So will it ever be possible to run a JeeNode or JeeNode Micro off solar power?
Well, that depends on many things, really. First of all, it’s good to keep in mind that all the low-power techniques being refined right now also apply to battery consumption. If a 3x AA pack ends up running 5 or even 10 years without replacement, then one could ask whether far more elaborate schemes to try and get that supercap or mini-lithium cell to work are really worth the effort.
One fairly practical option would be a single rechargeable EneLoop AA battery, plus a really low-power boost circuit (perhaps I need to revisit this one again). The idea would be to just focus on ultra-low power consumption, and move the task of charging to a more central place. After all, once the solar panels on the roof of JeeLabs get installed (probably this summer), I might as well plug the charger into AC mains here and recharge those EneLoop batteries that way!
Another consideration is durability: if supercaps only last a few months before their capacity starts to drop, then what’s the point? Likewise, the 3.4 mAh Lithium cell I’ve been playing with is rated at “1000 cycles, draining no more than 10% of the capacity”. With luck, that would be about three years before the unit needs to be replaced. But again – if some sort of periodic replacement is involved anyway, then why even bother generating energy at the remote node?
I’m not giving up yet. My KS300 weather station (868 MHz OOK, FS20’ish protocol) has been running for over 3 years now, I’ve never replaced the 3x AA batteries it came with – here’s the last readout, a few hours ago:
:41 KS300 ookRelay2 humi 77 :41 KS300 ookRelay2 rain 469 :41 KS300 ookRelay2 rnow 0 :41 KS300 ookRelay2 temp 18.2 :41 KS300 ookRelay2 wind 0
And the original radioBlip node is also running just fine after 631 days:
1:32 RF12-868.5.3 radioBlip age 631 1:32 RF12-868.5.3 radioBlip ping 852330
Even the JeeNode Micro running on a CR2023 coin cell is still going strong after 4 months:
1:42 RF12-868.5.18 radioBlip age 139 1:42 RF12-868.5.18 radioBlip ping 188449
So ultra-low power is definitely doable, even with an Arduino-compatible design.
No worries – I’ll keep pushing this in various directions, even if just for the heck of it…