SwitchDoc Labs SolarMAX2 User manual

SolarMAX2 Assembly and Testing Guide
September 2021
Version 1.51
For powering solar systems such as systems based on the
Raspberry Pi, Arduino and ESP32/ESP8266
and the SwitchDoc Labs System
Version 1.1 September 2021

Table of Contents
Errata 1.............................................................................................................................
What is SolarMAX2? 2......................................................................................................
SolarMAX2 Specifications 3..............................................................................................
What is in the SolarMAX2 Kit? 4.......................................................................................
What Else is Required for the SolarMAX2 Kit? 4..............................................................
SolarMAX2 Part Identification 6......................................................................................
Step by Step Assembly 11...................................................................................................
Wiring the SolarMAX2 17.................................................................................................
Solar Panel Wiring 17.................................................................................................................
Grove Wiring Table 20...............................................................................................................
433MHz Transmitter Installation 23..........................................................................................
USB Cable Wiring 23..................................................................................................................
Fully Wired SolarMAX2 for Reference 24..................................................................................
Lead Acid Battery Tab Wiring 25................................................................................................
Connect your 12 V Lead Acid Battery 27.....................................................................................
Testing Your SolarMAX2 System 29.................................................................................
Testing With SkyWeather 29......................................................................................................
Testing with a Raspberry Pi (without SkyWeathe2r) 30.............................................................
What is in the SolarMAX2 Data Packet? 31.................................................................................
Power Management and Pi Protection in SolarMAX2 32............................................................
WatchDog Timer Enable 34........................................................................................................
Installing Your SolarMAX2 System 34..............................................................................
The Science and Education Goals Behind SolarMAX2 36..................................................
Support 36........................................................................................................................
Disclaimer 37....................................................................................................................
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Errata
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What is SolarMAX2?
SolarMAX2 is a SwitchDoc Labs designed system to charge Lead Acid batteries from 18V Solar panels in order
to provide more power to small computer systems. SolarMAX2 is designed to collect and return data about the
solar panel system to the powered (or other) computer via a 433MHz link. SolarMAX2 collects and transmits
the following data every 30 seconds:
• Battery Voltage
• Battery Current
• Solar Panel Voltage
• Solar Panel Current
• Load Voltage
• Load Current
It also supplies the following about inside the SolarMAX2 box:
• Inbox Temperature
• Inbox Humidity
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SolarMAX2 uses a 433MHz module which can transmit up to 100 meters or further with larger antennas and
uses very little power.
This is a perfect system for powering SkyWeather2, Raspberry Pi and other small computer systems.
SolarMAX2 Specifications
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Table 1-1
Solar Max
LeadAcid
Solar Max
LeadAcid
Minimum
Nominal
Maximum
Solar Panel
Voltage
15V
18V
18V
Solar Panel Voltage
Solar Panel VOC
25V
Solar Panel VOC
5V Load Current
5A
5V Load Current
Solar Charging
Current
4A
Solar Charging
Current
Battery Type
12V Lead Acid
Battery Type
Size of Battery
Large
Size of Battery
Cost of Battery
Low
Cost of Battery
Available Output
Voltages
5V, 12V
Available Output
Voltages

