Solar charge controller selection help needed
I am looking to put in a solar system that will produce about 30 amps per day. I choose a semi-flexible 135 watt panel made by Sunpower which meets my capacity needs. My only problem is choosing t...
Forum Discussion
Almot wrote:
Have just noticed that the OP ordered not just a 40A controller, but an MPPT one. Cost about $260.
I'm usually the one who tells not to buy el-cheapo stuff for long-term projects, but 40A MPPT for 135W single 12V panel doesn't make sense.
A good PWM controller, with remote display and temp probe, like Xantrex C35, would cost about 2 times less. And it would likely result in higher daily output as well. MPPT becomes less efficient when input voltage is getting close to 12V.
The reason I had originally selected MPPT is my understanding that PWM could only be used when the panel and battery voltages where the same, or similar.
In my case, the panel is sending 25-29 volts going to a 12V battery. I also saw that MPPT controllers are also more efficient at lower and higher operating temperatures. I was also planning on adding 1 or 2 more 135 watt panels once I assess baseline performance.
I was also told that a 20 AMP controller would be at the limit for 2 135 watt panels. I tried to buy a 30 but EPsolar does not make one in the new Tracer series. I guess there is no significant price reduction for a 30 amp using their design.
Is this correct? If not I can always exchange it, I bought it locally.
