Computing stuff tied to the physical world

Still running on LiPo

In Hardware on May 21, 2011 at 00:01

A while back, a post on this weblog described a simple setup I had running to see how long the radioBlip.pde sketch would keep running on a single LiPo battery.

Here’s the setup again:

That’s a 1300 mAh battery, and the test sketch on it sends out an incrementing counter approximately once a minute (I extended the counter to 4 bytes, instead of the 2 bytes used in the original sketch).

It’s still going strong, i.e. this sketch has been running for 9 months on a single battery charge so far.

The counter is now at about 350,000 and I’ve determined that packets actually go out every 64 seconds, so that puts the counter at about 260 days. There’s a gap there, because the node was once reset some two weeks after being started for the first time.

So with some 275 days of running time, we can deduce that the average power consumption of this node has to be under (1300 * 1000) µAh / (275 * 24) h = 197 µA. This assumes that the battery would be empty, which it isn’t yet – so we know the average current must be lower (a lot lower, probably). Unfortunately, I didn’t include logic to measure and send out the LiPo voltage, which would be a good indicator of how far the LiPo battery actually is. The good news: a check with my multimeter shows the battery to still supply a whopping 3.985 V!

Anyway – I wouldn’t be surprised to get at least 4 times as much runtime, i.e. 3 years, out of this setup (which would translate to 50 µA average current draw).

Sooo… just hang around for another few years, and I’ll let you know!