November 8, 2012

MORE ON INVERTERS: Reader Richard Gardner writes:

Folks considering inverters should first check their automobile’s alternator capacity to figure out how much they can power long-term from an inverter without discharging the battery. Making rough calculations, your Mazda RX-8 probably came stock with a 100 Amp alternator (at 13.8V) = ~1400 Watts, so anything much more than that is overkill (not to include peak rating). You can get aftermarket high output alternators, usually in the 160-200A range; my older Toyota only has a 60A alternator. But some of that power is needed to run the car (20-40 Amps), so for a 100A alternator the best case is 1100W available for the inverter. These output ratings are at normal driving engine RPMs and at idle you are lucky to get 75% of the rating (and as low as 50%) so we’re now down to 800W (max, probably lower), which will provide you with ~7A @120V AC, enough to run the refrigerator (130-200W) and more. You’ll need at least a 750W inverter (“peak” 1500W – inverters typically have a peak rating 2x the normal rating) to handle the starting surge current for starting the refrigerator (~1200W) with the extra energy coming from the battery regardless of how much power your alternator produces.

To run a 3000W inverter continuously without discharging the battery you need a 300A alternator, what you would typically find on a fire engine.

Here’s an article on using inverters for emergency power, and here’s some guidance on how much power various devices use. And in response to my earlier post on inverters, reader Mark Wallace writes:

Kathleen Wallace is my sister. She sent me a picture of her inverter and running fridge. I was a little jealous as I was in darkness in NYC. Here’s the Amazon link for the inverter.

Funny, I was looking at that one online. Another note: Some inverters, especially the cheap ones, put out pretty “dirty” power, which isn’t good for electronics. Laptops are probably fine, but other computers and sensitive devices may have problems.

Meanwhile, reader Judith Sears writes:

I read the posts on using inverters with interest. However, I live in a high rise, 6 floors up from the garage, so running an inverter off my car isn’t possible. Any alternatives or MacGuyvers that people know of?

Well, you can’t have a generator — even if you’ve got a balcony you could put it on, it probably wouldn’t be safe with regard to carbon monoxide — and you can’t have an inverter because your car is floors away. So what can you do? Well, you can buy a big uninterruptible power supply — I have several of these with the add-on external battery. One of these will run a cable modem and wifi hotspot for a long time, and charge your laptop and cellphone. And I have a couple in the studio so that if the power cuts out while I’m doing a PJTV show there’ll be plenty to finish it — they even run the lights, which are fluorescent and so don’t hog too much power.

And there’s always this solar-powered phone recharger, with extra solar panels. I don’t know how fast this would charge when it’s cloudy, but it holds enough power to charge a phone a couple of times anyway. Then I’d have a couple of lanterns for light, and possibly a small propane stove, though it’s not safe to use most of those indoors.

Any other ideas out there for apartment-dwellers?

UPDATE: Reader Dave Lemieux writes:

Alcohol stoves are the best alternative for indoor emergency use — no CO problems and the fuel is widely available. You can go cheap for about $30 (typical for a backpacking stove) or better for a couple hundred like you’d find on a boat..

Good point. Here’s one.

And reader Steve Barkmeier recommends this for apartment power backup, adding that it’ll also keep you warm. You’ll be hungrier, though. . . .

MORE: Reader Stephen Skubinna writes:

I live in rural America and have a 3kw Onan. One thing to bear in mind if your potable water comes from a well is that submersible electric pumps have a hefty startup load. Factor in 20 amps at 220v if you’re calculating the requirements for a generator or inverter. Once they’re running they don’t draw much.

Incidentally I worked in IT during the Y2K panic. When people would ask how bad it was going to be I’d say it wouldn’t be an issue, and they’d smile knowingly, figuring that I was simply trying to head off panic at the impending end of civilization. However if they’d ask how to prepare I’d tell them to have extra blankets, candles and maybe an oil lamp, lots of flashlights and extra batteries, potable water and stored food for about a week, and perhaps a hand cranked radio. They’d make notes and ask “So that’s for Y2K, huh?” and I’d respond “No, that’s for ALL THE TIME! You should always be ready for at least a week’s interruption of service.”

People, at least urban dwellers, won’t even countenance roughing it for a few days. So far as their universe runs, if the power or water or phones and internet go out a man in a truck shows up and fixes it within a day. They have no idea of how fragile their urban environment is.


STILL MORE: Kathleen Wallace, mentioned in the earlier inverter post, writes:

Wow, Glenn!! I, my brother AND my husband (who spent half a day online choosing the unit) are over the moon seeing ourselves on the Insta!

My brother sent you the link to the Power Bright 2300; we also purchased these cables:

And these fuses:

All were purchased through the Amazon Instalink, of course.

We had plenty of heavy-duty (critical) extension cords on hand.

We called Power Bright directly, they were fantastic and helped us choose. We originally wanted one that would power a space heater, thus the 2300.

But then, on the third day, we were getting cold. As the family electrician, I went down to the basement to figure things out. I removed the furnace 110 line from the closest junction box, cannibalized a heavy-duty three-prong plug from an air conditioner, and spliced it IN THE DARK with husband holding the flashlight. Plugged it into the inverter. The spark of the furnace pilot was the sweetest sound. The peak draw was surprising low. Cables never even got warm.

Yeah, most furnace fans don’t pull a lot of power. Cool! Er, I mean, warm.

MORE STILL: More advice for apartment-dwellers from reader Paul Clithero:

When we lost power for nearly a week due to an ice storm, I robbed a battery from one of our cars and would charge it using jumper cables from our other car. I realize that this is a bit of a trick for those with one car, or who might need all of their vehicles running, but it is always an alternative to sitting in the dark.

If one lives in a multi-story apartment building, it might be nice to have a dolly capable of hauling the battery up the stairs, unless you can carry the thing by hand. There are straps and battery grabs available at auto parts stores intended for the purpose of carrying car batteries around.

Another alternative would be to hit the Interstate Battery store, Wal-Mart automotive center, etc. and purchase a deep cycle RV battery if it looks like a Sandy/Katrina situation is in the works.

Good advice. And you can get those from Amazon, too. You could even keep it and charge it in your apartment when there’s power.

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