Can I use two separate controllers to 2 separate battery banks (different chemistry) from one Panel?

Doug183
Doug183 Registered Users Posts: 1 ✭
in Solar Beginners Corner #1
RV setup:
- I have one big panel on my RV - 350 Watts.  (70 Volts)
- Installed one 100ah lithium ion battery for the coach.  (I don't have much 12v Draw)
- Installed a Victron MPPT (100/30) and is now set for lithium chemistry.
- On board charger can be manually set to set to lithium when either plugged into shore or when generator is used.
- I separated out the starter battery from the coach battery, so the alternator will not damage or be damaged the new lithium.  As a consequence, the starter battery no longer gets charged by the on board house battery charger (via Shore Power or Generator) - not that it did much before. 


RV use:
- RV is really used for boon docking.
- RV rarely gets used, only a few weeks a year and mostly sits outside.
- I honestly have very little energy draw for the 12V system - no TV's or inverter.  All lights are LED and I have a bunch of 12V-5V USB chargers on the system.
Basically this upgrade was because I came into some affordable parts and was tired of the stress while on boon docking trips if my house batteries would keep pumping out power.  Lead Acid deep cycle batteries were dying on me every 2 years.

So questions:
1) Can I add a second MPPT charger from the Solar panel and run separate wires to the starter battery?
 1a) Is it a problem to have the separate controllers set to different chemistry?
  1b) Is there a feedback / common ground problem I am causing by doing this?  All grounds are tied to the chassis.
  1c) Have I reconnected the two batteries through the solar system?  So now alternator/ house charger/ generator are.... all reconnected?
2) How to split the Solar wires?   Just two bus blocks?  Then one set of wires to each Solar charger?
3) Do I need some other component to add to this? 

After writing this, I think I can't do this to operate automatically because basically the electricity doesn't run only one way and now I have reconnected the two systems though the solar array.  Right?

Any and all help is appreciated.

Doug
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Comments

  • wellbuilt
    wellbuilt Solar Expert Posts: 763 ✭✭✭✭
    #2
    Hmmmm , you really can’t use 2 charge controllers On one solar bank . 
     You could add a small panel to charge your start motor , I’m Assume you just need it to keep the battery charged when you are parked . 
      You could us a A/B switch with a charge controller to choose witch bank you want to charge and switch the back and forth every few weeks .
     I’m sure you can charge thru you house bank with some type of eco charger but I’m not sure how to regulat the voltage . 
       I would disconnect the battery’s when I was not going to use the rv  
    Out back  flex power one  with out back 3648 inverter fm80 charge controler  flex net  mate 16 gc215 battery’s 4425 Watts solar .
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,917 ✭✭✭✭✭✭
    #3
    I think I would do what was said by Mr. Wellbuilt. You can use 2 or more controllers but I think he meant the set-points are different.

    You are up against a problem in larger systems that is solvable but not really worth the money it cost in a small system.
     
    The problem of different set-points in the same DC bus or even separate DC busses. A good chess game, and winnable also.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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