Blast (love the moniker!),

A chemist, huh?? My quantitative analysis professors tried for 2 quarters to teach me how to figure molar quantities (or is it volumes?). I promised never to try & titrate anything if they'd just give me a 'C' and let me get the he## out of the Chem Building!

My baby sister, though, got a Ph.D. in organic chemistry from UC Berkeley. Go figure. She got all my chemistry genes. <img src="images/graemlins/mad.gif" alt="" />

It sounds as though you're in good company with your neighbors. All of you can contribute & no one will be leeching off the others with the genny use.

In your first post about your 25W TV-- I thought that was kind of high until I doublechecked my little 'Tornado Room' 5" B&W TV. It pulls 18W! I was surprised at that -- thought it would have been way less. It will also run off TEN 'C' cell batts, so I guess I shouldn't have been surprised.

Look into the LCD TV's for a low power unit with decent picture quality - problem is they cost $$$$$$

Hey, Mamabear, good explanation! I didn't check your math, but your method is good.

Technically, W= VxA is only accurate for DC and it takes a bit more math to figure wattage for AC supplies, but for the purpose of figuring this sort of thing out, how you demostrated it is practical and good enough.

My inverter knowledge is sadly out of date (other than owning some), but for other reasons I've been asking some questions lately. The modern inverters are pretty much all true sine wave now (or close enough to not matter) and efficiences are supposedly 90% or better. (hmmm - I am confident of the sine wave, but need to see real figures to believe the efficiency claim - maybe. Dunno.)

All the inverters we have are well-protected against overcurrent. All will deliver 2x rating (or 3x in one case) for a brief period to account for starting loads. If any of them are overloaded, they simply shut down, no fuss. The surge capability can be misleading if one doesn't do the math like you did. Example: I can fire up a Bosch reciprocating saw with one of the 600 watt inverters and it runs great, just like on line power - the surge capacity is more than ample to fire it up. And the NO LOAD current draw once running is well within the rating, taking only about 3 amps (maybe 360 watts, more or less). Try to cut something with it, and poof! no juice after a couple of seconds. That's because the working power requirement is much higher than that inverter can deliver for very long - it takes about 900w to actually USE that saw.

Battery capacity is a whole 'nother topic, but your advice was pretty good. Like you said, do the math!

Regards,

Tom

Tom the last thing i read on inverter efficiencies was about as clear as fog. The efficiencies are measured against a load that is the most efficient for the inverter in question. As in if you have a 500w inverter that works the best with a 400w resistive load, that is the efficiency stated. Going to a motor load that is 400w such as your saw would have a different efficiency rating.

Blast, being a chemist this is something you probably already know all of this, but here is a couple of links to battery theory and operation. Basically what kind of battery to chose and how to take care of it so you can get the most out of your inverter.

http://www.uuhome.de/william.darden/dcfaq.htm

http://www.wind-sun.com/Batteries/Battery_FAQ.htm

RayW,

Thanks for the links, they did teach me stuff I didn't know. The part about deep cycle batteries not reaching their full potential until being cycled ~10 times was new to me. I assumed like most things each time they're run they come back weaker.

I may be a chemist, but like most scientists 80% of what I know is very specialized. If you need to know the absorption characteritics of quaternary amines onto high-chrome steels I'm the guy you want. But if you are trapped on a tropical island with a sailor, a rich older couple, and two babes then maybe I'm not...huh...actually, count me in on that!
<img src="images/graemlins/grin.gif" alt="" />

-Blast

Unplugging from the wall anything you *don't* want fried during a lightning storm is a good idea.

Cheap surge protectors are basically a MOV (metal oxide varistor) between the "hot" leg of your power and ground that will hopefully shunt voltage spikes to ground. And there's a lot of "hope" in that "hopefully".

More expensive surge protectors will have three MOVs (one between each pair of inbound wires - hot-ground, hot-neutral, & neutral-ground) of beefier specifications, some RF choke coils to block radio frequency signals induced onto outside transmission lines acting as an antennae loading your inbound 60 Hertz AC with a bunch of hi-freq signals, plus a few other line-conditioning components.

Voltage spikes sufficient to fry electronics (especially digital, like computers) are an incredibly tiny fraction of the power contained in a lightning bolt hitting a power transmission line, coming into your house, and through your equipment on its way to electrical ground. Below is a sales blurb for a surge protector from Tripp Lite you can get for under $25. I'm not familiar with the 3570 joules-to-kilovolt conversion (or the number of kilovolts contained in a lightning blast) to figure if they are actually providing sufficient security for electrical equipment attached to the surge protector. If not, it'd be a quick quarter-mil to collect on their guarantee. <img src="images/graemlins/wink.gif" alt="" /> The TLP810SAT Surge Protector from Tripp Lite is a cost-effective way to protect a satellite TV entertainment center against surge damage. The TLP810SAT has 8 outlets and a 10-ft. cord with a space-saving right-angle plug. The unit provides 3,570 joules of surge energy absorption, enough to handle the strongest surges. ... Built-in RJ11 jacks prevent surges from damaging equipment connected to a phone line. Diagnostic LEDs and an audible alarm alert the user to potential power problems. This surge protector comes with $250,000 Ultimate Lifetime Insurance plus data recovery. No warranty cards required for coverage!

All that said, IMHO using a quality surge protector (which can be had cheap!) and even a UPS on your digital equipment is a good investment.

Unplugging is the best way to go. Buying better surge suppressors and ups's afford you a warranty for your equipment, but even these will not stop a lightning strike. My neighbor had a near strike from lightning and two ups's and the three computers that were plugged into them smoked. The ups company paid off and he bought new equipment, which he now unplugs when a storm is coming.

Back when i used to sell surge suppressors customers would ask, will this protect my equipment from lightning? What i used to tell them, a bolt of lightning will jump several miles to hit your house, do you think that there is anything in this little box that will stop it? That would usually get the point across that unplugging is the best way to go.

I picked up a 400 watt continuous/ 800 watt peak inverter for 25 bucks! at Culver City Costco, in Los Angeles. A lot cheaper and smaller than a generator for temporary power outages.

One problem with MOVs is that they will eventually fail. That is what they are designed to do - "absorb" the spike and dissipate it as heat, to the point of failure. And you will not know when they are going to fail.

MOVs backed up with a true “lightning arrestor” are the best option. If you can still find surge suppressors with gas-tube lightening arrestors and MOVs, you have a good combo. The gas tube will fire (like a florescent tube) sending the surge to the ground wire before the MOV can fail. The MOV will suppress the small spikes.

BlueFlame,

Check out www.omegaps.com and their ERICO / CRITEC line of surge suppression equipment, as well as their lightning equipment. Their TVSS units utilize the gas tube technology. Cruise through the *.PDF files for more detailed info.

Comanche7

disclaimer
I'm not an owner, business partner or even have a vested interest in this company. I've known the owner, and have purchased their equipment for almost ten years now, and never had cause to regret buying from them.