This post is all about the RV solar charge controller. “The what?”, you may ask. This essential component of an RV’s solar power system is seldom the focus when people talk about solar. Solar panels and battery banks seem to get top billing. But the solar charge controller is a critical element of any RV solar system, and today we’ll tell you why.
Harnessing the awesome power of the sun for your electrical needs is an amazing privilege. Because we lived and ran businesses from our RV full-time for more than 20 years (mostly while boondocking off the grid), our power needs were considerable. So we went all out in building the solar array and electrical system on our former motorhome. But some RVers only need a portable solar panel and a battery or solar generator to top off their electronics. Others need a little more than that to power their RV and a few small appliances.
Regardless of the size of your solar array and your battery bank, all you’ve gotta do is connect a solar panel to a battery, and you’ve got power, right? Not so fast! This post focuses on what’s missing in that scenario – the RV solar charge controller. We talk about what it is, what it does, how it works, and why you absolutely need it. If you’re considering powering your rig (or anything that requires power) with solar, this information is critical to your plan.
Let’s dive in…
- 1) What Is an RV Solar Charge Controller?
- 2) What Does an RV Solar Charge Controller Do?
- 3) What Is a PWM Charge Controller?
- 4) What Is an MPPT Charge Controller?
- 5) Which Type of Charge Controller is Better – PWM or MPPT?
- 6) What Are Amp Ratings on a Solar Charge Controller?
- 7) What Amp Rating Do I Need For My RV’s Solar Charge Controller?
- 8) Can I Connect a Solar Panel to My RV Battery Without a Charge Controller?
- 9) Can I Use My Batteries While They’re Being Charged With Solar?
- 10) What to Look For When Choosing an RV Solar Charge Controller
-
11)
What Are Some of the Best RV Solar Charge Controllers?
- 11.1) Victron Energy SmartSolar MPPT 100V/50 amp 12/24-Volt Solar Charge Controller (Bluetooth)
- 11.2) Renogy 30A Adventurer 12V/24V PWM Solar Charge Controller
- 11.3) Xantrex 30A MPPT Solar Charge Controller
- 11.4) Renogy Wanderer Li 30A 12V PWM Solar Charge Controller
- 11.5) Victron Energy SmartSolar MPPT 75V 15 amp 12/24-Volt Solar Charge Controller (Bluetooth)
- 12) Do I Need a Solar Charge Controller for My RV?
What Is an RV Solar Charge Controller?
With any solar power system, your energy source is the sun, and the component that harnesses that energy is your solar panel (or array of solar panels). Your battery bank is where the energy coming from your solar panels is stored.
Between the two – solar panel(s) and battery bank – you need a voltage regulator. Without it, your batteries could be damaged by excessive voltage and overcharging, and your solar panels won’t output their maximum power.
An RV solar charge controller is that voltage regulator. The rate of charge and the volume of energy going into your battery bank are regulated by your solar charge controller. Typically, it can be configured to provide the proper charging profile for your battery’s chemistry — typically flooded lead-acid, AGM (absorbed glass mat), or lithium. It’s an absolutely essential component of your RV’s solar system.
A solar charge controller sits between your solar panel(s) and your battery bank. It acts as a voltage regulator to prevent overcharging and stops the current from flowing back into the solar panels.
What Does an RV Solar Charge Controller Do?
In addition to protecting your battery bank from excessive voltage and overcharging, a solar charge controller stops the energy that’s stored in your batteries from flowing back out into the solar panel when the sun goes down.
So, it regulates the energy going into the battery bank, and it prevents the stored energy current from flowing in the other direction, (back to the solar panels), when darkness falls.
Your RV solar charge controller is the smallest, lightest component of your solar power system, but no less essential than solar panels and batteries.
What Is a PWM Charge Controller?
There are two types of solar charge controllers – PWM and MPPT. PWM stands for “Pulse Width Modulation.” In order to charge your battery bank, a PWM charge controller uses a series of short pulses (as opposed to a steady stream) of power.
