Installing a Battery Monitor for Solar in a Camper Van or RV
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The battery monitor in a solar electrical system for a camper van conversion or RV may help you run the system safely.
Plus, knowing how many watts of solar electricity are pouring in or how much current our coffee maker is consuming gives us a thrill!
A battery monitor isn’t required.
Not in the sense that solar panels and cabling are required.
A battery monitor, particularly a good one, makes it easy to comprehend and track how you’re utilizing your battery power.
It also has a good chance of extending the life of your batteries.
We’ll go over what a battery monitor does, if you need one, and what to look for when comparing battery monitors in this article.
We’ll also recommend some of our top battery monitors for various budgets.
We provide background and how-to information so that you may make an educated purchasing choice.
Our guidelines are based on technical study and personal experience, including constructing our van on a shoestring budget and now living in it full-time.
We hope this information is useful.
Table of Contents
- Best Solar Battery Monitors for Vans and RVs
- What is the Purpose of a Battery Monitor?
- Is a Battery Monitor Necessary?
- What to Look for When Buying a Battery Monitor
- How to Connect a Battery Monitor to a Computer
Best Solar Battery Monitors for Vans and RVs
#1. Renogy 500A Battery Monitor
Our Recommendation For Almost Any Electrical System Is As Follows:
The best price-to-quality ratio
All of the features and materials of a premium Victron monitor, but at a reduced price of around 35%.
There’s no Bluetooth, but do you really need it?
This Renogy battery monitor has all of the features of a high-end Victron battery monitor at a much lower cost.
On the other hand, it avoids all of the low-cost battery monitors’ quality difficulties.
It is simple to read and use, as well as to mount.
It comes with a user handbook and an instructional video (see our guide at the end of this post).
Most layouts may be easily placed because to the sturdy build and 10-foot data wire.
We strongly advise purchasing a battery monitor for the health of your electrical system, even if it is not technically essential.
Renogy’s is our favorite because of the cost-benefit ratio.
#2. AiLi 100A Battery Monitor
The Following Is A List Of Inexpensive Battery Monitors That Will Function And Are Better Than Nothing:
It’s dirt inexpensive!
Has the following critical features: % battery life and amp current
In a terrible manner, it’s really inexpensive.
Material quality is poor, the design is poor, the paperwork is poor or non-existent, and there is no guarantee.
The AiLi battery monitor is the kind of knockoff we’ve all seen: essentially functioning but suspiciously cheap.
It tells us the fundamentals, such as the battery’s level of charge (how much power it has left), and how many amps are moving in and out of the batteries.
However, it is severely poor in all other areas. Here are a few of its flaws:
- When the current goes in or out, which might take hours at a time, the display backlight remains bright. That’s a real pain.
- There are no technical specifications and there are no instructions.
- Construction of poor quality. The shunt housing is made of plastic, which may shatter when the connections are torqued.
- The hole for installation is a non-standard 2-1/8′′ hole saw.
- There is no guarantee at all.
- Because the monitor wire is just 2 feet long, you’ll need to splice on extra cable to get it farther away from the batteries.
You’ll be ecstatic to spend so little if nothing goes wrong and you can cope with these concerns.
You’ll have to rewire things if the shunt ever breaks since you can’t draw from your batteries.
Choose AiLi’s 350A version if you’ll be operating any gadgets that might demand more over 1,000 watts.
Unfortunately, this product was not available when we designed our solar system.
We have the Victron BMV700, which is a higher-end model.
#3. Victron BMV700 Battery Monitor
High-End Battery Monitor of Choice (we have one):
Exceptional quality and dependability.
We’ve been enjoying it for the past two years.
Documentation that is simple to utilize
A higher price
Our vehicle is equipped with a BMV700.
In the van, RV, and boat sectors, Victron’s battery monitors are the industry standard.
They’re dependable and simple to use.
Installation was simple and well-documented.
It has everything you need in a battery monitor; you just have to spend a little extra for it.
