Charge controller sized

[Jtb]

Hi. I have two 330w panels and I'm needing to get them in use asap and at this moment I don't have enough money to buy a controller that i would like to have that automatically recognizes voltage input etc . So for the mean time im gonna just buy a very very basic cheap one off ebay. I'm a little confused in what I need exactly to make sure specs are rt without have the auto reconition could you explain how they are rated as far as pv input. Most that are rated for 12/24v say that I can hook the 36v panels I have to them so are the 36v panels i have actually considered 24v. I'm confused if that's the case but the info I've read leads to that. As well if I understand correctly my panels are about 9 amps or close. With two in parallel seems a 30 amp controller would work with some to spare ? Please help clarify for me. So I can get these panels up and going. I've got a small 12 v system already that is much simpler to understand so I do have some knowledge of what I'm trying to do but still yet I want to get it rt. Oh I have 4 agm batteries to use and planned on a 24v battery bank with at least two of them and all four of panels will keep the charged. Thanks ahead of time
james

[littleharbor]

Most inexpensive controllers have auto recognition for voltage. How they work is you need to always connect the battery bank to them first. They will auto set based on the voltage they see.

Your 36 volt panels, are they 60 or 72 cell panels? If 60 cell, the voltage you're giving us is Voc. A 72 cell panel, which is considered 24 volt, nominal will have a Vmp. of about 36 volts and a Voc. in the 45 volt range. You should be fine connecting 72 cell panels for a 24 volt system. One thing you need to keep in mind is that your charging current should be between 5% and 13% of the battery bank amp hour rating. Two 9 amp panels(18 amps) is perfect for a 180 - 220 amp hour battery bank. You can get away with a larger battery if your use is intermittent, such as a weekend cabin.