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Old 06-09-2021, 12:25 PM   #1
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Can I run 2 Solar Charge Controllers on Same Battery Bank?

I currently own the Renogy 200 Watt Portable Solar Suitcase that comes attached with the Voyager 20A PWM Charge Controller. I would like to purchase 200 Watts of additional Solar Panels which will be mounted to the rooftop of my RV to increase my total Solar setup to 400 Watts when combined and using simultaneously. I understand that in addition to purchasing the additional panels I would need a new charge controller to support the higher voltage but is it possible to utilize 2 separate charge controllers devices simultaneously on 1 single battery bank without conflict if panels are setup in parallel? If it is possible and safe to connect 2 separate charge controllers from 2 different panel arrays what would be the best installation procedures for wiring? Would it be most ideal to purchase an identical 20A Charge Controller to insure the highest efficiency?

Additionally, My RV is also equipped with 110v Shore Power and Automatic Charging from vehicle alternator when engine is running. Since my new rooftop solar panels will be permanently connected to the battery bank, is it necessary to install an automatic transfer switch or other similar safety disconnect to prevent overvoltage or shorting out the system when other secondary charging sources (e.g. power received from 110v shore power or alternator) are connect to my RV? I greatly appreciate any advice or specific product recommendations to help me expand my current solar setup and generate maximum efficiency.
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Old 06-09-2021, 02:45 PM   #2
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Connecting multiple charge sources to a battery bank is not a problem.

Each charge source, be it the Converter/charger, Inverter/Charger, Engine Alternator, or multiple solar arrays (each with their own controller) will have their output controlled by their own "regulators".

Each will contribute to the charging current and as the batteries reach full charge, and voltage rises, each of the charge sources will start to "disconnect" (reduce their output) as the voltage reaches their individual programmed levels.

Contrary to an often stated myth that the charge sources will "fight each other", nothing other than a faster charge will occur.

If you have a large battery bank the benefit of utilizing more solar, each array with it's own controller, will be more current going into the battery and faster charge times.

When you think about it it's no different than the Power Grid that keeps the lights on in our country. Hundreds or more power stations feeding power into a common grid, each with their own controls that prevent "over-voltage".

In short, "Go For It".
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Old 06-10-2021, 11:26 AM   #3
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How would I wire the 2 controllers into the same battery bank? I spoke with someone at Renogy customer service and they told me that the 2nd charge controller would most likely just shut off or not really provide any significant power if it detected power source coming in from another source (in this case the other solar array and controller behind that one)

I just don't want to run into a situation where only half my panels are actually operating since 200 watts are controlled on one controller and the other 200 watts of panels are run my a second controller.
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Old 06-10-2021, 11:36 AM   #4
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I have not had much use for my Renogy since I got it, but yes it is connected to batteries through side power inlet on RV when I use it, and the OEM rooftop panel is on there as well. I can't comment on whether one or the other will trigger one another off.
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Old 06-10-2021, 12:23 PM   #5
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How would I wire the 2 controllers into the same battery bank? I spoke with someone at Renogy customer service and they told me that the 2nd charge controller would most likely just shut off or not really provide any significant power if it detected power source coming in from another source (in this case the other solar array and controller behind that one)
I just don't want to run into a situation where only half my panels are actually operating since 200 watts are controlled on one controller and the other 200 watts of panels are run my a second controller.
Renogy is telling you the truth. This topic was recently discussed on this forum. You might wish to read an answer at:
https://www.forestriverforums.com/fo...ml#post2503659
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Old 06-10-2021, 12:42 PM   #6
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There are a number of ways to accomplish this. I give you my example as it is pretty safe as all connections are fused and with proper gauge wire.

I have 2 Victron Solar Charge Controllers, One runs the solar from the roof, 550 watts & the the other Victron Charge Controller is connected to a 100 Watt portable solar array that is on the ground.

My output from both arrays are connect to a Victron Energy Lynx Distributor or simply put a huge positive & negative Bus bar with fuses.
My battery bank is connected to the bus bar as well with fuses & shunt ect..

The Lynx distributor also contains the location for your fuses and where I connect all my other solar & power items.

There are a number of videos online

I am slightly over simplifying but yes you can do it!

https://www.victronenergy.com/dc-dis...nx-distributor
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Old 06-10-2021, 01:06 PM   #7
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I currently own the Renogy 200 Watt Portable Solar Suitcase that comes attached with the Voyager 20A PWM Charge Controller. I would like to purchase 200 Watts of additional Solar Panels which will be mounted to the rooftop of my RV to increase my total Solar setup to 400 Watts when combined and using simultaneously. I understand that in addition to purchasing the additional panels I would need a new charge controller to support the higher voltage but is it possible to utilize 2 separate charge controllers devices simultaneously on 1 single battery bank without conflict if panels are setup in parallel? If it is possible and safe to connect 2 separate charge controllers from 2 different panel arrays what would be the best installation procedures for wiring? Would it be most ideal to purchase an identical 20A Charge Controller to insure the highest efficiency?

Additionally, My RV is also equipped with 110v Shore Power and Automatic Charging from vehicle alternator when engine is running. Since my new rooftop solar panels will be permanently connected to the battery bank, is it necessary to install an automatic transfer switch or other similar safety disconnect to prevent overvoltage or shorting out the system when other secondary charging sources (e.g. power received from 110v shore power or alternator) are connect to my RV? I greatly appreciate any advice or specific product recommendations to help me expand my current solar setup and generate maximum efficiency.
My suggestion would be to get rid of the PWM controller, and get an MPPT controller large enough to make use of all 400 watts of solar. You'll get better performance from your suitcase panels with the MPPT over the PWM, and you won't have to worry about any issues with two controllers, especially of different types (PWM vs MPPT). This will cost a little bit more, but you'll get better performance out of your panels.
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Old 06-10-2021, 01:18 PM   #8
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How would I wire the 2 controllers into the same battery bank? I spoke with someone at Renogy customer service and they told me that the 2nd charge controller would most likely just shut off or not really provide any significant power if it detected power source coming in from another source (in this case the other solar array and controller behind that one)

I just don't want to run into a situation where only half my panels are actually operating since 200 watts are controlled on one controller and the other 200 watts of panels are run my a second controller.
This only happens when the battery voltage approaches the point when controllers switch from Bulk to Absorption voltage and again when switching from to Float.

