SOTA LithiumBatteries

Equipment Radios & Power
1

State Of The Art batteries are always of interest to us weight weenies. Every week it seems there are new battery materials that have 4x the density of existing batteries, instant charging, so light they carry your pack for you etc etc

I have been following silicon anode batteries for a few years now and Amprius appears to be actually entering mass production of these batteries, and has published some actual cell datasheets. The front page boasts 500Whr/kg , 6 minute charge, 1200 cycle life, 10C discharge…

What do the datasheets say?

SiMaxx 4.2Ah pouch cell

  • 450Wh/kg
  • 150 cycles life
  • 32g
  • Vnom 3.45V, 1C 4.2A
  • Special Note Cell requires external clamping of 30 PSI (~50kgF)

SA10 18650 style cell

  • 300 Wh/kg
  • 600 cycles
    -48g
  • V=3.65, 3C 12A

So the the 18650 at 4Ah is a bit better than a Panasonic NCR650B at 3.4Ah 265Wh/kg.
The SiMaxx cell is a lot better - until you have made a 50kg clamp, and look at the cycle life, and somewhat worse voltage.
(A note about clamping is that the clamp force won’t increase when you stack up more cells as it just goes on the ends of the stack.)

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2

What? A battery that needs a physical 50kg force to hold it together, or am I barking up the wrong tree?

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3

That is also true of existing lithium pouch cells (LiPo, LiFePo4, etc). If you don’t keep them tightly squeezed together, they don’t perform as well and you get less cycles out of them. Most decent battery manufacturers take this into account when building multi-cell packs, but some of the really cheap stuff from China won’t have the pouches bound properly.

Glad to see some of the newer stuff finally getting to mass production!

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4

I built my custom battery packs for SOTA and POTA (all LiCoO2 cells) with great care, watching the weight but at the end of the day, when I throw in extra bottle of water for hot days, lunch for a long 10 pointer hike, and some fruits and maybe coffee, all the weight saved become negligible. When I did my first 10 pointer, my pack weight was 12-13kg. The fancier battery chemistry would save 100g from that (I carry 2 packs of 3S1P 3Ah). It seems that I need to give up all the backup pieces, comfort items, food, water etc. before making sense in lighter batteries. That’s my problem.

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