The BMV700 and BMV712 are two popular models.
The primary difference is that the BMV712 includes a bluetooth connection and can show full battery information on a smartphone app.
We couldn’t justify spending $50 more on an app.
We are never more than 8 feet from the battery monitor because vans are little houses.
It is not necessary for us to check it on our phones.
#4. Simarine Pico
Shout-out to Ultra-High-Tech:
This is the futuristic battery monitor.
It’s capable of determining the levels of separate liquid tanks! You can attach a sensor to a fresh water tank, propane tank, grey water tank, or other container, and then check the water/propane levels on the monitor.
Temperature and humidity may also be shown via sensors.
A sensor might be installed inside or outside the car, in the refrigerator, in the sleeping space, and so on.
All of this may be seen on a screen and, of course, on an app.
It also serves as a battery meter in the traditional sense.
Of course, all of this comes at a cost in terms of money and installation complexity.
If you’re looking for a nerdy toy for your van, this looks like a good option (if you can get it set-up right).
What is the Purpose of a Battery Monitor?
The majority of battery monitors show (among other things):
- The percentage of the battery’s capacity that is still usable (its state of charge).
- Voltage of the battery
- The battery’s net amperage moving in and out
Battery monitors that are less expensive may only show voltage and net amperage.
For quick glances at battery status, a display screen can be installed in the van’s living area.
A shunt near your electrical components provides this data to the screen.
The shunt is a connection between two electrical components.
What is a Shunt, Anyway?
A shunt is a small device that you should keep near your battery.
The shunt monitors the voltage of the battery and how it changes over time.
A shunt is a resistor with a very low but precise resistance.
The voltage drop across the shunt is detectable, but not high enough to cause a circuit disruption.
The measured voltage drop can be scaled to show how much current is flowing (amps).
The shunt measures all current flowing into and out of the battery.
The shunt is usually connected to the battery’s positive and negative terminals.
The data is sent to the monitor display screen through the little data wire on the shunt.
At any one moment, the battery monitor displays the “net” Amp current.
For example, if your solar panels generate +10A of current and you use (-6A), the monitor will show positive 4A of current.
Battery Monitors’ Limitations
The problem is that battery monitoring isn’t a precise science.
In summary, their estimates are erroneous owing to differences in battery performance.
However, battery monitors come close and are (much) superior to nothing.
A battery monitor is sometimes likened to a car’s gas gauge, although this is a poor comparison.
The voltage and current entering and exiting the battery are used to operate the battery monitor.
However, there are several issues:
- Over time, batteries lose capacity, which the battery monitor cannot account for.
- The voltage of a battery fluctuates substantially depending on temperature, size, discharge rate, age, and how recently it was drained, among other factors.
- When you don’t know how effectively they’re being absorbed, it’s practically hard to add up the quantity of Amps absorbed.
The state of charge calculation in a battery monitor is similar to that of a gas gauge – except that the amount of gas in the tank (battery voltage) is constantly altering.
Because it was colder or hotter, the battery voltage may go up or lower.
The voltage of the battery is a moving objective.
Statistics on battery utilization are also shown on battery monitors (Amp-hours consumed).
It’s like if your automobile was attempting to tell you how many miles per gallon you were getting without knowing how fast you were going.
Manufacturers of battery monitors, of course, are aware of the difficulties.
We pay for the knowledge to program the battery monitor to compensate for these circumstances!
We suggest reading https://marinehowto.com/programming-a-battery-monitor/ for more information on how to improve the accuracy of a battery monitor.
Is a Battery Monitor Necessary?
You must safeguard your batteries.
The battery’s lifetime may be substantially shortened if the current is pulled too low.
Furthermore, batteries are costly!
If you just remember one thing from this article, it’s that you need a way to consistently verify your battery’s remaining capacity (state of charge).
Obviously, you’re curious as to how near the battery is to dying.
The longevity of your battery is severely reduced when you drain it to a low depth of discharge.
