Archive for November, 2008

Wire size considerations

Getting the right wire size is a matter of distance and current. There are two issues to consider. Voltage loss is important as most equipment is rated for best operation at a particular voltage. Power loss in the cable is important because it indicates a risk of overheating cable or connections.

The table shows common wire sizes and the resistance in ohms per thousand feet. The “line” column shows the resistance you’d have in a ten foot cable powering some device. This is for 20′ of line as you need to consider the round trip. Voltage loss and power loss are show for that 10′ cable for 5 amps, 10 amps, and 100 amps. The voltage loss is shown as a percent loss for a 12v circuit.

From Wikipedia on wire gauge: use the resistance table and calculate the voltage loss and power consumed by a ten foot run of wire at 5, 10, and 100 amps. Here’s the result.

size

resistance

Voltage loss as percent at 12v

power loss in watts

AWG

per k-ft

line

5

10

100

5

10

100

4/0

0.049

0.0010

0.04%

0.08%

0.82%

0.02

0.10

9.80

2/0

0.078

0.0016

0.06%

0.13%

1.30%

0.04

0.16

15.59

2

0.156

0.0031

0.13%

0.26%

2.61%

0.08

0.31

31.26

4

0.249

0.0050

0.21%

0.41%

4.14%

0.12

0.50

49.70

6

0.395

0.0079

0.33%

0.66%

6.59%

0.20

0.79

79.02

8

0.628

0.0126

0.52%

1.05%

10.47%

0.31

1.26

125.64

10

0.999

0.0200

0.83%

1.66%

16.65%

0.50

2.00

199.78

12

1.588

0.0318

1.32%

2.65%

26.47%

0.79

3.18

317.60

14

2.525

0.0505

2.10%

4.21%

42.08%

1.26

5.05

505.00

18

6.385

0.1277

5.32%

10.64%

106.42%

3.19

12.77

1277.00

22

16.140

0.3228

13.45%

26.90%

269.00%

8.07

32.28

3228.00

24

25.670

0.5134

21.39%

42.78%

427.83%

12.84

51.34

5134.00

The voltage loss area marked in red is where the drop is more than ten percent at 12v. Note that the power loss columns apply to any voltage.

Comments off

Navigation aids: comments about brands

If you are thinking about one of those GPS boxes for your rig, you might want to check out the opinion from GPS Tracklog.com. The post offers a few comments about Garmin, TomTom, Magellan, Navigon, Mio, and “all the rest” that you can use to figure out what is different between them.

These things can be handy as a ‘one box on the dashboard’ thing. The alternative would be a computer, such as one of those new netbooks, with DeLorme’s Wired Laptop Street Atlas USA GPS BUNDLES or an I’net connection to Mapquest or Google Maps and attached to a simple GPS device like the Garmin eTrex.

Update: See also the Consumer Reports Best GPS navigation deals for Black Friday 2008
So many options mean tough decisions. Can be fun, maybe.

Comments off

Phishing and – about that e-mail

While they did manage to shut down one major source of unsolicited soliciting e-mail, you are likely to still be subject to people trying to part you from your money in unscrupulous ways. Phishing Scams in Plain English provides some good advice for you to follow to minimize your risk.

Internet con artists are clever. Even smart people can be duped sometimes. Even those who keep active watch against scams and schemes can make mistakes.

When you set up a financial relationship with a bank or company on the I’net, you go to an address you got via a reputable source. When you get your account set up, you’ll get to a login page. Bookmark that page. Whenever you get an e-mail that appears to be from one of your financial partners, never ever click on the link in the e-mail. Instead, go to your browser and open the login page bookmark. Then you can login and check whatever the e-mail message was about.

These same rules apply to telephone solicitations. Never reply with any information. Always go back to a know telephone number or web page, one that you know is good for the company you are trying to reach, and follow up that way.

Learn about phishing and other scams – see the video at the link and carefully review the list of suggestions to minimize your risk.

Comments off

Propane

A convenient fuel for the RV often sits in bottles standing at the tongue of a trailer or in a tank alongside the frame underneath a motor home. Propane in the tank is under pressure (up to about 250 psi) to keep it a liquid. These tanks contain about 430,270 (20#) to 860,542 (40#) BTU’s of energy. That won’t last long if using propane to heat the RV in winter but does quite well for water heating, cooking, and refrigeration most of the time.

Propane 101 promotes propane safety through better understanding. Consumer propane cylinders describes the common bottles you’d see on the tongue of a trailer. Understanding Your Propane Tank and Propane Cylinders provide a good description of the parts and pieces involved in propane storage. Check out the index for other pages with good information.

The GasCo glossary of terms is oriented towards residential use but still provides a good start on terms you need to know about propane and its use.

Some other propane safety articles to peruse include Camping World’s Play it safe with propane with good note about alarms, New Car Buying guide Propane safety for RV Owners with a checklist, Funroads with when full is too full, Propane safety dot com to get technical, or Dave and Helen’s on propane tank valves and re-certification.

Raso enterprises provides some interesting pictures and discussion about proper propane tanks as vehicle fuel sources. It provides some insight into the differences between the motorhome and trailer propane tanks.

Comments off

Weather Service Briefings

The National Weather Service Forecast Office has a new service, the Latest Online Briefing for the Current Storm. It is a Flash presentation you can view to see what is going on and what is expected when a storm is brewing.

Comments off

How to kill your batteries

Ample Power has a very nice list of ways to kill your batteries. Since winter storage time is pending, a look at this list might give you some ideas about what to do or not do to be sure you have a lively battery next spring.

The first two points involve the delicate balance between overcharging and undercharging. You don’t want to let the float or trickle charge to take the battery above 13.8v for any length of time but you also don’t want to let your battery sit without experiencing that kind of voltage now and then.

The next two center on compensating for the battery self discharge rate. Then there is the excess discharge warning and a number of other issues.

Take care of your batteries if you expect to get the most from them!

Comments off