Sunday, 4 November 2018

6 months milestone, finding winter space

This post marks the 6 month milestone of going solar-powered, which is about twice as my as my previous effort. The phone I'm writing this on and the watch it's connected to haven't seen mains electricity since the end of April.

Even better, we're now into the start of November, a month and a half after the equinox, and my three little batteries are still pretty full.

(The grey battery was on 4 lights, but dropped to 3 in the five minutes it took to get the photo...)

(I'm thinking of naming the batteries. Maybe Huey, Dewey and Louie after Silent Running's little helpers?)

The extended summer, probably thanks to climate change, has seen fairly dry weather with a decent amount of light recently, and I've been able to keep things topped up despite often having to start off in shade, and unplugging batteries in the 6pm dark. The grey battery seems to charge up whatever, but Big Red may possibly prefer to start with some voltage - I'm not convinced it charges if it starts out in the dark, with sunlight showing up later on. A simple experiment with some shade and a USB power meter should tell me though.

More generally, I've been mostly occupied with issues of space, and the idea of land ownership that goes with it. In built up areas, the big challenge of winter is in battling the long, pendulous shadows which are much more pervasive and unpredictable than in summer. My old charging spot is no longer viable. And while we're lucky to have a decent sized garden on a south facing slope (despite the effort to mow grass up it), I'm aware people in flats or smaller plots might struggle to find a decent spot as the sun gets lower. I can think of a few places I've lived where this experiment just wouldn't be viable past September.

But this is turning into a different, socio-political question, which I'll return to one day. For now, I'm concentrating on the basics - such as being ready to come up with a suitable tilting mechanism to hold your panels. Or "appropriating" whatever you can find lying around that fits the bill...

As I try out different places, I'm becoming more aware that being able to either fasten your panels and batteries, or get them at the right angle, is a key part of 'nomadic efficiency'; portability is one thing, but effective portability is another thing entirely. I can imagine an accompanying set of travel utilities, such as carabiners, bits of string and wire, and lightweight angled blocks to get everything just so. And that's assuming you don't plan to track the sun as the earth spins on, soundlessly and endlessly.

Anyway, time to sign off to save on battery. Keep your leads short, your screens clean, and your software lean.

Sunday, 9 September 2018

Oh, poop

Most days I get home and rush to check how much power has been transferred into my batteries. Yesterday something else got "transferred".

The dangers of outside harvesting ;) Still, at least it wasn't on the panels themselves.

September is hitting - feels like autumn is trying to approach, but the warmer summer is still keeping it at bay a little. Sunny day today, and I'm pretty much at full charge capacity. Ambient light is keeping me topped up well still.

Sunday, 2 September 2018

17 weeks - on shadows and cables

17 week update. Weather-wise, we've started to see some signs of Autumn approaching - people have talked of _putting the heating on_, and backpacks tend to contain a mix of sun cream, and waterproofs.

That said, it's still mostly warm, if cloudy, and the sky is having a blue period this weekend, so should be good to get a full charge up. Saturday has been very warm indeed.

However, warmth for us doesn't necessarily make for good charging. The main difference in noticing now is in shadows - it takes longer in the morning for the sun to reach my standard charging slope, and it leaves it faster in the evening. There are also extra shadows passing over during the day - the long fingers of chimneys now reach further than in the summer. And the solar panels seem to perform best when they are completely free of shade - a small patch can drag the power down quite a bit.

The importance of cables

A few weeks ago, I ended up reading about USB charging cables for an evening, which descended rapidly into the basics of electricity and resistance. This was kicked off by seeing some claims of "fast charging ports" on USB power meters (more on these below) - these turn out to remove 2 of the 4 connections within a USB connection, namely the 2 which transfer _data_ instead of _power_.

In cable terms, removing these 2 data wires generally means that there is more physical space for the power lines. Bigger power lines means less resistance from the walls of the cable, which means more _current_ and faster electricity transfer.

This rate of transfer is really important as charging gets harder, as above - we need a faster flow rate to fill the same battery in less time. Not only are there fewer sunny days, each day gives us less charging hours. (And, I assume, the Sun is weaker than in the height of summer?)

Generally, wires are about "28 gauge", but fast-charge cables (usually supplied with tablets with larger batteries) are "24 gauge" - see this blog post for a good explanation. I was about to order some new cables, but checked quickly, and the Syncwire cables I have already seem to do the job. (The Amazon page explicitly says they do full transfer speeds up to 2.4A.) So woo.

Length matters

Today I also realised I have a really short USB cable that came with one of the batteries - as in, 10cm rather than my 1m Syncwire ones. In theory, this should improve the amps too, as less length means less resistance as well.

So I plugged it in and measured it - wow! What a difference! No clouds to affect measurements - the 1m cable was giving me about 0.8A, while the tiny wire pushed that up to about 1.05A, so an extra 25% or more power.

The disadvantage, of course, is that it's harder to arrange your battery so that it's out of the sun, but I find it's usually OK to tuck it behind the panels anyway. I'm going to have to rethink my cables very soon - it really feels like maximum efficiency is the only way to go, with the days getting shorter so quickly.

Bring on the equinox!

Sunday, 26 August 2018

Hold all my calls (overnight)

One of those small changes in routine recently - I've switched back to putting my phone on Airplane mode overnight. I'm sure I used to do this, and stopped for some reason - maybe I wanted to keep my watch connected.

I had mixed results just switching off WiFi overnight though. Got a gut impression that the power management in Android 6 was better when left to its own devices, as it were. Sometimes the phone seemed to use more battery overnight when I turned the WiFi off. Airplane mode seems to give a consistent, fairly flat line though, and I lose a few % on my charge, but generally a very minimal amount. Airplane mode also removes the risk of falling back to network data usage if I've left that on.

Sadly I don't have controlled experiments on this stuff. I seem to have developed a bit of an "instinctual" approach, which works for experimenting quickly, but leaves write-ups a little vague and subjective ;)

Anyway, for now I'm sticking to Airplane mode overnight for both my phone and my watch - the setting for both is easy to get to so only takes a few seconds. (On the phone, I do a double slide-down, and there's an Airplane option. On the Pebble, I've set up a long-press shortcut to toggle it.) Given my routine is fairly regular - young kids wake me up early so not many late nights - I'm thinking of using an automater like IFTTT or LibreTasks (for free software fans) to toggle Airplane mode. Making power management easy is the name of the game, when it comes to getting a process and mindset in place.

Fairphone have also announced that Android 7 is coming , probably in the next month. The default power management will be different again, so expect some new experiments when it hits.

Solar clock: 16 weeks, 2 days, and counting

Friday, 17 August 2018

New hardware

More details to follow soon, but I've been hitting the hardware this week. Here's a sneak preview of a cheap but useful USB power meter I picked up to measure things. Already finding it extra useful, and battery charge is up to about 90% across the three batteries.

I've also learned a bit about cables, which I'll write up in a separate post soon too.