Do It's Education Center
Subsidiary of Do It Homestead Inc.

"Mr. Solar's Solar Electric Course"

Session # 11 - Controls & Switches



UL Listing:

Please read and study Chapter 7 in your text book.


- Over Voltage Protection:

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Sun Selector
Cruising Equipment Company

Charge Controls

Charge controllers or voltage regulators protect batteries from becoming overcharged, which can shorten their lives as well as the lives of some loads powered by them. Electronic circuitry in the regulator measures battery voltage, which rises as the battery state of charge increases. At some voltage, which will be different for different types of batteries and at different temperatures, the regulator will stop the charging of the battery. When the charging stops, the battery voltage begins to fall At some preset lower voltage, the regulator allows the charging to resume. Regulators for photovoltaic, wind and water power systems perform the same function as voltage regulators in automobiles, but they do it in different ways. Automotive regulators are not suitable for use in remote power systems.

All of the charge controllers use electronic circuitry to measure battery voltage, but there are two different methods of actually controlling the large amounts of current coming from the charging source. Some controllers use electromagnetic relays and some use solid state power transistors for this function. There are advantages and disadvantages to both methods, but in my years of use we have found both to be very reliable.

How Controllers Work and Options

The circuitry in a controller reads the voltage of the batteries to determine the state of charge. Designs and circuits vary, but most controllers read voltage to reduce the amount of power flowing into the battery as the battery nears full charge. Features that can be included with controllers include:

Some systems require all of these functions, others require only one or a certain combination.

Sizing a Controller

Charge controllers are rated and sized to the systems they protect by the array current and voltage. Most common are 12, 24 and 48 volt controllers. Amperage ratings run from 1 amp to over 100.

For example, if one module in your 12 volt system produces 3.5 amps and four modules are utilized, we produce 14 amps of current at 12 volts. Because of light reflection and the edge of cloud effect, sporadically increased current levels are not uncommon. For this reason we increase the controller amperage by a minimum of 25% bringing our minimum controller amperage to 18.7. Looking through the products we find a 20 amp controller, as close a match as possible. There is no problem with going to a 30 amp or larger controller, besides possible additional cost. If you think the system may increase in size, additional amperage capacity at this time should be considered.

On small systems where a 10 watt or smaller module charges 100 amp hour battery or larger, no regulator is required. Typically this module to battery ratio cannot overcharge the battery.

Heliotrope General Series Type Charge Controller


The series type design of charge controller without a relay is accomplished with the use of POWER MOSFETS. Because the life of the MOSFET is not decreased by frequent on/off switching as with a relay a different charging strategy can be employed. When the full state of charge in the battery is reached with a relay type controller the incoming current shuts off the charging sequence and the battery voltage immediately drops.

With the PWM Taper Charge, Pulse Width Modulation, the state of charge voltage is maintained by frequently switching on and off the photovoltaic current source. The PWM type charge assures that the battery is kept at the fullest possible charge. After the preset voltage is maintained a float or trickle charge is effected to offset the losses expected in a inactive system. Heretofore series type charge controllers have utilized relays to turn on and off the charging sequence of the photovoltaic array to the batteries. Relay reliability is severely affected by the frequent switching of high DC current loads because of relay life concerns the relay series type of charge controller do not bring batteries to their fully charged state of charge as with the Pulse Width Modulated or PWM type charge controller. Unique to the CC-60E is an over temperature shutdown indicator light.

When the charging rate exceeds the heat dissipation capabilities of the unit, the unit stops the charging sequence. When this happens there is no further heat build up as in shunt types and cooling occurs allowing the unit to turn back on. The indicator light shows when this over temperature situation exists and addition of cooling via heat sink or fan will prevent this stopping of the charge sequence. Protection of all the electronic components due to overheat is accomplished which is impossible with shunt-type controllers. The CC-60E delivers maximum reliability by eliminating the relay and positively prevents overheating.

