I'm fairly big into ham radio. I'll probably post more on ham radio in general and why I got into it, but this post specifically is about one piece of equipment I got for the car.
I bought an Epic PWRGate from West Mountain Radio, in order to run my ham equipment while mobile. I actually have my radio installed directly to my battery (I'll do another post on that), but I like to be able to run my radio when my car is off and not run down my battery. For that reason, I have a Amstron 12V / 75Ah sealed lead acid battery, which I connect my radio to in the car.
I did however want to be able to charge my second battery from the alternator in my car only when it was running (as to not draw down my car battery for my radio), and I wanted to be able to plug my solar panels directly into my battery box. The Epic PWRGate is perfect for this.
It works great out of the box to charge my spare battery from my power supply, but I wanted to specifically set the parameters of my specific battery / car setup. You can program the PWRGate through a USB serial connection. The problem is that West Mountain has windows-only software, and I specifically have a Arch linux laptop that I use for all my personal projects.
Luckily it's pretty easy to connect to the PWRGate through dterm, the arch wiki has pretty good documentation (as always) on using serial connections. If you're not using Arch Linux specifically, you can probably still install dterm, or use whatever serial program comes with your distro or that you are comfortable with. The important parts are the connection parameters:
- 115200 baud
- 8 data bits
- no parity bit
- 1 stop bit
I chose to use dterm, and with my laptop, the PWRGate shows up as /dev/ttyACM1. I can connect to it with the following:
dterm ttyACM1 115200 8 1 n
This will start spitting out debugging information from the PWRGate so that you can see various stats. Mine looks like this:
Chrg Off PS=12.29V Bat=13.05V, 0.00A Sol= 0.04V Min=0 Chrg Off PS=12.29V Bat=13.05V, 0.00A Sol= 0.04V Min=0 Chrg Off PS=12.29V Bat=13.05V, 0.00A Sol= 0.04V Min=0 Chrg Off PS=12.29V Bat=13.05V, 0.00A Sol= 0.04V Min=0 Chrg Off PS=12.29V Bat=13.05V, 0.00A Sol= 0.08V Min=0
You can then press the
s key at any time to enter programming. You should look up the various numbers using your battery spec sheet. For example, my battery's spec sheet says:
Limit initial current to 22.5A. Charge until battery voltage (under charge) reaches 14.4 to 14.7 volts at 68°F (20°C). Hold at 14.4 to 14.7 volts until current drops to under 750mA. Battery is fully charged under these conditions and charger should be disconnected or switched to “float” voltage.
Therefore, you can set those numbers in the PWRGate, where you can cut charging off once it reaches a certain voltage, and then trickle charge after that. The spec sheet also specifies the float voltage, of 13.6-13.8V.
You can then disconnect from the serial port and yank the cable, and you're good to go! I recommend you leaving the serial port connected while you make sure that you aren't charging all the time in your car.