While I’m looking forward to adding PV panels to my array, I’ll first have to replace my 20 amp charge controller with a bigger one. After careful consideration of available products, I’ve selected the Morningstar TriStar-60. I considered the Outback MX-60, but decided that the TriStar would be a better choice for my small system.
The Outback is a maximum power point tracking (MPPT) charge controller, which means that it can convert DC voltage to a higher or lower value. In some cases, this can result in more efficiency, but it probably wouldn’t benefit me much because my PV array is small. The TriStar is a pulse width modulation (PWM) charge controller, and it charges batteries in four stages. The strength of the charging signal is controlled by varying the pulse width. This has proven to be an efficient charging scheme for small systems.
The Outback charge controller can match any common PV array voltage to any common battery voltage. This feature allows the user to economize on wiring, and minimize losses that would otherwise occur. The TriStar can operate at 12, 24, or 48 volts, but cannot convert a high PV panel voltage to a lower battery voltage as the Outback can. While the Outback MX-60 is also a four-stage charge controller, its dc voltage conversion feature would not benefit me greatly, considering the limited wiring options I have with my small system.
The TriStar-60 uses less than 20ma (0.02amp) of current for its operation, much less than the Outback, an important consideration for a small system. More of the solar-generated power will be applied to the load. And the TriStar-60 comes with a 5-year warranty, while the Outback MX-60 controller is only warranted for two years.
Perhaps the most interesting feature of the TriStar-60 is its digital meter (option). I’ll be able to monitor system performance more easily, and I’ll return my digital multimeter to the toolbox where it belongs. In addition to instantaneous readings, the TriStar-60’s meter can display performance over time (data logging), and remote monitoring via the Internet is possible.
Before the year ends I’ll install at least one more solar panel. My ultimate goal is not only to power my home with PV-generated electricity, but to eliminate my use of fossil fuels entirely. I already burn corn to supplement natural gas heating, and I hope to purchase a plug-in car (PHEV) within the next two years. Using cfl lighting and replacing old appliances are other ways that I’m moving closer to my goal. I might just be the first person in my town to accomplish this. How cool is that!