bearing wholesales place prob pick it up from a welding joint.
Worked like magic with fluxless solder. _________________ Tim Team Reaper.
Mon Aug 10, 2009 11:38 am
Glen Experienced Roboteer
Joined: 16 Jun 2004
Posts: 9481
Location: Where you least expect
havent been reading up on a123s for a while, how do these ones compare to the others?
Joined: 16 Jun 2004
Posts: 9481
Location: Where you least expect
simple question i cant seem to work out myself (smashed my head on NYE and i cant think properly still XD)
if the outside of the can is one polarity on the A123 cells and hypothetically say the heatshrink breaks apart like it used to on nicads sometimes and the cells touch, would that affect how the pack works. cant thrash out in my retarded mind what would happen if the cells are in series and the negatives are in parrallel on a pair of cells.
Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW
Chances are that you will be shorting out one or more cells. The can of each cell is connected to the centre of the next cell; if you touch the cases together, you will short one of the cells . That's why I had to be so careful with those intercooled Nicad packs I made for Jolt.
Sun Jan 03, 2010 10:36 pm
Daniel Experienced Roboteer
Joined: 30 Aug 2005
Posts: 2729
Location: Gold Coast
Very dumb question time:
I have A123's made into 3-cell packs. All up I have 6 packs made, which I number to keep track of charging and performance. Only packs 1 to 4 have balancing leads since I don't know where t buy them. Pack number 3 and pack number 5 both refuse to charge on my charger which comes up with Low Voltage Error. I've tried balancing pack 3 but the error shows during the balancing check. After 6 months I got frustrated and tricked the charger to think it was an SLA and force feeding it 0.4amps but that still got me the low voltage error when I changed back to LiFe charging. I'm guessing a cell in each of the packs have died, which I'm not surprised about since they are cheap eBay A123s.
I want to rebuild my A123s into at least one 6-cell pack but i don't own a multimeter. So how can I figure out which cells are good and which ones I should chuck and replace? I'm guessing more cells may fail in the future and i don't want it to happen during a fight.
Mon Jul 12, 2010 8:26 am
Spockie-Tech Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
Get a multimeter
Seriously, they're like $40 for one with a serial PC interface from Jaycar.
It seems to be making things harder than they need to be without one. With one, you could easily measure each cell and positively ID the suspect ones. _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
Mon Jul 12, 2010 10:05 am
Daniel Experienced Roboteer
Joined: 30 Aug 2005
Posts: 2729
Location: Gold Coast
oh, but that's complex technology. Why can't I just hit it with a hammer?
I guess I'll try charging everything and maybe borrow my brothers multimeter.
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