Sun-starting in winter

Hello, and happy shortest day of the year! The switch towards longer, warmer, lighter days is so very welcome.

While away last week I ignored the "low balance" emails for marina shore power, and on Tuesday it eventually hit £0.00, but I didn't find out until everything went dark at 11pm. Inverter clunked off, and the battery went to 0%.

So I topped up with monies hoping to recharge, but then I realised the battery manages its own charging via its internal Battery Management System, or BMS. And the battery was dead... even the relays for the inverter/charger are battery-powered, so I was left with the challenge of giving the battery juice, but it was the squeezer. The first option was sunlight, for which I'd have to wait, so I went to bed.

It's a funny predicament, needing a battery to resurrect itself, but when I've rewired the engine this won't be an issue — I could simply run the engine. That reminded me of the backup option: over the summer I did install the 12V-48V charger, so connecting that via a car battery charger to shore power would also do the trick.

Anyway the next morning I retried, but by 10am there was no power and I had to run. So I left things switched off and hoped for the best, returning on Thursday. I was nervously excited to walk in and find it at 1% — 50Wh from over a day of winter greyness! — and I turned on the inverter. I configured it to be gentle with the battery, charging at no more than 2A, and it clicked into action bringing the cells to life.

Over the next hour I kept coming back to watch it climb, from 2 to 5 and up to 10%, and I slowly released the breaks as the cell temperatures rose and equalised. At 20% I put the settings back to normal, and it got the full 3.5kW from the grid to continue. This was also a good opportunity to tune some of the parameters, like disconnecting the grid when the battery hits 55.4V instead of the vague-and-unpredictable "finished bulk charging," and having it cut-in at 35% charge instead to preserve its life. But even after ~6 months it's only done 67 cycles by its own measure, out of a supposed 4,000 cycle lifespan, and with any luck it'll go for many more years still.

In other news I ordered an anemometer to measure wind speed and direction, to see if a lil' turbine would be worth it. My feeling is ~2.5kWh per day in winter would be, but small ones really need wind speed and a high RPM to be effective.

And the chimney re-sealing I did, it held! A few heat cycles since and no leaks, it is toasty and cosy:

Until next Sunday!

- Nick