Solar panels for dummies

[Bill]

Ahh, Bruce - geeks always have too many projects, and we have to spread our available funds widely! But believe it or not, full networking capabilty is available on a couple of these controllers

Bill

Yes but to be of real value, it should have bluetooth capability so it can be monitored real time by your smartphone as you rest in your hammock

[Lesherp]

Thank you all for your time and efforts here. I told the man at Wind-Sun I was looking at getting two 12V panels one 85 watts and the other 140 watts. One to be mounted and one to be portable and told him I was considering the MPPT Blue Sky 2512I - 25 amp controller and wanted to know if this would work. I never said anything about my batteries. I can't imagine why he would think I needed the $400 Morningstar TriStar 45 Amp MPPT Solar Charge Controller if any controller would work with panels with two different watt ratings. Maybe he misunderstood me, maybe his first day at work, who knows.

I am still leaning towards having the versatility of a roof mounted panel for charging in transit and a portable panel I could deploy when clouds or parking in the shade limits its output. They would have a total of 225 watts with 12.75 amps. and if I understand correctly there would be no problem putting them together using the Morningstar ProStar15 - 15 amp.

I have limited electrical and wiring knowledge. Wiring one panel seems straight forward. Wiring two panels requires them to be connected and one wire from each panel running to the controller. When hooking up my portable panel it seems like I would have to figure out a way to disconnect one of the wires running from the mounted panel to the controller, connect it to the portable panel and connect the other wire from the portable panel to the controller. I suppose I could just have a connector terminal on the end of both wires and bolt them together but there must be a better way. Lol, like I said limited knowledge. Any suggestions?

I am still weighing the pros and cons of roof mounted, portable or a combination. I have two 6 V batteries and a clipper battery monitor. Do you think parked in a sunny location and with conservative energy consumption the140 watt roof mounted panel would be sufficient without deploying the second panel ? How effective do you think whatever I might be getting from the 140 watt panel in partial sun or shade and the 85 watt panel in sun will be?

[Bill]

Wait a minute. The wind-sum web site confirms that panels above 120 watts are quite often "high voltage panels", meaning 24 volts or more. During your conversation with Wind-Sun, unless you identified the specific panel you have in mind, he might have assumed it would be a 24-volt panel. As I mentioned above, many controllers, including the 2512I and others in my list, won't accept a 24-volt panel (although the Tri-Star 45 amp controller will). In addition, although you can mix 12-volt panels of different wattages, and you can mix 24-volt panels of different wattages, I don't think you can mix a 24-volt panel with a 12-volt panel. You need to check this before you go further.

Why don't you tell us what you have in mind? Until you do, we are kind of shooting in the dark.

Bill

[Lesherp]

These are the panels I am considering.

http://www.solar-electric.com/kykd140wasom1.html
http://www.solar-electric.com/so85wa12voso.html

You can hard wire the roof mounted to the controller through a "Y". Base of the "Y" gets hardwired to the controller. One top branch of the "Y" gets hard wired to the roof mounted panel. You then add a low resistance good quality connector to the other top leg of the "Y". The remote panel then plugs in there. I am using the morning star pro star 30 ( extra capacity if I need it) at home with a total of 280 watts of 12v panels. I have had good luck with it.

[Bill]

Originally Posted by Lesherp

These are the panels I am considering.

http://www.solar-electric.com/kykd140wasom1.html
http://www.solar-electric.com/so85wa12voso.html

OK, good, you've done your homework. Both of these are 12-volt panels, and they should mix just fine. We're back to the original question - why an expensive MPPT controller instead of a less expensive PWM controller. I still have no idea.

Bill

[Lesherp]

Bill,

I am thinking he may just not be very good at his job. I may not have specified that they were both 12 V or he could have assumed a 140 Watt would be 24. You would think he would have advised me to go with two 12 watt panels if he thought that was what I was suggesting. Maybe he had little experience with small RV type projects and just always recommends that controller. From what I am reading here it sounds like it was misinformation. Do you think there is any chance he knew what he was talking about?

Rumbleweed,

I kind of have a basic understanding of electricity but little experience working with it. Can you give me a little more information about the y's and connectors you are suggesting I use. I am not at all sure what kind of Y you are talking about. I understand it would split the wiring allowing two panels to be plugged in to the controller, but I don't have a clue what to look for. I would not know a low resistance good quality connector from a poor quality high resistant one. Can you give me more specific information, like a brand name? If I am understanding you correctly this would wire the panels in series rather than parallel. I think most of the diagrams I have seen wired to WPM controllers have been parallel. Does it matter?

[Bill]

No, Rumbleweed will agree the panels get wired in parallel. Think of a big letter "Y". The + (plus) terminal of one panel goes to one of the top branches of the "Y", and the + terminal of the other panel goes to the other top branch of the "Y". The stem of the "Y" goes to the + terminal of the controller.

Now make another "Y", and do it again on the - (minus) side of everything.

Bill

Bill is right. You don't buy a "Y" you just connect wires in a "Y" I will try to draw this up later. There are many good quality polarized connectors. Power Pole is one example,

Bob