Do you really know how much battery power you’re using in your RV? If you’re relying only on voltage readings, the answer is probably no. That’s why serious RVers and solar users rely on a tool called a shunt.
In this Tech Tip Tuesday, brought to you by the National RV Training Academy (NRVTA), we’ll explain what a shunt is, why it matters for your solar setup, and how to use it properly so you’re never left in the dark.
What is a Shunt?
A shunt is a small device installed on the negative side of your battery bank. Its job is simple but powerful: it measures the current flowing into and out of your batteries, then relays that data to a battery monitor.
Think of it like an accountant for your RV power system. It tracks every electron that comes in (charging from solar or shore power) and every electron that goes out (powering your fridge, lights, or AC).
The result? You get an accurate picture of your true state of charge (SOC), expressed as a percentage.
Why You Can’t Rely on Voltage Alone
This is especially important if you’re running lithium batteries. Unlike lead-acid, lithium batteries have a flat discharge curve. That means whether you’re at 80% or 50%, the voltage often still looks about the same—around 13.6 to 13.8 volts.
Without a shunt, you don’t know if you’ve got hours of power left… or just minutes. That uncertainty could leave you stuck without power for essentials like air conditioning or refrigeration.
Setting Up a Shunt Correctly
A shunt isn’t just “plug and play.” To work properly, it needs to be calibrated:
- Fully charge your batteries. Connect to shore power and allow the system to reach float voltage.
- Program the shunt. Using your shunt’s software (Victron is a popular option), set the state of charge to 100%.
- Recalibrate regularly. Over time, electronic devices can drift. A good rule of thumb is to plug into shore power and reset your SOC every 3 months.
👉 This prevents your monitor from showing inaccurate readings and ensures you know exactly what’s left in your batteries.
Smart Shunts vs. Basic Shunts
Not all shunts are created equal. While you can find inexpensive shunts online, many of them are just bare resistors with no “brains.” These simple shunts can measure current, but they don’t have a circuit board to process or relay meaningful information.
A smart shunt, on the other hand, includes onboard electronics that communicate data to your battery monitor or app. That’s the kind you want for an RV solar system—because it tells you, in real time, exactly what’s going on with your batteries.
Why a Shunt is Essential for RV Solar
With solar, power management is all about balance—how much energy is coming in versus how much is going out. A shunt gives you that real-time picture:
- Is your solar array keeping up with your usage?
- Are your batteries slowly draining even while charging?
- How much time do you have before you need to plug in or run a generator?
Without a shunt, you’re left guessing. With it, you have the confidence to boondock longer, run your systems smarter, and avoid the dreaded “everything just went dark” moment.
Final Thoughts
A shunt may be a small piece of hardware, but it’s one of the most important components in your RV solar power system. It tells you where your power is going, how much battery capacity you have left, and when it’s time to recharge.
So whether you’re installing solar for the first time or upgrading your battery monitoring system, make sure a smart shunt is part of your setup. It’s the difference between guessing your power status—and knowing it with confidence.
There’s your Tech Tip Tuesday!