Solar Sequencer Solar Battery Charger

Charge lead-acid batteries of different sizes and capacities

Designer: JohnG aka John Guyer
Skill Level: Intermediate
Assembly Time: 1-2 hours

Solar Sequencer The Solar Sequencer enables a single solar panel to charge multiple lead-acid batteries of different sizes and capacities, while keeping them isolated from each other. John's used it on his truck, lawn mower and ATV batteries. It is also possible to use a solar panel and battery to run a garage door opener in a building with no access to utility power - handy in a power-outage!

The kit uses the Parallax Basic STAMP 1 microcontroller, which reads the batteries voltages by reading an ADC0834 analog to digital converter. Using these readings the solar sequencer can determine if a battery needs to be charged and can load test the solar panel.

Build your own Solar Sequencer

Required Tools and Components:

BASIC Stamp 1 module
BASIC Stamp 1 serial adapter
LED, Yellow Diffused T1-3/4
Rectifier, 50V 1 AMP Silicon
NPN Amplifier, 40 Volt 0.2A
Transistor, 2NH3906, 40V
Capacitor 1µF 25 Volt 10%
Capacitor 10µF 25 Volt 10%
Diode, Rectifier Schottky 35V 30A
Automobile Fused DC Power Plug
Header, ST Male 1RW 3 pin
Terminal Block, 3-pole
Terminal Block, 2-pole
Switch, tactile pushbutton SPST
Resistor, CF, 390Ω, 1/2W
Resistor, CF, 1KΩ, 1/4W
Resistor, CF, 2.2KΩ, 1/4W
Resistor, CF, 4.7KΩ, 1/4W
Resistor, CF, 5.6KΩ, 1/4W
Transistor MOSFET P 55 Volt 31A 3-Pin
Resistor, Molded SIP, 10KΩ 1W
Analog to Digital Converter Serial
Solar Panel, 25W Multicrystaline
Solar Panel Battery Clamps

Soldering iron and solder
Wire strippers
18-14 AWG wire
Enclosure or mounting board (optional)

Step-by-Step Instructions


Step 1 - Introduction

If the PCB is going to be mounted in an enclosure or onto a piece of thin plywood, it is easier to mark the holes before the components are installed, or make a template out of a piece of cardboard. The board measures 3.8" x 2.5". The figure below shows the bare circuit board component side up. Install the components starting with the shortest, ending with the tallest. That way the components stay in the board when it is flipped over for soldering.

Tip: when soldering parts with multiple leads, you can partially solder one lead to hold the part in place and then check its alignment. This works well for IC chips like the ADC0834 and the Blue Terminal Blocks.

Step 2 - Installing the 1/4 watt resistors

Bend the leads of the resistors and install them in the locations outlined in red on the diagram. The resistor values and color codes are as follows (from top of board to bottom):
2.2K - (red, red, red, gold) there are four
5.6K - (green, blue, red, gold) there are five
4.7K - (yellow, violet, red, gold) there are two
1K - (brown, black, red, gold) there is just one

Installing the 1/4 watt resistors

Step 3 - Installing diodes and 390Ω resistor

Bend the leads of the diodes and resistor and insert them into the board in the locations shown in the diagram, and solder. The diodes and the 390Ω resistor have heavy leads, trimming them about 1/16" from board prior to soldering makes it easier.

Installing diodes and 390Ω resistor

Step 4 - Single inline package resistors

Don't forget the ground connection at the very bottom, as part of a trace it is hard to see some of them.

Single inline package resistors

Step 5 - Transistors

There are five NPN 2N3904 transistors. Install them with the flat facing right. The one PNP 2N3906 transistor, with the double red rectangles, flat facing left.


Step 6 - Progress check

This is what the board should look like at this point.

Progress check

Step 7 - Capacitors

Install the plus + (longer lead) to the square pad. You may need to use some tape to hold the smaller one in place. These must be installed with the correct polarity, the positive lead is marked with +++++.


Step 8 - Pushbutton switch

Install the switch. It only fits one way.

Pushbutton switch

Step 9 - LEDs

Install the LEDs with the long leads to the square pad, flat to the right. There are four LEDs.


Step 10 - Progress check

The board should look like this at this point. Inspect the board, making sure all solder joints have been made securely.

Progress check

Step 11 - MOSFETs and diodes

Install these, alternating as follows: MOSFET-Diode-MOSFET-Diode-MOSFET-Diode.

Tip: insert all of them into the board and hold them in place with a ruler while flipping the board. Then lay the ruler next to the TO-220 package tabs and slide it to keep them in a nice straight row, and sticking straight up from the board ready to be soldered.

MOSFETs and diodes

Step 12 - Programming pins

Install the programming pins. Use tape to hold in place while soldering.

Programming pins

Step 13 - Analog-to-digital converter

Install the ADC0834 analog-to-digital converter with the small half-circle notch facing to the left. There is also a dot at pin 1 which goes into the square pad.

Analog-to-digital converter

Step 14 - Progress check

The board should look like this at this point. Check components and solder joints.

Progress check

Step 15 - BS1 Stamp

Install the BASIC Stamp with the components on the Stamp facing toward you.

BS1 Stamp

Step 16 - Terminal blocks

Install the blue terminal blocks Make sure they stay pressed against the board, and fill the hole around the post with solder. Also, make sure the opening on the blocks, where the wires will go, faces toward the edge of the board.

