Don Harmon said:
Jozzer: In all fairness the A123 Spec. Sheet you link to is a much smaller format cell than the LiFeBATT Cell. This A123 is an 18650 Cell while our cells are 40138. It also has a 2.3 Ah rating while the LiFeBATT Cell is 10 Ah. As far as the spec. goes Nanotech and Phostech are basically trademarks for Lithium Iron Phosphate (LiFePO4) and for all intents & purposes are identical. Small changes in forumulas being granted.
I believe anyone who compares our LiFeBATT 40138 Cell Specs with A123 will concur that they are on the same playing field. Granted A123 has been around longer, but as you pointed out, they really have made NO effort to address the needs of the e-bike market, now have they?
http://www.lifebatt.com/LiFeBATT%20Web_5.html
Attached is our Cell Spec. in case you haven't seen it before and in case you want to make some direct comparisons with A123. Keep in mind, these smaller A123 Cells require 3 times the number of cells to make the sampe pack that LiFeBATT can do with 1/3 the number of cells. Makes the VMS that much more efficient in managing our packs. Plus our threaded posts require no spot welding or soldering !
Cheers!
Don Harmon
Actually, even though the cells have 1/4th the capacity, they
still have much better performance. If you parallel four a123s together you end up with a continuous current rating of 280A, and a burst rating of 480A, vs 120A and 140A for the LiFeBatt cells. Also, there is a
big difference in how the cells are constructed. A123Systems' propriietary nanotechology manufacturing technique results in electrodes with lithium cyrstals that are orders of magnitude smaller than any of the Chinese LiFePo4 variants, including the LiFeBatt cells. This is what makes the cells perform so much better, and the main reason why GM is dumping a ton of money into a123Systems in order to accelerate development of the larger format cells.. This is a lot more than "trademark" differences.
As for the BMS/VMS issue, I think you are missing the mark here as well. You are forcing people to use an expensive VMS board for every four cells. In 90% of the ebike applications here, people will want a minimum of 48V setups, or at least 8 cells. In my case, I would like to use 10 cells and that means I'd need three boards, with one only being half-used. Each of these boards have positive cutoff of power, as part of the LVC protection implementation, which means these will need fairly high-powered FETs, to switch that power, which means more heat that has to be dealt with somehow. The controllers already have a way to cut the load on the packs if need be and by using a dollar's worth of parts per cell, a VERY simple LVC protection circuit can be implemented. Here's what a 10s 9.2Ah a123-based pack looks like with such a protection circuit:
Granted, it takes more cells, but the total cost for something like the pack shown above is about $450. To get anything close to this with LiFeBatts, it would be at least $550 for the cells and then another $150 for three VMS boards, for a total of $700. In actuality, I'd have to buy 12 cells in order to get 10, plus three chargers at $155 each, and I'd still have to figure out how to package/mount the cells.
-- Gary