I added a little display wich shows the voltage of the batteries. 13,8V means the batteries are fully charged, at 10,8V they are empty. Got this display at Amazon for 3€, will use it until i get a proper battery protection.
This is the very first post about my music box:
What is it? Well basicly it is a big battery, combined with a Raspberry Pi, an amplifier and speakers, used to play music. Some more pictures:
This is the rear side, here i house the control switches (not visible, they are hidden behind the wood. On the left part of the hub is the USB sound card, wich connects the Pi to the amplifier. The little stick you see on the top is a WLan-stick, used to connect to the Pi and control it. Behind the hub is a LAN connection, wich can turn the Pi into a WLan hotspot and is used to update the Pi. The hub is of course not only powered by USB, but got another power supply too. (500 mA are just WAY too few)
Top view on the music box, you see my way of mounting the speakers here. Its not pretty but it works.
Another top view, here you can see the wooden frame i used to mount all the stuff in the box.
Close up of the internal stuff. Here you see the amplifier (red, to the left) wich claims to be 300 W (it feels to be a lot less). In the center is the Raspberry Pi with its SD-card and USB connection to the hub. To the Right you see the power regulator (the little black box) wich turns the 12V comming from the batteries into the 5V needed for the Raspberry Pi and the USB-hub. The amplifier works on 12V. On the top you see the three switches wich controll the box. Under all this you see the batteries. This are 4x 17 Ah batteries. They got a lot of weight but are needed to make the box run ~5 days of average use off the grid. Average use includes a few cellphone charges.
All this is mounted on a wooden frame, wich inturn is screwed to the box from the bottom side. The carrying strap is connected to the frame too. I do not feel safe about the connection to the box, but for now it seems to work.
With the top cover included, the box got a basic waterproofing and is great for outside use.