I have a few very basic meters and testers for working with RV electrical systems. You don’t need to have all these, but it sure helps. None of them are expensive.
Clamp-On Volt / Amp meter
The clamp on volt/amp meter is likely the most versatile and useful tester you can buy. This Sears model 82369 measures DC Amps as well as AC and is a steal at under $60. Few meters in this price range will measure DC Amps. Most will only measure AC Amps. So I highly recommend this one.
No, it isn’t a Fluke (that’s a high end brand name – the Rolls Royce of meters) but it also doesn’t cost $300!
More options for clamp on meters here on Amazon
This is an inexpensive digital multi-meter with acceptable quality and accuracy for routine work. I got this one at Radio Shack back in 2004 for under $30. DC Volts scale is accurate in the 12 to 15 volt range for testing battery charge status. My only complaint; I’m an old electronics tech from the 70′s, and I really hate digital meter’s for continuity testing. Sure, they’re more accurate, but it’s so simple with an analog meter to touch the ends and watch the needle swing instantly across. Digital meters have a little lag, and I find it hard to adapt. Just my little gripe
Here you’ll find a wide variety of multimeters on Amazon
Here’s the latest addition to my collection. Shown here plugged into a 30 amp plug adapter (the black thing) with a simple AC outlet tester (the yellow thing) plugged into it. For less than $30 this Kill-A-Watt allows you to measure Amps, Volts, and Watts, Frequency, and KWH used for any AC appliance of 15 amps or less.
This meter has several uses. Serious boondockers use it for doing an “energy audit”. You can see how many watts each appliance uses, and figure usage time allowable with your particular solar/wind/battery combination.
When we had a 30 amp motorhome I used it when we arrived at a new hookup campsite. I plugged the KAW into a 30 amp adapter. Then I plug a circuit tester into the KAW. Finally, I plug it all into the power post. In a matter of a few seconds I knew if the post is wired right, and what the voltage was. It’s a different process for me now that we have 50 amp service I have to check the outlet manually with a multimeter.
Several other models of the Kill-a-Watt are available on Amazon
What am I Missing?
A couple of things. First, if you have regular flooded-cell lead acid batteries you need a good hydrometer. We have AGM batteries, which are sealed, so we don’t need one.
You use a hydrometer to measure specific gravity of the electrolyte in each cell of your battery. This is the most accurate way to determine your battery’s condition. Voltage measurements are useful, and important, and you monitor voltage each day; however, a volt meter can’t tell you the condition of each CELL of a battery. The hydrometer can.
Your hydrometer will come with instructions, so I won’t go into detail on how to use it. I will recommend frequency of use — at minimum once every three months when dry camping. If storing the RV you should check batteries before putting it away, and as soon as you take it out. If you take frequent trips, you could switch over to the 3 months schedule. Keep all the readings in your maintenance log for future comparison. If you have a situation where batteries seem to not be performing as well as before one of the first things to do is check them with the hydrometer.
Which hydrometer to buy? DON’T buy one that looks like a plastic anti-freeze tester. This is junk, you may as well not bother. What you need is a professional tool that will accurately measure specific gravity so you can detect small changes, and so you can see differences between cells. They used to be expensive, but these days you can get a good one for under $25. Some battery shops carry them, but I’ve found that most do not. It will be glass, not plastic. It will have instructions for use, and a scale for correcting the measured values for temperature correction. Some hydrometers include a built in thermometer, although many people use air temperature if the batteries are in shade and have not been charging (and therefore heating up). This link to Amazon displays several options
One item I’m missing is a good battery monitor system, like a Trimetric from Bogart Engineering. Without getting technical, these are like “fuel gauges” for your battery bank. They’ll tell you how many amp hours you’ve used, battery % of charge, and much more. You can buy these, and similar meters, from about $140 up to $350. More advanced units run well over $400, but for a basic battery bank they’re overkill. Some people swear by their TriMetric and feel it’s an indispensable component of their system. I believe they’re very useful, but not an absolute requirement. I may get one some day.
Continue on to Battery Types — or choose another topic from the top line menu under Technical and Projects.