Heliotrope's Charge Controller Features

This breakthrough POWER MOS FET design, the CC-60E, includes the following features; - Field select able 12 or 24 Volt - 60 Amp Schottky type blocking diode - Sixteen different battery charged voltage levels are field select able from 13.5 to 16.5 in .2 Volt increments of 12 for 24 V - Low battery voltage warning light with remote audible warning capability. This low battery voltage threshold is field select able at 10.5 or 11.0 Volts. - Battery Temperature Compensation of 3MV/~C/Cell - Pulse Width Modulated or PWM charging occurs when full battery state of charge voltage is approached. This feature guarantees that the batteries are fully charged when PV power is available - Float charge continues after the selected state of charge voltage has been reached - Indicator light for charging, charged, low battery voltage warning, over temperature shut down, and low voltage disconnect - 250 MCM lug size for PV and battery connections - Reverse polarity connection protected - Protected against accidental short to ground while user is wiring any of the options - Size: 11 X 9 X 3.75 inch

CC - 30 Charge Controller, 30 amp maximum
CC-60E Charge Controller, 60 Amp maximum
CC-120E Charge Controller, 120 Amp maximum

Heliotrope's FPC-15

The FPC-15 is a POWER MOS-FET design, 15 Amp photovoltaic series type, battery charge controller with out a relay. The FPC-l 5 is rated for continuous duty at 15 Amps. The FPC-l 5 will charge your battery bank to the fullest possible charge from the photovoltaic array with the least amount of water consumption. The breakthrough POWER MOS FET design, the FPC-15 includes the following features:

Sun Selector Charge Controls

M-8 and M-16 micro charge controllers are designed to control charging currents of up to 10 or 18 amps respectively. Both units can charge any number of parallel batteries. A minimum OPEN CIRCUIT Panel Voltage, the battery voltage + 15 VDC, is required for the unit to charge properly.

The M-35 and M-60 Sun Selector 35 and 60 ampere photovoltaic charge controllers are ideal when using a large PV array. The units provide photovoltaic control, mercury contactor switching, and convenient DC terminals. The units can process a nominal 35 or 60 amps of charging current, respectively.

The NDR-30 has a limited, lifetime warranty. It is a dedicated photovoltaic charge control device. It eliminates the need for internal or external blocking diodes, and provides exceptional throughout efficiency while charging lead acid batteries in a manner that will optimize the available limited charging period.

There are five LED status indicators which can give a large amount of information about the status of the PV system. These LED's are labeled as follows:

The Sun Selector M-2 micro charge controller is ideal for very small systems which still need battery protection, but can't afford parasitic power drain by the charge controller. The nominal input current rating is 2 amps or up to 4 amps surge, and the maximum input VOC is 25 VDC in 12 volt unit ; 50 VDC in 24 volt unit.


The Enermaxer is the only controller that will work with a combination of charging sources such as photovoltaic modules, wind generators, water turbines and even battery chargers powered by generators. It can do this because it is a parallel shunt regulator that draws power from the battery and sends it to a load.

By automatically controlling charging sources of up to 120 amps at 12 or 24 volts and up to 60 amps at 32, 36 and 48 volts, the Enermaxer can manage moderate to large power systems. If more power control is needed, additional Enermaxer's and diversion loads can be added for more power regulation.

Circuitry in the Enermaxer continuously measures battery voltage. If the voltage is lower than the float voltage setting, the regulator stays off and all of the incoming power goes directly to the battery. As the battery charges, its voltage increases. When the battery voltage reaches the float setting, the Enermaxer turns on only enough to keep the battery at float level. When the battery is fully charged, most of the incoming power is diverted and only the small amount of power needed to maintain the optimum float voltage is allowed to flow into the batteries.

Power not needed by the battery is diverted to perform useful work. It can be used to heat water, run pumps or fans or any DC load that can run on a variable voltage. A load that draws as much current as the maximum possible charging amperage must be provided for the Enermaxer to work. A 100 amp load is the maximum that each 12/24 volt Enermaxer can regulate. Order diversion loads below.

