[Caevlist] FW: Recent battery claims

[David Ullman]

A colleague sent me an article on LiS battery which led to this mini-report I put together and you might find of interest.

 

Battery Update

Dec 23 2019

 

A recent article “E-plane maker bets LiS battery technology could double the range of electric-powered flight“ ( https://www.powerelectronictips.com/e-plane-maker-bets-lis-battery-technology-could-double-the-range-of-electric-powered-flight/) focuses on George Bye’s relationship with Oxis Energy who is developing LiS batteries.  They are claiming the potential of >500wh/kg batteries.  They show the LiS upside on a graph:

 



 

It is valuable to compare the cell numbers with delivered numbers.  To do so, I use a metric “packaging factor” that is the percent of the cell energy density (aka specific energy) that can be delivered by a cell pack. 

 

For example, on the JabirWatt (my electric testbed airplane)  I used relatively inexpensive, but very safe CALB CA 72FI:72Ah LiFePo4 cells, 16x cells (bought from Kirk)

Each battery:

*	3.2 volt Nominal (3.6 v max,2.5 v min)
*	72 Ah
*	230 wh
*	Cell length: 1.1875 in
*	Cell width: 5.375 in
*	Cell height: 9.625 in
*	Weight 1.9kg
*	Energy density (cell) 121 wh/kg

 

Battery pack

*	16 batteries in series: 3.7 kwh
*	51.2 volts
*	Batteries 68 lbs. (31kg), entire system with wires and EDFs 110 lb. (50 kg)
*	Can draw 330 amps for 10 sec (Kirk) so the rating is 330n2 = 4.6C (some batteries can do up to 50C)
*	A 1C discharge rate says I can draw 72 amps for one hour. Discharge is sometimes referenced as "E" rather than "C"
*	Cost - batteries alone $2400, all together with labor about $5000
*	Pack Energy density (3700/50kg)  = 74 wh/kg
*	Packaging factor (74/121) = 61%

 

This value can also be calculated for Tesla cars. For the Model 3 battery (extended range) https://cleantechnica.com/2019/01/28/tesla-model-3-battery-pack-cell-teardown-highlights-performance-improvements/ 

 

*	2170 batteries (Dia 21mm, length 70mm)
*	4 volts peer battery
*	4416 batteries in total
*	80 kwh
*	1.050 lb (447.3 kg)
*	168 wh/kg delivered. (raw density 247 wh/kg)
*	Packaging factor 68% 

 

The battery on the earlier Model S (18650) (18x65mm) also had a raw density of 240wh/kg but a packaged factor of 127 wh/kg for a factor of 53%

 

Conclusion is that packaging factors will be in the 65% - 70% range for now.

 

George Bye and Oxis Energy -The 350 wh/kg LiS battery of today (based on at 70% packaging factor) will have a pack energy density of 245wh/kg and if they get to a cell of 500wh/kg then a pack value of 350 wh/kg.

 

 

David G. Ullman

Emeritus Professor of Mechanical Design

ASME Life Fellow

www.davidullman.com <http://www.davidullman.com> 

ullman at davidullman.com <mailto:ullman at davidullman.com> 

541-760-2338

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