Terminal blocks

Step 17 - Finished board

The finished board's component side should look like this. Check your component orientation.

Finished board

Step 18 - Solder side

Inspect the solder joints. The solder joints should all be shiny with no gaps between the component and the hole, with a small fillet between the lead and the pad. There are some open holes in the board where no components are installed.

Solder side

Step 19 - Programming

This requires a Windows® computer running Windows® 95 or later, with a serial port or a USB to serial adapter, and a serial cable.

Quick steps (follow if you have programmed a Basic Stamp before)

Download the from, unzip it and save the three files. Open the STAMP editor, find the SolarSequencer.bs1 file and open it. Connect a 9V battery, a 12V lead acid battery, or a power supply set to between 9 and 25 volts, to one of the battery connections. The bank of terminals on the right alternate +-+-+-. It doesn't matter which ones as long as the polarity is correct. Connect the programming adapter and cable, and download the program to the STAMP. Disconnect the power supply or battery.


Step 20 - Installation and testing

The installation of the solar panel is a project itself. Pick a location that faces South with the least amount of shading as possible. The solar panel is connected to the solar input, and a lead-acid battery is connected to one of the battery outputs as shown in the diagram, double checking the positive and negative connections. Connect wires to the Solar Sequencer blue terminal blocks first, and then connect to the battery. If the battery voltage is less than 13V, the LED for that battery output will light. If the LED does not light, and the battery voltage is above 13V, connect a load such as an automotive light bulb to the battery. If the battery is in a vehicle, opening the door will load it when the interior lights turn on. This will usually lower the voltage enough that the LED will light.

Close the door or remove the load, and once the battery voltage is above 14.2V, the LED will turn off. This will happen rather quickly if the battery is near full charge on a sunny day. Repeat this procedure for the other battery outputs. For operation connect the wires for the other batteries to the blue terminal block first, then to the battery. The Solar Sequencer will charge all of the batteries in sequence, starting with Battery 1. There is quite a bit of information about how this works in the software comments. Connect the battery for the garage door opener to the Battery 1 position, so it is the first to be charged every morning.

Installation and testing

Step 21 - Solar panel mount

Below is a picture of the solar panel mount I built. There are a lot of different ways to do this and everything is unique to a building and the way the sun shines on it. This is just an example.

Solar panel mount

Step 22 - Garage door opener

This is where we connect the garage door opener and get it operating from the battery. My garage door opener is a Craftsman/Chamberlain belt drive with battery backup. It is designed to run on 12V DC and I usually run it from a car battery because my garage has no utility power. It comes with a 12 volt 5 A-Hr lead acid battery, but is only intended as a backup. Everything but the lights work with no AC power, and it draws about 40 mA when in standby. It does need AC power applied initially, but will work from the battery afterward. This garage door opener uses 4 amps DC to open the door, and 3.5 amps to close it. Both take about 20 seconds.

The small battery included with the garage door opener is a 12 volt 5 A-Hr lead acid battery, but it only lasted about six months. It is only intended as a backup, not a primary power source. I replaced it with a lead acid battery that was still good, but out of warranty, removed from a Jeep Grand Cherokee. It is a size 26 battery, which has a standby power number of 150, meaning it can supply 25 amps for 150 minutes. I plan to add another opener, and this should be more than enough to power both. It also can run the lights that came with the solar panel kit. The Jeep's battery is on a shelf in the back of the garage and wired to the garage door opener with 14 gauge wire.

To get the garage door opener working, connect its battery power leads to a 12 volt lead acid battery (it uses 1/4" female quick connectors), and the battery to the Solar Sequencer. It won't come on unless it is plugged in to AC power. Connect a power inverter to the battery, and plug the garage door opener into it, or use a long extension cord (or generator) to plug into AC power. I used a 400 watt inverter, but 100 watts is probably enough as long as it doesn't have to open the door. The garage door opener's LCD display will show "charging battery". Unplug it and it will continue to run on the battery. The display will still alternate between time and temperature, and the time can still be set. The only things I don't like are the display always scrolls "battery backup enabled" across the bottom; if the voltage drops below 12.5 it will beep every minute, and there is an orange LED on all of the time. The lights also don't work, they need AC power.

I have been using the prototype version of this design for two years as a maintenance charger, and an additional year with the garage door opener, but only six months of that was with the Jeep's old battery. A 15 Watt solar panel will maintain three batteries. With the garage door opener, the 15 Watt panel needs a while to make up for the 40 mA draw all night. Cloudy days and long nights in the winter make the 15 Watt panel not quite enough. This will depend on the location and how much direct sunlight the panel receives. In Maryland, the 15 Watt panel was not quite enough. Everyday use of the garage door opener will likely require a higher wattage solar panel. This has been a fun project, and a great way to use solar energy to power the garage.

Garage door opener

About the designer

John Guyer John Guyer has been an electronic engineer for 25 years. His hobbies include electronics, software, dirt biking, mountain biking and home improvement projects. He also enjoys maintenance and repair of their small engine-powered lawn/garden equipment.

The Solar Sequencer project and using it to power the garage evolved out of necessity and convenience over the past four years. John also built, installed, and programmed a home weather station. It is a JAVA program running on a PC with various one-wire sensors.

John has been married for 22 years to his wife, Karen and they have two sons, Kevin, 15 and Kyle, 13.