How to Read RV Battery Monitor Panel?

Normal voltage reading

Cruising across America in an RV is a great way to spend your vacation. There’s so much to see in the United States that you could spend your lifetime glamping around the nation.

Monitoring your state of charge is critically important to avoid mishaps while on the road

However, owning an RV isn’t all smiles and hugs. There’s a multitude of things that can go wrong with your RV while you’re on the road or camping out for the night. One of the most common problems RV owners face is issues with the battery.

To keep your battery in tip-top shape, and avoid powerless evenings inside your motorhome, you need to ensure you have an accessible battery monitor wired into the electrical system. Driving or glamping in an RV without a battery monitor panel is the same as driving a car that has no gasoline gauge.

Using this analogy, you could get away with never running out of gas if you fill up on the way to work every morning, and only drive short distances. 

However, if you have to drive from New Jersey to Cape Hatteras on the Outer Banks of North Carolina, how will you know when you’re running out of gas?

It’s the same scenario for your RVs battery power bank as well. If you don’t have a battery monitor, you’ll never know the remaining power level of the unit, and you could end up losing power if you deplete the batteries.

If you like glamping in your RV without a generator or any electrical hookup, it’s critical that you monitor your battery life.

Lithium-ion batteries are the gold standard for RV electrics, and they’re fussy about holding a charge. RV owners should never deplete their batteries past 1/3 full. Depleting past this zone results in efficiencies developing in the battery that shorten its service life.

Similarly, overcharging your battery will also reduce its service life, and it’s a potential hazard as well. Overcharged batteries can end up getting hot to the touch, presenting an explosion and fire risk.

Those RV owners using solar power systems to charge the batteries will also require the use of a battery monitor panel, as it’s impossible to tell how much charge you got from the sun that day.

Checking battery power with a voltage meter

A voltage meter provides RV owners with an easy method of checking on their batteries. A deep-cycle lithium-ion battery has an output of 12.73-volts. When the battery reaches 50%, the reading is 12.10-volts, and when the battery enters the critical area of below 20% charged, it displays a reading of 11.66-volts.

Below is a chart that lists battery voltage and what it means to the State of Charge of your battery:

However, there is a catch to using the voltmeter method for measuring your battery charge. You’ll need to ensure that your batteries are sitting idle for at least 6-hours before you can get an accurate reading of your electrical system on the battery monitor.

Therefore, you’ll need to disconnect the battery charger and unplug any solar or generator connections from the electrical system. Essentially, you can’t use any of the electrical features of your RV while you’re waiting for the reading.

If the battery is not in a rested state, it displays an inaccurate reading. Even if you’re only running a simple light inside the vehicle, it can throw off the accuracy of the monitor panels reading.

Using our car gas tank analogy from earlier, can you imagine if your cars fuel gauge was only accurate when you pull over and rest for 6-hours. That’s not an ideal situation for anyone. Therefore, RV owners must view the voltage meter as only a good guess, and not an accurate reading that you can trust.

Many RVs now include a battery monitor panel that allows you to see the status of your electrical system at a glance – which is far easier than dragging a voltmeter around with you.

Checking battery power with a specific gravity (SG) test

For lead-acid batteries, it’s easy to check the charge on a well-rested unit using a hydrometer that measures the specific gravity (SG) of each of the battery cells. You’ll need to purchase a battery cell dropper, which is similar in shape to a standard dropper but designed to work with checking battery cells.

You’ll squeeze the rubber bulb on the top of the dropper, and the vacuum sucks the distilled water in the cell up into the transparent glass or plastic viewing chamber.

While this is a somewhat effective method of checking your battery charge, it requires a fully-rested battery and the purchase of specialized equipment – neither of which is ideal.

Install a battery monitor

Take the guesswork out of monitoring your battery life by measuring the charge on your battery using a battery monitor for your RVs electrical system.

The Victron BMV 700 series battery monitors are a very popular battery monitors, They can be integrated with other Victron equipment or as standalone battery monitors. A shunt is also included.

Victron BMV-712 Battery Monitor

After the battery monitor detects that the unit is full, it tracks the outflow amperage, providing you with a bar gauge or percentage remaining readout for easy reference. There’s no waiting for the batteries to rest, and you get a far more accurate reading than with the previous methods mentioned above.

Comparing it to our analogy, the battery monitor acts as a “gas gauge” for your RVs electrical system, providing you with an accurate readout on your remaining power supply in your battery bank.

Battery monitors are somewhat expensive, but they are well worth the money. You’ll never have to worry about losing power inside your RV again, and your batteries will last longer as a result of efficient monitoring and charging of the cells.

Know your usage

One of the appealing features of using a battery monitor in your RV is that you can see your power usage in real-time. Every time you flip a switch inside your RV, you’ll be able to see how much current that device or electrical fixture is drawing from your battery bank.

Therefore, you can quickly figure out which appliances or electrical components of your RV are drawing the most power.

After installing your battery monitor, it’s a good idea to test all of the appliances, gadgets, and electrical components of your RV. Start turning them on and off, one-by-one, and take notes on the current they draw from the battery.

Collecting this data will prove invaluable later in your RV adventures, as you’ll have an idea of what you can use if you’re facing a low-energy situation in your RV.

In Closing

When purchasing your battery monitor, you want to ensure that you’re using the right type of batteries. We recommend that you never go with the cheaper batteries, as these units have a lower service life than other top-quality brands.

You might have to pay a bit more for a good battery, but it will last far longer.

Always ensure that you pay careful attention to the battery voltage, and never run it until the lighting inside your RV starts to dim.

If you’re a serious camper that loves getting out on the road for days at a time, then a battery monitor is a piece of essential equipment you can’t do without in your RV. Never get caught in a powerless situation again.

We recommend that you visit a qualified auto-electrician when fitting your new battery monitor. If you have no previous electrical experience, you might end up damaging the system or the batteries during the installation process.

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