Looks like the new 15ah headway are available
- Thread starter patrickza
- Start date
liveforphysics
100 TW
Horray!!! 50% improvement in energy density, and an improvement in power density!!! Outstanding!!!
Lock
100 MW
Surprised more ebiker folks are not excited by this...
John in CR
100 TW
swbluto said:
Aren't the new cells larger, so what's the big deal?
John
liveforphysics
100 TW
Ohh.... I didn't notice they were larger size cells. Boo!!! I thought it was an example of battery technology making an improvement. Dang, that's kinda a bummer that they just made larger cells, but it does make the idea of a 1P pack from headways cells a more practical choice for E-bikes. I guess if nothing else, it should simplify the complexity in building a pack.
Doctorbass
100 GW
For the same chemistry, when using cylindrical cells, the Energy or power density OF THE PACK decrease as the diameter of the cell increase.
The free room between these cylindrical cells is space lost... the only good point for that is that the thermal management of the air in the pack may be better due to larger space.. but...
The free room between these cylindrical cells is space lost... the only good point for that is that the thermal management of the air in the pack may be better due to larger space.. but...
Lock
100 MW
I calculate the increase in volume from their 38120S at less than 16%. Good point about PACK density though. I expect these larger cells will mean fewer wires and connections and electronics per Wh...
tks
tks
RoughRider
100 W
- Joined
- May 17, 2009
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- 208
and now they can take 10C continuous...better than the old 10Ah cells
EVnewbie
100 W
Great news!
A small 36V 15Ah pack can be had that will handle a 35 to 40 amp controller without strain. I like the 10C rating, no worries about burning up the pack if bumping up the amps to the motors. Headway also makes "automotive" batteries in the 12V 30Ah size. If they are using the new 15Ah size, it might be an option. The test will show the results but I am feeling confident
A small 36V 15Ah pack can be had that will handle a 35 to 40 amp controller without strain. I like the 10C rating, no worries about burning up the pack if bumping up the amps to the motors. Headway also makes "automotive" batteries in the 12V 30Ah size. If they are using the new 15Ah size, it might be an option. The test will show the results but I am feeling confident
liveforphysics
100 TW
Doctorbass said:
Did you know when you stack up an assortment of circles, it makes no difference if they are 1mm circles, or 100m circles, once you put a box around it, the percentage of dead space is the same. If you stagger stack cells, and enclose the box to lay against the ends making a trapezoid, then it still makes no difference in the deadspace vs circle size relationship.
liveforphysics said:
That's readily visualizable for 90-90-90-90 degree type of stacking (Square stacking), but it doesn't seem as visualizable with angled stacking. I had a thread on this once and the percentage of dead space seemed to differ depending on row and height length (I think a greater row length decreased the percentage of dead space since that "side of dead space" per row decreased as a percentage of the total dead space per row as the row increased, and the "per cell" additional of dead space was a lesser percentage than the side so it'd converge to that as the row length approaches infinity), so if greater size cells decreased the row length in a given amount of space (Often the case for a size-limited motorcycle), then the dead space percentage would increase. The actual formula can be found in the thread - someone else accurately deduced it and my original calculation was flawed. Okay, I just found it - it's at http://endless-sphere.com/forums/viewtopic.php?f=14&t=6800
However, I think there are some special cases where squared packing would be more efficient (More of these special cases existing as the row number decreases and the height increases), so that'd be true for those cases.
John in CR
100 TW
swbluto,
Yes, the pack density changes with shape, but Luke is reminding us that for a given shape the pack density doesn't change with a change in the cylinder diameter. If volume only went up by 16% and capacity went up by 50%, that is indeed a good thing. If they end up performing to spec long-term, then I can't wait till the price is in the $200-300/kwh range. Getting away from tab soldering or welding will be a very welcome change.
John
Yes, the pack density changes with shape, but Luke is reminding us that for a given shape the pack density doesn't change with a change in the cylinder diameter. If volume only went up by 16% and capacity went up by 50%, that is indeed a good thing. If they end up performing to spec long-term, then I can't wait till the price is in the $200-300/kwh range. Getting away from tab soldering or welding will be a very welcome change.
