A123 / M1 cells

Forget to mention - anyone after genuine A123 LiFePO4 cells ( 2300 version ) - I have just ordered 12 from an ebay seller in HK tonight for the measly sum of circa £70 including P+P.
Considering these things are usually at least a tenner each, I am pretty pleased.
Of course, they have yet to arrive, so I may be premature in my pleasure.
Thyey are destined for my Hangar 9 Camel - I will be making them up into a "double ring" and fitting with-in the large radial cowl instead of the 1.5lb of lead siuggested in the manual!
Thats the plan anyway

Hey Tim.

Does the Ebay seller you got them from have any more? I may be looking for a few more of them in the near-ish future, destined for the next project

I've made the ones I bought up into a couple of packs. I have two 2s packs in my Jet, on receiver duty, and they seem to perform really well (without a regulator!). They quickly drop to around 6.5v or so after a charge, and then seem to hold it to within 0.3v or so, regardless of what the 7 digital servos I have on board are doing!

The other cells have been made into a 4s pack, and have been used with a little EDF delta. Nice a consistent power for about 5 minutes, followed by a drop off that is so sharp, it is like running out of fuel in an IC model! The throttle activated timer is gettinga right hammering on my models now!

Cheers
Andy

Claims to have plenty...and I received notification that the order has been shiupped within a few hours of buying. Pity we didnt get together on this earlier - we could have saved on shipping. Yes the M1s do have a rather sudden "knee" in the discharge curve dont they!
Here's the link mate.
HERE

Hmmm, seems I havent quite mastered the linking procedure on this here forum
Incidentally, do you have, or know a man who does the facility to weld the connections on these cells? They dont have tabs, and although I have managed to solder reasonably well the other ones I have used in the past with a BIG hammerhead 100Watt iron, I would feel happier if they were welded - I did flirt with the idea of building a big capacitor discharge resistance welder, but never got around to it.

I don't unfortunately, sorry Tim. On the packs I made, I soldered them without too much trouble. I used my normal 50Watt temp controlled Iron, with the temperature dialled up to 390°C (as hot as it would go). I used a fairly chunky bit on the end too.

It would be a bit better to get them with welded tabs, or construct the pack by welding the cells together, but you would need to use a fair number of weld points to get the same sort of junction resistance as a soldered connections.

Perhaps a word with one of the battery pack manufacturers might see if they have access to this sort of equipment?

Cheers
Andy

PS. I got the link anyway
PPS. do you have any plans/info for building a Cap discharge welding machine?

A friend on another forum was planning on doing this one here. I must contact him later and see how he got on, it was whil back now.
http://www.philpem.me.uk/elec/welder/

First the good news.
Ordered May the 7th, arrived today 15th so not bad.
The bad ? -They are used cells from different batches - ex DeWalt I would guess
Will do some testing soon, for IR and capacity etc, but just beware of this if you are planning on buying some.
Still not bad I suppose for the money - assuming they all test OK

Any results yet on cell tests???

Yeh...initial test of 5 x in series is not brilliant... they took in around 2100 mahr after running them at 16C down to 2V per cell. They are not holding voltage particualarly well under load - circa 2.6V only, also, as yet, not balanced them. They really need a few cycles on them, and a fast charge rate at around 10A b4 I can tell for sure.
I am just in the middle of making them up into a 5s2p pack and will see how that holds up, however my 80 WATT iron has just packed up ( second one in as many days ! )
Will have to revert to the gas torch and hammerhead tip.
I am away for a week or so in a coule of days, so wont have the lot done for a while.