A PWM charge controller is constantly checking the status of your batteries and uses that information to determine the timing and the size of the energy pulses it sends.
So, if your battery bank is significantly discharged, a PWM charge controller would send out long pulses of energy to your batteries continuously. But, if your battery bank was fully charged and there was no load on the system (i.e. you weren’t running anything requiring power), the PWM charge controller would send out only a very tiny pulse every few seconds.
As your battery bank becomes fully charged, a PWM solar charge controller will reduce the volume of power coming into the battery accordingly. Once your battery bank is fully charged, it will send out only a tiny trickle charge to keep your battery bank full. (This is often referred to as float charging.)
There are two types of solar charge controllers – MPPT (Maximum Power Point Tracking) and PWM (Pulse Width Modulation).
What Is an MPPT Charge Controller?
MPPT stands for “Maximum Power Point Tracking”. An MPPT solar charge controller takes the high-voltage power output supplied by a solar panel and converts it to a lower, more acceptable voltage so that your battery bank charges safely and without damage, and your devices and appliances are charged efficiently.
So, an MPPT solar charge controller is an electronic DC-to-DC converter that takes the high-voltage DC output from your solar panel and converts it to the lower voltage required to charge your battery bank.
In addition, “maximum power point tracking” means that an MPPT solar charge controller is constantly analyzing your solar panels and determining the exact voltage required to maximize the panels’ power output to your batteries. This changes constantly depending on the amount of light going into the panels, the ambient temperature, and other variable factors.
This is why MPPT charge controllers allow more efficient solar panel performance (by up to 30%) than PWM charge controllers. They allow the panels to operate at their optimal (higher) voltage for the conditions… and convert that extra voltage into additional charging amps.
Which Type of Charge Controller is Better – PWM or MPPT?
The answer to this question depends largely on your needs.
If you have low power needs and thus a low-power solar system, then a PWM solar charge controller would be a less expensive option and perfectly suitable. This would require that you have solar panels equaling no more than around 150 Watts and your power needs aren’t significant.
A PWM charge controller is also best for trickle-charging a battery for maintenance when it’s not being used.
Perhaps the greatest feature of a PWM charge controller is its very low voltage loss, which means that if your devices and appliances are turned off, your battery power is not being consumed.
But if your solar system is greater than 150 Watts and you have high power needs and multiple solar panels as we do, an MPPT solar charge controller is what you need.
If your RV’s solar system is greater than 150W, then you’ll want an MPPT controller. A PWM controller may be sufficient for smaller systems.
First, MPPT controllers allow for multiple solar panels to be wired together in series (increasing the voltage output), creating a very significant solar array. They also give us greater control with a large solar system and can utilize the maximum output from our solar panels (which a PWM charge controller would not be able to do). For anyone with a larger solar system, MPPT solar charge controllers provide up to 30% more efficient than PWM controllers.
So, while MPPT solar charge controllers are more expensive, they’re also more efficient in an application like ours, and thus the greater cost balances out with the greater efficiency.
Depending on the degree of sunlight and ambient temps, a PWM charge controller may produce anywhere from 65% to 85% efficiency (they’re actually best in sunny, warm climates) while an MPPT controller will provide maximum efficiency coming from a generous solar array, even in climates where ambient temperatures are cool.
To summarize this PWM vs MPPT discussion, if you’ve got a 100-150 Watt solar panel you’re using to keep your RV’s house battery topped off and you generally travel in fairly warm, sunny climates, a PWM solar charge controller may be perfectly sufficient for you, and they’re a simpler (fewer parts) and less costly option.
But, if you’re looking to supply more than around 150 Watts from your solar panels to your battery bank, or if you’re looking to connect multiple solar panels in series, you’ll want an MPPT controller to do the job.
What Are Amp Ratings on a Solar Charge Controller?
