Test for charging house batt

otrfun wrote:

ktmrfs wrote:

otrfun wrote:
IMO every RV'r should have a cheap, clamp-on ammeter that can read DC current. Most clamp-on ammeters include all the standard functions found on a simple voltmeter, so no real need for a separate, dedicated voltmeter (2 for 1).

A clamp-on ammeter is easier to use than a voltmeter when making current readings. Simply clamp the ammeter jaws around either battery cable to make a reading. It will tell you exactly how much charge current your battery is or is not receiving. It will also tell you much current is being drawn from the battery when it is not being charged. Important readings that a voltmeter cannot provide.

Not all clamp on ammeters are equal. The very inexpensive ones use a toriod (transformer) to sense current and only measure AC current. Not much use for an RV. Luckily the hall effect probes have come way down in price and can measure DC, AC and in some cases DC+AC current.

If the probe does measure DC and does NOT have a button to zero the reading, pass it up. Hall devices look at the magnetic field induced by current flow and also are sensing the earths magnetic field. Orientation affects the fields so there needs to be a way to zero the stray fields. If it does have a zero button check how close to "0" the reading is. should be within 1 or 2 digit(s) of zero. If so you likely have a clamp meter that is good enough for the qualitative measurements needed for most RV troubleshooting.

Another issue is many of the meters have a single range near the 0-200A reading, and pretty large jaws, which isn't real great when looking for readings in the few amp range. But they will at least give you a qualitative indication of current and are far better than having to break the circuit to measure current.

many of the reasonably priced decent useable clamp on hall sensor current probe (and combo current/voltage probes) are made by two companies based in Tiawan. Those meters are sold under various names and OEM'd to some of the more well known brands used and trusted by professionals.

They are a valuable tool, have one in my house toolbox, one in my truck toolbox and one in the trailer toolbox.

Good info, ktmrfs. You've obviously used and have a clamp-on or two!

For our needs, we've found inexpensive, no-name DC/AC current capable clamp-on ammeters (<$50 on Amazon) more than adequate for general RV troubleshooting purposes while we're on the road. We've purchased 2 or 3 over the last few years. Have yet to experience any accuracy issues that hindered any troubleshooting.

Inrush current is the only function we've found to be wildly inaccurate and unusable on many (so-called inrush capable) clamp-on ammeters. Only trust our Fluke 375 for inrush.

yes, $50 ish will get you a hall sensor current probe adequate for many RV and home related troubleshooting task. good ones for inrush current or low current (ma- few amps) another story. low current hall sensor probes exist, but they aren't inexpensive. And lots of the technology around them is protected by "trade secrets" not patents. There is lots of "art" involved in making a low current accurate quantitative hall device current probe.

An inexpensive unit with a smaller detachable smaller jaw would be a welcome addition to my toolkit. The large fixed jaw units can be a PITA to get hooked up in tight spaces.

Fluke 375 is a nice unit.