IMR or High-Discharge 14250s/RCR2s?

[Wolfman29]

Hey everyone - I am looking for a source of IMR or high-discharge LiFePO4 14250s or RCR2s, as was implied by the title. That said, I can't seem to find any.

The most I am seeing is a 3C rating on standard LiFePO4 batteries, implying a maximum discharge of around ~600mA, and I need to be able to put out at least 1.5A or so from these batteries, which would imply either the nanophosphate technology from A123 Systems or an IMR chemistry. However, I can't seem to find any -.-

Anyone know where to find some of these? I need to be able to get 1.5A from two batteries the size of half a 14500.

Halp!

 

[LarryDFW]

Wolfman;

The best power I have seen is a 840 mah Sanyo 14500 cell . . .

which will deliver 1.6 amps @ 4.2 VDC.

I think the power level you are seeking is unrealistic.

LarryDFW

 

[rhd]

I think it is realistic, but you're going to have to give up on capacity.

I take it you need the voltage of 2x cells in the space of a 14500 (AA)?

The only way I can see this working, at the current level you're seeking, is to use two narrow but long LIPO packs. If you find one with the right shape, you can probably get two 100 mAh packs, capable of 20C, in that space. These would almost work:
FR 90mAh cell
Micron Radio Control : Full River LiPo Cells
http://www.bsdmicrorc.com/index.php?productID=522

But you'd be better off finding a longer, narrowing pack. You'll get more capacity if you can find a pack that better fits your dimensions.

 

[Wolfman29]

Yeah - basically, I just need two IMR 14250s or RCR2s -.- But I'll look into the battery packs...

Unfortunately, it would be best if I could get cylindrical batteries... but they don't seem to want to be in IMR form

Btw, @Larry: It certainly is possible for me to get that kind of power out of a small battery like that. I dangerously ran 7A out of an IMR 10440. IMRs have like NO internal resistance.

EDIT: Hmm... two of these in series may do well to serve my purposes.

http://www.batteryjunction.com/tenergy-37-160-lip-30530.html

They are 44mm x 12mm x 6mm. Two stacked one on top of the other would be 44mm x 12mm x 12mm. At that size, I may be able to make an adapter to a standard 14500 size. Still looking though.

 

[BShanahan14rulz]

What Larry meant to say is that kind of power safely extracted within the limits deemed safe by extensive quality testing is not possible. In the same way that you can set a copper bolt across the electrodes of a cell and pull more current than it was rated for.

You should look at capacitors too. I mean, as long as you are going to be recharging something after 30 seconds of use...

 

[Wolfman29]

I have to disagree - it certainly is possible if IMR cells are made of this size. There are cells that can easily handle 10-30C discharge rate. If these cells only have 90mAh of capacity and have 15C discharge rate, that'd be more than enough.

 

[BShanahan14rulz]

Are you sure IMR cells of that size will have a safe discharge rate of 15C? Because I don't think you will find any small LiMn cells with those characteristics.

Why not go with an IMR14500 and a boost driver?



BTW, the generic imr10440 states 5c max pulse discharge current, 3c constant, at a quoted 350mAh of capacity. I don't know if it's really IMR or if it's just labeled that way.

AW's smallest dia. cell is the 14500, discharge rate of 4A @600mAh cap., and that is <7C.

 

[Wolfman29]

Well, I am having trouble finding a suitable boost driver, or I would. However, I just got some boards in the mail, so if these work as they should, then I may not have this problem anymore anyway ^_^