10:30 in the blessed AM, and it’s not 20 outside yet.

Never got above freezing yesterday. Heavy clouds, occasional flurries, no accumulation. Probably won’t get above freezing today – hell, might not get near it – though we are currently getting some on-and-off sun. Yesterday I left the inverter off all day just because the only thing I’d have needed it for was the computer, and why run the batteries down when I don’t know when I’ll see the sun again? So this morning we’re in very good shape, electrically.

Yesterday for the first time all winter I ran the woodstove all day and right till bedtime, and had no trouble at all keeping the interior temperature in the high sixties and seventies with zero resort to propane. Which is darned nice, and it’s likely to continue because the forecast calls for one of those weeks where it just never gets above freezing at all. Since I have no way of running a heated waterer, I go out to the Fortress of Attitude every few hours with a bowl of liquid water and bring in their old bowl of ice. Until it warms up a bit I won’t even bother with their waterer. It’s at times like this I’m happy I sweat over all those old pallets in August and September, because the firewood supply causes me no anxiety. Most winters I’ve been more just-in-time with my wood cutting, but screw that: It’s cold outside.

Speaking of electrical issues, way back in August when that lightning strike fried my old RV-surplus 4000w Xantrex inverter, we had a discussion about whether I wasn’t better off with a smaller inverter after all, in terms of parasitic drain. Apparently there’s a rule of thumb that the size of the drain caused by the inverter is proportional to the potential output of the inverter. I’d never heard of that rule, but it makes an instinctive sort of sense.

This being the season of the solstice, when every unnecessary voltage loss becomes significant and pretty easy to identify, I’ve been putting that to the test. I never kept records about the evening voltage, but I have routinely recorded the morning voltage every day for the past 2 1/2 years so while this isn’t scientific, I do have some basis for my view that that rule above isn’t universally true. In fact, my new Magnum Energy 600w inverter…
magnum-energy-mm1512-ae-15-kw-inverter-47451
…causes at least as much overnight voltage drop as the old Xantrex ever did. Possibly a little more. For the past three frigid afternoons I’ve been shuffling out to the powershed to turn it right off at sunset (and oh HOW I wish I knew how to put a remote on/off switch on that thing) and the voltage drop is significantly less when I do that – on the order of .3 volt. That’s even with the voltage drop you can normally expect when the batteries’ ambient temperature is in the low teens. That’s pretty much right in line with what the Xantrex used to do to me, though the Magnum is a much smaller inverter. So there’s that, make of it what you will*.

So I’m just hunkering down through this projected cold snap and hoping that damned pipe manifold at the base of the cistern doesn’t freeze up again. Whether this will be a slow blogging week depends mostly on sun and mood – right now I’ve been enjoying a Larry Correia reading festival because I never get sick of him and reading dead-tree books requires no electricity. Thanks for all the comments. Hope you all are staying warm.


*And those of you who said for years I should have installed 12V lighting in the Secret Lair can pour yourselves a nice big steaming cup of I Told You So, because I can testify that a 12V LED run for five hours in the evening won’t even take the surface charge off my batteries. Man, I’m glad for that retrofit lighting kit my brother sent me a year ago November. I’ve got one by the reading chair and one in the sleeping loft, and now I’m thinking maybe I want to run a third over into the kitchen corner because the past few nights I’ve been brewing tea by flashlight.

About Joel

You shouldn't ask these questions of a paranoid recluse, you know.
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6 Responses to 10:30 in the blessed AM, and it’s not 20 outside yet.

  1. ben says:

    I seem to remember that there are a variety of remotes for that inverter at differing prices. The down side is that they require a phone cable, which is one more path for lightning to wipe out your system.

  2. Mutti says:

    I don’t know if it work for your watering system, but we’ve stuffed an old tire with insulation and placed the water container in the center of the tire. The whole shebang is placed on a make shift platform to keep it up off the ground. So far this has worked well for us out in the pastures.

  3. Zane says:

    Remotes are just a momentary switch, just have to find a schematic with the pin out of the remote plug. But as Ben said, it is another path for lightning, so you’d want to run it with your other wiring to keep risk down. Probably more hassle than it’s worth.

  4. No One says:

    I am guessing an automotive solenoid would work. Something like an ABS solenoid could be wired in to to remotely control the on-off at the DC supply side and powered by a 9v battery on the controller/remote switch side.

  5. s says:

    I’m not surprised that the battery drain on the smaller inverter isn’t appreciably less than that of the 4000W unit.

    As I commented earlier, the “rule of thumb” is high-octane BS. Serious solar inverters (when you’re leaching off the public tit by throwing up tax-subsidized 500,000 watt “green” solar fields, 1% loss represents 5,000 watts) are typically 97.5% efficient or better. Both the customers and the inverter manufacturers know exactly how much 1% extra loss is worth in subsidies/revenues. They might be willing to pay/sell for a few thousand dollars more to capture that last 1%.

    Consumer class inverters run the gamut; your Magnum 600 is a typical product that is “only” 95% efficient at best. Best efficiency is usually around 3/4 maximum power. But at 600W total output the difference between 95% and 97.5% is only about 15 watts. You wouldn’t want to pay an extra $100 for those last 15 watts.

    The Magnum 600 no-load loss is about 10 Watts. It’s loss at “best” efficiency is less than 30 watts. If you aren’t running anything but it is drawing 10 watts, the efficiency as far as you are concerned is 0%. That’s why shutting it off at night helps so much.

    The next model up Magnum, and many other brands, offer an automatic cut-out feature that shuts off the inverter when output is below 5 watts or so. Sadly, the Magnum 600 doesn’t offer this. They offer a remote, but at $58 shipped it is a rather large fraction of the inverter’s cost.

    The losses at night come from the inverter making AC and from leakage current in the DC capacitor bank. This current is relatively high because for safety there is a resistor wired across those caps so that they discharge when the battery power is disconnected. Please don’t disconnect that resistor – it has functional as well as safety purposes.

    Your deceased 4000W unit had a similar (probably a bit larger) capacitor bank, and similar idling losses.

    LED lights don’t have idling losses, and as you’ve found are very efficient. I’ve been playing with 1,000 lumen modules that pull 10 watts or so. At $8 each I’m not afraid to experiment a bit. A bit much for reading, but not at all bad for flashlight or outdoor security floodlight when things go bump in the dark.

  6. Judy says:

    I started to suggest a couple of bales of hay setting on top/around the water manifold. Then I remembered your field mouse/pack rat problem so never mind.

To the stake with the heretic!