An amp is a unit of electrical current, and all solar charge controllers have a maximum amp rating. The current rating is the maximum charging current the solar charge controller can supply to the attached battery bank. However, the power rating of solar panels is measured in Watts and is determined by the output current and voltage (for most RVs, the battery-charging voltage is either 12V or 24V).
An equation to bear in mind when determining the appropriate amp rating for your RV’s solar charge controller is amps × volts = watts (and its corollary: amps = watts ÷ volts).
For example, a 30-amp (30A) charge controller with a 12V output can handle up to 360 Watts (30A x 12V). That same charge controller (30A) charging a battery bank with a 24V output will be capable of charging up to 720 Watts (30A x 24V).
The Xantrex inverter-charger control panel in our old motorhome.
What Amp Rating Do I Need For My RV’s Solar Charge Controller?
The general rule of thumb for determining the appropriate amp rating for an RV solar charge controller is to select one that is 25% higher than the total peak power amperage of your solar array. The additional 25% is due to the fact that, under certain conditions, your solar panels may produce more than their rated output. Having room for 25% additional charging capacity will accommodate those conditions.
Remember that the amp rating is the maximum charging current (or maximum amperage output) to the batteries. Remember also that amps x watts = volts. This allows you to calculate the charging current of your solar panels in amps by using the equation watts ÷ volts = amps.
You can find the maximum rated power of a solar panel in watts on the back of the panel (or in the spec sheet or manual that comes with it). You’ll also see the maximum power voltage expressed in volts. You’ll want to calculate the current your solar panel produces at its maximum power. You can calculate the current in amps by dividing watts by volts.
Now let’s say, for example, you have two 100 Watt solar panels with a peak power output of 6 amps each. Wired in parallel, 6 amps x 2 panels means your two solar panels will produce 12 total amps. In this case, you’ll want a solar charge controller rated for 25% more, so you’d want a minimum of a 15A controller (note that in this particular scenario, buying a 20A charge controller would allow you to add another solar panel in the future, should you desire to do so).
To make this easier, many solar panel kits come with the appropriate solar charge controller as determined by the manufacturer.
Can I Connect a Solar Panel to My RV Battery Without a Charge Controller?
If you want to use a solar system to power your RV, you will absolutely need a charge controller. Without it, you’re very likely to damage your battery bank due to the overcharging that’s likely to occur because the panels alone are not capable of limiting or regulating the voltage going into your batteries.
It should be noted that in theory, you can connect a very small solar panel (no more than 5 Watts) directly to a battery for the purpose of trickle charging the battery for maintenance purposes while in storage.
Every RV solar system needs a solar charge controller. The only time you might be able to get away without a charge controller is when using a tiny solar panel to trickle charge a battery.
Can I Use My Batteries While They’re Being Charged With Solar?
You can certainly use your batteries while your RV’s solar system is charging them. You can use the power/electricity in your RV (taken from your battery bank) while the sun continues to send more energy to your solar panels, and your panels (through the solar charge controller!) continue to charge your battery bank.
What to Look For When Choosing an RV Solar Charge Controller
There are a number of features to look for when choosing an RV solar charge controller. We’ll take a look at those features, in brief, followed by five excellent choices of solar charge controllers on the market today.
Quality
The first thing you want to consider when shopping for an RV solar charge controller is quality. You want a charge controller from a manufacturer recognized in the industry as a provider of quality solar components, with a strong historical reputation for both products and customer service, and a warranty to back it up.
Poorly made solar charge controllers can create electrical noise that interferes with the electronic frequencies of devices in your rig. So, be certain to only buy a charge controller that is UL-certified. UL (Underwriters Laboratories) is an independent, nonprofit organization that tests electrical components & equipment for potential hazards. UL-certified solar charge controllers have been tested by UL and meet its safety requirements.
