Solar Panels and Charge Controllers

JASPak Solar Generator Solar Power Panels

To generate and use solar power, you need to have a solar panel and a solar panel charge controller.  Perhaps the most expensive parts of any solar system, these two components collect and manage the collected power to keep your system charged and running.  Our JASPak Portable Solar Generators use panels from 100 watts to 300 watts. We only use monocrystalline panels and our larger panels are made in the U.S.A.! For controlling the power from our panels, we use PWM and MPPT solar charge controllers.

The Solar Panel

By it’s very nature, the solar panel itself is not a very intelligent component.  It simply sits in the sun and individual solar cells collect the suns energy and convert it into electricity.  These individual cells are wired together to provide the total voltage, current and wattage that is displayed in the specifications.  One of the first decision factors in choosing a solar panel is the cell and how it is made.  Today, the primary technologies are monocrystalline and polycrystalline.  Poly or Mono cells are techniques on how the cell was built.  Both are made out of silicon.  The mono cell is cut out of a single crystal and the poly is cut from many crystals fused together.  A brief review of their qualities:



Crystal Composition

Single Crystal

Many fused crystals


Very dark/black

Light blue/marbled











Actual Solar Power

We are asked all of the time – why does the JASPak Portable Solar Generator come with such large solar panel options like 300 and 520 watts?  The answer is simple – what good is an emergency backup system if it can only be used once every 30 or 40 hours of sunlight?  Once the battery has been depleted, it has to be recharged before it is useful again, and if it is a battery of decent size (110Ah or more), smaller solar sizes are simply not going to do that in one day.  Even a 200 watt panel will have a hard time achieving that.

First, a bit of honesty – any advertised wattage for a solar panel is based on laboratory conditions that will likely never be met in the real world.  The best power that we have seen from real-world use on our 300 watt panel has been 240 watts at 31 volts and 7.7 amps.  For math and planning purposes, we use 225 watts as our solar panel wattage.  70% to 75% is what you can expect from ANY panel out there.  So, when you see a system with a 60 watt solar panel – it is really going to be about 40 or 45 watts. All of our recharging calculations are based on 75% of rated solar panel wattage so you actually get what we advertise!

Second, the solar panel SHOULD BE MATCHED TO THE BATTERY AND CHARGE CONTROLLER.  A solar generator system can boast a HUGE 250Amp-hour battery, but yet only be shipped with a 150 watt solar panel.  Sure, that battery is going to last 24 or 36 hours – but it will take several days to recharge.  While it is recharging, your system cannot provide you with much power, if any at all because you need to reserve all of the power to go the battery.

The JASPak Portable Solar Generator product line is built with matched battery sizes, solar panel sizes and charge controller sizes and designed to bring just about every system to a full charge at the end of every sunny day…even with a load on the system.  Our average 24 hour test scenario for our 300 watt system involves use of a 27″ tube television, cable box and 18.2 cubic foot refrigerator.  We use the television and cable box for several hours and keep the refrigerator plugged in and running for the entire 24 hours.  We start our tests at 8pm – after the sun has gone down to simulate the worst case scenario for a solar generator.  By 8:30am, we will have used about 50% of our battery.  By 5:30pm, after a day of sunshine – we have recharged our system to 100% AND ran the refrigerator ALL DAY!  That is what a matched system can do!  Our panel and charge controller produces about 1500 kilowatt hours, or about 110Amp-hours in a day.

What If There Is No Sunshine?

The question has to be asked!  The Achilles heel of the solar industry – NO SUN!  Yes, it is true, if there is no sunshine, solar power is difficult to produce.  On a cloudy day with no visible shadows or direct sunlight, we have seen our panel produce 0 to 45 watts.

On the same topic, let us tell you about shadows!  When you put your solar panel out in the sunshine, you will see immediate wattage production.  It is instant and plentiful!  Now, let just one tree branch cast a shadow on one cell in the panel and watch it fall in an instant.  Put your hand in front of the panel and you get the same instant loss of power.  Your panel MUST be in 100% sunshine to produce maximum power.  The slightest bit of coverage and you will lose most of your power immediately.  Why? Well, there are entire college courses on this, but the simple explanation has to do with the fact that several solar cells are connected in series and “feed” each other.  Each cell is producing current.  When one cell is shadowed and not producing the same current as the others – they all fall to the lowest producing cell.  Again, that is the simple explanation and this is informational.  If you would like to learn more, search for topics on Solar Panel Hot Spots.

Solar Tracking

While it may seem to be common sense to aim your solar panel at the sun, you may learn that aiming at different angles can produce different levels of power.  This is called solar tracking.  The JASPak Portable Solar Generator solar panels feature a full-tilt axis to allow for simple and easy solar tracking.  As the sun rises and sets, you will find that you can get better performance from the solar panel if you tilt it towards the sun and track it’s progress across the sky several times a day.  This is one of the advantages of a mobile panel.  Many other mobile panels are simply set at a 45 degree angle and you get what you get.

The Charge Controller

Collecting the power of the sun is a magnificent feat all by itself, but now that it is collected, how do we manage it and charge our system?  We use a charge controller.  The controller regulates the voltage generated from the solar panel and works to properly maintain the battery while protecting it from being over and under charged.  As with the solar panels, there are choices to make in charge controller technology.  There is PWM and MPPT.

PWM, or Pulse Width Modulation technology is similar to high quality battery chargers. When the voltage of a battery reaches the regulation setpoint, the PWM algorithm slowly reduces the charging current to avoid heating and gassing of the battery, yet continues to return the maximum amount of energy to the battery in the shortest time.  Although PWM was considered HUGE progress in solar battery charging, MPPT has gone even further. PWM still serves a very important segment of the solar industry and is best utilized with systems using panels matched to the batteries they are recharging. An example is using panels that produce 18-22VDC to a battery that is 12VDC. Panels that produce voltages over 28VDC will simply be wasteful and better managed with an MPPT charge controller.

MPPT, or Maximum Power Point Tracking goes beyond PWM charging and takes any additional “un-usable” voltage and further converts it into higher amperage.  To simplify this statement, we use the following math.  To charge a 12VDC battery, let’s say you need an 18VDC supply.  A PWM charger will provide your battery that 18 volts at the available amperage.  If that PWM controller gets more than 18VDC from your panel, it is simply thrown-off, or wasted and not used.  The MPPT controller will take that extra voltage over 18VDC and simply convert it into higher amperage at 18v which results in a faster charge time for your battery.  MPPT controllers provide increased efficiency, higher amperage and overall better battery management than PWM controllers when dealing with higher solar panel voltages.  While MPPT controllers do cost considerably more than PWM, the efficiency gained in performance and charge time are well worth the investment.