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.

Monday, 13 August 2018

The Holiday post - how to stay charged in a strange place

Having returned recently from a week in France for holiday, I thought I'd write up some quick notes on how solar life went.

Details: We were out there for just over a week, staying on a shady campsite for most of it, and in a more urban setting for a couple of days. The weather was basically sunny and hot, until the last few days when we hit storms and clouds, with intermittent sun.

Having seen the forecast before we went, I was pretty confident that topping up batteries wouldn't be a problem. Some types of travel might be harder (eg. cities with high buildings, or walking tours where you're always walking south with the sun on your front?).

The ideal routine for charging batteries is to leave the panels and battery somewhere all day, or at least as long as possible. This meant an interesting first few days, scoping out the campsite, looking for possible good spots. But what counts as 'a good spot' when you're traveling around?

1. Decent angle for solar input. At home (see previous post), I have a handy low shed roof, angled at 45 degrees and south-facing. It turns out that such a handy surface isn't always available - in this case, most of the campsite was shaded by trees (good for humans...) or roofs were high and inaccessible. You might need to climb a little. Or you might be able to find a decent tree with sturdy branches that you can 'nest' the panels in. Get creative when looking, be bold.

2. Somewhere you can leave a panel for as long as possible. Bearing in mind that the Sun moves round (or, ok, the Earth does), you may need to move your panel part way through the day. It took me a day to realise this so lost half a day to shade, and I ended up picking two sites, and knowing roughly when to transfer the panels from one site to another. Don't forget to pick your panels up at the end of the day! But also - don't let your solar routine ruin your holiday activities ;-)

3. Somewhere generally safe. This is trickier. You'll have to use your intuition and sense of trust here - are the people in the area generally trustworthy? Or are there any people you can ask to keep an eye on your panels? I ended up leaving mine by a cafe which was open from early til late - the campsite was safe enough, to be honest, but I asked the cafe staff if I could leave the panel there, and let them know when I picked it up. Be safe, be respectful.

My second spot was near our tent, but slightly out of view. There was public access to the path it was by. My main concern was more about dogs peeing on the panels, rather than someone pinching them, so I experimented with attaching kit to a nearby fence too:




With spots and security sorted out, I managed to do some semi-decent charging up. I also used the holiday as a great excuse to throw my phone in a bag and leave it there as much as possible. Apparently data roaming in Europe works just like being at home these days, so there are no more data excuses for not checking emails.

But staying off the phone meant my battery life got stretched out more. Not as much as I hoped, I admit - I spent some time tidying up my phone when I got back home, but more of this in another post. Enough to say that turning off Background Data made my phone oddly unresponsive, and I'm not sure if it helped the battery much overall. One to experiment more with, anyway.

So, that was holiday. It's not easy when everything is unfamiliar, when you're not so sure how long you have to re-settle. Take enough batteries, get them charged as much as possible before you go. Recce like a pro. Preserve your energy. Take what sun you can get.