It's caused by the small differences in voltage settings (one or two tenths of a volt) in each Controller. By the time that happens the need for maximum power from solar panels will be behind you.

What would be a bigger issue is whether one set of panels, most likely the ones on the roof of the RV are shaded or at a less than optimum angle to the sun. The portable panel setup will more likely than not carry the load just fine when in Absorption Phase and the rooftop panels will be the slackers, even on a good sun day.

My 200 watt panels (portable) can charge my LiFePo4 batteries by noon on a sunny day as they aren't in the shade and can be oriented at 90 degrees to the Sun.

As another post said, dump the PWM controllers that waste power, wire each set of panels in series and install MPPT controllers for each set of panels. Non Bluetooth MPPT controllers can be purchased for <$50 and will work just fine. Bluetooth costs more.

Plug them in and don't worry.
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Old 06-10-2021, 04:24 PM   #9
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Yes, you can use two charge controllers. Watch Amy (RIP).
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Old 06-10-2021, 07:50 PM   #10
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I'm always learning. It seems that many more solar controllers synchronize when serving parallel charging than I first realized. Thank you all for leading me to look at this topic again.
Here is a link regarding TriStar MPPT controllers in parallel (include for general information):
https://www.solarpowerworldonline.co...-requirements/
A brief review of other systems seem to be similar. Smart chargers may connect in parallel without harming the system, but some charge controllers may not compliment charge power. Adding the amperage from various charge controllers during charge cycles requires the controllers to synchronize.
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Old 06-11-2021, 09:10 PM   #11
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Hey Titen, which 200 Watt portable do you have?
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Old 06-11-2021, 09:48 PM   #12
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It's not that they don't work together its that the first one to supply voltage makes the other one "see" a voltage that indicates a charged state since the first controller is putting out 14.x volts to the same system. This the second one won't push much, maybe a float charge only
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Old 06-11-2021, 10:22 PM   #13
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Hey Titen, which 200 Watt portable do you have?
I built my own.

Two HQST 100 watt panels for $79 ea on amazon.

A pair of butt hinges, a suitcase handle, and some small lock hasps with a pair of snap hooks to lock it closed.

i used an adjustable "roof mount" that had handles on the bolts and wing nuts.

Installed some cage nuts in ends of panel frame (back side) and secure the mout to the panels using some long bolts with handles. This allows the handles to clear the angle of the mount and to keep bolts from going too far in and damaging panel itself I added some nylock nuts for stops.

For controller I have a victron Smart MPPT controller mounted next to my batteries. Panels are connected in series and feed the controller through a 40' heavy extension cord.

Takes me about 15 minutes to deploy.

This 200 watt setup with panels in series and feeding the MPPT controller is providing up to 212 watts as logged on the app for the Controller on a nice sunny day.

Not bad for an under $200 panel setup. My MPPT controller is just over $100 but others are available starting at $40 and if one wants to go low $$, just hinge the panels and then lean them against the side of the RV or a tree.


The HQST panels are a well performing product and one can just use their imagination on how to prop them up.

Next time I have them set up I'll try and remember pictures so I can post for anyone who is interested in a simple DIY project.
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Old 06-11-2021, 10:25 PM   #14
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It's not that they don't work together its that the first one to supply voltage makes the other one "see" a voltage that indicates a charged state since the first controller is putting out 14.x volts to the same system. This the second one won't push much, maybe a float charge only

Yes, but by that time the batteries are approaching full charge anyway.

Remember that when the batteries are less than full charge they will draw the voltage down to their level and as long as that voltage remains under both controllers switching voltage they will contribute as much as they can put out to charge.
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Old 06-11-2021, 10:31 PM   #15
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Yes, but by that time the batteries are approaching full charge anyway.



Remember that when the batteries are less than full charge they will draw the voltage down to their level and as long as that voltage remains under both controllers switching voltage they will contribute as much as they can put out to charge.
What is the voltage at the dist block or battery terminals during that time? If you put a meter on the controller output terminals will it show what being pushed by the controllers or what the battery is "seeing" internally on that draw down?

Serious question, this is getting outside of my understanding.
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Old 06-12-2021, 09:12 AM   #16
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What is the voltage at the dist block or battery terminals during that time? If you put a meter on the controller output terminals will it show what being pushed by the controllers or what the battery is "seeing" internally on that draw down?

Serious question, this is getting outside of my understanding.
When multiple charge sources are connected to a common "bus" that is connected to the batteries the voltage they "see" will be the battery voltage.

This will be the signal voltage to each controller and from there it's up to the controller's internal settings that determines what charge phase they enter. Manufacturing tolerances may cause one or the other controller to switch to a lower charge rate but usually this is only a tenth of a volt or so.

Again, not a big deal as during the Bulk phase the controllers are putting out as much current as they can based on the input from the PV panels. The big difference will be on the pV panel end as unless each array is aligned with the sun exactly the same, each will have different outputs.

If one is worried about one set of panels or the other is "slacking" it will be most likely the amount of solar energy each is absorbing, NOT the difference in controllers.
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