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  1. #1
    Join Date
    May 2005
    Location
    Loch Snizort, Isle of Skye
    Posts
    4,800

    Default Can I use two solar charge controllers to charge the same bank?

    New (to us) boat has an existing charging system with a controller that accepts up to 160w of solar.
    We want to increase this to around 400w total, but rather than get rid of the quite nice Marlec unit already installed, can we add a second charge controller alongside it, and have them both charging the same battery bank(s)?
    The Marlec is also connected to a wind gen so I would prefer to leave that whole system as-is.
    Deb 33- Wayfarer- Wanderer

  2. #2
    Join Date
    Jan 2003
    Location
    Portland
    Posts
    1,517

    Default Re: Can I use two solar charge controllers to charge the same bank?

    Well, I have done what you propose for years with no problem. There might be circumstances where if using different types of chargers ie pwm or mppt might cause one not to be charging at the same time. But in practice it is not noticeable in the overall scheme of things.
    I used to be indecisive, but now I'm not so sure...

  3. #3
    Join Date
    Nov 2009
    Location
    Home UK Midlands / Boat Croatia
    Posts
    18,327

    Default Re: Can I use two solar charge controllers to charge the same bank?

    Presumably you intend to put the entire 400W of solar through the new controller and leave the Marlec to manage just the wind gen because the Marlec cannot take 400W?

    That will work OK.

    Richard

  4. #4
    Join Date
    May 2016
    Location
    Suffolk
    Posts
    7,454

    Default Re: Can I use two solar charge controllers to charge the same bank?

    Having two charging sources can cause issues, depending on the controllers and the charging regime to which they are set. For instance, early in the morning when the Sun starts to shine there is a strong breeze and the wind gen' is charging the batteries nicely, the solar controller wakes up and sees the voltage from the wind gen' controller and thinks the batteries are charged, so it doesn't start.

    All you can really do is to fit the solar controller and monitor what happens, you may need to adjust some settings, so fit a decent controller that can be configured. It's usually the case that two sources work better together when the charging regime of both controllers is as close to identical as possible.
    Rainbow Marine.
    www.rainbowmarine.co.uk

  5. #5
    Join Date
    May 2005
    Location
    Loch Snizort, Isle of Skye
    Posts
    4,800

    Default Re: Can I use two solar charge controllers to charge the same bank?

    Thanks for the replies.
    This is the Marlec controller in question: https://www.marlec.co.uk/product/hrd...v=79cba1185463

    It's already hooked up to a Rutland wind gen, and a small solar panel. As I understand it, it can take 160w of solar in addition to the wind gen.

    My plan is to max out this charge controller, and add a second controller for further solar panels. Of course I could just make the second controller bigger, to handle all of the solar by itself, but that presumably means spending a bit more money.
    Deb 33- Wayfarer- Wanderer

  6. #6
    Join Date
    Feb 2003
    Posts
    15,005

    Default Re: Can I use two solar charge controllers to charge the same bank?

    Quote Originally Posted by Kelpie View Post
    Thanks for the replies.
    This is the Marlec controller in question: https://www.marlec.co.uk/product/hrd...v=79cba1185463

    It's already hooked up to a Rutland wind gen, and a small solar panel. As I understand it, it can take 160w of solar in addition to the wind gen.

    My plan is to max out this charge controller, and add a second controller for further solar panels. Of course I could just make the second controller bigger, to handle all of the solar by itself, but that presumably means spending a bit more money.
    As Paul said, things can happen! Its all in the sensing! I had a weird situation in my previous boat. solar putting max in, Sterling Alternator booster saying, ah, full charge and shutting down alternator and so I then get weird situation of VP panel charge light coming on and alarm sounding that alternator is not charging!

  7. #7
    Join Date
    Nov 2009
    Location
    Home UK Midlands / Boat Croatia
    Posts
    18,327

    Default Re: Can I use two solar charge controllers to charge the same bank?

    Having read Paul and Stu's thoughts I'll change my response to "it might work OK ... but it might not".

    Richard

  8. #8
    Join Date
    Jun 2004
    Location
    UK and NW Caribbean, Belize Mexico & Guatemala
    Posts
    361

    Default Re: Can I use two solar charge controllers to charge the same bank?

    Quote Originally Posted by skipper_stu View Post
    As Paul said, things can happen! Its all in the sensing! I had a weird situation in my previous boat. solar putting max in, Sterling Alternator booster saying, ah, full charge and shutting down alternator and so I then get weird situation of VP panel charge light coming on and alarm sounding that alternator is not charging!
    I have this situation as well so now turn the solars off whilst motoring.

    I have been thinking about splitting my 400 watts of solar into 2 banks Port and starboard to (hopefully) reduce the effects of shading

  9. #9
    Join Date
    Feb 2013
    Posts
    913

    Default Re: Can I use two solar charge controllers to charge the same bank?

    We have been around this one before.

    Give it a try, it cant do any harm.

    I run two chargers, a solar controller and the alternator often at the same time and / or in combination and dont have any issues. My systems just dont "see" the charge from the other sources and the combination works very well.

  10. #10
    Join Date
    Apr 2018
    Location
    Mooring, Faro
    Posts
    1,285

    Default Re: Can I use two solar charge controllers to charge the same bank?

    For 10 years, I've had a small panel regulated by the Aerogen reg and larger panels via an MPPT, both regs charging the same batteries with no problems. Have just virtually doubled panel size so, until I get back with larger reg, have 2 x small mppts in parallel charging same batteries, Aerogen removed but small panel still temporarily connected to that reg.

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