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.

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