Cadillac Jack wrote:
I am after voltage. Higher voltage will push more amps into the batteries. Thus the MPPT controller.
Lower line loss, and more voltage.
Not sure why it matters that the batteries are in parallel.
Parallel batteries means you are running two 12V batteries parallel, as in your whole electrical system is 12V based. Running parallel combines the Amp hours of the two 12V batteries. Two 110AH batteries at 12 V gives you 220AH at 12V total.
If you were wired in series, your electrical system would then be 110AH, but your voltage would now be 2 x 12V, or a 24V electrical system.
Since you have a 12V system, your batteries are in parallel to run everything at 12V.
You need 14.8 to 15.0V to charge your 12V system. That's plenty high voltage. A Solar 30 PWM charge controller is one of those controllers that is Voltage adjustable up to 15.0V. It does 12V and 24V system charging.
Solar 30 PWM adjustable charge controllerYou can find this exact same PWM charge controller rebranded and sold in the USA for $55-80, all day long on Ebay. You can buy this one, it's sold from Los Angeles, and it will be at your door in 3 working days, if you order first thing in the morning. I know this is true, I just bought one. It does indeed deliver 14.8, or 14.9 or 15.0V. Connect it to one positive terminal on one battery, and one negative terminal on the other battery since you are running your batteries parallel.
Adding another panel to this 30 amp charge controller, regardless of size, on the input side of the solar panel, is fine... with a PWM charge controller, it is all about the AMPS of input, the charge controller takes care of the output voltage and makes it all the same, it does not have problems like a MPPT does with mismatched panels. It's about the amps on a PWM charge controller.
You are making this more complex and difficult than it needs to be, when you are working with 12V solar panels in small sizes. MPPT's are for huge 200 watt plus high voltage 29V panels, to get them down to 12V usage and charging a 12V system. If you have more questions, ask BFL13 about the differences, and small charging 12v panels vs large 24V panels, where MPPT controllers become a factor.
With a PWM and 12v panels, the line run is such that you can afford to lose up to 2 to 3V and not have an effect on pre voltage on the input side of the controller having an effect on the OUTPUT voltage of the charge controller. You worry about big V losses only between the output of the charge controller run to the battery terminals. You over come that loss by mounting the controller as close to the battery as possible without getting gassed by the battery, and short fat wires, to limit the loss on that wire run only.
