Has anyone tried larger format A123 cells?

[sikeston34m]

It's time for me to revisit the A123 line of batteries.

In the beginning there were only the 26650 cells. They perform pretty awesome.

Then came the 18650 size A123. Not bad, but not so awesome.

Now I see two different large format cells on the market for EV use.

The 32113 cell and the 20ah flat polymer type cell.

The 32113 cell is 4400mah.

The 20ah Polymer type cell is 7.2mm thick X 161mm wide X 227mm long.

Please feel free to express your thoughts or tell about your experiences.

[BrianG]

No experiences, but I've been looking at their cells too. For any kind of decent capacity like ~15Ah (for those of us who want to run under 2,000v ), you'd need to parallel a bunch of the 26650 cells, times that by the s count and you get quite a wiring job! Personally, I'd like a 1p pack whenever possible.

That said, the 32113 cells (4.4Ah) have less than double the capacity, but more than double the weight (205g) of the 26650 cells. The prism 20Ah cell, even though it's almost 500g, would be worth it in terms of wiring simplicity and only 1p setup. Not to mention the prism cells would have less wasted space. I wonder how much they are per cell (if we could even get raw cells)?

[sikeston34m]

I find the 20ah Polymer cell the most appealing also.

Trying to work out a $30ish per cell deal on a lot of 4 or 8 cells now.

You might have seen the post I did on the headway cells that I built a 4S4P pack from.

40ah of Lifepo4 pushes my trolling motor around for a full day of fishing.

I like the idea of a 4S2P pack of the flat cells.

It would fit inside the front tackle box on my boat!

A123 is boasting 90% capacity retention after 3000 cycles on the flat cell.

[BrianG]

If you can say, where are you sourcing the 20Ah cells? I'm looking at them for ebike use. $30 per cell for a 12s pack would be much cheaper than pretty much anything comparable.

90% retention after 3000 cycles? At what DOD?

[sikeston34m]

Originally Posted by BrianG

If you can say, where are you sourcing the 20Ah cells? I'm looking at them for ebike use. $30 per cell for a 12s pack would be much cheaper than pretty much anything comparable.

90% retention after 3000 cycles? At what DOD?

At 100% DOD!

I'm a little concerned about soldering to the tabs on these.

One is aluminum and the other is nickel plated copper?

Solder to aluminum using the special solder and paste? I have some, but how difficult is it?

I'll pm you Brian.

[BrianG]

I just read some forum posts about the thinness of the tabs too. Further reading at the A123 site leads me to believe the prism cells would probably be better suited for more constant drain, low pulse applications (like UPS usage and the like) - if for no other reason than cooling of the cells at higher discharge.

Maybe those 32113 cells or even the old 26650 cells aren't so bad after all. They're relatively heavy, but they do seem to be more physically robust and easier (and more forgiving) to solder. Gonna have to do more research on cost vs weight vs wiring complexity to make a better judgement.

BTW, did you see the SLA replacements they have? Seems like a really cool way to replace battery types for lots of devices out there that use the 12v/7Ah SLA packs, and at 1/2 the weight. The "SLA pack" is in 4s2p config of the 26650 cells, so a it has less capacity than the typical 7Ah SLA pack. But since that 7Ah figure only applies to low discharge rates, it's probably closer in usable capacity than it seems. Oddly enough, A123 recommends a max config of 4 modules in series and 10 modules in parallel.

[sikeston34m]

Is this a viable option to soldering the tabs? Hmmm..........



The 20ah cells are rated at 3C continous (60 amps) or 10C bursts (200 amps) Plenty for my application. 60 amps continous is tops for me, plus using 2P leaves plenty of head room.

Makes me wanna see a discharge graph though.

Yes, the SLA replacements are also being designed by others also. Using the 26650 cells in a 4S1P configuration, or in the 4S2P configuration.

They are marketing those as motorcycle and ATV batteries.

[sikeston34m]

After doing some forum searching, I am seeing mixed "C" rating reports on the 20ah polymer cells. Some as high as 30C.

If anyone locates a discharge graph on these cells, please post it. Or at least post a link to it.

In the meantime, a better solution to tab soldering? Tab Clamps! I kinda like the idea. This gives the user the ability to take the pack apart, should the need arise. Also, high discharge capability, provided the design is right.

[sikeston34m]

After alot of research, the "good" high discharge A123 20ah Polymer cells say "Made in the USA".

Here is a dead short test of a cell also hooked up to a CBA

Interesting. More than 3C for sure!

http://www.youtube.com/watch?v=lWk24MbYEBg

[BrianG]

Originally Posted by sikeston34m

...More than 3C for sure!...

So what you're saying is that it isn't suitable for a flame sticker?

[snellemin]

Naah, seems these cells need a lighting sticker.

[bruce750i]

I'm trying one of those 26650 4s4p in my atv. I haven't tested the winch yet, but it should be able to pull me up a tree.