Self discharge of C6

[jkougoulos]

Most of battery power is consumed by self-discharge of C6 during idle time. Need to measure somehow if the calculations are correct on the amount of battery capacity we lose and consider if the capacitor plays an important role on helping the battery for the high consuming pulse during TX. Perhaps using a 1-10uF X7R just for bypass would work better (and cost less)

[jkougoulos]

See also: https://www.embedded.com/electronics-blogs/break-points/4430050/Using-a-capacitor-to-sustain-battery-life

http://www.ti.com/lit/wp/swra349/swra349.pdf (Coin cells and peak current draw By Mathias Jensen)

https://m.eet.com/media/1121454/c0924post.pdf

http://data.energizer.com/pdfs/lithiumcoin_appman.pdf

https://electronics.stackexchange.com/questions/43306/pulse-powering-heavy-loads-with-a-coin-cell

http://www.ganssle.com/reports/ultra-low-power-design.html

https://www.embedded.com/electronics-blogs/break-points/4429960/How-much-energy-can-you-really-get-from-a-coin-cell-

https://www.embedded.com/electronics-blogs/break-points/4418098/A-sneak-preview

[jkougoulos]

testing required to see if large C6 actually helps. Actually it is 100uF but at 3v probably the usable is ~50uF. In any case, at 45mA of RFM69W full power, we need significantly bigger capacitor. The question though is if it helps mitigating the effects of increased IR of the battery (coin cell) at eg half life etc. Test proposed: fast cycles (8-16s) with 100uF (measure days until low bat & end of service) fast cycles (8-16s) with 10uF slower cycles (eg 64s) and check if the performance is linear, according to calculations. Always start with same battery type, (cheap CR2032), similar environmental conditions (indoor).

at 14s delay, calculations predict at 180mAh ~448 days of operations. hmmm, that seems to long for a coin cell transmitting every 14s @45mA

[jkougoulos]

http://cache.freescale.com/files/rf_if/doc/app_note/AN4573.pdf