John
John in CR said:
But with certain forms of stacking within a given box, the pack density does change as the the cylinder's diameter changes since the row length decreases with a greater diameter and the formula derived in the posted thread shows that this results in a greater percentage of dead space. And the angled form of stacking is almost always more efficient than square stacking with a row length greater than some small number, so this applies to larger packs.
However, these cells do have a greater energy density (according to someone else), so I wonder how the decreasing packing efficiency and the increased energy density balance out within a given volume. You might still have a greater pack energy density though you'd likely have a decreased packing ratio.
Lock
100 MW
John in CR said:
...and fewer wires and connections and electronics per Wh also. More reliable plus less wire losses? Dying to write Victoria to ask how much... Whether any product have already shipped to distributors or retailers...
I have been shopping for a 48V 10Ah pack (and thinking 10Ah not enough.) With only one 15s string of these cells I get my 48V, but 15Ah, in a form factor that's two feet long, six inches wide and about two inches thick w/BMS and weighs less than 13lbs for the cells (important to me `cause I want the pack as a "cassette" that pops in/out for fast pack swaps and to take indoors for charging/security.
tks
lock
EVnewbie
100 W
I would love to see a review on the 15 Ah cells in the flesh
15 Ah is enough for my needs and when I need more, add another pack. 35 amps is now not the killer in the equation and it has the capacity and discharge rate to give some room for experiments. Figure a pack would weigh 15 pounds if 36V or 20 pounds if 48V including the case, wires, breakers etc. Things are looking up.
15 Ah is enough for my needs and when I need more, add another pack. 35 amps is now not the killer in the equation and it has the capacity and discharge rate to give some room for experiments. Figure a pack would weigh 15 pounds if 36V or 20 pounds if 48V including the case, wires, breakers etc. Things are looking up.
liveforphysics
100 TW
Swbluto-
Like I said in my post, and its still 100% correct, straight stacked, or staggered in trapazoidal shapes, the cell diameter makes no difference.
Like I said in my post, and its still 100% correct, straight stacked, or staggered in trapazoidal shapes, the cell diameter makes no difference.
liveforphysics said:
Please specify all of your relevant constraints when making a claim. Under the constraint of a fixed box width and height, it appears the packing ratio does change depending on the circle's diameter due to a changed number of cells in a row and the math demonstrates this. What constraints are you considering? A fixed number of cells in a row and a fixed column height and a tightest fit box around that number? The math also demonstrates that.
I still haven't heard any concrete evidence or reasoning for this, but yet the claim is continually insisted upon, so some sort of proof or reasoning is needed for your claim to be verified.
liveforphysics
100 TW
Here you go. I wasted my time making this diagram for you to show something that is self-evident once you apply logic towards thinking about it.
I see - your constraint was a tightest wrapped parallelogram around the cells (That is, treating rectangles and parallelograms with non-perpendicular angles as interchangeable). Thanks for resorting to "time-wasting" graphical means, as it seemed to be your optimally efficient means of communication.
Anyways, when you're working with a rectangular "box" (the right one) - and the shape of the container is often dictated by your vehicle - the squared arrangement doesn't offer the best packing ratio for sufficiently large packs, so that's kind of a null demonstration for many classes of packs.
Anyways, when you're working with a rectangular "box" (the right one) - and the shape of the container is often dictated by your vehicle - the squared arrangement doesn't offer the best packing ratio for sufficiently large packs, so that's kind of a null demonstration for many classes of packs.
boostjuice
10 kW
A comparison shot between the long standing 10Ah cell and the new 15Ah cell. Although the new 15Ah cell is larger, it is obvious that energy density has increased together with (hopefully) the C rating.
liveforphysics
100 TW
If the internal resistance turns out to actually be correct for a 10c cell, that's going to make these cells a better choice than 10Ah headways, PSI or BMI cells.
michaelplogue
10 kW
BMI will also be coming out with a 'red' cell.
http://lithbattoz.com.au/index.php?page=battery-cells
http://lithbattoz.com.au/index.php?page=battery-cells
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