Battery monitors are the best way to track the state of charge of your RV or solar battery bank.
After testing the best battery monitors on the market over the course of 2 months, here are my 4 steps to finding the right one for your system.
1. Check the Monitor’s Battery Voltage & Capacity Ratings
Before considering anything else, make sure the battery monitor you’re looking at is compatible with your battery bank.
Most battery monitors work with virtually all types of RV and solar batteries, regardless of whether they’re lithium iron phosphate (LiFePO4) or lead acid batteries. But the two main things to look at are the battery voltage and capacity ratings.
Battery voltage range: Most battery monitors are compatible with 12V, 24V, 36V, and 48V lithium and lead acid batteries. These are by far the most common battery voltages in RV and DIY solar systems. But if your battery bank is a different voltage, check that it falls within a monitor’s voltage range before buying.
Battery capacity rating: Budget battery monitors tend to be able to handle battery banks with amp hour capacities of 999 amp hours or less. Premium battery monitors, such as the Victron SmartShunt and Victron BMV-712, tend to be capable of handling battery banks with amp hour capacities of 9,999 amp hours or less. You can use our solar battery calculator to find out how much capacity your off-grid solar system needs.
2. Check the Shunt Current Rating
True battery monitors come with a shunt. That shunt has a current rating. Check the shunt’s current rating and make sure that it exceeds your system’s max current.
100A-350A: Budget battery monitors tend to have shunt current ratings of 100 to 350 amps. Though that is less than the more premium options, that is still a significant amount of current that most small RV, boat, and solar electrical systems are unlikely to exceed.
≥500A: Premium battery monitors generally come shunts with current ratings of at least 500 amps. Some have upgraded models available with current ratings of 1,000 amps or more.
3. Decide on Bluetooth Monitoring
Being able to monitor your batteries from your phone is a worthwhile upgrade in my opinion. However, a lot of battery monitors do not have this feature.
Bluetooth monitoring in a battery monitor works in conjunction with a free mobile app provided by the brand. Victron is the main brand that offers Bluetooth monitoring in their battery monitors, although it doesn’t come built-in to every monitor they offer.
However, Bluetooth monitoring is certainly not necessary. If a battery monitor doesn’t have Bluetooth, it will have a screen that will display all the necessary specs such as battery percentage, battery voltage, and charging or discharging current.
4. Decide on Extra Features
Lastly, consider what extra features you may want from a battery monitor. Here are the main ones I came across during my testing:
Some battery monitors let you program alarms to alert you when the battery capacity is running low, or when the voltage hits a certain setpoint. The alarms fall into 2 categories:
Audible and visual alarms: Monitors with these alarms start flashing and/or beeping once the battery reaches the set capacity or voltage. They are the most useful in my opinion, because they’re best at getting your attention.
In-app alerts: Monitors with companion apps sometimes have ‘alarms’ that are actually just in-app alerts. These are far less useful at grabbing your attention because you need to open up the app to see them.
The alarms can always be disabled if desired.
Operating Temperature Range
If your battery monitor will be placed outside, or in a building or vehicle without AC, then look at a monitor’s working temperature range before buying.Some of the cheaper battery monitors, such as the AiLi monitor I tested, don’t work below freezing or above 95°F.
Note: If your batteries will also be placed outside, consider their working temperature ranges as well. For instance, lithium iron phosphate (LiFePO4) batteries should not be charged below freezing unless they have low-temperature charging protection.
If your battery monitor will be placed on a boat or in another environment where it could get wet, pay attention to the IP rating of the monitors you’re considering. For instance, the Victron SmartShunt has a new IP65 version which is rated for use in marine environments.