I have an update on my original post about installing a volt/amps meter in my trailer. When I started this topic I had just installed the 20 volts/20 amps digital meter I bought on eBay from eBay vendor "e3b6ay5." I didn't mention the vendor name in my post because I was not happy with the original meter they sent me, and they were shipping me a replacement.
I just installed the replacement. It is even less accurate and dependable than the original, with the volts and amps figures dancing all over the place (17v . . . 15v . . . 19v . . . 13v . . . etc) every 1/2 second at times, and when the volts display is undependable, so is the amps display, showing totally unreasonable values (e.g. 2-3 Amps) at times when the only device running is the meter itself; if you then switch some lights
on, increasing the amps load, the reading will then drop to a more reasonable value.
So, if you plan to install a volts/amps meter avoid buying your meter from this vendor: e3b6ay5!
[quote]When you depend on solar power
and a single battery
to supply your juice it really helps to know what your battery condition is as well as how fast your are charging/discharging the system. I installed a digital Amps/volts meter and ampere shunt I found on eBay for around $55 so I could get Amps and Volts readings at the push of a button.
Here's a picture of the meter showing the battery is being charged at a rate of 3.18 Amps. There's a round button in the bottom corner of the meter that switches the display from Amps to volts. The switch just under the meter turns the meter on and off.
I made a pressboard template of the hole I needed to cut in the side of the cabinet and test-fit my meter in the hole. Then I marked the outline of the hole on the fiberglass withe a fine-point sharpie and scribed just outside the lines with a sharp utility knife to prevent the fiberglass gelcoat from flaking off when I cut the hole. Next I drilled 1/16" holes at all four corners of the opening, and made 1/4" holes next to two of them so I coould get my saw blade in place.
The pictures here shows me using a coping saw hand-tool to cut the opening and a rotary tool (like a Dremel) with a sanding drum to smooth out my cut lines and slightly enlarge the opening in a couple spots. (Wear a dust mask when cutting or sanding fiberglass!)
Amp meters require a special device, called a "shunt" to measure the amount of current flowing through the system. One side of the shunt connects to the wire heading to the negative (ground) pole of the battery; the other side connects to the rest of the ground wires for the trailer. An additional wire pair, with one wire connected to each side of the shunt, connects back to the meter.