The LM2596 can be easily changed to the XH-M404 regulator as shown in the image below. Just consider that the regulator may just use the two upper holes for the screws of the regulator support.

Change of regulator

The change is required as when connecting the RPi, the voltage has a huge change and cannot maintain the nominal 11.1 V of the 18650 batteries on the configuration presented previously. So, start by taking off the regulator wall.

Then check that all the connections aren't tangled and that you can take off the battery stack safely.

Dismount the nuts that ensure the 3 state switch, take off the batteries wall and disconnect the charging port. Ensure that the robot is turned off.

With the help of pliers remove the nuts and washers of the stack. Also with the help of a screw driver, disconnect the ports of the 3 state switch, be careful with the short circuits.

Prepare you soldering iron and a copper tap to remove the thin.

Place the battery stack as shown in the picture below and remove the insulate tape.

By using the soldering iron and the copper tape, remove all the connections of the BMS, thsi is going to be used when building the module again.

Do the same process with the cables. Then you can remove the screws and safe the battery holder platform for later.

Prepare the battery stack support, and eight spacers M3 hex standoffs (4 of 10 mm and 4 of 20 mm). If you do not have a support, you can print a footprint and cut it on cardboard, reinforcing with insulate tape.

Mount the spacers, like shown in photo below. If the structure seems to be weak. Add flat washers to both sides of battery platform.

Prepare four M3 x 10 mm button head screw, four washers, four nuts and two B18650 x 3 battery holder.

Place the battery holders on the platform. Make sure they are tight.

Prepare the BMS, glue it to the platform and weld the output cables if you haven't.

Prepare cable that allows a curret flow of more that 5A, and also keep near your tools to weld.

Let's start by making the GND connection on both battery stacks. For this make sure, pass the cable through the holes of the stack, weld it on both sides (preventing to use too much space on the battery side as it may not fit later) and check continuity with a DVM.

Extend the cables and check the proper size to connect them to the 0 V place of the BMS.

Weld, then secure continuity.

Prepare more cable for the other connections.

Weld the connections at the 4.2 V point as shown in the image below.

Then weld the pair to the BMS module at 4.2 V too.

After letting it to cool down, check that the voltage for the two batteries (or one placed) allows the voltage as displayed in the image below. Take the batteries out after the test.

Prepare cable for the third connection.

Weld the connection at 8.4 V in the battery holders.

Weld the connection at the 8.4 V connection on the BMS.

Review that there is no short circuit and that all the welded components will keep in place.

After the weld is cold again, check the batteries at this point by inserting them. After the tests... remove them as there is more to weld.

Prepare the fourth pair of cable of the battery stack, then weld it as done with the previous steps in the 12.6 V zone.

Before moving on, do not forget to cut and insulate the original cables of the stack of batteries.

Make test with all the batteries and partial arrangements to test voltage and continuity. As ORION consumes a lot of energy, if one battery or one part of the stack do not work, then the robot won't work either.

With the help of insulate tape, organize the cables and keep them in position.

Prepare the second floor's battery holders.

Then prepare fragments of cable to connect the second with the first floor. You will require six cables of 4 cm and six cables 8 - 10 cm.

Start by welding the 0V points on the battery stacks.

Prepare more cable for the next connection that will be at 8.4 V.

Weld them and check continuity with a DVM.

Prepare a pair of longer cables.

Weld the pair to the 4.2 V section of the battery holder.

Prepare other pair of cables and weld it to the 12.6 V section on the battery holders.

Ensure the original cables in position and insulate them.

Prepare the battery holder platform with four M3 x 12 mm button head screw, four flat washers and four nuts.

Add the battery stacks to the platform, and tighten the screws.

Prepare 2 M3 x 16 Button Head Screws to help (temporal) to keep in place the stack.

Add the two screws

Weld the 0V and 8.4 connections as shown in the image below, then take off the two screws.

Then weld the other side, the reason this cables are longer is to ensure you can open the battery stack to access the down batteries.

Now, start final test on the battery connecting the twelve 18650 batteries on the model.

Make sure to validate each voltage point has the required value of voltage and that this applies for the group and the individual battery holders.

After the test, proceed to insulate the connections with insulate tape.

If you note that the space between the batteries stack is bigger than 20 mm and the spacers are too short. Add more spacers to reach the distance required.

Approximately, the distance is between 26 mm to 36 mm. Make sure that all the battery stack isn't higher than 80 mm, otherwise it won't fit on the robot.

Prepare six M3 x 6 mm screw and six flat washers, then place the battery stack.

As suggested above, if you see it is unstable, be careful and add flat washers.

Make test with the robot and ensure it is capable to power it on.

Then place, the battery stack on the robot, ensure to add the nut and washers. Here you are done with the change, end up by placing the walls, the switch and ensuring all is in place.

Two caster wheel demo

Remove the left servo wall (including the arm).

Add the connector to the ON position, and you can have feedback on your battery.

Adding microphone to the robot.