Float voltage is the precise voltage at which the battery will last the longest and store the most charge. Different types of batteries have different float voltages and as lead acid batteries age, their optimum float voltage decreases. Optimum float voltage also changes with battery temperature. The Enermaxer allows you to set the float voltage at the right level to get the maximum life and usefulness out of a set of batteries. The Enermaxer has a 2 year warranty.

Specify voltage when ordering system voltage.

Water Heating Elements for Diversion Loads

The 25 and 40 amp elements have 1 inch pipe threads for mounting in most electric water heaters. The 15 amp elements have 3/4 inch male pipe threads. Mounting in a standard electric water heater will require a threaded adapter or a flange adapter.

Air Heater for Diversion Loads

Heating elements are mounted in an 18 x 7 x 7 inch aluminum box with a fan to disperse the heat. Order one or more heaters with a total Max Amps equal to the maximum current available from all charging sources. The terminal block accepts up to 1/0 wire.

UL - Listed DC Lightning Arrester

We have U L Listed Arrester to protect against surges caused by nearby lightning for AC and DC system use. They are Silicon Oxide Varistor type Arrester with a maximum current rating of 60,000 amps and 2,000 joule's per line. Their response time is 25 nanosecond to clamp 50,000 amps. They are waterproof and they mount easily in a 1/2 inch knockout. Install on the put terminals of the PV system charge control.

GenMate - Automatic Generator Starter

Ultra-reliable generator control. Install it and forget it. Used by more motor coach manufacturers than any other device.

GenMate is an automatic computer-operated generator controller for all electric start generators which can be controlled with 2, 3 or 4 control wires. It can start, stop and exercise a generator based on a variety of conditions, user controls and remote inputs.

Other uses include; on-demand water pumping, simplified remote generator control, automatic generator powered greenhouse ventilation and other applications where unattended generator operation can be of benefit.

Protection from over-cranking is automatic and user programmable.

The device is available either as a board-only unit, ready to mount in an enclosure of your choice, or in a polycarbonate weatherproof enclosure.

GenMate is software driven, with the program permanently stored in non-volatile ROM.

The generator is started and stopped through the action of two UL approved relays. Both are SPDT with electrically isolated contacts. The contact rating is 240 VAC @ 20 amps with a resistive load.

Typical generator control circuits are far less demanding than the contact ratings thus assuring long mechanical life.

The industrial quality circuit board is protected with clear over spray on all foil runs and solder connections.

Selection of a 12 or 24 VDC operation is automatic. 24 VDC operation is selected when GenMate is initially connected to a battery of 16 VDC or more.

Low Battery Voltage Disconnect - Load Control Device

Ultra-reliable battery protection. Install it and forget it. These are available in sizes from 3 amps to 16 amps - as outlined below.

The LVD-8/16 is a load control device that is designed to work as a matching unit to photovoltaic charge controllers M-8 and M-16. It will control loads of up to 16 amps DC. The purpose of the LVD-8/16 is to turn OFF the load device when battery state of charge level drops to a preset low condition. The device does NOT work on a simple battery voltage set point principle. Two features of the device work to reduce premature load disconnect.

First is the 10-second time delay circuit. Any time the battery voltage falls below the controller disconnect voltage of 11.0 V or 22.0 V, a ten-second timer will start. Only if the battery voltage is still below the controller set point after ten seconds can the load disconnect. Re-connect will occur at 12.4 V or 24.8 V +/- 5%. This ten-second delay will reduce the probability of temporary surge conditions that can trip normal controllers.

Secondly, a current measuring circuit inside the unit will slide the load disconnect set point downward in proportion to the amount of the surge current. This provides protection in a system where the battery may be very cold and therefore subject to substantial temporary voltage changes depending on load current. The LOAD COMPENSATION circuit insures that the load system is not unnecessarily disconnected during normal operation due to cold batteries.

Linear Current Booster - LCB

Different than the above battery charge controller, these units work in systems that directly link the solar module to a motor, no battery storage is utilized.

These controllers alter the incoming amperage and voltage to what is required by the motor. In low light conditions, modules produce little current yet relatively constant voltage. These motor controllers will reduce the voltage to increase the amperage, starting and running the motor in low light. The effect is an increased motor run time throughout the day, moving more air or water in a day than an array direct system with no controller.

