Initial mock-up of the components began with a universally available templating material: cardboard. I cut the pieces as accurately as possible and fitted the central components in order to determine the layout of the components in the case. I wanted to establish a high component density, and so layering the charge controller and amplifier was critical. Mocking this up properly was necessary in order to determine if my concept layout would work functionality. This is good to do before spending the time and money in cutting Plexiglas, and additionally the templates you create can be easily drawn onto your final material to simplify cutting and fitting.
I wanted the system to be allowed to work while locked and sealed, and this required universal external connectors. I selected a standard, 4-Pin Amphenol connector, of which I sourced from e-bay. For the audio input I selected the recording and entertainment industry standard XLR connector.
Building the connectors themselves takes some time and patience, as the small pins need to be carefully soldered in order to keep them isolated from each other. Each connection was then shrink wrapped when possible. Having these built ahead of time made the installation go much quicker, and provided a few nights worth of after-work projects.
Once the Plexi was cut, it test fitted, filed where necessary, and glued into place using white liquid nails. Plexiglass was selected because it is light weight and flexible. It also does not deteriorate. For these reasons it is better than wood, which was used in V1 of the Briefcase.
Initial wiring was routed, all connections were soldered and shrink wrapped, and potential wear points were also shrink wrapped. The best wire I had available was a red, 14 gauge wire which was used throughout the case. I had black wire but it was not of the same grade and I chose to use the red wire instead, wrapping electrical tape around the ends of the negative in order to differentiate it.
A shunt was installed on the left side of the picture. This added some weight but made it possible to have the built in amperage meter. The Amp meter is connected to both sides of the shunt and the resistance delta is measured across the terminals to determine the current flowing through the system. All power used from the batteries flows over the shunt, and all power use required from individual components is managed by and outputted from the Solar Charge Controller.
The DC/DC Buck/Boost circuits were installed next. Two separate units were selected and purchased for this project in order to provide voltage flexability for additional components.
On the Left is DC/DC Boost Converter that can take 10-32 volts DC and convert to any range between 12-35 volts as a Step Up only power supply. In other words this unit cannot reduce voltages. This unit provides 24v to the Dayton DTA-100A T-Class amplifier which is designed to be powered by 24 volts. I put a small 1,000 uf capacitor after this unit’s output and before the amplifier to smooth out the power further, however the unit does contain two 1,000 uf capacitors on-board already so this was not necessarily required.
- Input voltage :10-32V
- Output voltage: 12-35V (adjustable)
- Output Current: 10A (MAX)
- Input Current: 16A (MAX) (Please enhance heat dissipation if more than 10A)
- Output Power: natural cooling 100W (MAX), enhance heat dissipation 150W (MAX)
- Conversion efficiency: 94%
On the Right is a DC/DC Converter Auto Boost / Buck Power Supply that can be adjusted to provide any voltage between 8 and 30 volts DC with an output current adjustable from .5 – 6 Amps. The purpose of this unit is to allow the case flexibility for many uses. This component is hooked up to the Voltage Output wire, which is in pair with the solar input connector. It can allow you to run anything in the stated range of power and can both increase and decrease output voltage regardless of input voltage. Most recently I have used this to run a diaphragm water pump for a water filtration system. The variable voltage settings allow me to dial down the pump to the speed that works best for my application.
- Input Voltage: DC 8 ~ 30 V ( input Change, Output not Change )
- Output Voltage: DC 2 ~ 16 V ( auto Buck & Boost; Input change, output constant voltage, adjustable )
- Output Current: 0.5~6A ( adjustable, Constant current )
- Maximum Power: 80W Natural cooling
- Efficiency: 94 %
Here the components are going in and the amp is being installed. If you look close you can see the multi-colored wire with white connector that plugs into the back of the LCD meter on the front panel. The wires in use here are the two which read the current crossing over the shunt, and the others must connect up to a power source that is isolated from the source being measured from. This is required as to not affect the metering. To solve this without installing a separate battery I used a very small, B0505S-1W voltage isolation module, which cost about $1.
Here the face plate is installed with the master power switch, LCD and Cig/USB power box installed.
Here is the first look at the system together and powered on. The face plate of the system is now on with all of the components installed. The big switch I used to switch between battery 1 and 2 is installed. That switch may or may not be necessary, but the design consideration ended up making it into V2 after having it in V1. One of the reasons I had a switch, or several, in the V1 design was so that I could charge and play off opposite batteries if I wanted to. Because of the need to monitor Lithium battery voltage levels in order to prevent a low voltage situation, all loads have to be run through and managed by the charge controller. This makes it impossible to charge and play on separate batteries. Still, it provides a good way to keep power on reserve as well as easily shut down the system without unplugging batteries.