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The Perfect Multimeter For Overlanders, RV'ers & Van Campers | Southwire 21550t Review

The Perfect Multimeter For Overlanders RV’rs and Van Campers | Southwire 21550t

A multimeter is an exceptionally useful tool for anyone to have in their garage or vehicle tool box. Particularly if your vehicle is set up with aftermarket electrical accessories such as lighting, power inverters, auxiliary battery systems, solar power systems or recovery winches. Pretty much all the things you might find in your average overland or camper van build, as well as RV’s. A standard multimeter can tell you a lot of what you need to know to monitor and diagnose any issues in such systems. But not all. That’s where the Southwire 21550t comes in.

*Why a clamp meter Instead of a standard multimeter?

Technically speaking the 21550t isn’t a multimeter. It’s a clamp meter. What’s the difference? Well on first glance the physical difference and name become quite obvious, but in use they are slighly different. A clamp meter is designed to measure current in an electrical system (AMPs). Most standard multimeters can measure amps but typically only around 10 amps at max. Where many of the aftermarket systems we install in our camping / adventure vehicles can run over 30amps. Trying to measure a 30amp system with a standard multimeter that is rated for say 10amps will result in a burnt up melted set of lead cables. The benefit of a clamp meter is that it can take a measurement of high amp systems (up to 400amps in the case of this clamp meter) without making any physical contact with the system. Simply adjust the meter to the appropriate settings, and clamp the jaws around the wire you want a reading from. Using this meter, I was quickly able to diagnose a bad circuit breaker in my dual battery system. I set the meter to display the highest amp reading it saw, waited for my breaker to trip, then saw that my 30amp breaker was in fact tripping at 23amps. I replaced the breaker and haven't had an issue since.

What about the other features a multimeter has?

Luckily, the 21550t also can still take the reading that are most useful for automotive applications such as, voltage, electrical resistance (ohms) it can even measure capacitance (this could be helpful for those who have ac in an RV or travel trailer, possibly your refrigerator too, but I won’t pretend to understand exactly how RV fridges work i'm not even sure if they cave capacitors,. I’m a car camper) But if you feel like you need all the other features as well, luckily multimeters can be picked up for under $10. Sometimes Harbor Freight even has a coupon for a free one.

What to look for.

One thing that is very important to make sure is that the clamp meter you choose can read DC amps. NOT ALL DO. These meters are typically used in commercial and residential HVAC systems, so many of them are made to only read AC current. Vehicles systems are DC so it’s important to pick a clamp meter that specifically states that it can read DC.


I purchased the Southwire 21550t at Lowe's Home Improvement when I noticed my battery system had failed on a trip to Florida. I paid around $79.99 for it which is close to the same price I found HERE on Amazon. Price wise its about middle of the road for what you can find out there for DC rated clamp meters so I think it works out to be a good balance of cost and quality. Again, there are much cheaper ones out there but most are not rated for DC current. For vehicle and RV use, the ability to read DC current is essential.

Southwire 21550t Features & Specifications

Reads up to 400amps AC/DC current

AC/DC Voltage

Capacitance (ohms)

Non-Contact AC Current Detector

Built-In Flashlight

Illuminated Screen

You can see all the specs and features as well as the user manual on Southwire’s website HERE.

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