Remote Monitoring Ability
The ability to monitor your system remotely can be very important. Some solar charge controllers come with a Bluetooth feature that lets you download an app to monitor the system from your smartphone, up to 30 feet away.
Many RV solar charge controllers offer remote monitoring via Bluetooth through the manufacturer’s smartphone app.
This means that you can be sitting in the comfort of your RV, or even outside your RV, and you’ll be able to actually see the current flowing through your controller to your battery bank, check the voltage regulation, and take a look at how much power your solar panels are generating.
Some charge controllers provide a monitor panel to be installed in your RV so that you can check the activity of the controller from there. Some monitors allow you to log in remotely to check on the functioning of your system.
Adjustable Voltage Setpoints
Adjustable voltage setpoints let you tune the charging voltage to match the type of battery you have, whether it’s lead-acid, AGM, gel, or lithium-ion. In some controllers, you simply select the appropriate battery type, and it has the correct charging parameters pre-programmed. Other controllers may allow you to manually configure custom charging voltages for each charging stage. Either works.
On/Off Switch
An on-off switch is extremely handy because it lets you turn off the charge controller whenever you want to stop charging your batteries. Without this feature, you’ll need to remove the fuse of the battery bank anytime you want to turn off your RV solar charge controller, or wire in your own on/off switch.
Ability to Easily Switch from Shore Power to Dry Camp Mode
This is an interesting feature that lets you adjust the battery charge set point based on how you’re camping. If you’re boondocking, you’ll want to be charging to maximum capacity. But when you’re connected to shore power, you can switch to standby mode. You can also use stand-by mode to help maintain your batteries when your rig is in storage.
What Are Some of the Best RV Solar Charge Controllers?
Let’s take a look at five excellent RV solar charge controllers in several budget ranges, and the features they offer.
Victron Energy SmartSolar MPPT 100V/50 amp 12/24-Volt Solar Charge Controller (Bluetooth)
The Victron Energy SmartSolar MPPT charge controllers are among the most popular models on the market. This particular model is a 100-volt, 50-amp charge controller for 12V and 24V battery banks, making it suitable for up to 700 Watts of solar panels at 12V or 1,400 Watts at 24V.
The SmartSolar feature allows your batteries to be charged to full capacity very quickly (the manufacturer states it can operate with a battery voltage as low as 0 volts, meaning it can recharge a deeply discharged battery as long as the cells aren’t permanently sulfated or otherwise damaged). This charge controller also has an internal sensor that gauges the ambient temperature and compensates accordingly.
It has built-in Bluetooth, allowing you to configure and monitor the charge controller through the VictronConnect app on your smartphone or tablet.
Reviews for this Victron SmartSolar MPPT controller are stellar.
- SMART SOLAR CHARGE CONTROLLER: Solar charge the smart way with the Victron Energy SmartSolar MPPT charge controller, to ensure that every ray of...
- MAXIMIZE POWER OUTPUT: With lightning-fast optimum power point tracking and intelligent charge algorithms the Victron MPPT solar charge controller...
Renogy 30A Adventurer 12V/24V PWM Solar Charge Controller
The Renogy 30A Adventurer automatically detects whether your system is a 12V or 24V DC system, and offers Smart 4-stage PWM charging while protecting against overcharging, reverse current, reverse polarity, and short-circuiting. This unit flush-mounts to your RV’s wall, and the easy-to-read LCD screen displays solar charging and battery operation information, plus more, with customizable parameters.
This is a negative ground controller with adaptability for AGM, gel, flooded, and lithium-ion batteries.
- 𝐒𝐦𝐚𝐫𝐭 𝟒-𝐒𝐭𝐚𝐠𝐞 Renogy Solar Charge Controller- PWM controller can automatically detects 12V/24V systems & charges...
- 12v Solar Charge Controller for RV- 𝐃𝐞𝐬𝐢𝐠𝐧𝐞𝐝 𝐟𝐨𝐫 𝐬𝐞𝐚𝐦𝐥𝐞𝐬𝐬 𝐑𝐕...
