Two MPPT Solar Charge Controllers into a single battery bank

[oldjohnt]

Hey you Solar Equipment Experts and users, I have a question:

I have a Renogy Rover 60 Amp MPPT Solar Charge Controller feeding my SOK 412 Amp Hour 12.8 Volt Lithium Battery Bank, has worked perfect two years using the Renogy FACTORY lithium charge parameter setting which charges around 14.4 Volts.

I want to add a second Renogy Rover 20 Amp MPPT Charge Controller fed by another new panel ALSO SET at its same factory Lithium 14.4 Volt charge.

QUESTION with the outputs of both controllers,,,, identical other than size,,,, each at same factory charge rate of 14.4 Volts,,, feeding the same battery bank,,,  WORK OKAY AND EACH ADD CHARGING AMPS AND NOT FIGHT EACH OTHER ????

The reason I asked is I've seen 2 or even 3 charge controllers feeding a common battery bank and they worked TOGETHER and added charging amps, however I've been told by someone (supposed to know??) NOT to do this ????? I could series up panels, but my Renogy may not be capable of either the new total higher voltage or all the charging amps capacity my panels could deliver grrrrrrrr A new single bigger Volts and Current  MPPT ???

PS I could bump up EACH controller to 14.6 charging voltage but that's NOT my issue/question, Im concerned if they will work TOGETHER add charging amps and not interfere with each other ???

Thanks yall

John T

Edited July 11, 2023 by oldjohnt

[Randyretired]

I have 2 Epever controllers and an Outback controller.  On occasion I will add the inverter/charger.  It works great.  Since the controllers are voltage regulated these keep the voltage needed or as high of voltage as the solar will support.  On occasion I have seen one controller working a little harder than another but I don't see that as a problem.  Each controller has different panels and the panel voltages vary significantly. 

[Randyretired]

I would also like to add that as long as the charge controllers combined are within the  total amp capacity of the batteries I cannot think of a reason that this isn't a good idea.  With LifeP04  it would take a really powerful charger or solar array to push to many amps.  The controllers I use are all different sizes. 

[GlennWest]

I have 2 all in one units. So two different mppt controllers feeding same battery pk. Works fine. Also both units have dual mppt controllers so I could have 4 feeding same pk if more solar added.

Edited July 11, 2023 by GlennWest

[oldjohnt]

UPDATE  I finally had a good bright day to pull the RV out into the sun to see what happens. With BOTH the 60 Amp Renogy hooked to 4 panels and the 20 Amp Renogy hooked to its own new separate panel (for necessary reasons) ALL TO THE SAME LITHIUM BATTERY BANK.......BOTH set at the same factory lithium charging voltage and parameters.......

BOTH were pumping charging amps into the battery,,,,,Neither changed + or - of what charging amps they were contributing together versus if one or the other was shut off..............

NOTE it was Renogy Technical Support that told me doing that was NOT recommended... I can envision the case where if two controllers had different charging algorithms there could be conflict issues, none appear in my case.. 

 For now Im leaving things as is, its not broke (for now) so Im NOT gonna fix it lol

Thanks gang

John T 

[Chad Heiser]

As you found, there are no issues running multiple charge controllers in parallel to a single battery bank.  I currently have three charge controllers going to my single battery bank.  I prefer controllers that can be networked to talk to one another to better coordinate charging, but this isn’t required.  The only thing you have to pay attention to is the battery max charge rate.  Every battery manufacturer has a recommended charge rate (how many amps the battery can accept).  You do not want to exceed this number or you could damage the battery (if AGM/Lead Acid) or cause the BMS to kick in and shut down charging (if Lithium).

[oldjohnt]

14 hours ago, Chad Heiser said:

The only thing you have to pay attention to is the battery max charge rate.

  Thanks Chad, I'm good as far as that, my max charge rate is 100 Amps and I don't anticipate over 75/85 amps max. I had seen multiple controllers used before and didn't anticipate problems, especially with my two matched controllers, but when Renogy Tech Support recommended NOT to do this I was concerned which prompted my post. However, as an attorney and engineer I understand why the corporate lawyers insist on such things in manuals with big caution warnings like CONSULT AND FOLLOW NEC GUIDELINES etc. etc. fills a page lol

 I'm good to go and felt better after todays experimenting

  John T 

 

Edited July 13, 2023 by oldjohnt