Lithium cell tests

[andy_kane]

Use of A123 cells are permitted providing that roboteers do so at the scrutiny of FRA event organisers.

Suitable charging equipment must be used and packs must be built to a safe standard.

Trials of the technology are still ongoing and while limited testing has shown favourable results the FRA advises, that this technology is used with caution particularly due to the charging requirements and energy density within this product.

[andy_kane]

Kan-opener team update on A123 trials

All parts have arrived now, the wait for the balancers has been tiresome.

Pack design has been approved and bench trials are to start soon.

[grant_ploughbot]

If you already have a lithium polymer/ion programmable charger there is almost deffinatly a new download for it to charge A123 cells. I have looked a little into this as my purely Lipo/LiIon charger can now be updated to use A123s, nicads, NiMhs by downloading the new software from the manufacturers websites.
The standard balancers will also work very well with them, especially if used inline with the charger.

[terrorhurtz]

I have started a thread in FRA General Chatter (A123 Lithium cell use), where hopefully people can describe their proposed setup and we can all learn how best to use these cells.

[knightrous]

quote:

I used the silver paste from MEC and it was tested at various loads on a 10 cell packs and it sounded like a kettle boiling at 45A from memory.

Ive never had this issue with the AS5, and I know its fairly good up to at least 90c, because Ive used the stuff on overclocked graphics cards which easily hit 80-90c when torture testing .

Also, someone said in a previous post that the A123s are hard to solder. I originally made up a 4 cell test pack that I soldered. Since I dismantled my cells from Dewalt packs, I just trimmed the tabs back to the cell. This left a good 10mm x 10mm to solder onto. Even though this is just spot welded on, you can flow solder over the edges of the tab (and the centre) onto the cell face and it seems to flow quickly and makes soldering easier.

[m2xt]

Having soldered some 5000 to 6000 NiCd cells, the A123s are by comparison far more difficult. So difficult that I will not be doing it again in the future. The A123s did not have previously spot welded tages and are in fact virgin cells direct from A123.

Having conducted tests on the cells in almost a lab environment, I can only state what I found when using the MEC paste. If it works for you then thats great but I wouldnt consider using the MEC packs for applications over 35A.

[terrorhurtz]

Paul, presumably it was the can of the cell that was tricky (the positive end)? Did these have the steel disc on that end?

The button end is very similar to nicads - nickel plated steel.

[m2xt]

John,

The button end is certainly better than the +ve end but still requires more heat and takes longer to flow than NiCds - extra heat makes me nervous. For the +ve end, I had to remove the disc to stand any chance of soldering onto the can. To be fair, I have only soldered 10 cells but will be soldering plenty more shortly. May just need to perfect the technique but give me Nicds any time for soldering!

[woody]

but will be soldering plenty more shortly ..personal use I hope!

[m2xt]

Hi Woody,

Im afraid not, theyre for someone else. In fact I would go retro now and go back to SLAs now NiCds are too hard to get. Trouble is I cannot afford another 6kg to use SLAs.