Xantrex 30A MPPT Solar Charge Controller
The Xantrex 710-3024-01 MPPT 30A solar charge controller offers an industry-leading 98% charging efficiency as well as dual-battery bank charging that allows you to simultaneously charge and maintain your house batteries and your rig’s starter battery.
A leader in the solar industry, Xantrex offers best-in-class protection for your batteries. This solar charge controller supports house batteries that are AGM, gel, flooded, or lithium-ion phosphate (LiFePO4).
- Advanced Maximum Power Point Tracking (MPPT) technology increasing daily energy harvest by 20-30% compared to PWM technology
- Dual-battery bank charging to simultaneously charge house and starter batteries
Renogy Wanderer Li 30A 12V PWM Solar Charge Controller
Renogy’s Wanderer automatically detects your 12V or 24V DC system voltage and offers Smart 4-stage PWM charging (Bulk, Boost, Float, and Equalization). Like the Adventurer, it provides intelligent protection against overcharging, reverse current, reverse polarity, and short circuits. Its simple interface is easy to use and offers multiple LED indicators of charge status and battery information.
The Wanderer is adaptable to AGM, gel, flooded, and lithium-ion batteries.
- 12V Universal Solar Charge Controller- Renogy Solar controller optimizes charging for 𝐋𝐢𝐭𝐡𝐢𝐮𝐦, 𝐀𝐆𝐌, 𝐆𝐞𝐥, &...
- 𝟒-𝐒𝐭𝐚𝐠𝐞 PWM Charging Controller 𝐰𝐢𝐭𝐡 𝐅𝐮𝐥𝐥 𝐏𝐫𝐨𝐭𝐞𝐜𝐭𝐢𝐨𝐧- Lithium solar charge...
Victron Energy SmartSolar MPPT 75V 15 amp 12/24-Volt Solar Charge Controller (Bluetooth)
Victron’s SmartSolar MPPT 75V, 15A solar charge controller is another feature-rich Victron product that’s very similar to the Victron SmartSolar charge controller noted above, though it’s a 75-volt, 15-amp charge controller. This charge controller also has built-in Bluetooth for remote configuration and monitoring via the VictronConnect app on a smartphone or tablet.
Victron uses a sophisticated 3-stage charging method that includes a float charge. This charge controller is highly recommended by 93% of 4- and 5-star Amazon reviewers.
- SMART SOLAR CHARGE CONTROLLER: Solar charge the smart way with the Victron Energy SmartSolar MPPT charge controller, to ensure that every ray of...
- MAXIMIZE POWER OUTPUT: With lightning-fast optimum power point tracking and intelligent charge algorithms the Victron MPPT solar charge controller...
Do I Need a Solar Charge Controller for My RV?
If you intend to harness the power of the sun using solar panels to store energy in your RV’s battery bank, then yes, you will need an RV solar charge controller that is consistent with your system.
Free RVing Tips, Tricks, Reviews & Giveaways
As 20-year full-timers, we share everything we’ve learned about RVing over the years. Join our online community to receive a wealth of great RVing knowledge delivered daily to your inbox.
Whether you’re a new RVer or a seasoned full-timer, you’ll love the wide range of RVing topics we cover. Don’t miss a single article or any of our famous Giveaways. Subscribe to our newsletter today!
Sam
Wednesday 1st of March 2023
Do you have to winterize your RV solar panels? If so how?
