115 DeWalt Tool Batteries... geesh...

[ted.lowe]

It seems like a lot of work (and money) but until we can buy the A123 cells directly....

http://ev.whitecape.org/insight/A123/

[terry.kane]

I was trying to do the math based on ~$150 per pack.  If there are 10 cells per pack and he made a pack with 115 cells, then he's got 12 x $150 = $1,800 in cells + BMS.  A bargain!  But there's no Ah rating that I can find on this pack.

[ted.lowe]

That would be a deal, but add a x10 to get $17,250! (115 * $150).  That doesn't include the BMS either!

115 packs * 10 cells/pack = 1150 M1 cells which are 2.4ah at nominal 3.3v.  So to get say a 99v pack, would need 30 cells in series.
That would be 1150 / 30 = 38 strings in parallel * 2.4aH = 92aH.  So, $18k for a small 99v 92aH pack is way pricey, but LIGHT!

Contrast the A123 way with my s-10: 20 * T-125's is 200+aH at 120V for $2k (but 1/3 the cycles of the M1's).

Imagine the work necessary to do 38 strings, with BMS, etc.  I'm sure this was a 'do it because it's possible' project, perhaps for bragging rights.
He can brag about it when he goes to his OCD support group meetings :-)

i bought one of the Dewalt 36v pack (DC9360)  today (for $149.40) on Amazon.  i will take it apart to understand the BMS and experiment with the M1's in various projects.

[terry.kane]

Ted, where did you find the 2.4 Ah rating per cell?  By the way, each module does include a BMS module and, if I'm not mistaken, he does utilize those in his pack.  It's agreed that this is not a practical project but more of a "Hillary on Everst" scenario.  Surely no one would expect to be able to harvest cells from a retail product and come out ahead, cost-wise.

I did get a quote from Headway for their 3.2V/10Ah LiFePO4 cells of about $19 each.  It would require 800 cells to achieve 128V/200Ah.  So without a BMS, we're talking $15,000 for the cells.  My Fiat could probably get by without 200Ah, especially if I have a range extender but this is still way out of my league, from a cost standpoint.  Maybe someday!

[terry.kane]

If we go by the evporsche.com web site that 15kWh will give a low Wh/mile vehicle up to a 75 mi range, then this picture looks a little better.  15,000 Wh @ 120V = 125Ah. 

Looking at the Headway LiFePO4 cells: Each 40 battery string of 10Ah/3.2V cells is $760.  You'd need 12 strings to achieve (128V/120Ah) so that's $9,120 for the pack, less BMS, assembly labor, charger, case, etc.  INDEX $1.90/Ah @ 3.2V

Using the same logic and the A123 cells scavenged out of DeWalt packs; these are 10 cell/36V/2.4Ah @ $150 including BMS.  So each cell is 3.6V/2.4Ah.  You'd need strings of 35 cells to get 126V/2.4Ah.  You'd need 52 strings or 1820 cells to acheive 126V/124.8Ah.  At $15 per cell, that's $27,300 but includes BMS modules.  INDEX $6.25/Ah @3.6V

The Thunder Sky LFP cells are another story.  They've quoted me roughly $2 per Ah @ 3V.  So comparing is relatively simple: 42 cell strings give 126 volts so 120 (Ah) x $2 (per Ah) x 42 cells = $10,080 before BMS, charger, etc.  There is also concern that these units violate a US Patent still under evaluation.  INDEX $1.97/Ah @ ~3V