Proper Wiring for two controllers to one battery bank

Wouldn't the Rogue just handle all three panels in series? There would be nothing to confuse it then. My mismatched panels are 24v and different types.

And we don't know if these two controllers will work together anyway. If one is slightly higher voltage, won't that tell the other controller the bank is charged?

JiminDenver wrote:
Wouldn't the Rogue just handle all three panels in series? There would be nothing to confuse it then.

No, series would be worse. The amperage in the circuit would be that of the 50w panel.

Here is where I saw that about the 2 minute hunting, part way down in DSchmidt's post here. ( Too bad he isn't here to help with the gizmo's etc)

http://forums.motorhomemagazine.com/index.cfm/fuseaction/thread/tid/26464298/gotomsg/26953604.cfm

2oldman wrote:

westend wrote:
Paralleling different panels with different electrical characteristics to one MPPT controller is not a good idea.

Not sure why that would be always true. It's pretty simple to try it and see the amperage reading at the controller.

It is because the "knee" of the IV curve is different in the two different panels. That "knee" is where the MPPT controller observes the characteristics of the panel's output and determines how to sort voltage, amperage and resistance.

Think of it this way: The MPPT controller is lecherous. It likes to rub knees. If it has Charlise Theron in on one chair and Rosie O'donnell in another chair, it will get confused and start examining just Rosie's leg rather than Charlise's appendages. The result will not be pretty.

westend wrote:
.. it will get confused and start examining just Rosie's leg rather than Charlise's appendages. The result will not be pretty.

ARG!

westend wrote:

2oldman wrote:

westend wrote:
Paralleling different panels with different electrical characteristics to one MPPT controller is not a good idea.

Not sure why that would be always true. It's pretty simple to try it and see the amperage reading at the controller.

It is because the "knee" of the IV curve is different in the two different panels. That "knee" is where the MPPT controller observes the characteristics of the panel's output and determines how to sort voltage, amperage and resistance.

Think of it this way: The MPPT controller is lecherous. It likes to rub knees. If it has Charlise Theron in on one chair and Rosie O'donnell in another chair, it will get confused and start examining just Rosie's leg rather than Charlise's appendages. The result will not be pretty.

I can't erase that from my mind... I am feeling gravely ill after visualizing that nasty scenario.

NinerBikes wrote:
If you have two matching 120W panels, those are each close to 7 amps each charge rate. Why even bother screwing with the 50 watt solar panel and it's measly 2.5 addtional amps, when you already have 14 amps? Get another matching 120W panel if you can, and sell the 50 watt panel.

120W panels for 89 AH group 27's AGM's is plenty, for most applications.

Next time when your replace the Group 27's Trojans, consider 6V T105's instead. Much, much, much easier to keep charged, they don't have the crappy acid to lead ratios that car type sized batteries do, so that the damn battery can fit under the hood without shorting out at the terminals.

Trojan should make a T-105 AGM Side terminal batteries for cars already, for no shorts.

When you match batteries, you should match panels also... seems to me just to be common sense.

Understood. Oddly enough I have already come to the same conclusion. I am going to concentrate on the two 120 watt panels. I am wiring them in series and running 8 gauge MC4 wire to the Rouge through a plumbing vent. This will decrease my wire run to well less than 10 feet.

From the charger to the batteries I only have a 24 inch run, and it will be 6 gauge fused before and after the charger.

Later on I will take down the 50 watt panel, and replace it with a 100 watt unit and use the same wire route to the second charger thus I will be gaining an additional 6 amps plus absolutely no combiner boxes or holes in my roof.

Unfortunately, I can no longer find the Evergreen 72 cell 120 watt panels, so I will have to build a second array.

As to the T 105s, already been down that road. They will not fit in my battery box. The Trojan 27 TMX was really the best I could do, and still have a fair amount of room to work on and water the batteries.

The Trojan group 27s that I have are 105 AH each. I should be sized pretty well with the two 120 watt panels in series. I bought a relatively cheap watering system from Amazon, and it works flawlessly.


I also have the remote meter for the Rouge. Very exited about this setup.

Thanks for all the replies.

Why would you run the panels in series, when you only have 2 12v batteries to charge, and they are wired in parallel?

Take both panels, in parallel and route them into a 12v PWM charge controller rated at 30 amps, in case you add one more panel. One short run of heavy thick wire from the charge controller to the paralleled 12v batteries, and you are complete.

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.