Brad
Saturday 28th of January 2023
If a B van has a 190 watt panel and a 10amp PWM solar charge controller, as well as a port on the side of the van for plugging in an external portable panel, will the external panel charge the 200Ah lithium battery bank? Will it be regulated by the 10amp controller/charger? What if the external panel has its own controller? An owners manual says: "When installed, a 10 amp solar charging system includes 1 - 10 amp solar controller and 1 - 190 watt solar panel. This factory-installation is wired with 10 gauge wire from the solar panel to the solar controller and to the auxiliary battery(ies). Due to controller capacity, it is not recommended to add additional solar panels to this system." Thanks, Brad
TheRVgeeks
Saturday 28th of January 2023
Hi Brad. You'll likely want to get out a multimeter and do some inspections to find, and follow, the wires from the port on the side of the RV to see where they go (try using the multimeter on the prongs in the port... if you read +/- 12V on them, they probably go straight to the batteries... if the charge controller was inline, you wouldn't get a reading at all). But, in all likelihood, it does NOT go through the built-in solar charge controller. You'd either need to have ground-deploy panels that come with their own built-in charge controller (check out our portable solar panel post)... or you'd need a dedicated one for any ground-based panels you use.
The limitation on the 10amp controller your van manufacturer installed is probably why they also installed the port for additional, ground-deploy panels.
Rich Fulton
Tuesday 4th of January 2022
Thanks for the great info. I don't understand when you said "But when you’re connected to shore power you can switch to standby mode". Is this required or just desirable? Is there damage if you don't? How is this done? I have 400W of Zamp solar on my trailer and a Victron Smart 150/35 solar controller installed last year. They did not say anything about the need to manually switch to "standby mode" when I'm plugged into shore power. I assumed it's all fine and automatic regardless of whether I'm on solar or shore power. They did install a manual solar panel cutoff switch to do this if needed....is that what you mean by "standby" mode?
TheRVgeeks
Tuesday 4th of January 2022
Hi Rich. That "Standby" feature is available on some charge controllers... but not all (our Xantrex doesn't have it... and probably not Victron, either). But you don't need it... even plugged in and the converter/charger running, the solar charge controller will adapt. When the battery is full, both charge controllers should shut off.
On the plus side... when staying in a park for a long-term stay (where you might be paying for separate, metered electric), having the solar on can help to offset your electric bill.
Don't worry about it... you'll be just fine.
Vic
Monday 3rd of January 2022
Any thoughts on the GoPower charge controllers and solar arrays? They appear to be conspicuously missing from your list of reviewed products. Thanks.
TheRVgeeks
Tuesday 4th of January 2022
Hi Vic. GoPower would've been next on the list (but we had to cut it off somewhere, right?). Nikki & Jason Wynn had GoPower solar on their RVs and had very good experiences with it.
Brad Wartman
Friday 31st of December 2021
My rig has 3 sets of solar panels, 2 portable panels:
1-ZAMP 120W, PWM controller 1-Dokio 300W, MPPT controller
and 1 fixed array:
350 watts, Blue Sky MPPT solar controller.
Our battery bank is 2 SOK 206 Ah batteries connected in parallel (12V, 412 Ah).
Can I connect all 3 sets of panels at the same time to charge the batteries? So far the fixed array (with occasional generator use) has been good enough to keep the batteries charged but I'd like to have the option to add the portable panel(s) if needed (for cloudy days, when parked in shade, etc.). Thanks!
TheRVgeeks
Friday 31st of December 2021
P.S... that is assuming that all three solar charge controllers can be set/configured to use a Lithium-compatible charge cycle, since your SOKs are LiFePO4. If not, don't connect that charger to the system, as it could over-charge the lithium batteries.
TheRVgeeks
Friday 31st of December 2021
Hi Brad. Good question! Technically, yes... there shouldn't be any problem connecting all three charge controllers to the batteries and letting 'em run. They should all see the same voltage at the batteries and run their charging cycles. But... you may notice that one or more of them cut out a bit sooner, depending on slight variations in the voltage they "see" the battery being at (i.e. the output from one charge controller could make one/both other controller think the voltage is high enough for it to stop charging), differences in their electronics, and/or the actual point they're connecting to in the electrical system. But, honestly, even if it happens, it shouldn't be an issue. It's likely to only occur when the battery is very near fully charged.