Double solar system hookup.

[AWCHIEF]

Another off the wall solar question. Is it safe to hook up two independent solar systems to the same battery pack? Ex: a Renogy 100 watt suitcase using a 10 amp controller and another independent 75 amp panel run thru another controller. Just a what if.

[dznf0g]

No, you should wire separate systems to a single controller. I installed connectors to my ZAMP portable system in order to remove the ZAMP controller while connected to the AS pigtail. I kept the ZAMP controller mounted to the suitcase so I could use the portable for other stand alone applications, but it is effectively removed from the system and creates a parallel with my permanent panel through a single Morningstar hard wired AS controller.

[AtomicNo13]

Parallel connections are typically permissible as long as there is not a gross mismatch from one another!
It's basically like having your converter and solar controller together.

[dznf0g]

Here is a rough drawing of my setup:

[dznf0g]

Any mismatch of output voltages will cause reduced efficiency of the system....when in the cycle(s), and how much of a mismatch determines how much inefficiency. Theoretically, there will be times in their respective cycles where there is zero gain from one subsystem or the other.

[AtomicNo13]

Voltage to the batteries is voltage to the batteries..... despite a differential.

[dznf0g]

Originally Posted by AtomicNo13

Voltage to the batteries is voltage to the batteries..... despite a differential.

Negative. A voltage differential on a parallel circuit will cause resistance in the lower voltage leg, reducing the amperage from the lower voltage leg.

[BoldAdventure]

Rich (dznf0g) pretty much explained all it. Friend here has a Renogy suitcase, same one you have with a 300 watt Renogy kit on the roof. He kept finding that the roof controller was still charging but the suitcase kept reading as full. Basically the systems were mismatched.

So I helped him bypass the PWM on the back of the suitcase, and we wired it with a SAE plug into the one controller for the roof solar. Works better that way.

The only good way to run two separate controllers is if they can communicate with each other. Like Bluesky and Victron units do.

For example, I have a the SB2512 and SB3024 - the 2512 is slaved to the 3024 for my ground deploy solar.

[AWCHIEF]

OK, bad idea. It was just feeble brain storming. I do have another new PWM 30 amp controller I could swap out the 10 amp Renogy unit and add the 75 watt panel. Effectively and guessing again would up my system to 175 watts or would that cause too much of a miss match? At this time wanting to stay away from hard wiring a solar system and keep it simple and cost effective.

[dznf0g]

I would need to know more about the specs of your two panels to comment, but if they are close in specs, you probably can parallel them into that controller.

[AWCHIEF]

The Renogy panels are two 50 watt mono. The other is a 25 year old Siemans 75 watt that still puts out close to its rated amps. I used it on my boat for 10 years in the Carribean.

[dznf0g]

Originally Posted by AWCHIEF

The Renogy panels are two 50 watt mono. The other is a 25 year old Siemans 75 watt that still puts out close to its rated amps. I used it on my boat for 10 years in the Carribean.

More specs on each please. Open circuit voltage (Voc), etc....as well as your controller specs.

[Kilroy]

Running a Trimetric controller and monitor. All neg wiring goes through a shunt that monitor uses to monitor charging. Just got a 100 watt Renolgy suitcase, hooked it up to negative to shunt and batt positive terminal. Working very well.

[JCWDCW]

Originally Posted by AtomicNo13

Voltage to the batteries is voltage to the batteries..... despite a differential.

Except that the lower voltage won't be doing anything! The higher voltage would normally feed back into the lower voltage except that the controller has a diode to prevent back voltage.
JCW

[twh731]

Don't mean to hijack the thread but this seems like an appropriate question. I am going to mount 2 100W panels on the roof and have them wired thru a controller. Would it be possible to prewire a recepticle that is wired thru the controller and have the recepticle easily accessible on the outside of the A/S so that you can just plug in a suitcase solar array? That way you can just plug in the extra solar panels or not as needed? Tom

[KJRitchie]

For 200w on the roof, combine them and send the cable down to the solar controller location to another combiner box. Then lay cable with a quick connector from that combiner box to outside the trailer for the portable panels. Disconnect/remove any controller on the portable panel. Then connect that combiner box output to the solar controller inputs. Disconnect any controller mounted on the portable panels.

I'm planning to do this hopefully this year; 200w on the roof plus my 200w Zamp portable.

Kelvin

[lewster]

Be sure to use an A/B selector switch just ahead of your solar controller, as 2 sets of non-matching panels will not play nicely together into a single controller.


Lew Farber
RVIA/RVDA Nationally Certified Master Tech
ABYC Certified Master Marine Electrician
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center*AMS Lithium Batteries
Lifeline AGM Batteries**Magnum Inverters
541-490-6357

[KJRitchie]

Really? So I can't really get 400w with say 2 AmSolar GS100 on the roof and two Zamp 100 of portable running together connected to either a Bogart SC 2030 or a Blue Sky controller?

I guess I need to buy two Zamp 100w panels for the roof if thats true.

Kelvin

[BoldAdventure]

You can if all the specs match.

[AWCHIEF]

Originally Posted by twh731

Don't mean to hijack the thread, Tom

Of course you did, but that is ok. The thread was dead.