What is in the SolarMAX2 Kit?
•Mini Pro Plus Low Power Computer"
•INA3221 High Current with Large Screw Down Terminals"
•18V Solar Panel Charger for 12V Lead Acid Battery"
•HDC1080 Temp Hum"
•433MHz Transmitter and Antenna"
•MC4 Solar Plus Female (and Pin)"
•MC4 Solar Minus Male (and Pin)"
•USB Weatherproof Plug"
•Short USB Cable Type A - Type A"
•20cm Grove Cable"
•30cm (or 50cm) Grove Cable"
•Grove Connector to Female Pin Headers - 1 Cable"
What Else is Required for the SolarMAX2 Kit?
12 V Lead Acid battery - We recommend >= 20000mAh - https://amzn.to/2qGCVd8 (This battery fits
PERFECTLY in the Bud Enclosure below)
M2 Nylon Hex Thread Assortment - https://shop.switchdoc.com/products/140pcs-box-m2-nylon-hex-
thread-assortment-kit
Solid Core Hookup Wire 22 Gauge - https://amzn.to/3202Ppa
Bud Enclosure NBB-22241 Style B - 6-25/32” x 10-23/32” x 6-25/32” - https://amzn.to/2zk8B8R
Spade Quick Connect Crimp Cold-Pressed Terminals (for 12V Battery) - https://amzn.to/2OgxqLm
100W 18V Solar Panel with MC4 Connectors - https://amzn.to/2rjjmYi (VOC 21.6V Max Power 17.4V)
Optional
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Solar Panel Crimping tools for MC4 (optional) - https://amzn.to/2U6IN9J
Tools
Soldering Iron
Straight blade Small Screwdriver
Crosspoint Small Screwdriver
Super Glue
Silicon Caulking
Wire cutter
Wire stripper
Pliers
Drill
Drill Bits for:
1” holes
2/3” holes
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SolarMAX2 Part Identification
•Part A - MC4 Minus Male (and Pin)
• Part B -MC4 Plus Female (and Pin)
• Part C -High Current INA3221 with Large Screw Terminals
• Part D -Solar Charger for 12V Lead Acid Batteries
• Part E - USB Weatherproof Plug
• Part F - USB Plug w/terminals
• Part G - 433MHz Transmitter and Antenna
• Part H - 16MHz Mini Pro Plus Computer
• Part I - HDC1080 Temp Hum
• Part J - Short USB Type A to USB micro Cable
Cables
• Part K -20cm Grove Cable
• Part L - 30cm (or 50cm) Grove Cable
• Part M - Grove Connector to Female Pin Header Cable
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Part C - High Current INA3221 with Large Screw Terminals
Part F - USB Plug with Terminals (Note + and - marking in plastic)!
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Part J - USB Type A to USB Micro Cable
Part A and Part B - MC4 Minus and Plus Plugs and Pins
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Part G - 433MHz Transmitter and Antenna
Part J - 20cm Grove Cable
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Part K - 30cm (or 50cm) Grove Cable
Part L - Grove Connector to Female Pin Header Cable
Step by Step Assembly
Step 1) Drill two 2/3” holes in the upper left side of the lower part of the Bud Box. (See Part A and Part B
location on pictures above)
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Step 2) Drill 3 1” holes in the front of the lower part of the box. Separate the holes by at least 2 inches, center
to center. (Two vent holes and one hole for the Part F- USB Weatherproof Plug.
Step 3) Insert Part E - USB Weatherproof Plug into the BUD Box, with the cap on the outside in the rightmost
1” hole. Screw down. If you are using a large capacity Lead Acid Battery, put the cap in the leftmost 1” hole.
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Step 4) Place the large heat sink on the back of Part D, the Solar Controller. Place the smaller heat sink on the
top of Part D, the Solar Controller. If the heat sinks don’t want to stay on, us a small amount of superglue under
the heat sinks.
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Step 5) Set the slide switch on the Solar Charger (Part D) to MPPT for the most efficient charging. Then set
the Battery Gauge slide switch to Off also on the Solar Charger (Part D).
Step 6) Attach Nylon Headers (with screws or nuts) to all the boards. Note that the Solar Charger has screws
and headers included in the package with the heatsink.
Step 7) Glue an additional nylon spacer on Part I (HDC1080 Temp/Humidity Sensor) and two on Part C
(INA3221) the same height of the spacers from Step 5) to provide a stable base.
Step 8) Removed
Step 9) Removed
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Step 10) Using the super glue, attach all the boards to the locations shown in the two two part identification
pictures above. Let dry. The plug in the USB PowerCentral board (Part E) into the Solar Charger Board (Part
D). Note you won’t have the battery in the box yet. But it’s OK if you do. Just don’t short out the terminals
on the battery!
Step 11) Label all parts - optional - but you will be happy you did.
Step 12) Using some Silicon Caulking, attach some door screen over the center and left 1” hole to keep the
bugs out of the box.
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Now we move on to the wiring of the SolarMAX2.
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Wiring the SolarMAX2
As you wire this unit, remember you are dealing with lots of current and voltages. Triple check your wiring!
Wiring things backwards or incorrectly can result in destruction of the electronics and possible over heating.
BE CAREFUL!
Solar Panel Wiring
Step 1) Take the male Part A - MC4 Minus Male (and Pin) and two 33cm lengths of black wire. Strip the ends,
twist them together (here’s a fast way of doing that - https://www.switchdoc.com/2015/07/handy-tip-building-
braided-cables-for-projects/ ). NOTE: We have now determined that if you are using 22 AWG wire you
do not need to to double the wires. One wire is sufficient for all the currents used inside the box.
Now insert one end of the braided wire (with then ends stripped of the insulation) into the pin (the male pin has
the larger hole in the end) and crimp it down. We recommend you buy the crimper tool for MC4 plugs as
mentioned above. Slide the Male MC5 Plug into the Minus Hole in the box and put on the other parts and
screw it down.
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Step 2) Place the other end of the black wire into the “-“ terminal of the Solar Charger SOLAR IN terminal.
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