Big News! Off the shelf Li down to -140C!...(on Mars - lol!)

[3_tons]

With just a ‘few tricks’ from NASA - Truly some uber synergetic and ‘MIND BENDING’ Technologies at play!!

https://www.youtube.com/watch?v=kb96kb_Nfxk


(Solid proof that at least some of our taxes $$ are being put to a good use - lol)

3 tons, in the high ‘Mars like’ NV Desert

[Itinerant1]

pianotuna wrote:
Hi 3 tons,

Yup. But I still wonder why they did not use Lithium Titinate. I first saw them retail about 3 years ago, but not in high amperage packs.

They are keeping the cells no lower than -15 c.

I guess since they only need to last 31 days--it doesn't matter?

This is the sort of thing that should make American's proud.

I'll bet size and weight is a factor, especially for that drone.Trade offs. 😉

[3_tons]

Well not unlike the Moon landing, it’s amazing what endeavors humans are capable of when they pull together in a open, cogent and coherent manner 🙂

3 tons

[pianotuna]

Hi 3 tons,

Yup. But I still wonder why they did not use Lithium Titinate. I first saw them retail about 3 years ago, but not in high amperage packs.

They are keeping the cells no lower than -15 c.

I guess since they only need to last 31 days--it doesn't matter?

This is the sort of thing that should make American's proud.

[3_tons]

PT, Thanks for the helpful link Sir!! Note that items G and H provide a fairly decent description of the battery’s operating parameters...

3 tons

[time2roll]

I have read plenty that you can charge lithium below 0C. Just has to be much much slower at maybe 1% to 5% of normal. This might be partly why they only get to 35%. Easily controlled by the BMS.

[pianotuna]

Hi 3 tons,

I copied the temperature numbers from the Nasa site about the helicopter, so I expect we are both right.

There doesn't seem to be a lot of detail on the Nasa and other sites about what the specifications are on the battery bank. I would dearly love to know the makers name. Found it! Sony. These are Sony SE US1865o VTC4 Operating Temperature (cell surface): Charge 0 ~ 50 degrees Celsius , Discharge -20 ~ 75 degrees Celsius

I loved the microphone on the rover--the first time anyone has heard sound from another planet.

https://rotorcraft.arc.nasa.gov/Publications/files/Balaram_AIAA2018_0023.pdf

6 Sony SE US1865o VTC4 Li-ion cells with a name plate capacity of 2 Ah. The maximum discharge rate is greater than 25 A and the maximum cell voltage specified by the manufacturer is 4.25 V. The continuous tested power load capability of this battery is 480 W with a peak power capability of 510 W. Battery voltage is in the range of 15–25.2 V and the total mass of the 6 cells is 273 g. A cell balancing charge management system controlled by the FPGA ensures that the all the individual cells are at a uniform voltage. A de-rated end-of-life battery capacity of 35.75 Wh is available for use. Of this capacity, 10.73 Wh (30%) is kept as reserve, night-time survival energy usage is estimated at 21 Wh for typical operation in the northern latitudes in the spring season, and approximately 10 Wh is available for flight. Assuming that 20% of the power is at the peak load of510 W and 80% is at a continuous load of 360 W, approximately 90 sec of flight is possible. These energy projections represent conservative worst-case end-of-mision battery performance at 0 C initial temperature. More moderate power loads will extend the flight time.

[3_tons]

theoldwizard1 wrote:
6:38 it has battery heaters.

Energy budget is 33% just for heaters.

Not sure what their chemical mix is but me guess is that the batteries are prevented from dropping much below 0 C...

3 tons

[theoldwizard1]

6:38 it has battery heaters.

Energy budget is 33% just for heaters.

[3_tons]

Well, I could be off but was just going off of a screen shot (comparison earth to mars - Mars: A low of 140C, an average of 63C, a high 30C) , but these may represent planet wide extremes (or my interpretation wrong, I donno??). Either way, quite a feat of engineering to witness and marvel upon - we are truly a most fortunate generation to have been so fully immersed in such a wide swath so much available knowledge!!

3 tons

[pianotuna]

Hi 3 tons,

I think it is -90 C (-130 f). Still quite a feat.

The batteries are being charged to 35% of their total capacity, and do have heaters.

It is certainly quite a torture test.

"Helicopter Warm Electronics Box, or HWEB. This box dangles between the helicopter landing legs and uses a combination of thin-film heaters and a layer of polyamide insulation to both absorb as much solar thermal energy as possible while reducing heat loss from the inside of the HWEB to the Martian atmosphere."