A SOLAR CHARGER is a Key Element of Your Power Solar System.

A solar charger has to be integrated in your power solar system.

This is after you have a fairly good idea of your daily usage of energy while boondocking and you established how many solar panels you need.

The function of the solar charger is to monitor the voltage produced by the panels keeping it at the right level to charge the batteries efficiently.

It also prevents the discharge of the batteries having a reverse flow of current at night when the panels are not producing energy.

During the charging process, the solar powered battery charger will reduce the charge rate as the house batteries approach full charge transferring only what they can handle without overcharging.

The solar charge controller is connected to the battery bank located in another storage compartment with the precaution of adding solid support underneath the batteries due to the extra weight.

It is important to place the controller as close as possible to the battery bank, in a location where its display can ideally be read. If it is not feasible, many solar controllers have the option of a remote display.

Knowing that 12 volt solar panels deliver 16-18 volts to the battery bank, you need this solar charger to control the energy into a form usable to charge the 12-volt house batteries at a 100 % charge without overcharging.

The solar charger is a high-end regulator designed to be used with a solar array.

There are really only two types of solar chargers worthwhile to mention with the use of higher voltage panels.

Both are multistage chargers with special technology:

1 ) the P W M (or Pulse Width Modulation) controller

The PWM is a technology used in many multistage charge controllers

This type of controller is very common.

Instead of tapering off the current as the battery is getting close to full charge, it keeps the full current but varies the length of time it is applied.

It uses very rapid pulses, usually in microseconds.With PWM, the current varies depending on the discharge level and condition of the batteries.

2) the M P P T (or Maximum Power Point Tracking) controller

This is a new technology done with the help of a microprocessor that a few controllers have adopted.

Somehow it provides a boost or a conversion of excessive voltage (when available) coming from the solar panels into additional current (amperage) for more rapid battery charging.

The current increase is very variable and depends on the level of discharge, the battery temperature and the intensity of the solar light.

It seems to be more pronounced in the winter season, exactly the time when we need a boost, when the sun is low, it is colder and the batteries are more discharged.

This increase can be 30 % or more. It can maybe save the purchase of an extra panel. The MPPT controllers are excellent devices and highly appreciated by boondockers.


Every solar charger is rated with maximum amperage.

Knowing that it is highly probable over time that you will have this desire to expand your solar array in adding another solar panel, it is very important to keep that in mind when you select your controller.

You do not want to have to replace your controller because you are installing another panel.

My suggestion is to buy a model that will serve you well now and for tomorrow. You may pay a bit more extra but you will not regret it later.

A MPPT controller costs between $250 (25-40 amp) to $600 (80 amp).

It is also suggested to get the option of a temperature sensor that will monitor the battery temperature and will adapt the charging algorithm to compensate accordingly. It is installed on the side of the battery or on its post.

You may have two temperature sensors: one for the solar charger and the other for the inverter/charger

LED readouts that display information like amperage being produced, DC loads, battery voltage etc.. are very useful.

The remote display is very convenient so you do not have to open a compartment to have visual access.

PROVIDERS of solar powered battery chargers:


  1. to estimate a solar panel output, use an average of 5 hours of sunlight per day for the calculations
  2. as a guide, you need 1.5 watts of solar panel output in the northern hemisphere for every 2 amps of battery bank capacity
  3. buy solar panels with the highest rated peak power (voltage)
  4. tilting the panels at the right angle depending of your latitude will give you a real gain (up to 30 %) in winter when the sun is low
  5. there is always a 5 to 10 % tolerance factor in the production of solar panels you have to take in consideration. Opt for the 5%
  6. when the solar panels get too hot, they loose their efficiency. The testing temperature is 77 F/25 C, a lot cooler than the reality in the southwest desert
  7. use the proper gauge of cable to limit the voltage drop (#4 welding cable)
  8. as a guide, remember that most 'boondockers' who want to live comfortably will use 100-120 Ah of energy daily that they have to replenish.
  9. every amp used, factor a need of 1.2 amp to return
  10. buy a solar charger or regulator that will give you the capability of future expansion of your system

OTHER TOPICS ( 4 total) directly related to SOLAR/WIND POWER

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