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{ Category Archives } Off Grid

The technologies you need when you are not connected to commercial power sources

1 to 10 kWh battery systems – rules of thumb

You’d think the Amateur Radio types would have Ohm’s law in their toolbelt and not be afraid to use it. Between QRZ forums and this month’s QST, it doesn’t seem so when it comes to emergency backup power systems. For medium sized solar systems with battery backup, systems in the one to ten kilowatt hour […]

Missing the point; Edison vs Tesla; AC vs DC power

DC for data centers at Gigaom has some good history and a few interesting tidbits on a trend towards DC in data centers. They miss the big issue, though. The reason that Tesla and Westinghouse won out over Edison in establishing AC as the power distribution standard was about electrical power delivery over distance. With […]

The Tueller Drill

Peter notes that Self-defense: things happen so fast! and refers back to police sergeant, Dennis Tueller, who wrote about the problem in the March 1983 edition of SWAT Magazine. He used a 7 yard distance as the attack approach and noted that a typical person of average fitness can cover 7 yards from a standing […]

Asimov’s Foudation Trilogy courtesy the BBC in 8 hours

The Foundation Trilogy by Isaac Asimov is a classic SciFi work and the BBC audio presentation is available for free download. The Foundation Trilogy is an epic science fiction series written over a span of forty-four years by Isaac Asimov. It consists of seven volumes that are closely linked to each other, although they can […]

NiFe Batteries

Lead acid batteries are common because they are cheap and do the job. They have a big edge on these criteria. Shortcomings include a rather limited life expectancy (less than ten years) and the sulfation problem. If you want a battery that can sit around for years but not suffer as the lead acid battery […]

electrolytic rust removal

Some recommend electrolysis to remove surface rust. You feed the rusted part electrons so the rusty iron can get its electrons from that rather than oxygen and turn the iron oxides back to plain iron. “Is it safe? The solutions used are not hazardous; the voltages and currents are low, so there is no electrical […]

Lithium batteries basics

Gigaom describes Why lithium-ion batteries die so young and provides a good rundown on how these batteries work. A lot of the ideas apply to most rechargeable batteries such as the lead acid batteries used in RV’s. One common problem I see a lot is about the difference between energy and power. When we talk […]

Mobile broadband with Novatel MiFi

Several of the cell phone carriers are offering the Novatel trademarked MiFi as an access device for their data services. It is a cell phone without the screen or keyboard but with a wifi router built in. The Virgin Mobile Broadband2go plan is a prepaid, $40/mo for unlimited but ‘reasonable’ use depending upon the Sprint […]

Chemistry in service: refrigeration

On Zephyrs, I described the operating principles of The RV ammonia based refrigerator. The key to understanding this is getting a handle on partial pressure in gases. It is this behavior of gases that is being manipulated to provide cooling. Compressor driven refrigeration uses physical pressure differences with an valve on one side and a […]

Josephine, a 76 Airstream Overlander

Vaughn’s brother was upgrading from 27′ trailer to a class A and the price was right so Jo was added to the yard as a better place to invest a few bucks. It was a bit well used but had a number of features to examine for ideas. The Onan Microlite was a nice idea […]