Solar 103!! Sizing the controller

[GallenH]

I'm trying to keep these topics separate for future searches. My plan is to put 2 100w solar panels on the roof. I'm pretty sure that I can squeeze them in. They would feed a 200AH battery bank.

How do I decide on the Amp of the controller?

I noticed that Renogy offers a package with 2 100w panels and a MPPT controller. But they offer an option for the controller of either a 20A one or a 40A one. Why would you choose one or the other?

I've read that a MPPT controller is more efficient than a PWM controller but some (Renogy for example) say it's better to use a PWM with a small battery bank (which I assume 200AH is)

thx again.glenn

[booster]

Originally Posted by GallenH

I'm trying to keep these topics separate for future searches. My plan is to put 2 100w solar panels on the roof. I'm pretty sure that I can squeeze them in. They would feed a 200AH battery bank.

How do I decide on the Amp of the controller?

I noticed that Renogy offers a package with 2 100w panels and a MPPT controller. But they offer an option for the controller of either a 20A one or a 40A one. Why would you choose one or the other?

I've read that a MPPT controller is more efficient than a PWM controller but some (Renogy for example) say it's better to use a PWM with a small battery bank (which I assume 200AH is)

thx again.glenn

As I mentioned in the other thread you have, it is not just bank size you need to look at. It is the interaction of the bank size, running loads, and the voltage of the panels MPP point you need to analyze.


If you want a very good, fully settable PWM controller, the Bogart unit is very nice, especially when teamed with their monitor as then the monitor can control the charging more accurately.


Two panels, if the voltage doesn't get pulled down because of running loads with have a MPP of around 35 volts in series, so an MPPT controller would be called for IMO.