Frequent Questions: Charge Controllers

Charge Controllers
Do I have to shut off the charge controller when I connect to shore power?
You can have multiple sources charging the same battery bank at the same time.  Whether it is shore power, an alternator, a generator, solar panels, etc., it doesn’t matter.  Connect them all.  Run them all at the same time.  No additional protections or switching of any sort are necessary.  Chargers of all types are protected against reverse current flows and base their output on the voltage of the battery bank they are charging.  When a battery is getting charged by any source, it’s voltage will go up proportional to the amount of current being fed onto that battery.  In some situations where you have a particularly strong charging source, like an alternator or shore power, the high current fed onto batteries will drive the battery voltage up to the point that the solar charge controller thinks the battery is full.  When that happens, the solar charge controller will temporarily stop charging until the voltage returns to a lower level.

What charge controllers do you sell? 
We mainly sell Blue Sky Energy brand charge controllers because of their proven performance in RV applications.  We offer both PWM and MPPT charge controllers to satisfy a wide variety of customer needs.  Decades of experience have taught us what works and what doesn’t work in an RV.  The goal of our charge controllers is to maximize battery lifespan and improve system usability.

What is the difference between PWM and MPPT? 
PWM type charge controllers are simpler and less expensive than MPPT type charge controllers.  MPPT type charge controllers have the ability to convert excess panel voltage into higher charging amps, which means that they will produce about 15% more power than PWM type charge controllers.  Read more about this on our Charge Controllers page.

What charge controller should I use? 
Charge controller selection is based primarily on the panel wattage and corresponding charging current.  For every 100 watts of solar panels, assume that there will be about 6 amps of charging current.  The charge controller’s current rating needs to be greater than or equal to the total panel charging current.  For example, a system with four 100 watt panels can use a 25 amp charge controller.

Beyond the current rating, you should also consider the differences between PWM and MPPT charge controllers.  The MPPT charge controllers are usually more expensive, but can harness about 15% more power from the solar panels.

To learn more, visit our Charge Controllers page.

Can I use multiple charge controllers? 
Yes, multiple charge controllers can be used on the same battery bank.  Multiple charge controllers are used in situations where a single charge controller is not able to handle the entire output of a large solar array.  When multiple charge controllers are used, communications cables connect the charge controllers, and help them work in unison.  Read more about this on our Charge Controllers page.

How do I repair/upgrade my Heliotrope RV30 charge controller? 
The Heliotrop RV30 was a popular two-stage PWM style charge controller that has been discontinued.  If you have one that isn’t working properly, we can connect you with an engineer who can service the unit and provide replacement parts.  Or, you might consider upgrading to a modern charge controller.  Click here for more details.

How should I adjust my charge controller settings for optimum performance? 
It is very important that your charge controller system is properly tuned for your battery bank.  An improperly set charge controller can destroy an expensive battery bank.

Tuning for lithium battery banks is the easiest because they do not require equalization nor do they need regular full charges.  The BMS (Battery Management System) handles most of the thinking for you.  But if your charge controller or converter are configured incorrectly, and the battery bank gets too high of a voltage, the mistake could be very costly.

Tuning for lead-acid (Flooded or AGM) batteries requires the most steps.  The voltage and current limits for absorption, float and equalize have to be set.  You may also have to program for automatic equalization frequency and duration.

All systems installed by AM Solar are programmed to optimize battery life.  If you have questions about how to configure your AM Solar system call or email our Tech Support at (541) 726-1091.  We will need to know the make and model of your batteries and the charge controller system you are using.

Charger Programming.png

Frequent Questions: Mounts

Do I have to penetrate my roof? 
With standard fiberglass roofs, 3M double-sided tape and Dicor sealant are usually sufficient.  On rubber roofs, we recommend using ¾” stainless steel sheet metal screws, along with the double sided tape and DiCor sealant, to ensure that your rubber roof stays bonded to the plywood structure beneath it.  Go to our Mounts page to learn more about our mounting hardware.

What will I gain by using tilting mounts? 
When solar panels are tilted toward the sun their cross-sectional surface area exposed to the sun increases.  In other words, the panel looks bigger from the sun’s perspective and therefore it can collect more solar energy.  Tilted panels also transfer more of the sun’s rays to your cells, as opposed to reflecting them off the glass.

Tilting is especially beneficial in the winter months.  In Phoenix, AZ during the month of December, a panel tilted at 30 degrees off horizontal to the south, will produce about 73%* more power on an average day than a flat mounted panel.  In the month of June, that same tilt angle will actually decrease production by 10%* since the sun is higher in the sky during that time of year.

*PV Watts analysis by NREL, 77% Derate Factor

With tilted panels comes responsibility.  If you don’t put the panels flat before driving it will be much easier for wind to rip them off of your vehicle.

Can I get an automatic tilt or tracking mechanism? 
We do not sell any automatic tilting or tracking kits, but we have run across some clever engineers who have designed automatic systems for their personal use.  It’s our opinion that these systems are certainly impressive, but reliability concerns and costs limit their practicality to a very small niche market.

Has anyone had a panel blow off? 
In all our years of working with RV solar panels, not a single panel that we have installed has blown off.  We attribute this successful track record to our well-thought-out designs, tight quality controls and attention to detail.

Frequent Questions: System

How will my alternator interact with my system? 
Our systems are designed to work in conjunction with your vehicle’s alternator.  You will not need to disconnect your solar system when charging your battery bank with an alternator.  You can have both sources running at the same time.  With lithium battery systems we occasionally install an alternator disconnect switch.

How will a generator interact with my system? 
Our systems are designed to work in conjunction with a generator.  You will not need to disconnect your solar system when using a generator to power AC loads or charging your battery bank.  You can have both sources running at the same the time.

When do I need to turn off my solar? 
The short answer is never when outside.  A well-designed RV solar power system will have a charge controller that automatically detects when your batteries are at full charge, and tapers off the charging current from your solar panels to prevent overcharging.

When stored inside a garage or covered area, you will want to turn your solar OFF at the circuit breaker (or remove fuse) to ensure the solar charge controller doesn’t become a load on your house battery bank. Your normal house disconnect switch will not turn OFF your solar.