Need small 12 volt power system

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-Bill

First play with DC Current Clamp meter with your car battery... Turn lights on/off, start car, run alternator and see how it works.

The "zero" button works very differently from other meters I have used. DC current clamp meters have zero "drift" (nature of the transistor used to sense the magnetic field). You will have to zero the meter every so often for the most accurate readings (at low current).

For this Sears Meter, make sure the ZERO in the LED is off (missing). You can zero with "zero current" or zero "with some current flow" -- Your choice. With the clamp having no wire in it, push the Zero Button so that "ZERO" is displayed (the micro controller simply adds/subtracts an offset voltage from the reading).

Now clamp one wire and you will see its DC current flow. Note, if you clip on the + and - leads, the net current flow is ZERO Amps (5 amps to the right is canceled by 5 amps to the left).

If you pay attention to the display, you will see a "-" sign occasionally, with DC current, the meter and tell you which direction the current is flowing (clip to battery you will see -10 amps when the headlamps are on, and perhaps +10 to +50 amps when the alternator turns on).

Next--When you start estimating your power needs... Note that some things draw constant current (light a light bulb). But an RV furnace or Refrigerator will only run XX minutes out of the hour--So you have to both measure the "on time" and "off time" to estimate the average current flow (or get a kill-a-Watt meter or Doc Watson type DC AH/WH meter to do the measurements over time).

A DC Current Clamp meter is almost "magic" for how easy they are to use (no more cutting a wire and attaching a DMM / Amp meter to measure current flow). And much safer too (cannot blow up the meter in normal operation).

-Bill

Don't let my math trying to figure out what the 400mA was (120 VAC input current--Was not the 12 volt output current).

Most of it is pretty straight forward. We start with some numbers and then walk through the equations to figure out what we need.

I agree with Alaska Man--Unless you have equipment that needs 12 VDC (for HAM Radios, they really want 13.8 volts for full power transmitter operation)--Many times simply getting efficient 120 VAC appliances (usually energy star rated) + an AC inverter (with its 85% efficiency) is usually a better deal. The 120 VAC equipment can be cheaper, and the 120 VAC power is easier to send longer distances and a bit more "rugged" input than 12 VDC circuits (lightning, short circuits, electrical isolation/ground isolation, etc.).

-Bill

You can Google around for various alarm options... This one (don't know anything about product or website) runs 12dc/24dc/120 VAC

http://www.ingramproducts.com/Alarm_Audible-12_24VDC_Alarm_Sounder.html

We have a few people here with Internet connected alarms--And some remote monitoring.

Figure out what you need (i.e., just noise, or cell phone, internet, etc. connected alarm).

-Bill

My suggestion... Run all of your loads at home--If DC, get a couple of golf cart batteries plus something like this DC AH/WH meter (there are a lot of different brands/models out there--Many look like clones of each other, but can have-what appears to be-different software/display options). Run the DC rig from a battery charger (if nothing else) so you can get good daily load numbers. Or a Kill-a-Watt meter if AC loads.

Yea--I repeat myself--But you really need to know your loads to build a cost effective and useful off grid system.

Next--Many people buy a 4 foot square sheet of ~1" thick subfloor plywood and build out there entire solar power system (wiring, charge controller, breakers, battery monitor, AC Inverter, etc.) in the garage and attach it to a couple of solar panels in the yard--And test it for a few days to make sure all is right. You might need/want to cut down the plywood sheet so it is small enough to fit the space/vehicle and easy for 1-2 people to hang on the wall.

Label & disconnect the wiring, put it in the back of the vehicle, drive to camp/cabin and install--Reconnect wires. Can save a lot of frustration if the nearest Hardware Store is several hour drive away.

-Bill