Step 5: Battery Board

These instructions are to build and test the Battery board version v1.3.2.1.

Here is the PCB top and bottom:

Here is the schematic

https://github.com/alanbjohnston/CubeSatSim/blob/beta/hardware/beta-v1.3.2/cubesatsim-battery-b1.3.2.1_schematic.pdf

Here is the board with the top on the left with the AMSAT logo and the bottom on the right:

You will need these tools:

• Safety glasses (to protect eyes while soldering or trimming leads)
• Soldering iron and solder (I use lead-free solder, but leaded solder is easier to work with)
• Liquid flux, either in a bottle or pen

Other tools that are helpful:

• Multimeter (to read battery voltage)
• Blue mounting putty(to hold components in place while soldering)

Checklist

The BOM has a sheet "By Steps" which lists the parts needed for each step in order. https://docs.google.com/spreadsheets/d/1Ta5UaJcinGozcheROrkfwXdGSDUZrXvQ1_nbIBdIIOY/edit?usp=sharing If you have a Google account, you can make a copy of this spreadsheet ("File" then "Make a Copy") and check off each part as you install it.

For example, here is the checklist of the through hole parts for this step:

Battery Board Instructions

Video

Here is a video of this step.

Assembly

The Battery Board stacks on top of the Pi Zero and under the STEM Payload Board.

SMT Steps

Start by mounting U2, R1, and C1 SMT components.

Apply solder paste using the stencil, then mount the components with tweezers. Note the orientation of U2, with the pin one strip facing up.

Run the board through the Reflow Oven on Wave 2.

After it cools down, continue with the Through Hole Steps.

Through Hole Steps

You will need the following parts to make the Battery board as described in the BOM https://cubesatsim.org/bom-beta:

• Battery PCB with SMT parts installed
• Stacking GPIO header J1
• Three Nickel Metal Hydride (NiMH) cells (AA size)
• Battery holders (AA size) BT1 and BT2
• JST 2.0 jumper cable
• JST 2.0 connector JP1
• Two small zip ties
• Liquid flux for soldering the battery holders

The parts are shown here:

Flip the PCB upside down and mount the stacking GPIO header J1 on the bottom of the PCB:

Insert it on the bottom as shown:

Flip the PCB to the top. Solder one pin on either side, using the pad next to each pin to heat both the pin and the pad.

Make sure the GPIO header is fully inserted and straight and on the correct side.

Only solder six pins on either side, as shown in the next photo.

On the top of the PCB, place a drop of liquid flux on the six pads for the two battery holders.

Then place the battery holders BT1 and battery holder BT2:

There is a small tab on the bottom of the battery holders that fits in a hole in the PCB - make sure it is inserted so the battery polarity is correct and the holder is flat against the PCB.

Put another drop of liquid flux on each of the pads, then solder the pads. Keep downward pressure on the part and keep applying solder until it flows over the whole pad.

Here's how it looks with both battery holders soldered in:

Next, on the top of the PCB, insert the JST connector JP1.

Make sure the slot is facing the edge of the PCB and hold in place with blue putty:

Solder the pins on the other side.

Insert the batteries, paying attention to the polarity as marked on the battery holders.

It is a good idea to test your battery polarity using a voltmeter. Use the BAT+ (J1) and BAT- (J2) test points on the board, being very careful not to short them together:

If you read a positive voltage in the range 3V - 4.5V, your Battery board is "nominal" and ready to be used. If you get a negative voltage, check that the red and black test leads are plugged into the positive and common inputs on your meter, or that your batteries aren't inserted backwards.

The batteries can secured with zip ties:

The two zip ties are inserted through the holes as shown:

Close the zip ties, tighten, and cut off the excess:

Here's how it looks on the bottom:

Here's how the completed board looks with the JST jumper wire connected to the JST connector:

The battery board is complete and ready for Flat Sat Testing.