I had forgotten about that LifeBatt graph. I really want to see Lifebatt/BMI on the same graph in comparison, but maybe this will do for the moment. Here is my crude 20aCBA headway test, compared to Bob's 20a graph using similar hardware:
dnmun wrote:LifeBatt----------23.2----23.2----25.3 (added by edit using the lifebatt graph at 20A from bob's old lifebatt thread)
first 3 done at 22C by doc. if anyone gets some other numbers at different temperatures, try to keep track of where in the discharge it is so we can interpolate, thanks, dm
I was babying the new cell and terminated at only 26v which makes the curves harder to compare, and the lifebatt has a lower nominal voltage, but...
The headway discharged 20a at 3.0v, at 6ah it has dropped .09v, and then trails off .4v to 2.6, where it has supplied 9.19ah.
The lifebatt- discharged 20a at 2.9v, at 6ah it has dropped .08v, and by the time it trails off an equivalent .4v it has supplied @9.75ah.
So based on these crude tests, I theorize that the lifebatt delivers a slightly flatter curve and slightly more ah, but at lower voltage meaning it probably delivers about the same wh as the headway. I know the lifebatt starts at a lower voltage, but if I remember correctly the headway was about 340g, I googled posts describing the lifebatt as 360g, so by weight/volume the headway is delivering slightly better voltage and probably equivalent wh. granted, this is only 2c, I wonder how the voltages compare at 5c.So please bear with me as I reason out the pros and cons, as I see them, for MY application, a large-vehicle EV Conversion.
The Headway is rated at 5c continous, and the LifeBatt is double that for 10c. For my Bus, I really need at least 80ah/cell simply to have enough KW for a meaningful distance. 80ah at 5c that delivers 400a, more than enough to supply my 500a controller, so I don't really need to pay a premium to get 10c. For vehicles like ebikes and electric motorcycles that can only carry smaller ah packs, but still need high discharge rates, the lifebatt sounds like a good fit - if the packaging is compact enough.
The cycle life of the pack is another issue. A 120v80ah pack yields 9.6kw/cycle, at 350whpm that will deliver 27.43 miles, more than enough for my daily travels. Headway estimates 1400+cycles, so even if I used a full cycle every day, it should be good for 4 years/38,400 miles. LifeBatt claims 3000 cycles so it could be good for 8.5 years of daily full cycles, which is far superior, but for MY application I'm happy to save the money now and replace them with whatever hot new technology is around in 4 years.
Which gets us to cost. One can buy a 320 cells from Victoria to build a 120v80ah pack, shipped air to your door, for $4,960. For comparison to Lifbatt's products, a 144v80ah pack would be $5,952. Lifebatt's 144v10ah pack lists at $3,000, you would need eight of them to build an equivalent 80ah pack, or $24,000 before any 'volume' discounts. ( http://www.lifebatt.com/retail_sheet.asp
- 14410-HPS 144V / 10Ah w/VMS, 2 Terminals 24.5 546 182 207 53.9 21.50 7.17 8.15 48 $3,000.00 )
So the way I look at it, LifeBatt's have twice the cycle life, have twice the c-rating, and include nice packaging/monitoring/charging. Headway's provide slightly higher voltage per cell, weigh slightly less, and cost 1/4 as much as LifeBatt, but you need to package them yourself - a learning experience I happen to enjoy and prefer