These are needed to operate your solar pump direct from the sun without batteries.

Automatic Water Level Sensor

The Sun Selector WLS-3 is a differential switch designed to be used with the LCB units. When the LCB is connected to the green wire on the WLS-3, it will serve as a differential switch that keeps the water level between two points.

This is accomplished by pumping water INTO a tank or other holding unit. When the LCB is connected to the yellow wire on the WLS-3, it will serve as a differential switch that will keep the water level below and between two levels.

This is accomplished by pumping water OUT OF a tank or other holding unit.

The LED indicator is ON when the HIGH probe has been touched by water and the LOW probe has yet to be reached. If FILLING a tank, this will indicate that the tank has been filled and the water level is between the HIGH and LOW probes. If EMPTYING a tank, this will indicate that the water has reached the HIGH probe and the water level is being decreased to the LOW probe, but has not yet reached it.


Why We Need Meters

We need sophisticated meters help you keep track of your battery's state of charge so you can get maximum life out of it. The main destroyers of Lead acid batteries is sulfating caused by undercharging. A digital ampere-hour meter is a great way to keep track of your batteries state of charge. As you use power, the meter counts how many amp hours are used. As the battery is charged, the meter goes backwards, toward zero. When the battery is full again, the meter reads zero. If you equalize the batteries, It counts how many extra amp hours you use during the equalization cyclic, then when you stop charging, it resets itself to zero. This type of meter is a must for nickel cadmium and nickel-iron batteries, where it is nearly impossible to tell state of charge from voltage, or specific gravity.

Omni Meter +

The Omni Meter + is the most advanced meter on the market.

OMNIMETER+ The plus + in Omnimeter's name indicates a new model with many improvements and changes. The meter now uses negative stunts, functions from 7 to 100VDC, has a brighter super twist backlit LCD, comes with 32K Ram standard, does 4 simultaneous channels of with OmniLink, has no on-volatile memory, won't lose settings when de powered, and will automatically boot and reconfigure after power surge or disconnect. This is the only meter on the market that is available with this memory capability as well as computer interconnect.

The Omni Meter measures volts, amps, amp-hours and kWH on up to 4 separate channels. Simple menu operation, programs for use with any shunt and measures up to 1 100 Amps DC. Automatically determines battery capacity. Can be used to control a two wire remote start generator.

Omni Charge feature includes menu driven dual channel charge control software at no extra cost.

Omni Link+ software allows remote access and control through the optional battery powered internal modem and phone line or links directly to your IBM compatible computer with standard PC type plug in connector for computer port.

Settings and data logging functions can be set remotely. Information can be displayed as percent, bar-graph, or numeric values. The system is capable of handling records and graphs up to 4 simultaneous data logs. A data log is a recording of selected values at a selected time interval/ i.e. battery voltage, charging current, and/or load current.
We have installed one to measure:

omnialarm software enables your omni meter to call you through a modem to your PC when any of the programmable alarms are activated. An alarm message is then displayed on your screen automatically. Includes 18 programmable alarms, 2 available for external inputs such as security, water level, smoke alarm. Dim. 5.25 x 6.5 x 21 inch. Limited one year warranty.

Battery Monitor - E-meter

A battery Ampere-hour meter keeps a net count on current flow into and out of the battery. It is a meter that tells us how much electric energy has been consumed from our battery. One chronic problem with all Ampere-hour meters is battery efficiency. No battery is 100% efficient. Some of the energy used to recharge the battery is lost as hydrogen and oxygen via electrolysis and some is lost to heat. A battery Ampere-hour meter must factor battery efficiency into its measurements.

Provides important information about the status of your battery. Selectively displays volts, amps, amp-hours consumed and time remaining. Multi-color bar-graph display tells battery level-of-charge at a glance. Monitors one battery bank. Key historic battery information includes deepest discharge, number of recharge cycles and average discharge. 2.5 inch diameter