A battery pulled to 80 percent depth of discharge has a lifetime of roughly 600 cycles, but a battery drawn to 25 percent DOD has a lifespan of 1,600 cycles.
The voltage of a battery may potentially reveal its remaining capacity (state of charge).
But it isn’t that easy.
Keep in mind that battery voltage is a shifting objective.
The voltage of a battery is determined by its level of charge, but only after the battery has rested for three hours.
That implies we can’t consume power and then check the battery voltage for an exact charge status.
An unusual battery fluctuation example:
Apply a 40 amp load on a fresh new battery.
You check the battery post for 12.6 volts before applying the load.
When you apply a load, the battery voltage drops to 11 volts.
Your battery, according to the chart, is entirely drained, even if nothing is wrong.
It denotes the presence of an internal resistance in your battery.
A 12 volt 100 AH battery should have a resistance of about 04 Ohms.
Take the same battery as before.
Except this time it’s 50 percent DOD with a 12.1 volt open circuit voltage.
The battery voltage will indicate 13.7 volts when a 40 amp charge current is applied.
That would indicate to a meter that your battery is over completely charged (13.7 volts) when it is really 50% DOD.
Exactly the same.
Internal Resistance of 04 Ohm is the culprit.
Battery monitors account for these variations and provide us with estimates of capacity and consumption.
Additional Advantages of Battery Monitors
The battery monitor not only tells you how long your pricey batteries are going to last, but it also makes your day-to-day life simpler.
We like having a battery monitor because it allows us to know how many watts of solar our panels are producing.
We’ll watch how quickly it comes in, how the clouds effect the power, and so forth.
Without the battery monitor, we’d have no way of knowing how successful our solar panels are.
Another advantage is that you can monitor how much energy each load (electrical gadget) consumes.
How many watts does the coffee machine or refrigerator take, for example? If we ran out of battery power, we’d be able to pinpoint the source.
What to Look for When Buying a Battery Monitor
#1. Rated Amps
The monitors from Victron and Renogy are 500A, while AiLi sells 100A and 350A versions.
This is the maximum amount of current that can flow through the shunt.
Only get a 100A monitor if you are certain you will not be using more than 1,200 watts of power.
There aren’t many 12V gadgets that consume 100A, but 120V equipment should be avoided.
If you have an inverter, you’re likely to draw more over 100A.
Even a 1,000W inverter may demand up to 2,000W of surge power, frying the shunt.
Read our Guide to Power Inverters for more information about inverter inefficiencies and selection.
#2. Bluetooth Functionality Is Available.
The BMV712 from Victron contains a bluetooth module that allows data to be shown on their phone app.
It shows the same data that appears on the monitor’s screen and keeps statistics history.
When you pair Victron’s bluetooth battery monitor and charge controller, you get some pretty cool real-time and historical data.
Do you need assistance selecting a charging controller? We’ve thought of everything: What to Look for When Purchasing a Charge Controller
The BMV700 is around $50 less expensive and has all of the same features, however it lacks a phone app.
We had a Renogy Rover 40A charge controller and couldn’t afford the additional expense of the app, therefore the BVM700 was installed.
#3. Construction Quality
On the shunt terminal of the AiLi battery monitor, there is a plastic enclosure.
That’s a horrible design since tightening the connectors requires a lot of torque.
How to Connect a Battery Monitor to a Computer
The good news is that wiring the battery monitor is one of the simplest tasks with a solar system.
We’ve got a Victron graphic and then some instructional vids.
We’ve got a few pointers for you:
- The P (power) and B (battery) sides of the shunt are usually labelled on most battery monitors. P should be viewed as your negative battery terminal. Every single one of your power pulls is linked to P.
- Place the shunt as near as possible to the battery. Because all loads are routed via the shunt, we want to keep the wire run as short as possible.
Aside from those hints, we’ll let the makers and experts explain you how to connect each of the battery monitors we suggest.
AiLi doesn’t have a video, which is no surprise.