Here are some instructions on disassembly as there are a couple of "tricks" one needs to know.
Opening the bottom lid: "Close the upper lid!!!"
You need to open the same as the upper door and on the same side. Except it's not spring-loaded so you may need to apply some upward force with your fingernail. Press on the side hard in the sweet spot is the secret. Once one gets used to using the top lid, it gets easier. The battery fit is very tight and if overly tight, it does make that sweet spot harder to push. When installing a new battery you will need to push on the end that the wires come out of to flatten as much as possible. The goal is to shorten the overall battery length a tad.
Frame removal instructions: "Close the upper lid!!!"
Remove the battery by pulling the wires laying on the top. The battery will slide out and be careful of the bottom door. Carefully undo the battery connector. Under the battery, you'll find a tool to pull off the internal door. Insert the tool into the slot on the inner lid and pull. It is tight and comes out quickly when it does. Then you push the tube until the assembly is close to the bottom door but NOT beyond. OK, you can open the upper lid for this, but remember to CLOSE IT when your finger is out.
Here's the non-obvious part. The little USB board will move towards the front by 1/2 mm to clear the rear hinge of the bottom door. The inside lid you pulled out has many functions, one of which is to hold the USB board toward the back of the unit. Upon re-assembly, the USB board needs to be pushed back and frame forward against the front before the lower lid will fit back in. This USB board movement will likely be missed by most and run into problems without this knowledge.
The inside lid also pushes up against the bottom of the activation switch and holds it up in place. Another important function of this door is to serve as a wedge to hold the frame in place. It pushes the frame forward against the front of the enclosure. There are two rubber pads mounted to the front of the frame which keep it from sliding up and down once assembled.
Opening the bottom lid: "Close the upper lid!!!"
You need to open the same as the upper door and on the same side. Except it's not spring-loaded so you may need to apply some upward force with your fingernail. Press on the side hard in the sweet spot is the secret. Once one gets used to using the top lid, it gets easier. The battery fit is very tight and if overly tight, it does make that sweet spot harder to push. When installing a new battery you will need to push on the end that the wires come out of to flatten as much as possible. The goal is to shorten the overall battery length a tad.
Frame removal instructions: "Close the upper lid!!!"
Remove the battery by pulling the wires laying on the top. The battery will slide out and be careful of the bottom door. Carefully undo the battery connector. Under the battery, you'll find a tool to pull off the internal door. Insert the tool into the slot on the inner lid and pull. It is tight and comes out quickly when it does. Then you push the tube until the assembly is close to the bottom door but NOT beyond. OK, you can open the upper lid for this, but remember to CLOSE IT when your finger is out.
Here's the non-obvious part. The little USB board will move towards the front by 1/2 mm to clear the rear hinge of the bottom door. The inside lid you pulled out has many functions, one of which is to hold the USB board toward the back of the unit. Upon re-assembly, the USB board needs to be pushed back and frame forward against the front before the lower lid will fit back in. This USB board movement will likely be missed by most and run into problems without this knowledge.
The inside lid also pushes up against the bottom of the activation switch and holds it up in place. Another important function of this door is to serve as a wedge to hold the frame in place. It pushes the frame forward against the front of the enclosure. There are two rubber pads mounted to the front of the frame which keep it from sliding up and down once assembled.