Tracking Battery Power - RV Enthusiast Magazine

Tracking Battery Power

by | May 10, 2022 | Pro Tip, RVEXPERT

The monitor was installed in one of the front compartments in a fifth wheel in a location close to the inverter. A spare piece of panel that matched the inside wall was used to mount the monitor.

For those without sophisticated remote monitors, keeping tabs of 12-volt DC consumption when camping off the grid can be as simple as adding a $20 amp meter.

Camping off the grid presents several challenges — one of which is managing battery power. Whether you have one battery or a bank of six, having the capability to monitor amperage draw can make a big difference when estimating how often you need to recharge the batteries — and if your system is capable of getting the job done. A solar system takes some of the guesswork out; however, several days of rain or clouds will affect charging status.

Inverters can be the biggest battery drain, depending on how many appliances are operating throughout the day. There are a few options for monitoring battery levels and, for the most part, these remote gauges are tied into the inverter or solar system and can be rather expensive; retrofitting can also be labor-intensive. An inexpensive induction amp meter can give you a general real-time battery condition along with your onboard voltmeter. Then, if you keep a log of voltage in conjunction with the amperage draw, it’s possible to figure out how long the batteries will provide enough power to the inverter before shutdown occurs.

The Baylite meter kit laid out
The Baylite meter kit included an induction pickup ring, a short and 6-foot cable. It sells for only $20 on Amazon.

For this project, we purchased a $20 ampmeter and installed it on the positive inverter input cable near the circuit breaker. The induction feature allows the cable to be routed through a plastic ring wired to the meter, which will read amperage without any hard wiring — in the same manner as an induction voltmeter functions. This meter can be used for monitoring charging inputs to your battery as well as either from a solar system or your on-board converter. It’s a no-frills ampmeter, which will probably be viewed as rather crude by electronic experts, but it can be purchased readily on Amazon (just Google Baylite DC 5-120V 100A Mini Digital Current Voltage Amp Meter). It’s capable of monitoring from 5 to 120 volts DC.

Installation is very straightforward. First, locate the positive cable that runs from the inverter’s circuit breaker or fuse to the input of the inverter. Be sure to disconnect this cable at the breaker instead of the inverter to ensure you won’t have a live wire floating around while you’re sliding on the induction ring. The induction ring has an arrow on top, which shows the directional amp flow.

marking the ring
A tiny triangle, barely perceptible, was molded into the induction ring to show direction. Rather than struggling with viewing the direction, a bigger arrow was marked on the induction ring.
removing the cable
When removing the cable to the inverter, make sure the wrench does not touch any metal. It’s best to remove the cable from the circuit breaker to ensure it won’t be live when moving it around to install the induction ring.
placing the parts together
The induction ring is placed over the positive input cable to the inverter. When the inverter was originally installed, only black wire was available, so the end of the positive lead was covered with red electrical tape for identification. If the cable lug is too big and won’t fit through the induction ring, it will have to be filed down.

Once you find a suitable location for installing the monitor, follow the cutout size listed in the instructions. This monitor only comes with a 6-foot cable from the induction ring and the power leads will have to be connected to 12-volt DC power. The power leads from the monitor will undoubtedly need to be extended, but the wire does not require a heavy gauge since there is very little draw; 22-26 gauge will be more than adequate. A 1-amp fuse and holder will need to be installed for circuit protection.

The ground wire can be attached to any metal surface or on the battery. The positive wire can be pulled from the inverter source or other location as long as it’s 12-volt DC, positive. Attach the cable from the induction ring to the monitor along with the positive/negative wires and the readout should light up. Once the monitor is fully installed, unplug any 120-volt AC source to the RV, turn on the inverter and a number (amp draw) will show up on the meter. If there’s a dot in the lower right corner, the induction ring needs to be reversed. Turn the inverter loads On and Off to make sure the meter is functioning correctly. The meter display will stay on permanently, but the voltage draw is miniscule.

using a caliper
Although the instructions indicated the dimensions of the monitor housing, a caliper was used to confirm exact size. There was a tiny lip that required an accurate cutout. In the end, the fit was perfect.
short power pigtails
The meter is supplied with short power pigtails, which were extended to reach a 12-volt DC source. Light, 22-gauge wire was all that was necessary to handle the minor load.

This is a simple project, but you will need a drill and bits, a wrench to remove the positive cable from the fuse block, a measuring tape (preferably metric since the dimensions in the instructions are labeled in metric), wire strippers and wire crimper and a device to cut the rectangular hole to mount the meter. You may need something to pull the wires through multiple holes for termination at the cut-out location for the monitor.

You’ll also need the aforementioned 20-26-gauge wire, cable ties, caulking or putty to seal the holes where the wires are routed, miscellaneous terminals and a roll of black electrical tape. While this meter does not record amp-hours, there are others on the market that will provide this information — but the cost is considerably higher. Take a few notes, do some simple math and you’ll quickly learn that this inexpensive meter will help keep you from running out of power unexpectedly.

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