0
\$\begingroup\$

I am working on a project (a disposible device) which requires significant power delivery from a small volume. This power delivery is very bursty, we're talking a handful of big pulses over the service life of the device. This is all super up in the air right now, but I am looking at around 0.35 mL of volume for the battery and I need to pump around 150 mW into a resistive load for a burst on the order of ten seconds (in order to heat something up). Primary cells are preferred for shelf life but secondary cells which can hold substantial charge for 2-3 years would be acceptable.

In order to bound the problem, I'd like to figure out what primary cell chemistry has the best volumetric power (not energy) density. Mass is not a concern. This would at least let me know what's physically possible, even if it's not neccessarily available off-the-shelf as a finished cell that fits exactly in my volume available.

I have started by taking a look at the comparison of commercial battery types article on Wikipedia. By dividing the volumetric energy density by the mass energy density of the battery, I can get the battery's density. From there, I can calculate the volumetric power density by multiplying by the specific power.

Unfortunately, Wikipedia's table isn't very complete, and is missing the specific power for a bunch of primary cell chemistries.

So, my question is: does anyone know what commercially-available primary cell chemistry has the highest volumetric power density? I am not adverse to paying NRE for a custom cell shape, but I need a battery chemistry which is used commercially, not something that's currently just a university research project.

PS: It also probably goes without saying, but molten-salt batteries, while technically a commercially available primary cell, are not practical for my application.

\$\endgroup\$
  • \$\begingroup\$ Most phone manufacturers seem to be using lithium technology (li-po...) for exactly the reasons you state : limited volume etc \$\endgroup\$ – Solar Mike Dec 1 '17 at 5:24
  • \$\begingroup\$ Normally % Load regulation is defined ratio of ESR source/load. What are your load specs? (R,X) and volume specs? \$\endgroup\$ – Sunnyskyguy EE75 Dec 1 '17 at 5:31
  • \$\begingroup\$ Why primary cell? Is rechargable out? Is it shelf life (10y primary, 1y rechargable)? A supercap or 100C LiPo can give huge output power, and be recharged from a high energy low power primary cell. You need to be more specific about your requirements for lifetime, total energy, peak power, energy of the burst. (edit) I like Jonk's idea, that's serious power, so, you need to reveal a lot more information, editted into the OP please, not spread out over comments (/edit) \$\endgroup\$ – Neil_UK Dec 1 '17 at 5:36
  • \$\begingroup\$ What is this energy to be converted into? I don't see any description, at all. I might therefore recommend a magazine of small, relatively safe explosive charges -- as in a rifle cartridge, for example. Given my ignorance, anyway. You only need a few, you say. So? A good answer only comes with some exchange of information. You need to start that process by allowing us to understand what the energy will be used to achieve. Better answers will be found that way. Otherwise, you are just forcing us through a contrived mental process. Which is more of a game, than reality. \$\endgroup\$ – jonk Dec 1 '17 at 5:37
  • 1
    \$\begingroup\$ I have come across (in various travels) some very small li-ion batteries (custom made) that might be the best you can get for high surges and your 0.3ml size limit. Zinc-air batteries have high energy density but miserable power density. We were actually looking at one that was ITAR (and if you need to ask the cost...) \$\endgroup\$ – Spehro Pefhany Dec 1 '17 at 6:23
1
\$\begingroup\$

Assumed essential Specs:

Volume: "5mm tall by 10mm diameter"
Power: 150mW power transfer momentary but over a 3 yr span
Type: Primary cell
Energy: TBD
Pulse duration: TBD
Temperature: TBD
Budget: TBD Not critical
Misc. Stress Factors: Ground Benign

Suggested solution:

2x SR57 Silver Oxide Buttons
Size: 9.5 mmD x 2.55 mmT ( 5.1mm thick for two) +/-<5%

enter image description here

Designation: ANSI-1162SO/1165SO, IEC-SR57
Nominal Voltage: 1.55 Volts
Typical Capacity: 51 mAh* (to 1.2 volts)
Capacity Test: 22K ohm continuous drain at 21°C
Typical Weight: 0.8 grams (0.03 oz.)
Typical Volume: 0.19 cubic centimeters (0.012 cubic inch)
Impedance (40 Hz): 10 to 25 ohms

Assumptions:

two cells ideally 440 watt-seconds (51 mAh * 3600s * 1.2V * 2bat )
must be derated by load life profile = TBD
perhaps derated to 1% of ideal with 22 kohm load

Average Capacitance in Farads, using E= C (Vi²-Vf²) depends on useful V range

Pd Max load = ½ Pd short cct. or matched impedance to battery string ESR.

est. Short Circuit Power = P=V²/Z = 1.2²/(10 to 25) per cell x2
est. Pmax = 1/2 of Psc = 1/2 x 280 mW max

Pmax = 140 mW @ 1.2V with Voc = 2.4 V and 20 ohm load

( This is insufficient but closest match 150 mW )

Datasheet:http://www.microbattery.com/microbat/pdf/energizer/energizer-watch-battery-042-2014.pdf

\$\endgroup\$
  • \$\begingroup\$ 10mm * 5mm is not volume... But still a good answer. \$\endgroup\$ – Solar Mike Dec 1 '17 at 8:09
  • \$\begingroup\$ @SolarMike Thanks for the suggestion/err compliment Mike ... \$\endgroup\$ – Sunnyskyguy EE75 Dec 1 '17 at 8:38
  • 1
    \$\begingroup\$ Which reminds me to tell everyone, a better answer only comes from better specs... \$\endgroup\$ – Sunnyskyguy EE75 Dec 1 '17 at 8:43

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.